Abstract:
A magnetic resonance imaging system ( 500 ) comprising: a magnet ( 502 ) for generating a magnetic field; a radio frequency system ( 516 ) for acquiring magnetic resonance data; a magnetic field gradient coil ( 510 ) for spatial encoding of the magnetic spins of nuclei within the imaging volume; a magnetic field gradient coil power supply ( 512 ) for supplying current to the magnetic field gradient coil; an anesthesia system interface ( 532 ) for sending control messages to an anesthesia system ( 524 ) for controlling the delivery of inhalation gases to a subject and a computer system comprising a processor ( 534 ) and a memory ( 538, 540 ), wherein the memory contains instructions ( 542, 544, 546, 548, 550, 552 ) for execution by the processor, wherein execution of the instructions causes the processor to: control ( 100, 200, 300, 400 ) the operation of the magnetic resonance imaging system to acquire magnetic resonance data, and to send ( 102, 202, 302, 402 ) control messages to the anesthesia system via the anesthesia system interface.

Description:
TECHNICAL FIELD  
       [0001]    The invention relates to magnetic resonance imaging, in particular to the simultaneous control of a magnetic resonance imaging system and an anesthesia system 
       BACKGROUND OF THE INVENTION  
       [0002]    Measuring the Magnetic Resonance (MR) response to Respiratory Challenges (RC) that induce elevated levels of O2 (hyperoxia) and CO2 (hypercapnia) gives insight into a wide range of physiologic parameters like blood and tissue oxygenation, vessel maturation and function, tumor hypoxia and cerebrovascular reactivity. These parameters play a major role in oncologic research e.g. in tumor therapy selection, planning (dosage) and monitoring. In those experiments, the patient inhales O2 and/or CO2-enriched air, which results in a modulation of blood flow, volume and oxygenation depending on the maturity and oxygen function of vessels and/or the amount of dissolved oxygen in blood plasma and tissue. In response, MR relaxation rates and thus the MR contrast changes, according to the impact of the challenge on the magnetic properties of tissue and blood and the relaxation parameters, respectively (oxygenated blood is diamagnetic increasing T2*, dissolved oxygen in blood and tissue is paramagnetic, decreasing T1, accelerated inflow during enhanced CO2 levels decreases T1 artificially, etc.). 
         [0003]    In journal article Mandell et. al., “Selective Reduction of Blood Flow to White Matter During Hypercapnia” Stroke, DOI: 10.1161/STROKEAHA.107.501692 an automated gas sequence was used to alternate between high and low end-tidal pressure of carbon dioxide states during a BOLD magnetic resonance acquisition. 
         [0004]    In the paper by L. W. Hedlund et al., ‘ MR compatible ventilator for small animals: computer controlled ventilation for proton and noble gas imaging’  in Magnetic Resonance Imaging 18(2000)753-759, it is mentioned that ventilation and imaging can be synchronised by having either the ventilator actively trigger imaging or by having the imaging trigger the ventilator. 
       SUMMARY OF THE INVENTION  
       [0005]    The invention provides for a magnetic resonance imaging system, a computer system, and a computer program product in the independent claims. Embodiments are given in the dependent claims. 
         [0006]    A difficulty with current Respiratory Challenge (RC) procedures is that the conventional regime comprises one or more MR scans, executed while the patient is inhaling changing compositions of O2, CO2 or inhalation of other inhalation gases, also known as a RC, units that are controlled completely separately and independently from the MR unit. In other words, the radiologist and anesthetist agree on a particular RC protocol (e.g. 1 min normal air, 4 min oxygen, 2 min normal air). Then, the MR scan(s) and the delivery and mixture of inhalation gases are synchronized manually and the exact timing of the truly applied breathing regime with respect to the MR scan has to be recorded manually for later analysis of the MR data. 
         [0007]    Problems arise, when the MR scan had not been perfectly synchronized to the RC protocol or vice versa, e.g. due to:
       misunderstandings of technicians and radiologists outside the MR room with the anesthetist inside the MR room,   timing uncertainties,   leakage of the inhalation mask, via which the patient inhales the applied mixtures, or   post-processing fails, when the (manual) RC protocol recording gets lost or is incorrect.       
 
         [0012]    For example, if the parameterized description of the MR response (i.e. the MR signal over time or relaxation constants over time) to the delivery of increased O2, CO2 levels reveals markers of physiologic tumor parameters (oxygenation, vasoreactivity). For this, a signal model is fitted to the recorded series of images. This model may be either obtained experimentally or is based on a tissue compartment model. Numerical fit routines require the appropriate initialization of the model parameters. These serve as start values of an iterative approximation of the true parameters. Depending on the algorithm, the fit result will be more or less sensitive to a wrong initialization of fit parameters, e.g. if a wrong RC protocol was communicated to the MR processing. For example, an anesthetist applies a RC protocol to the patient, which comprises 1/4/2 min of breathing air/Carbogen/air (Carbogen is a composition of O2 and CO2). Later on, during data analysis, the radiologist or MR technician enters the wrong RC protocol (2/4/1 min) into the postprocessing module (typing error, misinformation, mixing up of the two “air” periods, etc.). 
