Patent Description:
Conventional medical imaging devices, such as computed tomography (CT) and magnetic resonance (MR) imaging devices, are typically fixed, immobile devices located in a discrete area reserved for imaging that is often far removed from the point-of-care where the devices could be most useful.

It would be desirable to make these imaging devices mobile, so that they can move to various locations within a hospital or other health services environment. This is difficult due to the size, weight and overall number of components required for making an operable imaging system. Furthermore, these systems typically require a power system that can provide high-voltages (e.g., <NUM> kV) to components that rotate within the system around an imaging bore. Conventional imaging systems generally utilize a dedicated high-voltage power source and a complex power delivery mechanism, such as a slip-ring or a high-voltage cable system, to deliver the required power to the rotating imaging components. While these power systems may work fine for conventional fixed imaging systems, they are not ideal for mobile systems, which are ideally much more compact and lightweight than conventional systems. Furthermore, when transporting a mobile system outside of the traditional radiology environments, it is typically not possible to obtain the power required to perform imaging procedures from standard power outlets.

<CIT> discloses an apparatus for energizing a large scale medical imaging system, preferably in the form of a CT scanner, so that the scanner operates off an uninterruptable power supply in the event that the external power falls below sufficient power to operate the system so that system operation remains uninterruptable. The system is designed to operate off a broad range and types of external power supplies including those providing DC, single or three phase AC power. The system therefore can operate from a common single phase AC outlet. In addition, power factor correction is provided so that the system can correct for phase differences between the voltage and current at the input line created by the input impedance of the system.

<CIT> discloses an x-ray tomography apparatus having a patient table, x-ray tomography components located around the patient table and in an imaginary plane which intersects the table, and structure for supporting the table and tomography components and including an apparatus for moving the tomography components along at least a portion of the table. In an alternate embodiment, an x-ray tomography apparatus includes an annular x-ray tomography system for continuously rotating around a patient, which structure has an electrically powered x-ray source and battery power for supplying electrical power to the x-ray source.

<CIT> discloses a docking assembly connected to a movable couch. The docking assembly docks the couch with an imaging apparatus. Couch alignment surfaces mate with corresponding alignment surfaces of a connecting region of the imaging apparatus to define a docked position of the movable couch with respect to the imaging apparatus. A docking sensor detects the movable couch approaching the docked position. A latch mates with the connecting region of the imaging to apparatus. An actuator cooperates with the latch to bias the movable couch into the docked position responsive to a signal produced by the docking sensor.

According to an aspect of the present disclosure, a mobile diagnostic imaging system is provided according to independent claim <NUM>. Preferred embodiments are recited in the dependent claims.

Various embodiments include an imaging system that comprises a rotating portion comprising a rotor and at least one imaging component mounted to the rotor, and a gantry comprising an outer shell that substantially fully encloses the rotating portion over one or more sides of the rotating portion, the outer shell further comprising a mounting surface for a bearing that enables the rotating portion to rotate <NUM>° within the outer shell.

In further embodiments, a mobile diagnostic imaging system may include a battery system and charging system. The imaging system may include a first portion and a second portion, wherein the first portion rotates with respect to the second portion. In one embodiment, the rotating portion rotates within an enclosed housing of a gantry.

In embodiments, the battery system may be located in the rotating portion of the system. The battery system may include one or more battery packs, each comprising one or more electrochemical cells. Each battery pack may further include a control circuit that monitors and/or alters the state of charge of each of the electrochemical cells. The control circuit may implement a control scheme that causes the electrochemical cells to have a similar charge state. The battery system may include a communication network that allows the packs to communicate with each other in order to implement the control scheme for causing the electrochemical cells to be of similar charge state. In some embodiments, the battery packs are able to communicate with a main battery control circuit to implement the control scheme for causing the electrochemical cells to be of similar charge state.

In embodiments, the charging system may be located on the non-rotating portion of the system. The battery system may communicate with the charging system to terminate charge when one or more of the electrochemical cells reach a full state of charge. In some embodiments, the battery system communicates with a main battery control circuit to terminate charge when one or more of the electrochemical cells reach a full state of charge.

In further embodiments, the imaging system may also include a docking system that selectively couples and decouples the rotating and non-rotating portions of the system. The charging system charges the battery system when the docking system engages to couple the rotating and non-rotating portions of the system. During an imaging scan, the docking system may temporarily electrically disconnect the rotating and non-rotating portions of the system. The battery system may provide power to the rotating portion of the system while the docking system is disengaged. In one embodiment, the charging system provides power to the non-rotating portion of the imaging system while the docking system is disengaged. Further embodiments relate to methods of docking and undocking the rotating and non-rotating components of an imaging system.

In further embodiments, the imaging system may also include a non-contact signaling system, such as an optical or magnetic system, that is provided at one or more discrete locations on both the rotating and non-rotating portions of the system. The signaling system is provided to coordinate the onset or termination of various functions within the system, such as motion or irradiation.

In further embodiments, the imaging system may include a drive mechanism for rotating the rotating portion relative to the non-rotating portion. The drive mechanism may include a belt that is provided on the non-rotating portion and a motorized system having a gear that is provided on the rotating portion. The gear meshes with the belt, so that when the gear is driven by a motor, the motorized system travels along the length of the belt, causing the rotating portion to which it is attached to rotate with respect to the non-rotating portion. The drive mechanism may be powered by the battery system.

In other embodiments, the present invention relates to methods of diagnostic imaging using an imaging system having rotating and non-rotating portions.

Other features and advantages of the present invention will be apparent from the following detailed description of the invention, taken in conjunction with the accompanying drawings of which:.

This application claims the benefit of priority to <CIT>. This application is also related to <CIT>, now <CIT>, <CIT>, and <CIT>.

