Feasibility study of a novel general purpose CZT-based digital SPECT camera: initial clinical results

Abstract

Background: The performance of a prototype novel digital single-photon emission computed tomography (SPECT) camera with multiple pixelated CZT detectors and high sensitivity collimators (Digital SPECT; Valiance X12 prototype, Molecular Dynamics) was evaluated in various clinical settings. Images obtained in the prototype system were compared to images from an analog camera fitted with high-resolution collimators. Clinical feasibility, image quality, and diagnostic performance of the prototype were evaluated in 36 SPECT studies in 35 patients including bone (n = 21), brain (n = 5), lung perfusion (n = 3), and parathyroid (n = 3) and one study each of sentinel node and labeled white blood cells. Images were graded on a scale of 1-4 for sharpness, contrast, overall quality, and diagnostic confidence.

Results: Digital CZT SPECT provided a statistically significant improvement in sharpness and contrast in clinical cases (mean score of 3.79 ± 0.61 vs. 3.26 ± 0.50 and 3.92 ± 0.29 vs. 3.34 ± 0.47 respectively, p < 0.001 for both). Overall image quality was slightly higher for the digital SPECT but not statistically significant (3.74 vs. 3.66).

Conclusion: CZT SPECT provided significantly improved image sharpness and contrast compared to the analog system in the clinical settings evaluated. Further studies will evaluate the diagnostic performance of the system in large patient cohorts in additional clinical settings.

Keywords: CZT; Clinical; General purpose; SPECT.

Fig. 1

Flexible architecture of the Valiance X12 enables multiple independent axes of motion. (A) Gantry rotation, (B) radial detector motion, and (C) swivel motion. The complex motion facilitates multiple angular acquisition capabilities, with numerous different viewing angles covering the target

Fig. 2

Planning a ^99mTc MDP SPECT study of the knees on the Valiance X12 prototype. The planning contours are overlaid on top of a transaxial slice of a low-resolution preview knee study. (1) Detector proximity contour (blue). Detectors are planned to encircle this contour. It is noteworthy that closer proximity for this patient was not possible due to the patient bed and cushions underneath the bent knees and bed straps on both sides. (2) Total activity contour (green), used to instruct the system to focus the detectors only within this ROI. (3) ROI contour (red). Used to instruct the system to dedicate more acquisition time when the detectors are focusing at this region, in accordance with user preferences (typically 50–90%)

Fig. 3

Examples of comparative clinical images (analog vs. digital CZT SPECT). Top: a 32-year-old female patient with facial asymmetry since childhood and left tempo-mandibular joint (TMJ) pain for 4.5 years referred for ^99mTc MDP SPECT. a No visible abnormality on analog SPECT. b Focal left TMJ uptake is seen on CZT SPECT (arrows) corresponding with clinical presentation. Bottom: A 64-year-old female patient with nonspecific foot pain referred for ^99mTc MDP SPECT. Representative sagittal slices of analog (c) and CZT (d) SPECT. Multiple foci, most likely osteoarthritic and stress-related (marked with arrows) are well visualized on CZT SPECT, while hardly seen or poorly visualized on analog SPECT

Fig. 4

An 18-year-old male patient status post recurrent urinary tract infection referred for ^99mTc DMSA SPECT for evaluation of renal function. Representative sagittal slices of a analog and b digital SPECT. Right kidney cortical lesion, consistent with focal scarring (marked with an arrow), is faintly seen on analog SPECT and clearly visualized on digital SPECT

Fig. 5

ROI-centric digital SPECT study of the lumbar spine in a 47-year-old female referred for lower back pain. A coronal maximal intensity projection (MIP) is displayed on the left side, and transaxial slices on the right side of a analog SPECT study, b digital SPECT study, and (c) ROI-centric digital SPECT study