         [0013]    One embodiment of the invention is a communication link module between the MR environment and the RC environment replacing the “manual” communication between the MR and RC operators to:
       perfectly synchronize the MR scan(s) and the respiratory challenge   to ensure accurate analysis of the MR data (e.g. if a signal model is fitted to a dynamic series of images recorded during inhalation changes, this mostly requires knowledge about when the challenge started/changed/ended).       
 
         [0016]    The interest of MR imaging during O2 and CO2 respiratory challenges, has significantly grown and is still growing especially in oncology. The conventional “manual” synchronization of respiratory and MR scan protocols is particularly difficult in the MR environment, the communication between the MR operator and the RC operator (anesthetist) is prone to misunderstandings, which translates into systematic errors in the analysis and interpretation of the MR data. The use of a synchronized and automated communication link between the MR and RC environment overcomes these issues and ensures an optimized and robust use of the experiment and will thus considerably improve this powerful diagnostic tool. Product implementation of oxygen or CO2 enhanced MRI necessitates at least the installation of some means for synchronization of the two environments to guarantee robustness (user independence). This is covered by the present invention. 
         [0017]    A ‘computer-readable storage medium’ as used herein is any storage medium which may store instructions which are executable by a processor of a computing device. The computer-readable storage medium may be a computer-readable non-transitory storage medium. The computer-readable storage medium may also be a tangible computer readable medium. In some embodiments, a computer-readable storage medium may also be able to store data which is able to be accessed by the processor of the computing device. An example of a computer-readable storage medium include, but are not limited to: a floppy disk, a magnetic hard disk drive, a solid state hard disk, flash memory, a USB thumb drive, Random Access Memory (RAM) memory, Read Only Memory (ROM) memory, an optical disk, a magneto-optical disk, and the register file of the processor. Examples of optical disks include Compact Disks (CD) and Digital Versatile Disks (DVD), for example CD-ROM, CD-RW, CD-R, DVD-ROM, DVD-RW, or DVD-R disks. The term computer readable-storage medium also refers to various types of recording media capable of being accessed by the computer device via a network or communication link. For example a data may be retrieved over a modem, over the internet, or over a local area network. 
         [0018]    Computer memory is an example of a computer-readable storage medium. Computer memory is any memory which is directly accessible to a processor. Examples of computer memory include, but are not limited to: RAM memory, registers, and register files. 
         [0019]    Computer storage is an example of a computer-readable storage medium. Computer storage is any non-volatile computer-readable storage medium. Examples of computer storage include, but are not limited to: a hard disk drive, a USB thumb drive, a floppy drive, a smart card, a DVD, a CD-ROM, and a solid state hard drive. In some embodiments computer storage may also be computer memory or vice versa. 
         [0020]    A ‘processor’ as used herein encompasses an electronic component which is able to execute a program or machine executable instruction. References to the computing device comprising “a processor” should be interpreted as possibly containing more than one processor. The term computing device should also be interpreted to possibly refer to a collection or network of computing devices each comprising a processor. Many programs have their instructions performed by multiple processors that may be within the same computing device or which may even distributed across multiple computing device. 
         [0021]    Magnetic resonance data is defined herein as being the recorded measurements of radio frequency signals emitted by atomic spins by the antenna of a Magnetic resonance apparatus during a magnetic resonance imaging scan. A Magnetic Resonance Imaging (MRI) image is defined herein as being the reconstructed two or three dimensional visualization of anatomic data contained within the magnetic resonance imaging data. This visualization can be performed using a computer. 
         [0022]    In one aspect the invention provides for a magnetic resonance imaging system comprising a magnet adapted for generating a magnetic field for orienting the magnetic spins of nuclei of a subject located within an imaging volume. The magnetic resonance imaging system further comprises a radio frequency system for acquiring magnetic resonance data. The radio frequency system comprises a radio frequency transceiver adapted to connect to a radio frequency coil. As used herein a radio frequency transceiver may also refer to individual radio frequency transmitters and receivers. The radio frequency coil may also be separate transmit and receive coils. The magnetic resonance imaging system further comprises a magnetic field gradient coil for spatial encoding of magnetic spins and nuclei within the imaging volume. The magnetic resonance imaging system further comprises a magnetic field gradient coil power supply for supplying current to the magnetic field gradient coil. The magnetic resonance imaging system further comprises an anesthesia system interface adapted for sending control messages to an anesthesia system. 
         [0023]    An ‘anesthesia system’ as used herein encompasses a system or apparatus adapted for controlling the flow of and for mixing gases which are provided for the subject. Although the term anesthesia system is used, this does not imply that gases for performing anesthesia are used. An anesthesia system is used for controlling the gas delivery of inhalation gases to a subject. For instance the concentration of oxygen and/or carbon dioxide may be controlled. The wording ‘anesthesia system’ is used because the anesthesia system is ideally supervised by an anesthesiologist. 