Referring to <FIG>, a mobile imaging system <NUM> according to one embodiment of the invention includes a mobile base <NUM>, a gimbal <NUM>, a gantry <NUM>, and a pedestal <NUM>. The system <NUM> includes image collection components, such as a rotatable x-ray source and detector array or stationary magnetic resonance imaging components, that are housed within the gantry <NUM>. The system <NUM> is configured to collect imaging data, such as, for example x-ray computed tomography (CT) or magnetic resonance imaging (MRI) data, from an object located within the bore of the gantry <NUM>, in any manner known in the medical imaging field. The pedestal <NUM> is adapted to support a tabletop support <NUM> that can be attached to the pedestal <NUM> in a cantilevered manner and extend out into the bore of the gantry <NUM> to support a patient or other object being imaged.

The gantry <NUM> and gimbal <NUM> are illustrated in <FIG>. The gimbal <NUM> is a generally C-shaped support that is mounted to the top surface of base <NUM> and includes a pair of arms <NUM>, <NUM> extending up from the base. The arms <NUM>, <NUM> are connected to opposite sides of gantry <NUM> so that the gantry is suspended above base <NUM> and gimbal <NUM>. In one embodiment, the gimbal <NUM> and gantry <NUM> can rotate together about a first axis (a) relative to the base <NUM>, and the gantry <NUM> can tilt about a second axis (a') relative to the gimbal <NUM> and base <NUM>.

In certain embodiments, the gimbal <NUM> and gantry <NUM> can translate with respect to the base <NUM> to provide an imaging scan. The gimbal <NUM> can include bearing surfaces that travel on rails <NUM>, as shown in <FIG>, to provide the translation motion of the gimbal <NUM> and gantry <NUM>. A scan drive mechanism can drive the translation of the gantry and gimbal relative to the base, and a main drive mechanism can drive the entire system in a transport mode. In the embodiment of <FIG>, both of these functions are combined in a drive system <NUM> that is located beneath the gimbal <NUM>.

In certain embodiments, the base <NUM> of the system can be omitted, and the gimbal <NUM> can sit directly on the ground to support the gantry <NUM>. In other embodiments, the gimbal can be omitted, and the gantry <NUM> is a stand-alone gantry that sits on the ground.

<FIG> is an exploded view of the gimbal <NUM>, illustrating how the gimbal <NUM> may be connected to the gantry <NUM> in various embodiments. As shown in <FIG>, the gimbal <NUM> may be assembled from multiple pieces. Upper portions <NUM>, <NUM> of the gimbal <NUM> may be securely fastened to opposing sides of the gantry <NUM>. The upper portions <NUM>, <NUM>, which may have a shape similar to "earmuffs," may include a bearing apparatus that enables the "tilt" motion of the gantry <NUM> relative to the gimbal <NUM>. The upper portions <NUM>, <NUM> may also be fastened to the respective arms <NUM>, <NUM> of the gimbal <NUM>. For ease of assembly, it may be preferable to fasten the upper portions <NUM>, <NUM> to the gantry <NUM> before connecting the entire gantry/upper portion assembly to the respective arms <NUM>, <NUM> of the gimbal <NUM>. Also shown in <FIG> is a cover <NUM> that may be placed over an access opening in one or both arms <NUM>, <NUM> of the gimbal <NUM>. An additional cover <NUM> may be provided over the base of the gimbal <NUM>, and may be removed to access a bearing and/or drive system positioned within or beneath the base of the gimbal <NUM>.

<FIG> is a cross-sectional view of the gantry <NUM> and gimbal <NUM> that illustrates a number of components of the imaging system <NUM>, which in this embodiment comprises an X-ray CT imaging system, including an x-ray source <NUM>, high-voltage generator <NUM>, x-ray detector <NUM>, battery system <NUM>, computer <NUM>, rotor drive mechanism <NUM>, docking system <NUM> and charging system <NUM>. A number of these components, including the x-ray source <NUM>, high-voltage generator <NUM>, x-ray detector <NUM>, battery system <NUM>, computer <NUM> and rotor drive mechanism <NUM>, are mounted on a rotor <NUM>, as is illustrated in the exploded view of <FIG>. The rotor <NUM> and the components mounted thereto, rotate within a housing defined by an outer shell <NUM> of the gantry <NUM>.

The system <NUM> thus has a rotating portion <NUM>, which includes the rotor <NUM> and the various components mounted to the rotor that rotate within the gantry <NUM> during an imaging scan, and a non-rotating portion <NUM>, that generally includes the other components of the system, including the base <NUM>, gimbal <NUM>, and the outer shell <NUM> of the gantry <NUM>. The charging system <NUM> is located on the non-rotating portion <NUM> of the system. The docking system <NUM> provides intermittent connection between the rotating and non-rotating portions <NUM>, <NUM> for transfer of power and/or data between the two portions.

During an imaging scan, the rotor <NUM> rotates within the interior of the gantry, while the imaging components such as the x-ray source <NUM> and x-ray detector <NUM> obtain imaging data for an object positioned within the bore of the gantry, as is known, for example, in conventional X-ray CT scanners. The rotor drive mechanism <NUM> drives the rotation of the rotor <NUM> around the interior of the gantry <NUM>. The rotor drive mechanism <NUM> may be controlled by a system controller that controls the rotation and precise angular position of the rotor <NUM> with respect to the gantry <NUM>, preferably using position feedback data, such as from a position encoder device.

Various embodiments of the imaging system <NUM> may be relatively compact, which may be desirable, for example, in a mobile imaging system. One way in which the system <NUM> may be made compact is in the design of the gantry <NUM> and its interface with the rotating portion <NUM> (e.g., the rotor <NUM> and the various components mounted to the rotor <NUM>). In embodiments, the outer shell <NUM> of the gantry <NUM> may comprise both a protective outer covering for the rotating portion <NUM> and a mounting surface for a bearing that enables the rotating portion <NUM> to rotate <NUM>° within the outer shell <NUM> of the gantry <NUM>.

