BackgroundThe 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.ResultsDigital 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).ConclusionCZT 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.
Background 99mTc-labelled bisphosphonates are used for imaging assessment of patients with transthyretin cardiac amyloidosis (ATTR). Present study evaluates whether quantitative SPECT/CT measurement of absolute myocardial 99mTc-labelled 3,3-diphosphono-1,2-propanodicarboxylic acid (Tc-DPD) uptake can diagnose patients with suspected ATTR. Methods Twenty-eight patients (25 male, age 80.03 ± 6.99 years) with suspected ATTR referred for Tc-DPD imaging had planar and SPECT/CT imaging of the chest. Three operators independently obtained Tc-DPD myocardial SUVmax and SUVmean above threshold (SMaT) (20, 40 and 60% of SUVmax), using a semi-automated threshold segmentation method. Results were compared to visual grading (0–3) of cardiac uptake. Results Twenty-two patients (78%) had cardiac uptake (2 grade 1, 15 grade 2, 5 grade 3). SUVmax and SMaT segmentation thresholds enabled separating grades 2/3 from 0/1 with excellent inter- and intra-reader correlation. Cut-off values 6.0, 2.5, 3 and 4 for SUVmax, SMaT20,40,60, respectively, separated between grades 2/3 and 0 /1 with PPV and NPV of 100%. SMaT20,40,60(cardiac)/SUVmean (liver) and SMaT20,40,60(cardiac)/SUVmean(liver/lung) separated grades 2 and 3. Conclusion Quantitative SPECT/CT parameters of cardiac Tc-DPD uptake are robust, enabling separation of patients with grades 2 and 3 cardiac uptake from grades 0 and 1. Larger patient cohorts will determine the incremental value of SPECT/CT quantification for ATTR management.
Purpose: To investigate masking portions of projection data to decrease motion‐related artifacts using iterative image reconstruction techniques. Method and Materials: A phantom was constructed from a water‐filled plastic canister with two air‐filled spheres fixed inside to simulate gas pockets. Inferior‐superior motion was applied to the phantom to simulate breathing. A SPECT/CT scanner (InfiniaVC Hawkeye, GE Healthcare) with a 140 kVp, 2.5 mA tube, and slice thickness of 1 cm was used to acquire data. A single CT slice is acquired in 14 seconds. Projections identified to contain motion via data consistency conditions were combined with forward projected sinograms of the spheres to produce projection object masks (POMs). POMs were given various weights, smoothed using a Gaussian filter, and applied to the phantom sinogram and projection blank file. An OSTR iterative algorithm was used to reconstruct the POM sinogram. Contrast and uniformity data of the POM image were taken from different regions and compared to the filtered backprojected (FBP) image. Patient studies involving anatomical areas with little motion were also analyzed. Results: Projection data with no motion could be reconstructed with minimal artifacts when 6.7% of the projection angles were removed prior to reconstruction. For the moving phantom, motion artifacts were greatly reduced in the POM images compared to FBP images. Contrast and uniformity data showed significant improvement with the applied POM. Conclusion: CT images were successfully reconstructed with missing projection data, and motion can be detected in the projections. Initial work demonstrates that artifacts caused by moving gas pockets and a slow rotating CT such as this SPECT/CT scanner may be reduced through iterative image reconstruction with projections removed. Conflict of Interest: Research sponsored by GE Healthcare Corporation.
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