         [0024]    The magnetic resonance imaging system further comprises a computer system comprising a processor and a memory. Memory contains instructions for execution by the processor. Execution of the instructions causes the processor to perform the step of controlling the operation of the magnetic resonance imaging system to acquire magnetic resonance data. Essentially the computer system performs as a control system for the magnetic resonance imaging system. Execution of the instructions further requires a processor to perform the step of sending control messages to the anesthesia system via the anesthesia system interface. The computer system essentially also functions as a control system for the anesthesia system. This embodiment is particularly advantageous because the computer system functions as a control system for both the magnetic resonance imaging system and for the anesthesia system. This allows more precise control of both apparatuses and allows their functionality to be more precisely synchronized. This enables the anesthesia system to be used for respiratory challenge studies using the magnetic resonance imaging system. By having the computer system control both apparatuses the magnetic resonance data which can be used to construct magnetic resonance images or other reconstructions is maybe more closely correlated with the respiratory challenge which is performed by the anesthesia system. 
         [0025]    In another embodiment the computer memory contains a pulse sequence for planning the acquisition of magnetic resonance data. As used herein ‘a pulse sequence’ is a set of instructions or a timing plan for controlling the operation of the magnetic resonance imaging system. The instructions control the operation of the magnetic resonance imaging system in accordance with the pulse sequence. The memory comprises a gas sequence for planning the control of the composition of the gas delivered to the subject for respiration by the anesthesia system during the acquisition of magnetic resonance data. The instructions send control messages to the anesthesia system in accordance with the gas sequence. 
         [0026]    In another embodiment the anesthesia system interface is further adapted for receiving gas sensor data from the anesthesia system. ‘Gas sensor data’ as used herein encompasses measurements from sensors within the anesthesia system for detecting properties of gas either inhaled or exhaled by the subject. The gas sensor data comprises time dependent gas concentrations in the gas inhaled and/or exhaled by the subject. The gas sensor data is time correlated with the magnetic resonance data in accordance with the pulse sequence. In this embodiment it is particularly advantageous because instead of purely relying on studying the gas flow to the subject the actual gas which is inhaled or exhaled can be measured using gas sensors which provide the gas sensor data. This allows any respiratory challenge procedure to be very precisely correlated with the pulse sequence. Correlating this with the pulse sequence allows the magnetic resonance images generated from the magnetic resonance data to be very accurately correlated with the portion of the respiratory challenge procedure. 
         [0027]    In another embodiment the gas concentrations measured in the gas comprise oxygen concentrations. 
         [0028]    In another embodiment the gas concentrations measured in the gas comprise carbon dioxide concentrations. 
         [0029]    In another embodiment the gas concentrations measured in the gas comprise nitrogen concentrations. 
         [0030]    In another embodiment the instructions further cause the processor to perform the step of analyzing the magnetic resonance data in accordance with a respiratory challenge algorithm. A respiratory challenge algorithm as used herein encompasses an algorithm which performs a statistical analysis of the magnetic resonance data in order to infer the effects of a respiratory challenge protocol. A respiratory challenge protocol as used herein encompasses altering the property of gases inhaled by a subject during a magnetic resonance imaging examination. The initialization of the respiratory challenge protocol algorithm is performed in accordance with the gas sensor data. Essentially the statistical analysis of the magnetic resonance data is correlated to the timing of data from the gas sensor data. For instance if carbon dioxide levels are elevated in the gas inhaled by the subject the respiratory challenge algorithm can be correlated to start when the elevated carbon dioxide levels are measured in the mask of the subject. 
         [0031]    In another embodiment execution of the instructions further cause a processor to perform the step of acquiring magnetic resonance data which may be reconstructed into tissue oxygenation level dependent contrast images. This may be accomplished for instance by measuring the so-called T2* or T1 or by instructing T2*- or T1-weighted images. Execution of the instructions further causes the processor to perform the step of reconstructing the magnetic resonance data into tissue oxygenation level dependent contrast images. Execution of the instructions further causes the processor to perform the step of determining a set of tissue oxygenation level measures. For instance the tissue oxygenation level measures may be determined by the value of T2* or T1 or from T2*- or T1-weighted images. The set of tissue oxygenation level measures is constructed by determining a tissue oxygenation measure for an oxygenation test volume in each of the tissue oxygenation level dependent contrast images. The respiratory challenge algorithm analyses the magnetic resonance data by at least performing a statistical analysis of a subset of a set of tissue oxygenation level measures. The subset is determined in accordance with the gas sensor data. 
         [0032]    In another embodiment each tissue oxygenation level measure is calculated during the acquisition of magnetic resonance data. The instructions further cause the processor to perform the step of modifying the pulse sequence and/or the gas sequence in accordance with the set of tissue oxygen level measures. The gas sequence could be modified by measuring the effect of the tissue oxygen level measures. For instance, if a sufficient change in the tissue oxygen level is detected then the experiment could be terminated and the gas sequence could be modified such that the subject is breathing normal air. Depending on the contrast of the set of tissue oxygen level measures detected in magnetic resonance images the pulse sequence can be modified. For instance the repetition time and the number of echoes used for the T2* measurement may be modified. 
         [0033]    In another embodiment the execution of the instructions further cause the processor to perform the step of acquiring magnetic resonance data which may be reconstructed into vasoreactivity contrast images. This may be accomplished for instance by acquiring magnetic resonance data which may be reconstructed into T1 weighted or T2*-weighted images or by measuring T2* or T1. The instructions further cause the processor to perform the step of reconstructing the magnetic resonance data into vasoreactivity contrast images. The vasoreactivity contrast images may for instance be T1 weighted contrast images. Execution of the instructions further requires a processor to perform the step of determining a set of vasoreactivity measures. The set of vasoreactivity measures is constructed by determining a vasoreactivity level for a vasoreactivity test volume in each of the vasoreactivity contrast images. 