<FIG> is an exploded view of a gantry <NUM> according to one embodiment that illustrates the outer shell <NUM>, the rotor <NUM> and a bearing assembly <NUM>. <FIG> illustrates the assembled gantry <NUM>. As is shown in <FIG>, the outer shell <NUM> of the gantry <NUM> may be a generally O-shaped covering of a structural material that may at least substantially fully enclose the rotating portion <NUM>, including the rotor <NUM> and any components mounted to the rotor, over one or more sides of the rotating portion <NUM>. The outer shell <NUM> of the gantry <NUM> may be conceptually considered an "exoskeleton," that both supports the rotating portion <NUM> of the system <NUM>, preferably in three dimensions, and also provides a protective barrier between the rotating portion <NUM> and the external environment. In embodiments, the outer shell <NUM> of the gantry <NUM> may support at least about <NUM>%, such as more than <NUM>%, and preferably more than about <NUM>%, such as more than <NUM>%, and even more preferably <NUM>% of the weight of the rotating portion <NUM> of the imaging system <NUM>. In embodiments, the outer shell <NUM> itself may be supported by one or more other components, such as a gimbal <NUM>, base <NUM> and/or drive mechanism <NUM>, as shown in <FIG>, for example. In other embodiments, the outer shell <NUM> may be supported directly on the ground, for example, or via other means, such as raised on a pedestal, table, cart or other support, or suspended or cantilevered from a wall, ceiling or other support structure. In certain embodiments, an outer shell <NUM> of the gantry <NUM> that comprises both a protective outer covering for the rotating portion <NUM> and a mounting surface for a bearing for rotation of the rotating portion <NUM> may provide the gantry <NUM> with various degrees-of-freedom, such as the "tilt" motion about axis (a') and/or rotation about axis (a) as shown in <FIG>, as well as translation motion for imaging applications and/or transport of the gantry <NUM>.

The outer shell <NUM> may be fabricated from a sufficiently rigid and strong structural material, which may include, for example, metal, composite material, high-strength plastic, carbon fiber and combinations of such materials. In preferred embodiments, the outer shell <NUM> may be comprised of a metal, such as aluminum. The outer shell <NUM> may be machined or otherwise fabricated to relatively tight tolerances. The outer shell <NUM> may be formed as a one piece, unitary component. In other embodiments, the outer shell <NUM> may be comprised of multiple components and/or materials that may be joined using any suitable technique to provide the shell <NUM>.

The outer shell <NUM> may have an outer circumferential surface <NUM> that may extend around the the periphery of the rotating portion <NUM> of the system <NUM> to substantially fully enclose the rotating portion <NUM> around its outer circumference. As used herein, "substantially fully enclose" means that the circumferential surface <NUM> encloses at least about <NUM>%, such as at least about <NUM>% (e.g., <NUM>% or more), and preferably at least about <NUM>%, such as at least about <NUM>% (e.g., between <NUM>% and <NUM>%) of the rotating portion <NUM> around its outer circumference. As shown in <FIG>, for example, the outer shell <NUM> may substantially fully enclose the rotating portion while also including one or more openings, such as opening <NUM> (where the gantry <NUM> is secured to the gimbal <NUM>) and access opening <NUM>.

The outer shell <NUM> may also include at least one side wall <NUM> that may extend from the outer circumferential surface <NUM> to a bore <NUM> of the gantry <NUM> and may substantially fully enclose the rotating portion <NUM> around one side of the rotating portion. In embodiments, the outer shell <NUM> may include two side walls, one on each side (e.g., front and rear) of the gantry <NUM>, and the two side walls may substantially fully enclose the rotating portion <NUM> around two sides of the rotating portion. In the embodiment shown in <FIG> the outer shell <NUM> includes a side wall <NUM> on a first side (e.g., the front side) of the gantry <NUM>. As shown in <FIG>, an opposite (e.g., rear) side wall <NUM> of the gantry <NUM> may be formed by the combination of the outer shell <NUM>, bearing assembly <NUM>, and/or the rear surface of the rotor <NUM>. The side wall <NUM> may substantially fully enclose the various components mounted to the rotor <NUM> around a side of these components. The outer circumferential wall <NUM> and the side walls <NUM> and <NUM> may define a cavity <NUM>, as shown in <FIG>, and the various components mounted to the rotor <NUM> may rotate within the cavity <NUM>. A protective outer covering may be provided over the rear side wall <NUM> and/or over the interior circumference of the gantry <NUM> (e.g., around the outer circumference of the bore <NUM>) to provide an additional barrier between the rotating portion <NUM> and the external environment. The protective covering may be comprised of a thin, lightweight material, such as plastic.

As will be discussed in further detail below, the drive mechanism for the rotating portion <NUM> of the imaging system may utilize a belt drive on the rotor <NUM>, where the belt for the drive is mounted to a fixed railing <NUM>, as is shown in <FIG>. In various embodiments, a railing <NUM> or similar fixed structure for the rotor drive <NUM> may be located on the internal surface of side wall <NUM>.

