C.8.16 Common CT and MR Descriptions
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### C.8.16 Common CT and MR Descriptions

This section contains descriptions of Macros and Attributes used in Modules and Functional Group Macros that are common to the Enhanced CT Image, Enhanced MR Images and MR Spectroscopy IODs.

#### C.8.16.1 Image Type and Frame Type

Image Type (0008,0008) and associated Image Type related attributes provide a high level description of a multi-frame SOP Instance. These attributes describe properties that provide key summary information to users of the SOP Instance. Image Type (0008,0008) contains the highest level summary of what is in the SOP Instance.

Frame Type (0008,9007) mirrors the corresponding Image Type attribute and applies to the frame level rather than to the image level.

If more than one value is used by the set of frames for a given Frame Type (0008,9007) attribute value or associated attribute value then the corresponding value of Image Type (0008,0008) or associated attribute shall contain a value of MIXED. This indicates that a mixed set of values exists within the multi-frame SOP Instance.

The value MIXED shall only be used in Image Type (0008,0008) when the corresponding values for the individual frames are not equal. When a value of an attribute is equal for all frames, the same value shall be used for the corresponding value of Image Type (0008,0008). Values 2 and 3 of Image Type (0008,0008) are an exception to the rule for MIXED: Values 2 and 3 may never have the value of MIXED as described in Section C.8.16.1.2 and Section C.8.16.1.3.

Image Type (0008,0008) and Frame Type (0008,9007) shall consist of four non-zero length values.

##### C.8.16.1.1 Pixel Data Characteristics

Value 1 of Image Type (0008,0008) and Frame Type (0008,9007) shall use one of the following Enumerated Values from Table C.8-127.

Value 1 of Image Type (0008,0008) and Value 1 of Frame Type (0008,9007) shall not be zero length.

Table C.8-127. Image Type and Frame Type Value 1

Enumerated Value Name | Enumerated Value Description
--- | ---
ORIGINAL | An image or frame is original if its pixel data was directly reconstructed from the original data that is obtained from the sensors of the imaging equipment, Image Type (0008,0008) Value 4 is NONE, and Volume Based Calculation Technique (0008,9207) is NONE. ### Note For MR, original data is data directly reconstructed from k-space data. For CT, original frames are those directly reconstructed from projection data.
DERIVED | An image or frame is derived if its pixel data was calculated from original or other derived pixel data (i.e., it is not original).
MIXED | Used only as a value in Image Type (0008,0008) if frames within the SOP Instance contain different values for Value 1 in their Frame Type (0008,9007).

##### C.8.16.1.2 Patient Examination Characteristics

Value 2 for Image Type (0008,0008) and Frame Type (0008,9007) follows the standard definition and shall have the following Enumerated Value from Table C.8-128.

Value 2 of Image Type (0008,0008) and Value 2 of Frame Type (0008,9007) shall not be zero length.

Table C.8-128. Image Type and Frame Type Value 2

Enumerated Value Name | Enumerated Value Description
--- | ---
PRIMARY | See Section C.7.6.1.1.2

##### C.8.16.1.3 Image Flavor

Value 3 is an overall representation of the image type. This value may be a summary of several other attributes or a duplication of one of the other attributes to indicate the most important aspect of this image. Value 3 Image Flavor is to be used with Value 4 Derived Pixel Contrast to indicate the nature of the image set.

### Note

For example Value 3 = DIFFUSION together with Value 4 = NONE indicates that the image set was originally collected for DIFFUSION.

If Value 3 = DIFFUSION together with Value 4 = DIFFUSION this indicates that the object contains DIFFUSION weighted post processed images.

Value 3 of Image Type (0008,0008) shall not be zero length.

Value 3 of Frame Type (0008,9007) may have the same value as found in Value 3 of Image Type (0008,0008), or may have a different value or may be of zero length.

The attribute value may not be MIXED as this value needs to be a summary of the primary purpose of the images, whether the frames have the same value or not.