         [0034]    The RC protocols used for acquiring the magnetic resonance data which may be reconstructed into vasoreactivity contrast images or tissue oxygenation level dependent contrast images differ in by the use of different gasses. The analysis of the magnetic resonance data is either the same or similar. Information about both oxygenation and vasoreactivity can be drawn from T1, T2* or T2 weighted images or T1, T2* or T2 values. 
         [0035]    The respiratory challenge algorithm analyses the magnetic resonance data by at least performing a statistical analysis of a subset of a set of vasoreactivity measures. The subset is determined in accordance with the gas sensor data. The gas sensor data may for instance be used to determine when the concentration of carbon dioxide or for instance carbogen is elevated. This may be used to determine when the statistical analysis should be performed. 
         [0036]    In another embodiment each vasoreactivity measure is calculated during the acquisition of magnetic resonance data. The instructions further cause the processor to perform the step of modifying the pulse sequence and/or the gas sequence in accordance with a set of vasoreactivity measures. The pulse sequence may be modified such that its contrast is changed to optimize the contrast versus the speed of the acquiring data period. For instance the repetition time and the number of echoes used may be changed. The gas sequence may also be modified in accordance with a set of vasoreactivity measures herein for instance if the vasoreactivity measure has reached a certain level of contrast in the vasoreactivity contrast images then the experiment can be terminated and the gas sequence can be ended and can be modified such that the subject begins breathing normal air again. 
         [0037]    In another embodiment execution of the instructions further cause a processor to perform the step of modifying the pulse sequence and/or gas sequence in accordance with the gas sensor data. If the subject is not inhaling or exhaling an expected concentration of the gas then the gas sequence can be modified to correct this air. The pulse sequence can also be modified by using new gas sensor data. For instance, if the subject is not breathing an expected mixture of gas then the timing of the pulse sequence may be delayed a period. 
         [0038]    In another embodiment the pulse sequence is a multi-gradient echo pulse sequence. This embodiment is advantageous because such a pulse sequence may be used to acquire images with different T2* weighted contrasts and to compute a quantitative T2* value from this set of images. 
         [0039]    In another embodiment the magnetic resonance imaging system comprises the anesthesia system. 
         [0040]    In another aspect the invention provides for a computer system for controlling a magnetic resonance imaging system. The computer system comprises a processor for executing instructions. The computer system is connected to a magnetic resonance imaging system. The computer system is connected to an anesthesia system interface for sending control messages to an anesthesia system. The computer system may also send control signals to the magnetic resonance imaging system. Execution of the machine readable instructions causes the processor to perform the step of controlling the operation of the magnetic resonance imaging system. Execution of the machine readable instructions further cause the processor to perform the step of sending control messages to the anesthesia system via the anesthesia system interface. 
         [0041]    In another aspect the invention provides for a computer program product comprising machine readable instructions for execution by a processor of a computer system. The computer program product may also be machine readable instructions stored on a computer-readable storage medium. The computer system is connected to a magnetic resonance imaging system. The computer system is connected to an anesthesia system interface for sending control messages to an anesthesia system. Execution of the machine readable instructions causes the processor to perform the steps of controlling the operation of the magnetic resonance imaging system. Execution of the machine readable instructions further cause the processor to perform the step of sending control messages to the anesthesia system via the anesthesia system interface. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS  
         [0042]    In the following preferred embodiments of the invention will be described, by way of example only, and with reference to the drawings in which: 
           [0043]      FIG. 1  shows a block diagram which illustrates an embodiment of a method according to the invention; 
           [0044]      FIG. 2  shows a block diagram which illustrates a further embodiment of a method according to the invention; 
           [0045]      FIG. 3  shows a block diagram which illustrates a further embodiment of a method according to the invention; 
           [0046]      FIG. 4  shows a block diagram which illustrates a further embodiment of a method according to the invention; 
           [0047]      FIG. 5  shows a magnetic resonance imaging system according to an embodiment of the invention; 
           [0048]      FIG. 6  shows a magnetic resonance imaging system according to a further embodiment of the invention; and 
           [0049]      FIG. 7  illustrates the effect of correct timing and incorrect for synchronization of the magnetic resonance data on a respiratory challenge experiment. 
       
    
    
     DETAILED DESCRIPTION OF THE EMBODIMENTS  
       [0050]    Like numbered elements in these figures are either equivalent elements or perform the same function. Elements which have been discussed previously will not necessarily be discussed in later figures if the function is equivalent. 
         [0051]      FIG. 1  shows a block diagram which illustrates an embodiment of a method according to the invention. In step  100  the operation of the magnetic resonance imaging system is controlled to acquire magnetic resonance data. In step  102  control messages are sent to the anesthesia system via the anesthesia system interface. 
         [0052]      FIG. 2  shows a block diagram which illustrates an embodiment of a further method according to the invention. In step  200  the operation of the magnetic resonance imaging system is controlled in order to acquire magnetic resonance data. In step  202  control messages are sent to the anesthesia system via the anesthesia system interface. In step  204  the magnetic resonance data is analyzed in accordance with a respiratory challenge algorithm. 
