Patent Publication Number: US-2015087964-A1

Title: Method for optimizing a medical imaging acquisition

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a method for optimizing an imaging acquisition of an object under examination by operation of a medical imaging apparatus, as well as a corresponding optimization unit and a medical optimization system and a non-transitory data storage medium encoded with programming instructions, that enable the execution of a method of this type. 
     2. Description of the Prior Art 
     Optimization of imaging acquisitions, in particular a temporal optimization of data acquisitions of this type, is a widespread field of activity in clinical medical applications. 
     In the daily operations of a medical clinic, an efficient and targeted optimization of imaging acquisitions can present an extremely complex problem, particularly if multiple boundary conditions are to be taken into account. 
     SUMMARY OF THE INVENTION 
     An object of the invention is to provide a method that facilitates optimization of a medical imaging acquisition, and with which a determination of the time required for the image data acquisition, dependent on various boundary conditions, is possible in a simple manner. 
     The above object is achieved in accordance with the invention by a method for optimizing an imaging acquisition of an object under examination by operation of a medical imaging apparatus, that includes the following steps. 
     A first time period is determined in the control computer of the imaging apparatus, within which a calibration process is executed for at least one adjustment of the medical imaging apparatus. 
     A second time period is determined in the control computer, within which a breathing process is executed for at least one breathing command of an image data acquisition protocol, wherein the breathing process is executed at least in part at the same time as the calibration process. 
     A point in time for an initiation of the imaging acquisition is determined in the control computer, such that the calibration process and the breathing process both have been completed at this point in time. 
     A medical imaging apparatus is a device, preferably an electronic and/or data technology device, for acquiring, processing, evaluating and/or storing image information in the form of image data. In order to acquire the image data, acoustic methods such as ultrasound (US), emission methods such as emission computed tomography (ECT) and positron emission tomography (PET), optical methods, radiological methods such as X-ray tomography and computed tomography (CT), are used, but the acquisition can also occur by magnetic resonance tomography (MR or MRT), or by combined methods. The medical imaging apparatus can deliver 2-dimensional (2D) or multi-dimensional, such as 3-dimensional (3D) or 4-dimensional (4D) image data, which are stored and/or processed in various formats. The medical imaging apparatus can be used in a diagnosis, for example in a medical diagnosis. 
     First, a first time period is automatically determined, within which a calibration process for at least one adjustment of the medical imaging apparatus is executed. As used herein, such an adjustment means an adjustment of at least one component of the imaging apparatus prior to the imaging acquisition. For example, for a magnetic resonance acquisition using a magnetic resonance apparatus, the calibration process may include a receiver calibration, a frequency calibration and/or a transmitter calibration. The receiver calibration includes, e.g. an adjustment of a receiver dynamic for an analog-digital converter; the frequency calibration includes, e.g. an adjustment of the frequency of a radio frequency system to the resonance frequency of the nuclear spins for the generation of magnetic resonance signals; and the transmitter calibration includes, e.g. an adjustment of a transmission power for the radio frequency pulses. During the at least one adjustment of the calibration process, parameters can also be determined that are dependent on the object under examination. 
     The first time period, within which the calibration process is executed, is either predetermined, or can be estimated in accordance with the invention. However determined, the first time period must ensure that after completion of the first time period, the calibration process is also completed. 
     A breathing process for at least one breathing command of an image data acquisition protocol is executed within the second time period that is determined. Breathing commands of this type are used in many imaging acquisitions, in which movements in an interior of the object under examination, such as the motion of a patient&#39;s heart, cause blurring in the image that is reconstructed from the imaging data acquisition. Breathing commands normally include time periods in which the patient inhales and/or time periods in which the patient holds his or her breath, and/or time periods in which the patient exhales. The breathing process thus includes at least one breathing command that is communicated to the patient. Preferably, the respiratory state of the patient achieved as a result of the breathing command should be maintained during the imaging acquisition. 
     With automatic breathing commands, the second time period is normally known, because the breathing commands comply with a previously established acquisition protocol. If this second time period is not known, then it can be measured in advance. 
     According to the invention, the breathing process occurs at least in part at the same time as the calibration process. It is thereby ensured that it is not first necessary to wait until the calibration process is finished, before the breathing process can be started, or vice versa. 
     The point in time for starting the imaging acquisition is then determined such that at this point in time, the calibration process and the breathing process have been completed. 
     The invention makes use of the at least partial simultaneity (overlap) of the calibration process and the breathing process for a temporal optimization of the initiation of the imaging acquisition. This results in shorter waiting periods, an increased patient turnover, and a more efficient workflow. 
     In an embodiment, a completion point for the first time period corresponds to a completion point for the second time period. The point in time for the initiation of the imaging acquisition thus is determined such that at this point, the calibration process and the breathing process are completed at the same time. This results in a further temporal optimization for the initiation of the imaging acquisition, and thus to a shortening of the actual recording time as well. 