The bearing assembly <NUM> according to one embodiment is shown in <FIG> and <FIG>. In this embodiment, the bearing assembly <NUM> includes a first race <NUM> that may be securely fastened to the outer shell <NUM> of the gantry <NUM>, and a second race <NUM> that may be securely fastened to the rotor <NUM>. A bearing element <NUM> (<FIG>) is provided between the first race <NUM> and the second race <NUM>, and is configured to allow the second race <NUM> (along with the rotor <NUM> to which it is attached) to rotate concentrically within the first race <NUM>, preferably with minimal friction, thereby enabling the rotor <NUM> to rotate with respect to the outer shell <NUM> of the gantry <NUM>. In the exemplary embodiment of <FIG>, the bearing assembly <NUM> may abut against a lip <NUM> in the rotor, and a plurality of fastening members <NUM> (such as bolts) may be provided through the lip <NUM> and into the second race <NUM> around the periphery of the rotor <NUM> to securely fasten the rotor <NUM> to the bearing assembly <NUM>. The bearing assembly <NUM> may also be provided at least partially within the outer circumferential wall <NUM> of the outer shell <NUM> and against a lip <NUM> in the outer shell <NUM> of the gantry <NUM>. A plurality of fastening members (similar to fastening members <NUM>) may be provided through the lip <NUM> and into the first race <NUM> around the periphery of the outer shell <NUM> to securely fasten the outer shell <NUM> to the bearing assembly <NUM>. A small gap <NUM> may be provided between lip <NUM> and lip <NUM>. In some embodiments, all or a portion of the bearing assembly <NUM> may be integrally formed as a part of the outer shell <NUM> or of the rotor <NUM>, or of both. For example, the first race <NUM> may be formed as an integral surface of the outer shell <NUM> and/or the second race <NUM> may be formed as an integral surface of the rotor <NUM>. In various embodiments, the entire bearing assembly for enabling the rotation of the rotating portion <NUM> with respect to the non-rotating portion <NUM> of the imaging system <NUM> may be located within the generally O-shaped gantry <NUM>.

The outer diameter of the gantry <NUM> can be relatively small, which may facilitate the portability of the system <NUM>. In a preferred embodiment, the outer diameter (OD in <FIG>) of the gantry <NUM> is less than about <NUM> inches, such as between about <NUM> and <NUM> inches, and in one embodiment is about <NUM> inches. The outer circumferential wall <NUM> of the outer shell <NUM> may be relatively thin to minimize the OD dimension of the gantry <NUM>. In addition, the interior diameter of the gantry <NUM>, or equivalently the bore <NUM> diameter (ID in <FIG>), can be sufficiently large to allow for the widest variety of imaging applications, including enabling different patient support tables to fit inside the bore, and to maximize access to a subject located inside the bore. In one embodiment, the bore diameter of the gantry <NUM> is greater than about <NUM> inches, such as between about <NUM> and <NUM> inches, and in some embodiments can be between about <NUM> and <NUM> inches. In one exemplary embodiment, the bore has a diameter of about <NUM> inches. As shown in <FIG>, the gantry <NUM> generally has a narrow profile, which may facilitate portability of the system <NUM>. In one embodiment, the width of the gantry <NUM> (W) is less than about <NUM> inches, and can be about <NUM> inches or less.

A number of features of the various embodiments may facilitate the compact size of the imaging gantry <NUM>. For example, as previously discussed the outer shell <NUM> of the gantry <NUM> may be a relatively thin yet rigid exoskeleton structure that provides a protective outer covering for the rotating components while simultaneously supporting the rotating components in multiple dimensions as they rotate relative to the outer shell <NUM>. Various additional features are illustrated in <FIG>, which illustrates the rotating portion <NUM> of the imaging system <NUM> according to one embodiment. The various components, such as x-ray source <NUM>, detector <NUM>, high-voltage generator <NUM>, heat exchanger <NUM>, computer <NUM>, battery system <NUM>, docking system <NUM> and rotor driver <NUM>, may be mounted to rotor <NUM> and configured to fit and rotate within the internal cavity <NUM> of the gantry <NUM> shown in <FIG>. As shown in <FIG> and <FIG>, for example, this may include providing the drive mechanism <NUM> within the interior cavity <NUM> of the gantry <NUM>, which may aid in minimizing the outer diameter and width dimensions of the gantry <NUM> while also enabling a relatively large bore diameter. Various other components may be configured to facilitate a compact gantry design. For example, as shown in <FIG>, the high-voltage generator <NUM>, which may be one of the larger components of the rotating portion <NUM>, may have at least one surface <NUM>, <NUM> that is angled or curved to substantially correspond with the curvature of the gantry <NUM> and/or bore <NUM>. Another example of a high-voltage generator <NUM> with an angled or curved outer surface is shown in <FIG>. Similarly, the battery system <NUM> may be housed in a chassis having at least one surface <NUM>, <NUM> that is angled or curved to substantially correspond with the curvature of the gantry <NUM> and/or bore <NUM>. In this way, the outer diameter of the gantry may be minimized while also maintaining a relatively large bore diameter.

The imaging system <NUM> generally operates in a conventional manner to obtain images of an object located in the bore of the gantry. For example, in the case of an x-ray CT scan, the rotor <NUM> rotates within the housing of the gantry <NUM> while the imaging components, including the x-ray source and x-ray detector, obtain image data at a variety of scan angles. Generally, the system obtains image data over relatively short intervals, with a typical scan lasting less than a minute, or sometimes just a few seconds. During these short intervals, however, a number of components, such as the x-ray source tube and the high-voltage generator, require a large amount of power, including, in some embodiments, up to <NUM> kW of power.

In one embodiment, the power for the rotating portion <NUM> of the system <NUM> is provided by a battery system <NUM> that is located on the rotating portion <NUM> of the system <NUM>. An advantage of the battery-based power supply is that the conventional schemes for delivering power to the imaging components, such as complicated and expensive slip-ring systems and bulky cable systems, can be avoided.

As shown in <FIG> and <FIG>, the battery system <NUM> is mounted to and rotates with the rotor <NUM>. The battery system <NUM> includes a plurality of electrochemical cells. The cells can be incorporated into one or more battery packs. In one embodiment, for example, the battery system <NUM> includes seven battery packs <NUM>, with sixty-four cells per pack <NUM>, for a total of <NUM> cells. The battery system <NUM> is preferably rechargeable, and is recharged by the charging system <NUM> when the rotor <NUM> is not rotating. In one embodiment, the battery system <NUM> consists of lithium iron phosphate (LiFePO<NUM>) cells, though it will be understood that other suitable types of batteries can be utilized.