         [0053]      FIG. 3  shows a block diagram which illustrates a further embodiment and method according to the invention. In step  300  the operation of the magnetic resonance imaging system is controlled in order to acquire magnetic resonance data. In step  302  control messages are sent to the anesthesia system via the anesthesia system interface. In step  304  magnetic resonance data is acquired which may be reconstructed into tissue oxygenation level dependent contrast images. The magnetic resonance data may be magnetic resonance data which contains T2* information. In step  306  a set of tissue oxygenation level measures are determined. Step  306  may include reconstructing the magnetic resonance data into tissue oxygenation level dependent contrast images And finally in step  308  the pulse sequence and/or the gas sequence is modified in accordance with a set of tissue oxygenation levels. 
         [0054]      FIG. 4  shows a block diagram which illustrates a further embodiment of a method according to the invention. In step  400  the operation of the magnetic resonance imaging system is controlled in order to acquire magnetic resonance data. In step  402  control messages are sent to the anesthesia system via the anesthesia system interface. In step  404  magnetic resonance data is acquired which may be reconstructed into vasoreactivity contrast images. In step  406  a set of vasoreactivity measures is determined. Step  406  may include reconstructing the magnetic resonance data into vasoreactivity contrast images. In step  408  the pulse sequence and/or the gas sequence is modified in accordance with the set of vasoreactivity measures. 
         [0055]      FIG. 5  shows a magnetic resonance imaging system  500  according to an embodiment of the invention. The magnetic resonance imaging system comprises a magnet  502  which is used to orient the position of magnetic spins within an imaging volume  504  of a subject  506  located within the bore of the magnet  502 . The magnet  502  is shown as being a cylindrical type magnet with a bore through the center for receiving the subject. However other varieties of magnets could also be used such as so-called open or toroidal magnets. The subject  506  is shown as reposing on a subject support  508 . Within the bore of the magnet  502  is a magnetic field gradient coil  510 . The magnetic field gradient coil  510  is connected to a magnetic field gradient coil power supply  512 . Magnetic resonance imaging systems typically have three separate coil systems. The gradient coil  510  and the gradient coil power supply  512  is intended to represent a standard gradient coil. Above the imaging volume  504  is a radio frequency coil  514 . The radio frequency coil  514  is connected to a radio frequency transceiver  516 . The combination of the radio frequency coil  514  and the radio frequency transceiver  516  is used to manipulate the orientation of magnetic spins within the imaging volume  504  and also to acquire magnetic resonance data by measuring the received radio signals. 
         [0056]    The subject  506  is shown as having a mask  518  over his or her mouth. The mask  518  has an inlet tube  520  for receiving gas to the mask  518  and an outlet tube  522  for removing gas as it is exhaled by the subject  506 . The inlet tube  520  and the outlet tube are connected to an anesthesia system  524 . The anesthesia system  524  is able to control the mixture and amount of gases that are in the inlet tube  520  and are breathed by the subject  506 . The inlet tube  520  is connected to the anesthesia system  524  through an inlet gas sensor  526 . The outlet tube  522  is connected to the anesthesia system  524  through an outlet gas sensor  528 . The inlet gas sensor and the outlet gas sensor  528  are for measuring a property of either the inlet gas in the inlet or outlet respectively. The inlet gas sensor  526  and the outlet gas sensor  528  generate gas sensor data. The anesthesia system  524  the gradient coil power supply  526  and the radio frequency transceiver  516  are all connected to a hardware interface  532  of a computer system  530 . The hardware interface  532  may be considered to be an anesthesia system interface. The computer system controls all of these components. 
         [0057]    The computer system  530  has a processor  534  which is connected to and controls the hardware interface  532  and a user interface  536 . The user interface  536  may include devices for an operator to interact with and control the computer system  530 . For instance the user interface  536  may also comprise a keyboard a common mouse and a display grid. Computer magnetic resonance images may be displayed on a display of the user interface  536 . The processor  534  is also shown as being connected to computer memory  538  and computer storage  540 . 
         [0058]    The computer memory  508  is shown as containing a magnetic resonance imaging system control module  542 . The magnetic resonance imaging system control module  542  contains executable code for controlling the operation of the magnetic resonance imaging system. The computer memory  538  is shown as further containing an anesthesia system control module. The anesthesia system control module  544  contains computer executable code for generating control messages for sending to the anesthesia system  524 . The memory is further shown as containing a respiratory challenge protocol algorithm  546 . The respiratory challenge protocol algorithm  546  contains computer executable code for analyzing magnetic resonance imaging data and/or images to analyze magnetic resonance imaging data acquired during a respiratory challenge protocol. The computer memory  538  is shown as further containing an image reconstruction module  548 . The image reconstruction module  548  contains computer executable code for transforming magnetic resonance data  560  into magnetic resonance images. The computer memory  538  is further shown as containing a gas sequence modification module  550  and a pulse sequence modification module  552 . The gas sequence modification module  550  contains computer executable code for modifying a gas sequence  556  using either magnetic resonance data  560  or gas sensor data  558 . The pulse sequence modification module  552  contains computer executable code for modifying the pulse sequence  552  in accordance with either gas sensor data  558  or magnetic resonance data  560 . 