Table C.8-129 specifies the Defined Terms for Value 3 for Image Type (0008,0008) and Frame Type (0008,9007) that are common to CT and MR. Additional Defined Terms are defined in the modality-specific Module and Macro definitions.

Table C.8-129. Image Type and Frame Type Value 3 Common

Defined Term Name | Defined Term Description
--- | ---
ANGIO | Collected for the purpose of angiography
CARDIAC | Images of the heart
CARDIAC_GATED | Cardiac gated images, other than of the heart
CARDRESP_GATED | Cardiac and respiratory gated images
DYNAMIC | An image in which the same anatomical volume is imaged at multiple times in order to capture images of a non-cyclic, time varying event. For example, imaging of the uptake of a tracer or contrast in a specific organ over time. ### Note This is different from gating techniques, in which the same anatomical volume is imaged during some portion of a cyclic event, e.g., inspiration or R-R Interval.
FLUOROSCOPY | Real-time collection of single slices (e.g., CT or MR Fluoroscopy)
LOCALIZER | Collected for the purpose of planning other images.
MOTION | Collected for looking at body motion
PERFUSION | Collected for the purposes of perfusion calculations.
PRE_CONTRAST | Collected before contrast was administered
POST_CONTRAST | Collected during or after contrast was administered
RESP_GATED | Respiratory gated images
REST | Cardiac rest image set
STATIC | A group of frames at varying spatial locations acquired at the same time.
STRESS | Cardiac stress image set
VOLUME | Set of frames that define a regularly sampled volume
NON_PARALLEL | Set of frames that are not parallel
PARALLEL | Set of frames that are parallel but do not constitute a regularly sampled volume
WHOLE_BODY | A group of frames of the whole body; the frames may be acquired at various times (as distinct from STATIC).

##### C.8.16.1.4 Derived Pixel Contrast

Value 4 shall be used to indicate derived pixel contrast - generally, contrast created by combining or processing images with the same geometry. Value 4 shall have a value of NONE when Value 1 is ORIGINAL.

### Note

If more than one of the following derived types is applicable, then it is up to the generating application to specify the value that best characterizes the derived image.

Value 4 of Image Type (0008,0008) and Value 4 of Frame Type (0008,9007) shall not be zero length unless the SOP Class UID is "1.2.840.10008.5.1.4.1.1.2.2" or "1.2.840.10008.5.1.4.1.1.4.4" or "1.2.840.10008.5.1.4.1.1.128.1" (Legacy Converted).

Table C.8-130 specifies the Defined Terms for Value 4 for Image Type (0008,0008) and Frame Type (0008,9007) that are common to CT and MR. Additional Defined Terms are defined in the modality-specific Module and Macro definitions.

Table C.8-130. Image Type and Frame Type Value 4 Common

Defined Term Name | Defined Term Description
--- | ---
ADDITION | Created through Pixel by pixel addition operation
DIVISION | Created through Pixel by pixel division operation
MASKED | Created through Pixel by pixel masking operation
MAXIMUM | Created through Pixel by Pixel Maximum operation
MEAN | Created through Pixel by pixel mean operation
MINIMUM | Created through Pixel by Pixel Minimum operation
MTT | Mean Transit Time
MULTIPLICATION | Created through Pixel by pixel multiplication operation
RCBF | Regional Cerebral Blood Flow (rCBF)
RCBV | Regional Cerebral Blood Volume (rCBV)
RESAMPLED | Pixels have been spatially re-sampled, e.g., MPR
STD_DEVIATION | Standard Deviation
SUBTRACTION | Created through Pixel by pixel subtraction operation
T_TEST | Student's T-Test
TTP | Time To Peak map
Z_SCORE | Z-Score Map
NONE | Not a calculated image
MIXED | Used only as value in Image Type (0008,0008) if frames within the image SOP Instance contain different values for value 4 in their Frame Type (0008,9007) attribute.

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