This Section describes Positron Emission Tomography Series and Image Modules. These Modules contain Attributes that are specific to Positron Emission Tomography images.
Table C.8-60 specifies the Attributes of the PET Series Module, which describe a PET Series.
Table C.8-60. PET Series Module Attributes
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Date the Series started. See Section C.8.9.1.1.2 for specialization. |
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Time the Series started. See Section C.8.9.1.1.2 for specialization. |
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Pixel value units. See Section C.8.9.1.1.3 for Defined Terms. |
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Type of Standardized Uptake Value (SUV). Enumerated Values: If absent, and the Units (0054,1001) are GML, then the type of SUV shall be assumed to be BW. |
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The primary source of counts. The primary source leads to the underlying image Units (0054,1001), as opposed to secondary sources that are used during reconstruction correction. |
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A multi-valued indicator of the type of Series. See Section C.8.9.1.1.4 for explanation. |
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Method for projecting volumetric data onto planar projection. Required if Series Type (0054,1000), Value 2 is REPROJECTION. |
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The maximum number of R-R Intervals that may exist in this Series. Required if Series Type (0054,1000), Value 1 is GATED. |
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The maximum number of Time Slots that may exist in this Series. Required if Series Type (0054,1000), Value 1 is GATED. |
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The maximum number of Time Slices that may exist in this Series. Required if Series Type (0054,1000), Value 1 is DYNAMIC. |
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One or more values that indicate which, if any, corrections have been applied to the images in this Series. |
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A textual description of the attenuation correction processing. e.g., measured vs. calculated, transmission source type (ring, line, point), assumed patient geometry (polygon, ellipse, segmented, attenuation coefficient, skull thickness), post-injection transmission, smoothing. |
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A textual description of the scatter correction processing. e.g., convolution-subtraction, dual energy window, model-based, use of attenuation data. |
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The real-world event to which images in this Series were decay corrected. See Section C.8.9.1.1.5 for explanation. |
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Diameter, in mm, of the region within which the data was used in creating the reconstruction of the image. Data may exist outside this region and portions of the patient may exist outside this region. The diameter defines a circular region that is entirely contained within the encoded Pixel Data (7FE0,0010), unless the encoded image has been cropped after reconstruction. |
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Textual description of the convolution kernel(s) used to reconstruct the data (e.g., name, cutoff, radial/axial/angular, mathematical form, DC handling). |
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Textual description of reconstruction processing, e.g., 2D filtered backprojection, 2D iterative, 3D PROMIS, 3D FAVOR, 3D iterative. |
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Textual description of which detector lines of response were used, mashed, or otherwise processed during tomographic reconstruction. |
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Description of how the data collection was started. Defined Terms: See Section C.8.9.1.1.6 for explanation. |
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Count density, change in count density, or physiological triggers causing data collection to start. |
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Description of how the data collection for the Series was stopped. Defined Terms: See Section C.8.4.9.1.3 for explanation. |
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Number of counts, count density, change in count density, or physiological triggers causing the termination. |
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Dimensions of the field of view, in mm. Transverse detector diameter followed by axial width. |
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Angle of tilt in degrees of the gantry. See Section C.8.9.1.1.7 for explanation. |
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Angle of slew in degrees of the gantry. Positive slew is moving the gantry on the patient's left toward the patient's superior, when the patient is supine. |
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Number of adjacent axial lines of response mashed together. See Section C.8.9.1.1.8 for explanation. |
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Number of adjacent transverse lines of response mashed together. See Section C.8.9.1.1.9 for explanation. |
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Size of an individual detector element, in mm. Transverse dimension followed by axial dimension. For a discrete crystal, this is the crystal size. For a continuous detector, this is the pixel bin size. |
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The width of the coincidence timing window, in nsec. The maximum time difference accepted between two single events. |
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Sequence of Items that describes the energy windows used for this Series. One or more Items are permitted in this Sequence. See Section C.8.9.1.1.10 for explanation. |
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Array defining the type of additional counts accumulated during acquisition. |
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Note
The formulas for the determination of SUVbw, SUVbsa, SUVlbm (James) and SUVibw are defined in Sugawara et al. Reevaluation of the Standardized Uptake Value for FDG: Variations with Body Weight and Methods for Correction. Radiology, 1999 at http://radiology.rsna.org/content/213/2/521.
Unfortunately, Sugawara used a parameter of 120 rather than 128 for males, propagating an error in Morgan DJ, Bray KM. Lean Body Mass as a Predictor of Drug Dosage: Implications for Drug Therapy. Clinical Pharmacokinetics. 1994;26(4):292–307, which misquoted the original LBM definition that used 128 in James WPT, Waterlow JC. Research on Obesity: A Report of the DHSS/MRC Group. London: Her Majesty’s Stationery Office; 1976. Implementations differ in whether they have used 120 or 128 when the DICOM Defined Term is LBM. See Kelly M. SUV: Advancing Comparability and Accuracy. Siemens; 2009. Available from: http://www.mpcphysics.com/documents/SUV_Whitepaper_Final_11.17.09_59807428_2.pdf.