The battery system <NUM> provides power to various components of the imaging system <NUM>. In particular, since the battery system <NUM> is located on the rotating portion <NUM> of the imaging system <NUM>, the battery system <NUM> can provide power to any component on the rotating portion <NUM>, even as these components are rotating with respect to the non-rotating portion <NUM> of the imaging system <NUM>. Specifically, the battery system <NUM> is configured to provide the high voltages and peak power required by the generator <NUM> and x-ray tube <NUM> to perform an x-ray imaging scan. For example, a battery system may output ~360V or more, which may be stepped up to 120kV at a high-voltage generator (which may also be located on the rotating portion <NUM>) to perform an imaging scan. In addition, the battery system <NUM> can provide power to operate other components, such as an on-board computer <NUM>, the detector array <NUM>, and the drive mechanism <NUM> for rotating the rotor <NUM> within the gantry <NUM>.

Each of the battery packs <NUM> includes an associated control circuit <NUM>, which can be provided on a circuit board. In certain embodiments, the control circuits <NUM> can communicate with one another and/or with a main battery controller that is also located on the rotating portion <NUM> of the imaging system <NUM>.

The battery pack control circuit(s) <NUM> are configured to monitor and/or alter the state of charge of each of the electrochemical cells <NUM> in the battery pack <NUM>. An example of a battery pack control circuit <NUM> is shown in <FIG>. In this embodiment, the control circuit <NUM> connects across each individual cell <NUM>. The control circuit <NUM> monitors the voltage of the cell <NUM>, and generates signals from the analog-to-digital converter <NUM> that indicate the charge-state of the cell. These signals are provided to the main battery controller <NUM>, which monitors the charge-state of all the cells in the battery system. The controller <NUM> may comprise a processor having an associated memory that may execute instructions (e.g. software) stored in the memory. The main battery controller <NUM> can send control signals to the respective control circuits <NUM> to alter the state of charge of each electrochemical cell <NUM>. In the embodiment of <FIG>, the main battery controller <NUM> alters the charge-state of the cell <NUM> by switching on transistor <NUM>, which connects the cell <NUM> across load resistor <NUM>. The cell <NUM> can then be partially drained in a controlled manner. The battery controller <NUM> can continue to monitor the charge state of the cell <NUM> and switch off the transistor <NUM> when the cell <NUM> reaches a pre-determined charge state. In one embodiment, whenever the cell <NUM> is in danger of overcharging, the load resistor is switched in until the battery is at a safe charge state. In certain embodiments, if an overcharge condition is actually reached in one or more cells, the charging system can be switched off while the load resistor continues to drain the cell. Other cell charging and balancing schemes can also be employed.

In certain embodiments, the battery system includes processing circuitry that is configured to implement a control scheme to cause the electrochemical cells to have substantially the same charge state. This control scheme can be implemented by a main battery controller <NUM>, for example, or can be implemented by the plurality of battery pack control circuits <NUM> in communication with each another. In one exemplary embodiment of the control scheme for the battery system, a load resistor is switched in for each cell when the cell either exceeds the desired charge voltage or when the cell exceeds the average cell voltage by a pre-determined threshold. The charging system is disabled if any cell exceeds the maximum charging voltage.

<FIG> schematically illustrates the battery system <NUM>, charging system <NUM> and docking system <NUM> according to one embodiment. The charging system <NUM> provides electrical power to the battery system <NUM> in order to charge the rechargeable electrochemical cells. In a preferred embodiment, the charging system <NUM> is located on the non-rotating portion <NUM> of the imaging system <NUM>. For example, the charging system <NUM> can be located on the gimbal <NUM>, the outer shell <NUM> of the gantry <NUM>, the base <NUM> or the pedestal <NUM> (see, e.g., <FIG>). In a preferred embodiment, the charging system <NUM> is located on the gimbal <NUM>. <FIG>, <FIG> illustrate one embodiment of a charging system <NUM> that is located on the gimbal <NUM>. The charging system <NUM> is electrically coupled to the battery system <NUM> at least during the times when the rotating portion <NUM> of the imaging system <NUM> is stationary relative to the non-rotating portion <NUM>, such as in between imaging scans. The charging system <NUM> need not be, and in preferred embodiments is not, electrically coupled to the rotating portion <NUM> during an imaging scan. In one embodiment, the docking system <NUM> couples the charging system <NUM> to the battery system <NUM> when the rotating portion <NUM> is in a stationary or "park" mode, as is described in greater detail below.

The charging system <NUM> is configured to receive input power from an external power source, such as a standard wall power outlet. The charging system <NUM> can include circuitry that conditions the input power to render it suitable for recharging the battery packs <NUM> on the rotor <NUM>. The charging system <NUM> can also include control circuitry that communicates with the battery pack control circuit(s) and controls the operation of the charging system.

In one embodiment, the charging system <NUM> is configured to automatically begin charging of the battery system <NUM> when the charging system <NUM> is electrically coupled to the battery system <NUM>. During the charging operation, the battery pack control circuits <NUM> and/or the main battery controller <NUM> monitor the state of charge of the individual cells <NUM>, and can instruct the charging system <NUM> to terminate charging when a pre-determined charge-state is reached. For example, charging can terminate when one or more of the electrochemical cells <NUM> reach a full state of charge.

