# US 2014/0153806 A1 · Mr scan selection for pet attenuation correction

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- Number: US 2014/0153806 A1
- Document ID: US20140153806A1
- Status: Published application
- Kind: A1
- Application number: 14/091,372
- Filed: 2013-11-27
- Published: 2014-06-05
- Earliest claimed: 2012-12-04
- Assignees: Siemens Medical Solutions USA, Inc.; Siemens Aktiengesellschaft
- Inventors: Christopher Glielmi; Christian Geppert; David Faul; Matthias Fenchel
- Web page: https://patentgrep.com/patent/US20140153806A1

## CPC

- G01R 33/481: {MR combined with positron emission tomography [PET] or single photon emission computed tomography [SPECT]}
- A61B 5/0037: {Performing a preliminary scan, e.g. a prescan for identifying a region of interest}
- A61B 5/055: involving electronic [EMR] or nuclear [NMR] magnetic resonance, e.g. magnetic resonance imaging
- A61B 6/037: {Emission tomography}
- A61B 6/4417: {related to combined acquisition of different diagnostic modalities}
- A61B 6/5247: {combining images from an ionising-radiation diagnostic technique and a non-ionising radiation diagnostic technique, e.g. X-ray and ultrasound}
- A61B 6/5258: {involving detection or reduction of artifacts or noise}
- G06T 5/50: using two or more images, e.g. averaging or subtraction
- G06T 5/94: based on local image properties, e.g. for local contrast enhancement
- A61B 5/0035: {adapted for acquisition of images from more than one imaging mode, e.g. combining MRI and optical tomography}
- A61B 2576/00: Medical imaging apparatus involving image processing or analysis (A61B1/00009, A61B6/52 and A61B8/52 take precedence)
- G06T 2207/10088: Magnetic resonance imaging [MRI]
- G06T 2207/10104: Positron emission tomography [PET]
- G16H 30/40: for processing medical images, e.g. editing
- G01R: MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES (indicating correct tuning of resonant circuits H03J3/12)
- A61B: DIAGNOSIS; SURGERY; IDENTIFICATION (usefulness limited to only animals A61D)
- G06T: IMAGE DATA PROCESSING OR GENERATION, IN GENERAL
- G16H: HEALTHCARE INFORMATICS, i.e. INFORMATION AND COMMUNICATION TECHNOLOGY [ICT] SPECIALLY ADAPTED FOR THE HANDLING OR PROCESSING OF MEDICAL OR HEALTHCARE DATA

## Abstract

A method of attenuation correction for a positron emission tomography (PET) system includes obtaining PET scan data representative of a volume scanned by the PET system, obtaining a plurality of magnetic resonance (MR) scan data sets representative of the volume, each MR scan data set being acquired in a respective time period during acquisition of the PET scan data by the PET system, detecting motion of the volume that occurred during the acquisition of the PET scan data based on an assessment of the plurality of MR scan data sets, the PET scan data, or the plurality of MR scan data sets and the PET scan data, determining attenuation correction data from the plurality of MR scan data sets based on the detected motion for alignment of the attenuation correction data and the PET scan data, and correcting the PET scan data with the attenuation correction data.

## Claims

### Claim 1

A method of attenuation correction for a positron emission tomography (PET) system, the method comprising:
obtaining PET scan data representative of a volume scanned by the PET system;
obtaining a plurality of magnetic resonance (MR) scan data sets representative of the volume, each MR scan data set being acquired in a respective time period during acquisition of the PET scan data by the PET system;
detecting, with a processor, motion of the volume that occurred during the acquisition of the PET scan data based on an assessment of the plurality of MR scan data sets, the PET scan data, or the plurality of MR scan data sets and the PET scan data;
determining, with the processor, attenuation correction data from the plurality of MR scan data sets based on the detected motion for alignment of the attenuation correction data and the PET scan data; and
correcting the PET scan data with the attenuation correction data.

### Claim 2 (depends on 1)

The method of claim 1, wherein detecting the motion comprises:
calculating a similarity measurement between each pair of the plurality of MR scan data sets; and
comparing the respective calculated similarity measurements to identify a time period during which the motion occurred.

### Claim 3 (depends on 2)

The method of claim 2, wherein determining the attenuation correction data comprises selecting an MR scan data set of the plurality of MR scan data sets acquired outside of the identified time period.

### Claim 4 (depends on 2)

The method of claim 2, wherein determining the attenuation correction data comprises:
selecting a pair of MR scan data sets of the plurality of MR scan data sets acquired outside of the identified time period; and
interpolating between the pair of MR scan data sets to determine the attenuation correction data.

### Claim 5 (depends on 1)

The method of claim 1, wherein detecting the motion comprises calculating a similarity measurement for each MR scan data set of the plurality of MR scan data sets.

