title: Combination of converging collimators for high-sensitivity brain SPECT.
abstract: The objective of this study, which is related to human brain SPECT, was to increase the sensitivity of a triple-camera SPECT system and reduce statistical noise in reconstructed images using a combination of converging collimators. The reason for combining collimators is to ensure both high sensitivity and sufficient sampling without trading off spatial resolution.
  
  
  METHODS
  A high-sensitivity half-cone-beam (HCB) collimator, designed specifically for brain imaging, was combined with other collimators and compared with conventional parallel-beam and fanbeam circular orbit acquisitions. For comparison, previously studied HCB collimation with a circle-and-helix data acquisition trajectory was also included in this study. Simulations of the Hoffman 3-dimensional brain phantom were performed to calculate the efficiencies of collimators and their combinations and to quantitatively evaluate reconstruction bias, statistical noise, and signal-to-noise ratios in the reconstructed images. Experimental brain phantom data were also acquired and compared for different acquisition types. Finally, a patient brain scan was obtained with a combination of HCB and fanbeam collimators and compared with a triple-fanbeam circular orbit acquisition.
  
  
  RESULTS
  A combination of 2 HCB collimators and 1 fanbeam collimator, compared with a triple-fanbeam collimator, can increase the photon detection efficiency by 27% and by more than a factor of 2, compared with triple-parallel-hole collimation, with equal spatial resolution measured on the axis of rotation. Quantitative analysis of reconstruction bias and visual analysis of the images showed no signs of sampling artifacts. Reconstructed images in the simulations, experimental brain phantom, and patient brain scans showed improved quality with this collimator combination due to increased sensitivity and reduced noise. Lesion visibility was also improved, as confirmed by signal-to-noise ratios. Alternatively, triple-HCB circle-and-helix acquisition has also shown competitive results, with a slight disadvantage in axial sampling and implementation procedure.
  
  
  CONCLUSIONS
  Combined HCB and fanbeam collimation is a promising approach for high-sensitivity brain SPECT.
authors.affiliation: Department of Radiology, Duke University Medical Center, Durham, North Carolina, USA. rt3ak@hscmail.mcc.virginia.edu
authors.forename: Ruben
authors.initials: R
authors.lastname: Ter-Antonyan
authors.forename: Ronald J
authors.initials: RJ
authors.lastname: Jaszczak
authors.forename: Kim L
authors.initials: KL
authors.lastname: Greer
authors.forename: James E
authors.initials: JE
authors.lastname: Bowsher
authors.forename: Scott D
authors.initials: SD
authors.lastname: Metzler
authors.forename: R Edward
authors.initials: RE
authors.lastname: Coleman
mesh_terms: D001921:Brain / Q000000981:diagnostic imaging*; D004867:Equipment Design; D019544:Equipment Failure Analysis; D006801:Humans; D007089:Image Enhancement / Q000295:instrumentation*; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D015899:Tomography, Emission-Computed, Single-Photon / Q000295:instrumentation*
references.citation: Phys Med Biol. 1998 Apr;43(4):1015-24
references.pmid: 9572524
references.citation: Phys Med Biol. 1992 Mar;37(3):535-48
references.pmid: 1565689
references.citation: IEEE Trans Nucl Sci. 2007;54(3):475-479
references.pmid: 18392114
references.citation: Phys Med Biol. 1998 Oct;43(10):2885-909
references.pmid: 9814525
references.citation: Phys Med Biol. 1995 Sep;40(9):1517-37
references.pmid: 8532763
references.citation: J Nucl Med. 1984 Aug;25(8):893-900
references.pmid: 6611390
references.citation: IEEE Trans Med Imaging. 1994;13(4):601-9
references.pmid: 18218538
references.citation: IEEE Trans Nucl Sci. 2008 Oct 1;55(5):2518-2526
references.pmid: 19802377
references.citation: J Nucl Med. 2002 Nov;43(11):1578-83
references.pmid: 12411562
references.citation: IEEE Trans Med Imaging. 2000 May;19(5):361-75
references.pmid: 11021680
references.citation: J Nucl Med. 2004 Jan;45(1):49-55
references.pmid: 14734673
references.citation: Med Phys. 2005 Jul;32(7):2236-44
references.pmid: 16121578
references.citation: J Nucl Med. 2001 Mar;42(3):408-13
references.pmid: 11337515
references.citation: J Nucl Med. 1996 Mar;37(3):498-502
references.pmid: 8772655