         [0059]    The computer storage  540  is shown as containing a pulse sequence  554  which is used in accordance with the magnetic resonance control system module  542  for controlling the magnetic resonance imaging system  500 . The computer memory  540  is further shown as containing a gas sequence  556  which is used in accordance with the anesthesia system control module  544  for controlling the anesthesia system  524 . The computer memory is further shown as containing gas sensor data  558  acquired using the inlet gas sensor  526  and/or the outlet gas sensor  528 . The computer storage  540  is further shown as containing the magnetic resonance data  560  and a transverse plane relaxation time weighted magnetic resonance imaging image  562 . The transverse plane relaxation time weighted magnetic resonance imaging image may be a T1, a T2, or a T2* weighted magnetic resonance imaging image. 
         [0060]      FIG. 6  is an example of a functional diagram  600  of the magnetic resonance imaging system  500  according to an embodiment of the invention. In  FIG. 6  the control aspects of the system  600  are discussed. There is an anesthesia system which represents the control of anesthesia gases  602 . The anesthesia system  504  receives inhalation air  604  from the anesthesia gases. Anesthesia system  524  controls the flow of a mixture of gases to a mask  518  via a inhalation tube  520  and receives them via an exhalation tube  522 . Mask  518  is on a patient  506  within a magnetic resonance system  500 . The anesthesia system  524  receives messages and sends messages to a host computer  612  via a communication link module  606 . A magnetic resonance imaging system operator  610  is shown as controlling the clinical protocol  614  send to a host computer  612 . The host computer  612  also generates results from the protocol  616  where they can be displayed for the operator  610 . The host computer sends scan parameters  618  to a scan control module  620 . The scan control module  620  is equivalent to the magnetic resonance imaging system control module  542  of  FIG. 5 . Scan control module  620  sends control signal  622  to the magnetic resonance imaging system  500 . The raw magnetic resonance imaging data  624  is sent by the magnetic resonance imaging system  500  to an image reconstruction module  626 . The reconstruction module  626  is equivalent to the image reconstruction module  548  of  FIG. 5 . The magnetic resonance raw data  624  is equivalent to the magnetic resonance data  560  at  FIG. 5 . The host computer  612  sends reconstruction parameters  628  to the reconstruction module  626 . 
         [0061]    The reconstruction module  626  sends the reconstructed magnetic resonance images  630  to a post processing and analysis module  632 . The post processing and analysis module  632  receives true respiratory challenge protocol data  634  from the host computer  612 . The true respiratory control protocol data was generated using data acquired from the communication link module  606 . 
         [0062]    The communication link module  606  performs a variety of functions. First the communication link module receives feedback levels  536  and oxygen and possibly carbon dioxide in expiratory and inspiratory air. The communication link module  606  is shown housing a respiratory monitor module  638  which receives the feedback levels  636 . The respiratory monitor module sends ventilation response data for the respiratory control protocol  640  to the host computer  612 . The host computer  642  sends data to a synchronization module  646  in the form of a challenge  642 . The synchronization module  646  sends the respiratory control protocol  648  to a respiratory challenge control module  650 . A synchronization module  646  also sends magnetic resonance imaging scan timing and respiratory challenge protocol data  644  to the host computer  612 . Combination of the scan timing and respiratory challenge protocol  644  and the ventilation response to the respiratory control protocol  640  is used to generate the true respiratory challenge protocol data  634 . The respiratory challenge control module  650  generates the control signals  652  which are sent to the anesthesia system  524  for controlling its operation. 
         [0063]      FIG. 6  outlines a set-up for an MR monitored respiratory challenge. Conventionally, it contains more or less completely separated MR and RC environments, controlled independently by an MR (radiologist, MR technician)  610  and RC  608  operator (anesthetist), respectively. 
         [0064]    The RC environment contains an anesthesia system  524  which comprises the arbitrary composition of inhalation gases  602 , delivery means  520 ,  522  for transporting the anesthesia mixture to the patient  506 , delivery means to transport the inhaled and exhaled air to and from the patient via expiratory  520  and inspiratory  522  tubes, sensors that monitor gas levels in the inspiratory and expiratory tubes, a carbon dioxide absorber, means to prevent rebreathing of exhaled air, demand valves to optimize consumption of the delivered anesthesia, etc. The anesthesia system is supplied with inhalation gases such as Carbogen, CO2, pure oxygen or others from a gas supply unit, normally positioned outside the MR suite and the system is further able to introduce “normal” room air into the inhalation mixture. The inhalation mixture is delivered to the patient via an inspiratory tube  520  and a mask  518 . The exhaled air is transported by a separate expiratory  522  tube from the patient to a scavenger system. Such an anesthesia system is normally controlled manually by an anesthetist, who further communicates abnormalities in the composition of inspiratory and/or expiratory air to the MR operator  610  to be considered in later post-processing. 
