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GatedSPECT

Support was added for gated (SPECT) studies, with attention to conversion between InterFile and DICOM. The usage of Gated SPECT in InterFile 3.3 was based on a referenced proposal. The following tables show useful relations between DICOM tags, InterFile keys and other terminology. Internally we preserve InterFile related keys, because they seem less prone to interpretation differences.

DICOM 
 "Image Type" (0x0008;0x0008)InterFile 
 "type of data :="
GATED <--> GATED
GATED SPECT <--> GSPECT (unreconstructed)
RECON GATED SPECT <--> GSPECT (reconstructed)
 Table 1.: Relation of gated acquisition types between DICOM and InterFile
 InterFile: alias = key
 DICOM
 calculated
 units
 N = total number of images
 Heart Rate (0x0018;0x1088)
 = (Cobs / S) * 60 * 1000
[bpm]
 S = study duration (acquired) sec
 Actual Frame Duration (0x0018;0x1242)
 = T * 1000
 [ms]
 I = image duration (sec)
 Frame Time (0x0018;0x1063)
 = I * 1000
 [ms]
 P = number of projections
 Time Slot Time (0x0054;0x0073)
 = ((Cacq * I) / N) * 1000
 [ms]
 T = time per projection (sec)
 Number of Frames in Rotation (0x0054,0x0053)
 = P
 -
 Cacq = cardiac cycles acquired
 Intervals Acquired (0x0018;0x1083) 
 = Cacqor divided by P repeated tags
 -
 Cobs = cardiac cycles observed
 Intervals Rejected (0x0018;0x1084)
 = (Cobs - Cacq)
or divided by P repeated tags
 -
 Astart = start angle
 Start Angle (0x0054,0x0200)
 = (180 - Astart + 360) % 360
 [degrees]
 Table 2.: Mapping of gated (SPECT) between InterFile keys and DICOM tags

DICOM "Image Type" (0x0008;0x0008)	InterFile "type of data :="
GATED <-	-> GATED
GATED SPECT <-	-> GSPECT (unreconstructed)
RECON GATED SPECT <-	-> GSPECT (reconstructed)

Important key relations for InterFile:

"% R-R cycles acquired this window" = (Cacq/Cobs) * 100
"time per projection (sec)" = T = (S/P)

Dimensions in DICOM mapped to (X)MedCon (= InterFile):

 GATEDGATED TOMORECON GATED TOMO
dim[7] =energy windowsenergy windows-
dim[6] =detector headsdetector heads-
--(rotations = 1)-
dim[5] =R-R intervalsR-R intervalsR-R intervals
dim[4] =-time slotstime slots
dim[3] =time slotsangular viewsslices
Table 3.: DICOM dimensions mapped in (X)MedCon

	GATED	GATED TOMO	RECON GATED TOMO
dim[7] =	energy windows	energy windows	-
dim[6] =	detector heads	detector heads	-
-	-	(rotations = 1)	-
dim[5] =	R-R intervals	R-R intervals	R-R intervals
dim[4] =	-	time slots	time slots
dim[3] =	time slots	angular views	slices

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InterFile: alias = key	DICOM	calculated	units
N = total number of images	Heart Rate (0x0018;0x1088)	= (C_obs / S) * 60 * 1000	[bpm]
S = study duration (acquired) sec	Actual Frame Duration (0x0018;0x1242)	= T * 1000	[ms]
I = image duration (sec)	Frame Time (0x0018;0x1063)	= I * 1000	[ms]
P = number of projections	Time Slot Time (0x0054;0x0073)	= ((C_acq * I) / N) * 1000	[ms]
T = time per projection (sec)	Number of Frames in Rotation (0x0054,0x0053)	= P	-
C_acq = cardiac cycles acquired	Intervals Acquired (0x0018;0x1083)	= C_acq or divided by P repeated tags	-
C_obs = cardiac cycles observed	Intervals Rejected (0x0018;0x1084)	= (C_obs - C_acq) or divided by P repeated tags	-
A_start = start angle	Start Angle (0x0054,0x0200)	= (180 - A_start + 360) % 360	[degrees]