System and method for cooling an x-ray tube in a tomography computer system

A system and method for cooling an X-ray tube in a computer tomography (CT) cooling system is shown having a heat exchanger that has at least one cooling passageway for receiving a coolant for cooling the X-ray tube and that is formed to define a tubular passageway having or defining a heat exchanger axis. The tubular passageway has a first open area and a second open area, and, in one embodiment a first axial fan and a second axial fan, respectively, are situated adjacent to the first and second open areas. The heat exchanger is mounted on a gantry of the computerized tomography system such that the axis of the axial fans and the heat exchanger axis are generally parallel to the gantry axis so as to reduce or minimize the effects of gyroscopic forces.

BACKGROUND OF THE INVENTION

This invention relates to an apparatus for cooling oil or other fluid or coolant which is used to carry heat away from an X-ray tube in a computed tomography (CT) diagnostic imaging system. More particularly, the invention is directed to an apparatus and method which will facilitate reducing the amount of patient time required to perform an examination using the CT diagnostic imaging system.

As is well known in the art, an X-ray tube generates substantial amounts of heat in the course of its operation. Accordingly, provision must be made for removing heat from the proximity of the tube and for dispensing the heat into the surrounding environment. In a common arrangement, a coolant fluid or oil, circulates around the tube to receive excessive heat and then flows through a conduit to a heat exchanger. In the past, the heat exchanger caused the heat stored in the oil to be exposed to the surrounding air, so that the heat can be convected thereinto. The coolant oil then flows back to the tube through a second conduit.

Cooling arrangements of the above type commonly employ a fan to move air past or through the heat exchanger, to enhance heat transfer. If the X-ray tube is used in connection with a CT system, the tube, the heat exchanger, and the cooling fan are respectively mounted on an annular gantry, which is rapidly rotated around the patient to acquire a CT image. The gantry may rotate, for example, at a minimum of 90 revolutions per minute. At present, the X-ray tube cooling fans used in CT systems tend to be axial. That is, both the intake and exhaust air streams generated by the fans are directed along the fan axis (i.e., the axis of blade rotation). To provide sufficient cooling power, axial cooling fans must be rotated at a speed on the order of 3600 revolutions per minute. The axial fans typically force the air through at least one planar radiator that was situated in the path of airflow.

Attempts have been made in the past to reduce the amount of noise and vibration caused by the axial cooling fan systems of the past. For example, U.S. Pat. No. 5,956,383 issued to Kendall discloses a radial fan arrangement for cooling an X-ray tube mounted on the gantry of a CT system. In that reference, the axis of the fan is maintained in parallel relationship with the axis of the gantry to prevent gyroscopic loading of the fan as the fan rotates about the gantry axis with the gantry.

Another problem with CT is that the cost is high. To reduce the cost per patient, there is a desire to reduce the time required to take an X-ray by increasing the operational speed of the CT system. Increasing the speed also means that the patient does not have to remain still as long to get the same image, which results in improved results. Faster processing of patients further results in higher patient throughput.

In the past, the rotational speed of the gantry of CT system increased from one revolution/second to three revolutions/second, which required more X-rays to maintain the same rate of X-rays per unit time to get the same image. This, in turn, resulted in an increase in the power requirements of the CT system, thereby requiring an increase in the cooling requirements of the cooling system in the CT system.

As the rotational speed increased, the gravitational and gyroscopic forces increase, which means that the weight of the components must be reduced while the power is increased. Therefore, the need for lighter weight radiators, fans and pumps in the CT system became important. The space available for heat exchangers in the gantry of a typical CT system is limited.

One of the problems with the prior art devices, such as the Kendall device, was that the planar radiators did not perform a cooling as quickly as desired and could not easily accommodate increases in cooling requirements.

SUMMARY OF THE INVENTION

It is, therefore, a primary object of the invention to provide a system and method for cooling an X-ray tube by providing a heat exchanger having an at least one or plurality of conduits which are formed to provide or define a passageway.

In one aspect a cooling system for a CT system is provided that utilizes a cylindrical radiator to provide a greater face area for airflow and room for more passages for liquid flow, which reduces the pressure drop across the air side and the liquid side of the radiator. This results in more airflow and more liquid flow for the same size fans and pumps. The large face area also reduces the weight of the radiator because it can be done with a thin single passage radiator instead of a smaller face area with thicker coils. This facilitates enabling the CT system to operate at higher rotational speeds, which reduces the time required to take an X-ray and also increases patient throughput.

Another object of the invention is to provide a system and method which is capable or utilizing axial fans in combination with such formed passageway.

Another object of the invention is to reduce or facilitate reducing the amount of patient time required to obtain a diagnostic image.