The Janmahasatian LBM formula is defined in Janmahasatian et al. Quantification of Lean Bodyweight. Clin Pharmacokinet. 2005 Oct 1;44(10):1051–65. at http://dx.doi.org/10.2165/00003088-200544100-00004 and its role in SUVlbm(Janma) calculation is discussed in Tahari et al. Optimum Lean Body Formulation for Correction of Standardized Uptake Value in PET Imaging. Journal of Nuclear Medicine. 2014 Sep 1;55(9):1481–4. at http://jnm.snmjournals.org/content/55/9/1481. See also CID 85 “SUV Unit” in PS3.16 .
Note
The meaning of a General Series in DICOM is determined by the Attributes in the General Series Module and by the Source Entities (Patient, Study, Frame of Reference, Equipment) that originate the Series. The Source Entities are the single-valued entities of the 1->n relationship, where the Series is the multi-valued entity. Therefore, a Series is a group of images that: are from the same patient and Study; are from the same Equipment; and, are from the same spatial Frame of Reference.
The PET Image IOD further refines a PET Series IE by the Attributes in the PET Series Module, the PET Isotope Module, the PET Multi-gated Acquisition Module and the Acquisition Context Module. These are the Attributes that shall not change from Image to Image. Therefore, in addition to the criteria above for a General Series (same patient, Study, Frame of Reference, equipment), the Attributes in the PET Series IE define a PET Series as a group of images that: are from the same temporal Frame of Reference; have the same fundamental meaning (e.g., same units: either activity density, metabolism, or attenuation); are derived from the same activity source (emission or transmission); are from the same isotope and radiopharmaceutical; were derived from the same reconstruction processing; and, originated from the same acquisition setup and parameters, including the patient conditions (cardiac stress or rest) if applicable.
C.8.9.1.1.1 Specialization of Image Plane Module and Image Pixel Module Attributes
For PET Series, the following Image Pixel Module Attributes shall not vary from Image to Image:
For PET Series, the following Image Plane Module Attributes shall not vary from Image to Image:
For PET Series where Series Type (0054,1000), Value 2 is IMAGE, the following Image Plane Module Attributes shall not vary from Image to Image:
Note
This means that for a Series Type (0054,1000) Value 2 of IMAGE, all images in the PET Series lie on parallel planes. The images, however, may have non-uniform spacing along the normals to the planes.
For PET Series where Series Type (0054,1000), Value 2 is REPROJECTION, Image Orientation (0020,0037) shall vary such that the images rotate about a single axis. Geometrically, the normal to each image plane is defined by the cross product of its row and column vectors. Each reprojection image has one Center Normal that passes through the center of the image. Reprojection images within a PET Series shall have their Center Normals be co-planar and pass through a single point.
For PET Series, Series Date (0008,0021) and Series Time (0008,0031) are specified to be Type 1. Series Date (0008,0021) and Series Time (0008,0031) are used as the reference time for all PET Image Attributes that are temporally related, including activity measurements. Series Date (0008,0021) and Series Time (0008,0031) are not tied to any real-world event (e.g., acquisition start, radiopharmaceutical administration) and their real-world meaning are implementation dependent.
The units of the pixel values obtained after conversion from the stored pixel values (SV) (Pixel Data (7FE0,0010)) to pixel value units (U), as defined by Rescale Intercept (0028,1052) and Rescale Slope (0028,1053).
Defined Terms:
- CNTS
- NONE
- CM2
- CM2ML
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centimeter**2/milliliter (cm2/ml, UCUM, "Centimeter**2/milliliter")
- PCNT
- CPS
- BQML
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Becquerels/milliliter (Bq/ml, UCUM, "Becquerels/milliliter")
- MGMINML
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milligram/minute/milliliter (mg/min/ml, UCUM, "Milligrams/minute/milliliter")
- UMOLMINML
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micromole/minute/milliliter (umol/min/ml, UCUM, "Micromole/minute/milliliter")
- MLMING
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milliliter/minute/gram (ml/min/g, UCUM, "Milliliter/minute/gram")
- MLG
- 1CM
- UMOLML
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micromole/milliliter (umol/ml, UCUM, "Micromole/milliliter")
- PROPCNTS
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proportional to counts ({propcounts}, UCUM, "Proportional to counts")
- PROPCPS
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proportional to counts/sec ({propcounts}/s, UCUM, "Proportional to counts per second")
- MLMINML
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milliliter/minute/milliliter (ml/min/ml, UCUM, "Milliliter/minute/milliliter")
- MLML
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milliliter/milliliter (ml/ml, UCUM, "Milliliter/milliliter")
- GML
- STDDEV
Note
The majority of these defined terms are equivalent to CID 84 “PET Unit”. Those that are used for SUV are not qualified by the type of SUV, which is encoded separately as SUV Type (0054,1006).