     In a further embodiment, at least one of a time period between the completion point for the first time period and the initiation of the imaging acquisition, and a time period between the completion point for the second time period and the initiation of the imaging acquisition, is minimized. The waiting period between the completion of the calibration process and/or the completion of the breathing process, and the initiation of the actual creation of an image is thus further reduced. In an embodiment, the imaging acquisition is initiated immediately after the completion point for the first time period and/or the completion point for the second time period. 
     In a preferred embodiment, with execution of at least two adjustments, the adjustments are executed in a sequence, such that adjustments with a higher noise level are carried out initially, and adjustments with a lower noise level are carried out at the end of the calibration process. At least one first adjustment thus is allocated to a first noise level, and a second adjustment is allocated to a second noise level, with the first noise level being higher than the second noise level. Such a sorting of the adjustments according to a noise volume within the calibration process ensures, in combination with the at least partial simultaneity of the calibration process and the breathing process, that background noise, resulting from the calibration process, have as little acoustic affect as possible on the breathing commands for the breathing process. 
     The present invention also encompasses an optimization unit for optimizing an imaging acquisition of an object under examination by means of a medical imaging apparatus is also provided. 
     The optimization unit includes a processor that is designed to execute the following steps: determination of a first time period, within which a calibration process is executed by the processor, for at least one adjustment of the medical imaging apparatus; determination of a second time period, within which a breathing process for at least one breathing command of an image data acquisition protocol is executed by the processor; wherein the breathing process is executed at least in part at the same time as the calibration process; and determination of a point in time for an initiation of the imaging acquisition by the processor, such that the calibration process and the breathing process have been completed at this point in time. 
     The invention also encompasses a medical optimization apparatus that includes such an optimization unit and at least one medical image data acquisition unit. 
     The present invention also encompasses a non-transitory, computer-readable data storage medium encoded with programming instructions that, when the storage medium is loaded into a computerized processor of an image acquisition unit, causes the processor to function as an optimization unit as described above, in order to implement one or more of the above-described embodiments of the method according to the invention. The programming instructions may require additional items, such as libraries or other auxiliary functions, in order to cause the embodiments of the method to be implemented. 
     The electronically readable storage medium may be a DVD, a magnetic tape, or a USB stick, on which electronically readable control information, in particular software, is stored. 
     Advantages and embodiments of the optimization unit according to the invention, the medical optimization apparatus according to the invention, and the electronically readable storage medium according to the invention correspond substantially to the advantages and embodiments of the method according to the invention, as described above. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  schematically illustrates a medical optimization apparatus according to the invention. 
         FIG. 2  is a flowchart of an embodiment of the method according to the invention. 
         FIG. 3  shows an example of an optimization of an imaging acquisition in accordance with the invention. 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       FIG. 1  shows a medical optimization apparatus  104  according to the invention. The medical optimization system  104  has an optimization unit  102  and a medical image data acquisition unit  101 , is equipped for operation in order to acquire medical image data from an object under examination. 
     The optimization unit  102  further has a processor  103 . The processor  103  itself can be embodied in the medical image data acquisition unit  101 . 
     The medical image data acquisition unit  101  is designed here as a magnetic resonance scanner. Alternatively, the medical image data acquisition unit  101  can be a combined magnetic resonance-positron emission tomography apparatus, or other medical imaging apparatuses  101  that appear appropriate to those skilled in the art. 
       FIG. 2  shows a flowchart for an embodiment of the method according to the invention. The method includes the steps  201 - 208 . In the following description of the steps  201 - 208 , components are referenced as we show in  FIGS. 1 and 3 . 
     The steps  201 - 208  are executed by the evaluation unit  103  of the medical optimization system  104 . 
     A first step  201  indicates the start of an optimization of an imaging acquisition  306  of an object under examination using the medical image data acquisition unit  101 . 
     A determination of a first time period  307 , within which the one calibration process for at least one adjustment  301 ,  302 ,  303 ,  304  of the medical image data acquisition unit  101  is executed, occurs in step  202 . Such an adjustment means an adjustment of at least one component prior to the imaging acquisition  306 . In the example of a magnetic resonance acquisition with a magnetic resonance apparatus, the calibration process can involve a receiver calibration, a frequency calibration and/or a transmitter calibration. The first time period  307 , within which this calibration process is executed, is either known, because it is automatically provided, for example, or can be estimated according to the invention, because it is manually determined, for example. It is thus ensured that after the first time period  307  is finished, the calibration process is also complete. 
     With an execution of at least two adjustments  301 ,  302 ,  303 ,  304  in step  203 , the adjustments  301 ,  302 ,  303 ,  304  are executed in a sequence such that adjustments  301 ,  302 ,  303 ,  304  having a higher noise level are executed at the start, and adjustments  301 ,  302 ,  303 ,  304  having a lower noise level are executed at the end of the calibration process. The adjustments  301 ,  302 ,  303 ,  304  are thus sorted according to the level of noise produced thereby within the calibration process. This step is optional and need not necessarily be executed. 