Still another object of the invention is to provide a system that employs an axial fan that is situated outside such a passageway defined by a radiator member formed to define such passageway.

Still another object of the invention is to provide a heat exchanger defining a passageway that is generally circular.

Still another object of the invention is to provide a heat exchanger defining a passageway that is generally rectangular.

Still another object of the invention is to provide a heat exchanger defining a passageway that is generally triangular.

Still another object of the invention is to provide a heat exchanger defining a passageway that is generally square.

In another aspect, this invention comprises a system for cooling an X-ray tube using in a radiographic device, the system comprising: a heat exchanger comprising at least one cooling passage for receiving a coolant, the heat exchanger being formed to define a tubular passageway having an axis, a first open area and a second open area, and at least one fan situated in relation to at least one of the first open area or the second open area to cause air to be forced through the heat exchanger.

In yet another aspect, this invention comprises a computerized tomography system comprising: a gantry having a gantry axis and a patient region for positioning a patient during an X-ray scanning procedure, a motor for rotatably driving the gantry, an X-ray tube mounted on the gantry, the X-ray tube having an X-ray tube axis, a heat exchanger for removing heat generated by the X-ray tube, the heat exchanger comprising at least one cooling passage for receiving a coolant and being formed to define a tubular passageway having a heat exchanger axis, a first open area and a second open area, and at least one fan situated in relation to either the first open area or the second open area to cause air to be forced through the heat exchanger to cool the X-ray tube, the at least one fan also comprising a fan axis that is substantially coaxial with the heat exchanger axis.

In still another aspect, this invention comprises a method for cooling an X-ray tube in a computerized tomography system comprising a gantry that is rotated about a gantry axis, the gantry comprising an X-ray tube mounted on the gantry, the X-ray tube having an X-ray tube axis, providing a heat exchanger for removing heat generated by the X-ray tube, the heat exchanger comprising at least one cooling passage for receiving a coolant for cooling the X-ray tube and being formed to define a tubular passageway having a heat exchanger axis, a first open area and a second open area, situating a first fan having a first axial fan axis at the first open area and a second axial fan having a second fan axis at the second open area to cause air to be forced through the heat exchanger to cool the X-ray tube, and mounting the heat exchanger on the gantry so that the gantry axis, the first fan axis and the second fan axis are generally co-axial.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENT

Referring now toFIG. 1, a computerized tomography or radiographic device or system10is shown. The system10comprises a gantry12that is rotatably driven about a gantry axis GA by a drive motor14which is under the control of a controller16. An X-ray tube18is conventionally mounted on the gantry. In a manner conventionally known, the X-ray tube18transmits x-radiation towards a patient20shown lying on table22as the gantry12is rotated about the gantry axis at a rate of, for example, about two–three revolutions per second.

In order to cool the X-ray tube18, the system10further comprises a pump24which is coupled to controller16as shown. The pump24pumps a coolant such as oil via conduit32to the heat exchanger30. The coolant is pumped from the heat exchanger30, through conduit28and into an X-ray tube18until the coolant returns to the pump24via line26. Note that the X-ray tube18comprises an X-ray tube axis TA and the heat exchanger30comprises a heat exchanger axis HA as best illustrated inFIG. 1.

It should be appreciated that the X-ray tube18operates within a typical predetermined temperature range, such as 30 Degrees Celsius to 80 Degrees Celsius. The system10further comprises a sensor34coupled to controller16. If the sensor34senses that a temperature of the X-ray tube18is outside the predetermined range, then the controller16responds by, among other things, terminating power to the X-ray tube18in response to the sensed temperature. It should be appreciated, however, that the predetermined range may vary depending on the application and the type or model X-ray tube used.

Referring now toFIGS. 2–4, the heat exchanger30comprises or defines at least one conduit36having one or more cooling passageways, such as conduits38and40which cooperate to define a radiator42. Note that the conduits38and40comprise a material43which further facilitates the exchange of heat from the conduits38and40and the coolant situated therein. In the embodiment being described, the material43may comprise metallic fins. Note that the cooling conduit36comprises an inlet36bwhich is coupled to the pump24and which receives coolant there from pump24. The passageway36also comprises an outlet36awhich is coupled to the X-ray tube18to permit the coolant to flow through the passageway36tubes, such as conduits38and40, where the coolant may be cooled.

As best illustrated inFIGS. 3 and 4, note that the conduit36and conduits38and40and material43are formed into a generally tubular shape to provide a generally tubular radiator42that defines a first open area44and second open area46.