### Claim 6 (depends on 5)

The method of claim 5, wherein:
calculating the similarity measurement comprises calculating the similarity measurement for the respective MR scan data set relative to diagnostic MR scan data acquired during the acquisition of the PET scan data by the PET system; and
determining the attenuation correction data comprises selecting an MR scan data set of the plurality of MR scan data sets most aligned with the diagnostic MR scan data based on the calculated similarity measurements.

### Claim 7 (depends on 5)

The method of claim 5, wherein:
calculating the similarity measurement comprises calculating the similarity measurement for the respective MR scan data set relative to the PET scan data; and
determining the attenuation correction data comprises selecting an MR scan data set of the plurality of MR scan data sets most aligned with the PET scan data based on the calculated similarity measurements.

### Claim 8 (depends on 5)

The method of claim 5, wherein calculating the similarity measurement comprises computing a normalized mutual information (NMI) measurement.

### Claim 9 (depends on 1)

The method of claim 1, wherein detecting the motion comprises partitioning the PET scan data into a plurality of PET data bins.

### Claim 10 (depends on 9)

The method of claim 9, wherein:
detecting the motion comprises calculating, for each PET data bin, a similarity measurement based on the plurality of MR scan data sets; and
determining the attenuation correction data comprises selecting, for each PET data bin, an MR scan data set of the plurality of MR scan data sets based on the similarity measurement.

### Claim 11 (depends on 10)

The method of claim 10, wherein selecting the MR scan data set comprises selecting, for each PET data bin, the MR scan data set of the plurality of MR scan data sets most aligned with the respective PET data bin based on the similarity measurement.

### Claim 12 (depends on 9)

The method of claim 9, wherein detecting the motion further comprises:
determining a center of gravity of each PET data bin of a plurality of PET data bins into which the PET scan data is partitioned; and
comparing the respective centers of gravity to identify a time period during which the motion occurred.

### Claim 13 (depends on 12)

The method of claim 12, wherein determining the attenuation correction data comprises selecting an MR scan data set of the plurality of MR scan data sets acquired outside of the identified time period.

### Claim 14 (depends on 1)

The method of claim 1, wherein each MR scan data set of the plurality of MR scan data sets is acquired via an MR scan sequence configured to support the attenuation correction of the PET scan data.

### Claim 15 (depends on 1)

The method of claim 1, further comprising initiating an alert to an operator of the PET system regarding the detected motion.

### Claim 16

A computer program product for attenuation correction for a positron emission tomography (PET) system, the computer program product comprising one or more computer-readable storage media having stored thereon computer-executable instructions for execution by one or more processors of a computing system to cause the computing system to perform operations, the operations comprising:
obtaining PET scan data representative of a volume scanned by the PET system;
obtaining magnetic resonance (MR) diagnostic scan data of the volume, the diagnostic MR scan data being acquired during acquisition of the PET scan data by the PET system;
obtaining a plurality of MR attenuation correction (MR-AC) scan data sets representative of the volume, each MR-AC scan data set being acquired during the acquisition of the PET scan data by the PET system when the diagnostic MR scan data is not being acquired;
detecting motion of the volume that occurred during the acquisition of the PET scan data based on a spatial alignment assessment of the plurality of MR-AC scan data sets, the PET scan data, the diagnostic MR scan data, or combinations thereof;
determining attenuation correction data from the plurality of MR-AC scan data sets based on the detected motion for alignment of the attenuation correction data and the PET scan data; and
correcting the PET scan data with the attenuation correction data.

### Claim 17 (depends on 16)

The computer program product of claim 16, wherein detecting the motion comprises:
calculating a similarity measurement for each MR scan data set of the plurality of MR scan data sets; and
comparing the respective calculated similarity measurements to identify a time period during which the motion occurred.

### Claim 18 (depends on 17)

The computer program product of claim 17, wherein determining the attenuation correction data comprises selecting an MR scan data set of the plurality of MR scan data sets acquired outside of the identified time period.

### Claim 19

A data processing system for attenuation correction for a positron emission tomography (PET) system, the data processing system comprising:
a data store in which PET scan data representative of a volume scanned by the PET system is stored, and in which a plurality of magnetic resonance (MR) attenuation correction (MR-AC) scan data sets representative of the volume are stored, each MR-AC scan data set being acquired during acquisition of the PET scan data by the PET system when diagnostic MR scan data is not being acquired; and
a processor coupled to the data store and configured to detect motion of the volume that occurred during the acquisition of the PET scan data based on a spatial alignment assessment of the plurality of MR scan data sets, the PET scan data, or the plurality of MR scan data sets and the PET scan data;
wherein the processor is further configured to determine attenuation correction data from the plurality of MR scan data sets based on the detected motion for alignment of the attenuation correction data and the PET scan data; and
wherein the processor is further configured to correct the PET scan data with the attenuation correction data.

### Claim 20 (depends on 19)

The data processing system of claim 19, wherein the processor is further configured to calculate a similarity measurement for each MR scan data set of the plurality of MR scan data sets.