         [0065]    The MR environment comprises a MR scanner  500  is operated by a radiologist  610  or MR technician, who selects or even optimizes the scan protocol with respect to the clinical question. The selected scan protocol  614  is sent to the scan control module  620 , which controls the MR machine  500 . This timing of the scan protocol (e.g. the number and length of dynamics in a dynamic scan) requires synchronization with the RC protocol  648  (e.g. the MR and RC protocols need to start at the same time, the number of dynamic images needs to appropriately represent the MR signal changes during the experiment). The acquired data  624  are sent to the reconstruction module  626 , reconstructing data, based on information and requirements determined by the scan protocol  614 , selected by the MR operator. 
         [0066]    The post-processing and analysis module  632  performs some preprocessing on the images  630  (e.g. motion correction, relaxometry, data filtering, etc.) and the quantitative analysis of the response (e.g. determination of the strength and kinetic of signal changes during oxygen breathing, etc.). The timing of the scan as well as the post-processing and analysis of the returned data may be manually synchronized with the breathing protocol  648  (e.g. the analysis module requires knowledge about the baseline and RC data to compare in statistical tests, signal models for numerical fits to the data depend on the timing of the RC protocol, etc). 
         [0067]    One embodiment of the present invention is a communication link module  606 , which automates and synchronizes the communication between the MR scan and processing/analysis environment and the RC environment. This replaces the control function of the anesthetist  608 . He is further necessary to supervise the patient and for possible security interrupts of the experiments. 
         [0068]    In a preferred embodiment the communication link module consists of a synchronization module  646 , a respiratory challenge control module  650 , and a respiratory monitor module  638 , described in more detail in the following paragraph. The communication link is driven by the scan administration environment on the MR host computer and controls an MR compatible anesthesia system  524 . 
         [0069]    In the embodiment shown in  FIG. 6 , the MR operator  610  selects a certain procedure with respect to a given clinical question. This contains the RC  648  to be applied (type of gas(es) and timing). The synchronization module adapts the RC to the MR scan and vice versa:
       It may adjusts the length of MR scans and the delivery and composition of particular inhalation mixtures: it ensures that the delivery does not change during the acquisition of an MR image, it synchronizes the length and the start time for both the MR and RC experiment, etc.,   If required, it modifies scan parameters according to the particular challenge (e.g. it may select flow-insensitive imaging protocols if inhalation mixtures are used that have significant impact on blood flow, it may optimize the imaging protocol to optimize contrast with respect to the delivered inhalation mixture).   The synchronization module  646  then sends the optimized MR protocol and the optimized RC protocol to the host computer and the respiratory challenge control module, respectively. The RC protocol is also provided to the post-processing/analysis module for later processing of the reconstructed data. The synchronization module can be realized as a piece of software, implemented on the scanner host.       
 
         [0073]    The respiratory challenge control module  650  consists of a computer-readable storage medium that receives the RC protocol  648  from the synchronization module  646  and transforms it into programming instructions  652  to control the anesthesia system  524 . Executed on a processor, it controls at least some of the valves of the anesthesia system to automatically select particular anesthesia gases and adjust the required gas pressures, flow, and compartments according to the RC protocol. It thus replaces the manual control of the anesthetist. In some embodiments, the respiratory challenge control unit is integrated in or attached to the anesthesia system. 
         [0074]    The respiratory monitor module  638  reads out the monitoring sensors of the anesthesia system  524 , which provide the patient respiratory signals (e.g. inspiratory and expiratory pressures of inhalation compartments). The patient respiratory signal is first represented by a graphical display and/or in a parameterized description. The representation may be provided by an LCD display integrated in the respiratory monitor module to be monitored by the anesthetist for security reasons. It may be useful to have a second representation sent to the MR host computer display for additional supervision by the MR operator (similar to how ECG signals are represented on the host computer display, conventionally). More importantly, the true patient respiratory signal, reflecting the true respiratory response to the challenge, translates into potential modifications of the RC protocol used in later post processing. The RC protocol is thus updated and sent to the post-processing/analysis module for later processing of the MR data. E.g., if the patient removes the mask after half of the experiment, the RC protocol and the signal model used by the analysis module would have to be shortened accordingly. The respiratory monitor module can also be realized as instructions contained on a computer-readable storage mediums, executed by the MR host computer  612  with communication to the sensors of the anaesthesia system, or it is integrated or attached to the anesthesia system, sending the monitoring results to the MR host computer, or it is part of the respiratory control unit with connections to both the MR and RC environment, etc. 
         [0075]      FIG. 7  is divided into two parts. The first part  700  illustrates correct timing  700  for synchronization of the magnetic resonance data and the respiratory challenge. The second part  702  illustrates incorrect timing between the analysis of the magnetic resonance imaging data and the timing of the respiratory challenge. In both halves  700 ,  702  there is a time line  704  which shows the intended timing for the respiratory challenge protocol. In this respiratory challenge protocol there is one minute air four minutes of carbogen gas and then two minutes of air is breathed by the subject. Time line  706  shows the actual respiratory challenge protocol performed with the correct timing  700  and time line  708  shows the actual respiratory challenge protocol performed when the timing was not synchronized. Time line  706  is identical with time line  704 . However time line  708  is not identical with time line  704 . 