Referring back toFIG. 2, note that the heat exchanger30comprises a pair of mounting brackets48and50on which a pair of fan shrouds52and54, respectively, are mounted by conventional means, such as a plurality of screws56which are received in threaded holes (not shown) in the brackets48and50. Note that the first fan shroud52is situated adjacent to the first opening44(FIG. 3) so that a first axial fan58can be mounted in the shroud52in operative relationship with the first opening44and passageway62. Likewise, the second fan shroud54receives and supports a second fan60in operative relationship with a second opening46and passageway62. Note that the first and second fans58and60are axial fan model numbers W2E200-HH86-01 available from EBM Corporation of Farmington, Conn. In the embodiment being described, the fans58and60are provided mounted in the shrouds52and54, respectively. The fans58and60are driven by motors58a(FIG. 4) and 60a,respectively, which are controlled by controller16(FIG. 1). It should be appreciated that the axial fans58and60are mounted such that their axes are co-axial and define the heat exchanger axis HA mentioned earlier herein.

Thus, note that the fans58and60are situated at the first open area44and second open area46, respectively. The fans58and60cooperate to force air into the tubular passageway62(FIG. 3) and through the tubular radiator42that surrounds the conduits38and40.

As shown inFIG. 4, the radiator42is sandwiched between the mounting brackets48and50which are secured together with a plurality of rods59a–59d.The rods59a–59beach have threaded ends for receiving the screws61.

FIG. 4illustrates an exploded view of the heat exchanger30. In the embodiment being described, the fans58and60cooperate to force air into the passageway62(FIG. 3); however, it should be appreciated that the fans58and60could cooperate to pull air out of the passageway62if desired. Also, although not shown, it should be appreciated that a single fan or series of fans could be used to provide the desired forced air. Also, the at least one of the fans58and60may be situated at positions other than outside the passageway62, such as inside the passageway62, if desired.

FIG. 2illustrates the assembled view of the heat exchanger30shown in exploded view inFIG. 4. After the heat exchanger is assembled, the heat exchanger is mounted to the gantry12using the extended portions48aand50aof mounting brackets48and50, respectively. The brackets48and50are secured to the gantry using a plurality of fasteners, such as screws, which are situated through the holes48a1and50a1and received and threaded openings (not shown) in the gantry12.

As best illustrated inFIG. 1, note that after the heat exchanger30is mounted on the gantry12, the heat exchanger30axis HA is generally parallel to both the X-ray tube axis TA and the gantry axis GA. It has been found that this is beneficial because of the gyroscopic forces that are in play as the gantry12rotates during use. It should also be appreciated that the tubular passageway defined by the radiator42comprises a tubular passageway axis TP (FIG. 3), and the tubular passageway TP is generally co-axial with the axes of the fans58and60and axis HA.

In the embodiment being described, the tubular passageway62defined by the conduits38and40may be formed to define a circular, generally rectangular, square, triangular, or any other suitable shape desired.

FIG. 5is a perspective view of another embodiment of the invention. Like parts are identified with the same part numbers, except that a prime mark (“′”) has been added to the part numbers inFIG. 5. Note that the embodiment shown inFIG. 5comprises the fluid pump24′ which is situated inside the passageway62′. It has been found that this facilitates reducing the amount of space required by the various components, such as the heat exchanger30′ and the pump24′, when they are mounted on the gantry.

Note that the heat exchanger30′ inFIG. 5comprises a pair of generally plainer housing members70′ and72′ that are coupled together with a plurality of support posts74′ and suitable fasteners or screws76′ which are situated in openings, such as openings70a′ and threaded into suitable openings, such as opening70a′ and member70′ and ultimately threaded into threaded openings, such as threaded opening74a′ in order to sandwich the radiator43′ between the member70′ and72′ as shown.

During operation, a technician activates controller16which energizes primarily to rotate gantry12. Controller16energizes X-ray tube18to transmit radiation toward patient20and receivers21(FIG. 1). Controller16energizes pump24to pump fluid through heat exchanger30to cool the fluid and circulate fluid past X-ray tube18. The technician may cause controller16to terminate power to the system10to turn it off. The controller16may also receive an out-of-range signal from sensor34in which case controller16terminates power to at least the X-ray tube18and the driver14.

Advantageously, the system provides a system and method for cooling the X-ray tube18by providing the heat exchanger30for removing heat generated by the X-ray tube18. As mentioned, the heat exchanger30comprises at least one or a plurality of coolant passageways36comprising at least one or a plurality of conduits38and40.

While the systems and methods herein described, and the forms of apparatus for carrying these systems and methods into effect, constitute one embodiment of this invention, it is to be understood that the invention is not limited to these precise methods and forms of apparatus, and that changes may be made in either without departing from the scope of the invention, which is defined in the appended claims.