     A determination of a second time period  308 , within which a breathing process for at least one breathing command  305  of a recording protocol is executed, occurs in step  204 , wherein the breathing process is executed at least in part at the same time as the calibration process. Breathing commands  305  of this type are used with many imaging acquisitions  306 , in which movements, such as a cardiac motion of a patient, for example, in an interior of the object under examination, cause a blurring in an image of the imaging acquisition  306 . With automatic breathing commands  305 , the second time period  308  is normally known, because the breathing commands  305  comply with a previously defined recording protocol. If this second time period  308  is not known, then it can be measured in advance. 
     In step  205  the completion point  310  of the first time period  307  corresponds to a completion point  311  of the second time period  308 . As a result, the point in time  309  for the initiation of the imaging acquisition can be determined such that at this point in time  309 , the calibration process and the breathing process are completed at the same time. This step is optional, and must not necessarily be executed. 
     Step  206  includes the determination of a point in time  309  for an initiation of the imaging acquisition  306 , such that at this point in time  309 , the calibration process and the breathing process have been completed. The at least partial simultaneity of the calibration process and the breathing process leads to a temporal optimization of the initiation  309  of the imaging acquisition  306 . 
     A minimization of a time period  313  between the completion point  310  of the first time period  307  and the initiation of the imaging acquisition  306 , and/or a time period  313  between the completion point  311  of the second time period  308  and the initiation of the imaging acquisition  306 , occurs during a step  207 . By this means, the waiting time between the end of the calibration process and/or the end of the breathing process and the initiation of the actual creation of an image, thus the point in time  309  for the initiation of the imaging acquisition  306 , is further reduced. Preferably, the imaging acquisition  306  is initiated immediately after the completion point  310  of the first time period  307  and/or the completion point  311  of the second time period  308 , and thus, the completion point  310  of the first time period  307  and the completion point  311  of the second time period correspond to the initiation of the imaging acquisition  306 . 
     A last step  214  indicates the completion of the optimization of an imaging acquisition  306  of an object under examination by the medical image data acquisition unit  101 . 
       FIG. 3  shows an example of an optimization of an imaging acquisition  306 . First, a first time period  307 , within which a calibration process for four adjustments  301 ,  302 ,  303 ,  304  of the medical image data acquisition unit  101  is executed, is determined in step  202 . The reference symbol  312  represents a time axis. The adjustments  301 ,  302 ,  303 ,  304  of the calibration process comprise, in this case for a magnetic resonance acquisition, a receiver calibration, a frequency calibration, or a transmitter calibration. The receiver calibration comprises, e.g. an adjustment of a receiver dynamic for an analog-digital converter, the frequency calibration comprises, e.g. an adjustment of a frequency for a radio frequency system to a resonance frequency of a magnetic dipole field of the magnetic resonance apparatus, and the transmitter calibration comprises, e.g. an adjustment of a transmission power for radio frequency pulses. During the at least one adjustment  301 ,  302 ,  303 ,  304  of the calibration process, parameters can also be determined, which are dependent on the object under examination. 
     In addition, the four adjustments  301 ,  302 ,  303 ,  304  are sorted according to a noise volume within the calibration process, as is the case in step  203 . Adjustment  301  represents the adjustment with the highest noise level, and adjustment  304  represents the adjustment with the lowest noise level. Background noises resulting from the calibration process thus affect the breathing command  305  as little as possible. 
     Analogously to step  204 , a determination of a second time period  308  takes place, within which a breathing process for at least one breathing command  305  of an image data acquisition protocol is executed, wherein the breathing process is executed at least in part at the same time as the calibration process. Breathing commands  305  normally include time periods in which the patient inhales, and/or time periods in which the patient does not breath, and/or time periods in which the patient exhales; the breathing process comprises at least one breathing command  305 . Preferably, the respiratory state of the patient obtained with the breathing command  305  should be maintained during the imaging acquisition  306 . With automatic breathing commands  305 , the second time period  308  is normally known, because the breathing command  305  complies with a previously established acquisition protocol. If this second time period  308  is not known, it can be measured in advance. 
     A point in time  309  for an initiation of the imaging acquisition  306  is then determined in step  206 , such that at this point in time  309 , the calibration process and the breathing process have been completed. In the illustrated example  307 , a completion point  310  of the first time period  307 , a completion point  311  of the second time period  308 , and a time period  313  between these completion points  307 ,  308  and the initiation of the imaging acquisition  306  are minimized. 
     In an embodiment, a time period between the completion point of the first time period and the initiation of the imaging acquisition, and/or a time period between the completion point of the second time period and the initiation of the imaging acquisition, is minimized, and with an execution of at least two adjustments, the adjustments are executed in a sequence, such that adjustments with a higher noise level are executed at the start of the calibration process, and adjustments with a lower noise level are executed at the end of the calibration process. 
     Although modifications and changes may be suggested by those skilled in the art, it is the intention of the inventor to embody within the patent warranted hereon all changes and modifications as reasonably and properly come within the scope of her contribution to the art.