         [0076]    In time line  708  the subject breathes initially air for two minutes instead of one minute. The effect of this is that the carbogen gas is breathed by the subject one minute later than was expected. Below the time lines are graphs which show the change in R2* the time line is given in seconds in both cases. In the first half of  FIG. 700  the box  712  indicates data points  712  that were used for performing the analysis. In the second half of the  FIG. 702  the graph the box  714  indicates the data which was used for the statistical analysis. The graph in the second half  702  shows two regions  716  where the timing is off. In the first half  700  the data is used to reconstruct a delta R2* response map  718  for a map of a tumor showing meningioma. R2* is the reciprocal of T2*. A delta R2* response map is a graph which shows the change in R2*. For the above mentioned reading protocol. Using the shifted timing the same image  720  is calculated using the incorrect timing  702 . A comparison of images  718  and  720  show that the contrast in image  718  is superior to that in  720 . 
         [0077]      FIG. 7  shows the effect of miscommunication/wrong synchronization of the RC and MR data analysis protocols on the tumor response map and the model (right column). The left column depicts the outcome using the correct settings. The response map is based on a statistical test that compares periods of baseline breathing with the last 2 min of the Carbogen challenge. Wrong synchronization of the respiratory challenge and the MR data analysis results in “darker” maps, since the response amplitude is underestimated as the test compares baseline data with the “wrong” data during Carbogen breathing. The model fit to the data fails due to wrong initialization of start and end points of the Carbogen challenge. 
         [0078]    While the invention has been illustrated and described in detail in the drawings and foregoing description, such illustration and description are to be considered illustrative or exemplary and not restrictive; the invention is not limited to the disclosed embodiments. 
         [0079]    Other variations to the disclosed embodiments can be understood and effected by those skilled in the art in practicing the claimed invention, from a study of the drawings, the disclosure, and the appended claims. In the claims, the word “comprising” does not exclude other elements or steps, and the indefinite article “a” or “an” does not exclude a plurality. A single processor or other unit may fulfill the functions of several items recited in the claims. The mere fact that certain measures are recited in mutually different dependent claims does not indicate that a combination of these measured cannot be used to advantage. A computer program may be stored/distributed on a suitable medium, such as an optical storage medium or a solid-state medium supplied together with or as part of other hardware, but may also be distributed in other forms, such as via the Internet or other wired or wireless telecommunication systems. Any reference signs in the claims should not be construed as limiting the scope. 
       LIST OF REFERENCE NUMERALS  
       [0080]      500  magnetic resonance imaging system 
         [0081]      502  magnet 
         [0082]      504  imaging volume 
         [0083]      506  subject 
         [0084]      508  subject support 
         [0085]      510  magnetic field gradient coil 
         [0086]      512  magnetic field gradient coil power supply 
         [0087]      514  radio frequency coil 
         [0088]      516  radio frequency transceiver 
         [0089]      518  mask 
         [0090]      520  inlet tube 
         [0091]      522  outlet tube 
         [0092]      524  anesthesia system 
         [0093]      526  inlet gas sensor 
         [0094]      528  outlet gas sensor 
         [0095]      530  computer system 
         [0096]      532  hardware interface 
         [0097]      534  processor 
         [0098]      536  user interface 
         [0099]      538  computer memory 
         [0100]      540  computer storage 
         [0101]      542  magnetic resonance imaging system control module 
         [0102]      544  anesthesia system control module 
         [0103]      546  respiratory challenge protocol algorithm 
         [0104]      548  image reconstruction module 
         [0105]      550  gas sequence modification module 
         [0106]      552  pulse sequence modification module 
         [0107]      554  pulse sequence 
         [0108]      556  gas sequence 
         [0109]      558  gas sensor data 
         [0110]      560  magnetic resonance data 
         [0111]      562  transverse plan relaxation time weighted magnetic resonance imaging image 
         [0112]      600  functional diagram 
         [0113]      602  anesthesia gases 
         [0114]      604  inhalation air 
         [0115]      606  communications link module 
         [0116]      608  anesthetist 
         [0117]      610  operator 
         [0118]      612  host computer 
         [0119]      614  clinical protocol 
         [0120]      616  results 
         [0121]      618  scan parameters 
         [0122]      620  scan control module 
         [0123]      622  control of magnetic resonance sequence 
         [0124]      624  magnetic resonance raw data 
         [0125]      626  reconstruction module 
         [0126]      628  reconstruction parameters 
         [0127]      630  magnetic resonance image 
         [0128]      632  post-processing and analysis module 
         [0129]      634  true respiratory challenge protocol 
         [0130]      636  feedback levels 
         [0131]      638  respirator monitor module 
         [0132]      640  ventilation response to respiratory challenge protocol 
         [0133]      642  challenge 
         [0134]      644  scan timing respiratory challenge protocol 
         [0135]      646  synchronization module 
         [0136]      648  respiratory challenge protocol 
         [0137]      650  respiratory challenge control module 
         [0138]      652  control commands 
         [0139]      700  correct timing 
         [0140]      702  incorrect timing 
         [0141]      704  intended respiratory challenge protocol 
         [0142]      706  actual respiratory challenge protocol 
         [0143]      708  actual respiratory challenge protocol 
         [0144]      712  box 
         [0145]      714  box 
         [0146]      716  region 
         [0147]      718  delta R2* map 
         [0148]      720  delta R2* map