Performance evaluation of a novel multi-pinhole collimator for dopamine transporter SPECT

Abstract

Purpose: There is a tradeoff between spatial resolution and count sensitivity in SPECT with conventional collimators. Multi-pinhole (MPH) collimator technology has potential for concurrent improvement of resolution and sensitivity in clinical SPECT of 'small' organs. This study evaluated a novel MPH collimator specifically designed for dopamine transporter (DAT) SPECT with a triple-head SPECT camera. Methods: Count sensitivity was measured with a 99m Tc point source placed on the lattice points of a 1cm grid covering the whole field-of-view (FOV). Spatial resolution was assessed with a Derenzo type hot rod phantom. An anthropomorphic striatum phantom was scanned with total activity representative of a typical patient scan and different striatum-to-background activity concentration ratios. Recovery of striatum-tobackground contrast was assessed by the contrast-recovery-coefficient. Measurements were repeated with double-head SPECT with fan-beam or low-energy-high-resolution-high-sensitivity (LEHRHS) collimators. A patient referred to DAT SPECT because of suspicion of Parkinson's disease was scanned with both LEHRHS and MPH collimators after a single tracer injection. Results: The axial MPH sensitivity profile was almost symmetrical around its peak, although it was shifted 7cm towards the patient to simplify positioning. Peak sensitivity of the triple-head MPH system in the center of the FOV was 620 cps/MBq compared to 225 cps/MBq for the double-head fan-beam system. Sensitivity of the MPH system decreased towards the edges of the FOV. The full width of the sensitivity profile at 200 cps/MBq was 21cm transaxially and 11cm axially. In MPH SPECT of the Derenzo phantom all rods with ≥ 5mm diameter were clearly visible. MPH SPECT improved striatal contrast recovery by ≥ 20% compared to fan-beam SPECT. The patient scan demonstrated good image quality of MPH SPECT with almost PET-like delineation of putamen and caudate nucleus. Conclusions: SPECT with dedicated MPH collimators provides considerable improvement of the resolution-sensitivity tradeoff in DAT SPECT compared to SPECT with fan-beam or LEHRHS collimators.

Performance Evaluation of a Novel Multi-PinHole Collimator on Triple-detector SPECT/CT for dedicated myocardial imaging

“…In all cases where image reconstruction was applicable, we used the same settings as for the patient scan, except in case of the spatial resolution results where lower reconstructed voxel size of 1.8 mm was applied. Measurements revealed increased TS pointsource of the triple head aperture system up to 1013 cps/MBq compared to the conventional LEHR sensitivity of 190 cps/MBq (49). In addition, this sensitivity gain is localized in the center of the FOV and decreasing towards the axial and radial edges, while for LEHR the sensitivity is relatively uniform throughout the entire FOV (49).…”

Multiple-pinhole collimators improve intra- and between-rater agreement and the certainty of the visual interpretation in dopamine transporter SPECT

“…MPH projection data were reconstructed to transaxial SPECT images with the Monte Carlo photon simulation engine and iterative one-step-late maximum-a-posteriori expectation–maximization implemented in the camera software (30 iterations, 3 subsets). A more detailed description of the reconstruction method has been given previously [ 16 , 21 ]. Chang’s order zero method with linear broad-beam attenuation coefficient μ = 0.12/cm was used for post-reconstruction attenuation correction [ 22 ].…”

“…The system count sensitivity profile of the triple-head SPECT system equipped with the novel general purpose brain imaging MPH collimator was measured as described previously by our group for a DAT-SPECT-specific MPH collimator [ 16 ]. In brief, a point source (5–10 MBq 99m Tc in about 5 µl in an Eppendorf tube) was placed on the lattice points of a 1 cm grid covering the whole field of view.…”

“…As a consequence, the interpretation of DAT-SPECT can be affected by the limited spatial resolution of conventional SPECT imaging, particularly at early disease stages. Multiple-pinhole (MPH) collimator technology has the potential for concurrent improvement of both spatial resolution and count sensitivity compared to conventional imaging with parallel-hole and fan-beam collimators in clinical SPECT of small organs [7], including DAT-SPECT with 123 I-FP-CIT [8][9][10][11][12][13][14][15][16].…”

Molecular Imaging in Parkinsonian Disorders—What’s New and Hot?

“…In particular, novel large-field cadmium–zinc–telluride and the use of a 360° detector ring may combine high-quality images, and high-speed recording increased by twofold in clinical conditions [ 201 , 202 ]. Improved contrast may also be achieved using multi-pinhole (MPH) collimators for DAT-SPECT, close to striatal delineation with PET [ 203 ]. As demonstrated before, interpretation has greatly improved using normative atlas and validation of innovative segmentation methods [ 204 ], and may greatly benefit from the use of machine learning in particular for differential diagnosis and prediction of individual prognosis for precision-medicine and use in neuroprotection trials.…”