C.8.4.11 NM Detector Module
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#### C.8.4.11 NM Detector Module

Table C.8-11 contains IOD Attributes that describe Nuclear Medicine Detectors used to produce an image.

Table C.8-11. NM Detector Module Attributes

Attribute Name | Tag | Type | Attribute Description
--- | --- | --- | ---
Detector Information Sequence | (0054,0022) | 2 | Sequence of Items that describe the detectors used. Zero or more Items shall be included in this Sequence. The number of items shall be equal to Number of Detectors (0054,0021). The first item corresponds to frames with value of 1 in Detector Vector (0054,0020), the second item with value 2, etc.
>Collimator/Grid Name | (0018,1180) | 3 | Label describing the collimator used (LEAP, hires, etc.)
>Collimator Type | (0018,1181) | 2 | Collimator type. Defined Terms: PARA Parallel (default) PINH Pinhole FANB Fan-beam CONE Cone-beam SLNT Slant hole ASTG Astigmatic DIVG Diverging NONE No collimator UNKN Unknown
>Field of View Shape | (0018,1147) | 3 | Shape of the field of view of the Nuclear Medicine detector. Defined Terms: RECTANGLE ROUND HEXAGONAL
>Field of View Dimension(s) | (0018,1149) | 3 | Dimensions of the field of view, in mm. If Field of View Shape (0018,1147) is: RECTANGLE: row dimension followed by column. ROUND: diameter. HEXAGONAL: diameter of a circumscribed circle.
>Focal Distance | (0018,1182) | 2 | Focal distance, in mm. A value of 0 means infinite distance for parallel collimation. See Section C.8.4.11.1.1 for further specialization.
>X Focus Center | (0018,1183) | 3 | Center of focus along a row. See Section C.8.4.11.1.2 for further explanation.
>Y Focus Center | (0018,1184) | 3 | Center of focus along a column. See Section C.8.4.11.1.2 for further explanation.
>Zoom Center | (0028,0032) | 3 | The amount of offset from (0,0) applied to each pixel in the image before application of the zoom factor, specified by a numeric pair: row value (delimiter) column value (in mm). See Section C.8.4.11.1.3 for further explanation.
>Zoom Factor | (0028,0031) | 3 | The amount of magnification applied to each pixel in the image, specified by a numeric pair: row value (delimiter) column value. See Section C.8.4.11.1.4 for further explanation.
>Center of Rotation Offset | (0018,1145) | 3 | Average center of rotation offset of Nuclear Medicine detector in mm. See Section C.8.4.11.1.5 for further explanation.
>Gantry/Detector Tilt | (0018,1120) | 3 | Angle of tilt in degrees of the detector. See Section C.8.4.11.1.6 for further explanation.
>Distance Source to Detector | (0018,1110) | 2C | Distance in mm from transmission source to the detector face. Required if Image Type (0008,0008) Value 4 is TRANSMISSION and Value 3 is not any of TOMO,GATED TOMO,RECON TOMO or RECON GATED TOMO.
>Start Angle | (0054,0200) | 3 | Position of the detector about the patient for the start of the acquisition, in degrees. Zero degrees is referenced to the origin at the patient's back. Viewing from the patient's feet, angle increases in a counter-clockwise direction (detector normal rotating from the patient's back towards the patient's left side). Should not be included if Image Type (0008,0008) Value 3 is TOMO, GATED TOMO, RECON TOMO or RECON GATED TOMO.
>Radial Position | (0018,1142) | 3 | Radial distance of the detector from the center of rotation, in mm. Should not be included if Image Type (0008,0008) Value 3 is TOMO, GATED TOMO, RECON TOMO or RECON GATED TOMO.
>Image Orientation (Patient) | (0020,0037) | 2 | The direction cosines of the first row and the first column with respect to the patient. See Section C.7.6.2.1.1 for further explanation.
>Image Position (Patient) | (0020,0032) | 2 | The x, y, and z coordinates of the upper left hand corner (center of the first voxel transmitted) of the image, in mm. See Section C.7.6.2.1.1 for further explanation.
>View Code Sequence | (0054,0220) | 3 | Sequence that describes the projection of the anatomic region of interest on the image receptor. Only a single Item is permitted in this Sequence.
>>Include Table 8.8-1 “Code Sequence Macro Attributes” | Baseline CID 26 “Nuclear Medicine Projections”. Code Meaning (0008,0104) shall be Type 3 for historical reasons.
>>View Modifier Code Sequence | (0054,0222) | 2C | View Modifier. Required if needed to fully specify the View. Zero or one Item shall be included in this Sequence.
>>>Include Table 8.8-1 “Code Sequence Macro Attributes” | Baseline CID 23 “Cranio-Caudad Angulation”. Code Meaning (0008,0104) shall be Type 3 for historical reasons.

##### C.8.4.11.1 NM Detector Attribute Descriptions

###### C.8.4.11.1.1 Focal Distance

Focal Distance (0018,1182) for NM Image data is the focal distance, in mm for converging or diverging collimators, measured from the front face of the detector to the focus. Positive values indicate converging and negative values indicate diverging collimators. A value of 0 means infinite distance for parallel collimation.

###### C.8.4.11.1.2 Focus Center

X Focus Center (0018,1183) and Y Focus Center (0018,1184) for NM Image data is used to define the projection of the focus for a converging or diverging collimator within the un-zoomed Field of View. It is defined in mm for row and column relative to the center of the un-zoomed Field of View.

###### C.8.4.11.1.3 Zoom Center

Zoom Center (0028,0032) is the offset between the un-zoomed camera field of view and field of view, measured from the center of the un-zoomed camera field of view to the center the of the zoomed field of view. The offset is measured in mm in the un-zoomed camera FOV dimensions. Positive values are to the right and down from the un-zoomed center, as viewed from the image plane. When this attribute is not given, the Zoom Center is assumed to be 0\0.

###### C.8.4.11.1.4 Zoom Factor

Zoom Factor (0028,0031) is the magnification factor that was used during the acquisition. When this attribute is not given, it is assumed to be 1.0\1.0.

### Note

Zoom Factor (0028,0031) is informational only. Pixel Spacing (0028,0030) already takes account of this and any other changes to pixel size.

###### C.8.4.11.1.5 Center of Rotation Offset

Center of Rotation Offset (0018,1145) is the average amount of offset in mm between the Detector Field of View center and the physical center of rotation of the gantry for circular orbital scans. Positive values indicate the physical center is to the right of the image plane center.

If:

1. Image Type (0008,0008) Value 3 is TOMO or GATED TOMO, and

2. Corrected Image (0028,0051) does not include the value "COR", and

3. Center of Rotation Offset (0018,1145) is non-zero,

then the receiver should assume that Center of Rotation correction has not already been done.

If the Center of Rotation Offset is zero, no correction shall be applied.

###### C.8.4.11.1.6 Gantry/Detector Tilt

Gantry/Detector Tilt (0018,1120) for NM Image data is the angle in degrees of the detector face relative to the patient's major (Head to Feet) axis (or the table supporting the patient). Positive tilt is towards the patient's feet.

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