The docking system <NUM> is configured to selectively couple and de-couple the rotating <NUM> and non-rotating <NUM> portions of the imaging system <NUM>. As schematically illustrated in <FIG>, a first portion 36a of the docking system <NUM> is located on the rotating portion <NUM> of the system, preferably on the rotor <NUM>, and includes a mating surface that faces towards the outer circumference of the gantry <NUM>. A second portion 36b of the docking system <NUM> is located on the non-rotating portion <NUM> of the system, such as on the gimbal <NUM>, and includes a mating surface that faces into the interior housing of the gantry. When the system is in "park" mode, the rotor <NUM> automatically rotates to a position where the first 36a and second 36b portions of the docking system <NUM> are aligned and facing one another. Mating features (e.g., pines) and socket(s)) on one or both of the first 36a and second 36b portions of the docking system are actuated to physically connect the two portions 36a, 36b. During an imaging scan, the two portions 36a, 36b disengage from each other, and the first portion 36a rotates with the rotor <NUM> inside the interior housing of the gantry <NUM>.

The docking system <NUM> includes at least one electrical connection for providing power to components on the rotating portion <NUM>, including the rechargeable battery system <NUM>. When the docking system <NUM> is disengaged, such as during an imaging scan, power for the components of the rotating portion <NUM> comes from the battery system <NUM>. Components on the non-rotating portion <NUM> of the imaging system <NUM> can remain powered by an external power source, such as grid power.

In one embodiment, the docking system <NUM> further includes at least one electrical connection for data transfer between the rotating and non-rotating portions of the imaging system <NUM>. The rotating portion <NUM> of the imaging system <NUM> obtains imaging data at the detector array <NUM>, and this data may be transferred off the rotating portion <NUM> via the docking system <NUM> for processing and/or display. In one embodiment, the rotating portion <NUM> of the imaging system <NUM> includes a computer <NUM> having a memory and processor. The image data obtained at the detector <NUM> may be sent to the computer <NUM> for temporary storage and optional processing while the rotating portion <NUM> is rotating. Following an image scan, the rotating and non-rotating portions of the system are connected by the docking system <NUM>, and the data from the on-board computer <NUM> may be downloaded off the rotating portion <NUM> for further processing and/or display.

An embodiment of a docking system <NUM> is shown in <FIG>. The first portion 36a of the docking system <NUM> includes a pair of moveable rods <NUM> that reciprocate between a first, disengaged position (<FIG>) and a second, engaged position (<FIG>). The first portion 36a is shown in <FIG>. An electrical connector 53a is secured between the rods <NUM> and moves with the movement of the rods. An actuator, which in this embodiment includes a motor <NUM> and lead screw <NUM>, drives the movement of the rods <NUM> and connector 53a. The second portion 36b of the docking system <NUM> is illustrated in <FIG>, which shows a pair of slots <NUM> and an electrical connector 53b that is configured to mate with the connector 53a on the first portion 36a. During engagement of the docking system <NUM>, the rods <NUM> from the first portion 36a move into engagement with the corresponding slots <NUM> in the second portion 36b of the docking system. This engagement prevents the rotating portion <NUM> from moving relative to the non-rotating portion <NUM> while the docking system is engaged. The rods <NUM> and slots <NUM> also ensure that the respective electrical connectors 53a, 53b on the first and second portions 36a, 36b are properly aligned as the actuator mechanism <NUM>, <NUM> moves the connectors 53a, 53b into mating engagement. When the docking system <NUM> is engaged (<FIG>), the connectors 53a, 53b carry electrical power to charge the battery system, and also enable data and control signals to pass between the rotating and non-rotating portions of the system.

<FIG> illustrate the location of the docking system <NUM> within the imaging system <NUM>. As seen most clearly in <FIG>, the first portion 36b is mounted to and rotates with the rotor <NUM>. Between scans, the rotor <NUM> rotates to the "park" position of <FIG>, and the docking system <NUM> is engaged. The second portion 36b of the docking system <NUM> is located on the gimbal <NUM>, as shown in <FIG>. In a preferred embodiment, the second portion 36b is mounted to the bearing on the gimbal that allows the gantry to tilt with respect to the gimbal, such that the second portion 36b rotates with the tilting motion of the gantry, which allows the docking system to dock and undock while the gantry is tilted.

In one embodiment of a docking sequence, the control circuitry on the rotor <NUM> causes the rotor drive mechanism <NUM> to rotate the rotor to the "park" position, preliminary to docking. Then, the control circuitry causes the actuator mechanism <NUM>, <NUM> to drive the rods <NUM> (fast) to the point where the tapered end portions of the rods <NUM> (see, e.g., <FIG>) engage with "rollers" that define the slots <NUM> on the second portion 36b of the docking mechanism. Then, the control parameters of the rotor drive mechanism are relaxed such that it can be back driven. The mating electrical contacts are then prepared to engage such that they are protected from damage during docking, as is discussed further below. Next, the rods <NUM> are driven (slow) to the "docked" position whereby the tapered portion of the rods pushes the rotor into alignment through contacting the rollers on the mating dock. The control circuitry then reads a loopback signal on the dock to determine proper engagement, and once proper engagement is determined, the electrical connections (e.g., power and data connections) between the rotating <NUM> and non-rotating <NUM> portions of the system are engaged. Rotor drive control parameters are then restored, and the position is assigned within the control software.

<FIG> is a schematic illustration of the system power circuitry during a docking procedure, according to one embodiment. The system is shown in a docked configuration, with the components on the non-rotating portion <NUM>, including charger <NUM> and one or more device(s) <NUM>, which branch off a main power bus <NUM>, electrically connected to the components on the rotating portion <NUM>, including battery <NUM> and one or more device(s) <NUM>, via docking system <NUM>. To un-dock the system, the electrical connection between the rotating <NUM> and non-rotating <NUM> components must be broken. However, at the voltages and currents used by the system, as the respective contacts physically separate, the electricity will continue to flow briefly across the gap, forming a spark. This spark tarnishes and erodes the contacts over time, and in some cases can weld the contacts together.

There is a similar problem when the system re-docks. If the voltages on each side of the docking system are significantly different, large currents may flow through the dock as the two sides of the power system equalize. These currents can overheat the contacts.