Series Type (0054,1000) Value 1 is used to identify the spatial location and temporal nature of the images within a PET Series.
Enumerated Values for Value 1:
- STATIC
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a group of images at varying spatial locations at the same time
- DYNAMIC
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a group of images at a set of spatial locations (e.g., slices) at varying time slices, with all spatial locations acquired at all time slices
- GATED
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a group of images at the same spatial location, same starting and ending time, but acquired in different time slots of (possibly) different R-R intervals
- WHOLE BODY
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same as STATIC, except covering multiple transverse fields of view (and therefore acquired at a different time)
Note
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Using this definition and the comments in Section C.8.9.1.1.1, here are some examples of PET Series and the encoding of Series Type (0054,1000) Value 1.
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Static acquisition: a group of n transverse images at varying superior<->inferior locations, all acquired between the same starting and ending time. Series Type = STATIC.
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Dynamic acquisition: a group of n*m transverse images at n superior<->inferior locations, acquired with m different starting and ending times. Series Type = DYNAMIC.
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Gated acquisition: a group of n*m*p transverse images at n superior<->inferior locations, all acquired between the same starting and ending time, acquired in m different R-R Intervals (as determined by Low R-R Value (0018,1081) and High R-R Value (0018,1082)), and acquired in p time slots of a given R-R Interval (as determined by Trigger Time (0054,1000)). Series Type = GATED.
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Whole body acquisition: a group of n transverse images at varying superior<->inferior locations covering a significant fraction of the entire body. Series Type = WHOLE BODY.
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Multiple transverse fields of view: a group of n transverse images at varying superior<->inferior locations. Series Type = WHOLE BODY.
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Interleaved: group of 2*n transverse images acquired at overlapped axial fields of view (AFOVs) to increase transverse sampling. Series Type = WHOLE BODY.
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Sagittal (Coronal, Oblique): sagittal (coronal, oblique) re-sliced images derived by reformatting transverse images. The Series Type is STATIC, DYNAMIC, GATED, or WHOLE BODY depending on source Series Type.
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Arithmetic: images derived by an arithmetic operation on operand images. The Series Type is STATIC, DYNAMIC, GATED, or WHOLE BODY depending on source Series Type.
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Metabolic: images derived by a metabolic model. The Series Type is STATIC, DYNAMIC, GATED, or WHOLE BODY depending on source Series Type.
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Using this definition, here are some images that are not stored in the same PET Series:
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Two images from the same scan that were reconstructed differently.
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Emission and transmission images for the same Patient and Study, even if acquired simultaneously (because emission and transmission images have different reconstruction processing).
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Two images of same patient, one after NH3 injection and one after FDG injection.
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Two images: an original image created from reconstructed scan data and its derived image based on a metabolic model.
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Series Type (0054,1000) Value 2 is used to identify the volumetric meaning of the images within a PET Series.
Decay Correction (0054,1102) is the real-world event to which images in this Series were decay corrected. If decay correction is applied, all images in the Series shall be decay corrected to the same time.
Defined Terms:
The time to which images have been decay corrected can be derived from Decay Factor (0054,1321), Frame Reference Time (0054,1300), Radionuclide Half Life (0018,1075), Series Date (0008,0021) and Series Time (0008,0031).
Acquisition Start Condition (0018,0073) is the method of starting acquisition data collection.
Defined Terms:
Gantry/Detector Tilt (0018,1120) for PET Image data is the angle in degrees of the gantry relative to the patient's major (Head to Feet) axis (or the table supporting the patient). Positive tilt is moving the top of the gantry towards the patient's feet.
Axial Mash (0054,1201) is multi-valued and is defined as the number of unique axial Lines of Response (LOR) that were mashed together (center of the axial field of view only). Value 1 is the number of LORs mashed for an odd slice. Value 2 is the number of LORs mashed for an even slice. For discrete crystal scanners, each unique LOR corresponds to a pair of crystals. For continuous detectors whose bin size is variable, the number of LORs mashed is determined by the actual bin size divided by the Detector Element Size (0054,1203), Value 2. The value of Axial Mash (0054,1201) is the same regardless of whether the mashing was done during acquisition or reconstruction.
Transverse Mash (0054,1202) is defined as the number of unique transverse Lines of Response (LOR) that were mashed together. For discrete crystal scanners, each unique LOR corresponds to a pair of crystals. For continuous detectors whose bin size is variable, the number of LORs mashed is determined by the actual bin size divided by the Detector Element Size (0054,1203), Value 1. The value of Transverse Mash (0054,1202) is the same regardless of whether the mashing was done during acquisition or reconstruction.
Multiple energy windows are allowed in order to allow coincidence events based on additional Energy Windows (e.g., Compton events scattered in the detector). All energy windows are assumed to contribute to all images in the PET Series.
Figure C.8.9.1.1.11-1a and Figure C.8.9.1.1.11-1b show the temporal relationships of images within a PET Series.