In one embodiment, both of these problems are solved by designing and operating the system so that the voltage on the non-rotating <NUM> (charger) side is higher than the voltage on the rotating <NUM> (battery) side whenever the dock is being mated or unmated. That guarantees that current can only flow in one direction through the dock. Then, before the mating or unmating procedure is performed, a switch <NUM>, which can be a solid-state relay (SSR), is opened to prevent current flow in that direction (i.e. from the non-rotating to the rotating side). The docking system <NUM> can then be safely docked or undocked.

An inrush current limiting circuit <NUM>, which can comprise an NTC resistor, for example, is provided in series with the relay <NUM> to protect components, including the relay(s) and the docking system <NUM>, against damage from current inrush during a docking procedure when the relay <NUM> is turned on.

Note that when the system is docked, power is always free to flow from the batteries <NUM> to components on the non-rotating side <NUM> of the system via diode <NUM> and docking system <NUM>. However, the rotating portion <NUM> cannot receive power from the non-rotating portion unless the relay <NUM> is switched on. The relay <NUM> can also be used to halt charging of the batteries in an over-charge or other emergency situation.

In practice, this configuration means that the system generally cannot be undocked while it is not plugged into the wall (i.e., the entire system is being run off the batteries) or when the main/transport drive for the system is active because this component can draw more power than the charger can source. However, neither of these cases is particularly restrictive within normal use of the system.

The systems can include additional safety/failsafe features, such as relays <NUM>, <NUM> to protect the various device component(s) <NUM>, <NUM> on both the non-rotating and rotating sides <NUM>, <NUM> of the system. For example, in the case where the non-rotating portion <NUM> loses power during a scan (i.e. with the system un-docked), the system can be configured so that all the relays <NUM> on the non-rotating portion <NUM> automatically turn off, so that the non-rotating portion <NUM> is essentially electrically inert when, after the scan, the rotating portion <NUM> re-docks. Similar relays <NUM> can be provided on the rotating portion <NUM>, for example, to selectively turn off components <NUM>.

In certain embodiments, data transfer between the rotating <NUM> and non-rotating <NUM> portions of the imaging system <NUM> can be accomplished using a slip ring system. With the slip ring system, continuous electrical contact is maintained between the stationary and rotating parts of the imaging system <NUM>. In one embodiment, a conductive ring is positioned on the outer circumference of the rotating portion <NUM> and electrical contacts, such as conductive brush(es), are located on the non-rotating portion <NUM> and maintain continuous contact with the rotating portion <NUM> during imaging. During an imaging scan, data is transferred from the rotating to the non-rotating portions via the slip ring in real-time. Power to the rotating portion <NUM> can be provided through the docking system <NUM> to the rechargeable battery system <NUM>, as described above. The slip ring system can therefore be optimized for high-speed data transfer. The slip ring system in this embodiment need not be designed for high-voltage, high-power operation, which can help minimize the complexity and expense of the slip ring system. In an alternative embodiment, a cable system can be used for data transfer between the rotating and non-rotating portions. As with the slip ring embodiment, the cable system need not be designed for high-voltage, high-power operation, since primary power to the rotating portion is provided by the rechargeable battery system.

In another alternative embodiment, the rotating portion <NUM> can include a wireless transmitter for transmitting the data off of the rotating portion <NUM> via a wireless communication link. In this embodiment, the image data need not be transferred over the docking system <NUM> or a slip-ring or cable system.

The docking system <NUM> may also be used to transmit control signals between the rotating and non-rotating portions of the imaging system <NUM>. The control signals can include, for example, signals from a main system controller <NUM> (<FIG>), located on the non-rotating portion <NUM> to components on the rotating portion <NUM>, such as the x-ray source and detector, battery system and on-board computer, as well as signals from the rotating portion to the non-rotating portion, such as signals from the battery system <NUM> to the charging system <NUM> with respect to the charge state of the electrochemical cells. It will be understood that these signals can also be sent over a slip ring or cable system or by a wireless link, as described above.

As previously discussed, an advantage of the battery-based power supply of the invention is that the conventional schemes for delivering power to the imaging components, such as complicated and expensive slip-ring systems and bulky cable systems, can be avoided. In one embodiment, during an imaging scan the imaging system <NUM> is essentially severed in two, with two independent sub-systems (i.e., the rotating and non-rotating portions) operating independently of one another. This is different from conventional imaging systems, in which the rotating components remain physically coupled to the non-rotating portion of the system, via a cable or slip-ring or the like.

In one embodiment, as shown in <FIG>, the present invention includes a non-contact signaling apparatus <NUM> located at discrete positions on the rotating and non-rotating portions of the imaging system. The signaling apparatus <NUM> allows for minimal communication between the rotating and non-rotating portions of the imaging system. In one aspect, the signaling apparatus <NUM> functions as a safety mechanism. For example, during an imaging scan, the signaling apparatus <NUM> on the non-rotating portion <NUM> communicates a signal to the rotating portion <NUM>, instructing the rotating portion <NUM> to continue the scan. This periodic signaling from the non-rotating portion to the rotating portion enables the scan to continue. However, if for any reason the scan needs to be terminated (such as due to a loss of power or because of a patient or clinician safety issue), the signaling apparatus <NUM> ceases communication of these "enable scan" signals. This lack of a signal causes the rotating component to immediately terminate the scan, without having to wait for the rotating portion to fully complete the scan and return to the docking position.

The signaling apparatus <NUM> can also be used to provide a signal from the rotating to the non-rotating portions to continue the scan. For example, if there is a malfunction on the rotating portion of the system (e.g., the x-ray generator fails to produce radiation, the rotor fails to rotate properly, etc.), it does not make sense for the non-rotating components to continue with the scan. In this embodiment, the scan is automatically terminated when the rotating portion stops sending signals to the non-rotating portion via the signaling apparatus <NUM>.

In some embodiments, the signaling apparatus <NUM> may be used to transmit synchronization information from the rotating portion <NUM> to the non-rotating portion <NUM> of the imaging system. For example, a signaling apparatus <NUM> on the rotating portion <NUM> may communicate a signal to the non-rotating portion <NUM> to assist in coordinating various functions between the two portions. In one example, the signaling apparatus <NUM> may be used to coordinate a z-axis translation of the gantry <NUM> relative to the patient with the rotational motion of the rotor <NUM>. Since the two halves of the imaging system become physically disconnected during a scan, this allows for the two halves to coordinate when they are going to start a scan sequence. A typical sequence is for the docking system to disconnect, the rotor to start accelerating, and then a signal is sent from the rotating portion to the non-rotating portion via the signaling apparatus <NUM> to trigger the start of the z-axis translation.

The non-contact signaling apparatus <NUM> may use, for example, optical or magnetic signals. One embodiment of the signaling apparatus <NUM> is schematically illustrated in <FIG>. In this embodiment, the non-contact signaling apparatus <NUM> employs optical signaling, and includes light-emitting diodes (LEDs) <NUM> and photo-detectors <NUM> at discrete positions on the rotating <NUM> and non-rotating <NUM> portions of the imaging system. Two sets of signaling devices, each set consisting of an LED <NUM> and a photo-detector <NUM>, are located on the non-rotating portion <NUM> of the imaging system <NUM>, such as on the gantry <NUM> or the gimbal <NUM>. Two additional sets of signaling devices, each also consisting of an LED <NUM> and photo-detector <NUM>, are located on the rotating portion <NUM> of the imaging system <NUM>, and in particular, on the rotor <NUM>. The two sets of signaling devices on the non-rotating portion <NUM> are on opposite sides of the gantry <NUM>; i.e., separated by <NUM> degrees. The two sets on the rotating portion <NUM> are separated by <NUM> degrees. In this way, the rotating <NUM> and non-rotating <NUM> portions of the imaging system <NUM> may exchange signals with one another at every <NUM> degrees of rotation of the rotating portion <NUM>.

According to another aspect, the imaging system <NUM> includes a rotor drive mechanism <NUM>, as shown in <FIG>, <FIG> and <FIG>, which drives the rotation of the rotating portion <NUM> relative to the non-rotating portion <NUM>. One embodiment of the rotor drive mechanism <NUM> is illustrated in <FIG>. In this embodiment, the rotor <NUM> is driven by an internal belt drive. The belt <NUM> extends around the outer circumference of a circular railing <NUM>. The railing <NUM> (which can be seen in the exploded view of <FIG> and in <FIG>) is mounted to an interior wall of the outer shell <NUM> of the gantry <NUM>. The drive mechanism <NUM> includes a motor <NUM>, gear <NUM> and rollers <NUM>, and is mounted to the rotor <NUM>. The belt <NUM> is looped through the drive mechanism <NUM>, running between each of the rollers <NUM> and the railing <NUM>, and over the gear <NUM>, as is most clearly illustrated in <FIG> and <FIG>. (When viewed from the side, the path of the belt <NUM> through the drive mechanism <NUM> somewhat resembles the Greek letter omega, Ω). The gear <NUM> is driven by the motor <NUM>. As the gear <NUM> rotates, it meshes with the belt <NUM>, which is held against the railing <NUM> by the rollers <NUM>. The rotation of the gear <NUM> causes the drive mechanism <NUM> to "ride" along the length of the belt <NUM>, thus driving the rotation of the rotor <NUM>, which is attached to the drive mechanism <NUM>, around the circumference of the gantry <NUM>.

As shown, for example, in <FIG> and <FIG>, the drive mechanism <NUM> is mounted to the rotor <NUM> beneath the detector array <NUM>, and opposite the x-ray source tube <NUM>.

This can be advantageous, since the motorized components of the drive mechanism <NUM> can result in EM interference with the tube that can affect the position of the x-ray focal spot. By placing the drive mechanism on the opposite side of the rotor <NUM> from the x-ray source <NUM>, the possibility of EM interference is minimized.

The foregoing method descriptions are provided merely as illustrative examples and are not intended to require or imply that the steps of the various embodiments must be performed in the order presented. Words such as "thereafter," "then," "next," etc. are not necessarily intended to limit the order of the steps; these words may be used to guide the reader through the description of the methods.

Claim 1:
A mobile diagnostic imaging system (<NUM>), comprising:
a rotatable portion (<NUM>);
a non-rotatable portion (<NUM>), wherein the rotatable portion (<NUM>) rotates with respect to the non-rotatable portion (<NUM>) to obtain an image of an object;
a power supply on the rotatable portion (<NUM>);
a docking system (<NUM>) that selectively engages to electrically connect the rotatable portion (<NUM>) and the non-rotatable portion (<NUM>) and selectively disengages to electrically disconnect the rotatable portion (<NUM>) and the non-rotatable portion (<NUM>) during an image scan;
wherein the docking system (<NUM>) comprises a first docking portion (36a) on one of the rotatable and non-rotatable portions (<NUM>, <NUM>) and a second docking portion (36b) on the other of the rotatable and non-rotatable portions (<NUM>, <NUM>),
characterized in that the first docking portion (36a) comprises a first electrical connector (53a) and a first alignment feature (<NUM>) and the second docking portion (36b) comprises a second electrical connector (53b) and a second alignment feature (<NUM>), the first and second electrical connectors (53a, 53b) and the first and second alignment features (<NUM>, <NUM>) configured to mate with one another when the system (<NUM>) is docked; and
wherein the first alignment feature (<NUM>) comprises a pin or rod and the second alignment feature (<NUM>) comprises a recess (<NUM>) configured to receive the first alignment feature (<NUM>) and further wherein the docking system prevents the rotable portion from rotating with respect to the non-rotable portion when the rotable portion is engaged to the non-rotable portion.