Purpose: Several cross-calibration schemes have been proposed to produce quantitative values in bone SPECT imaging. Differences in the radionuclide sources and geometric conditions can decrease the accuracy of cross-calibration factor (CCF). The present study aimed to validate the effects of calibration schemes using different sources under various geometric conditions. Methods: Temporal variations as well as variations in acquisition counts and the shapes of ⁵⁷Co standard and ^99mTc point sources and a ^99mTc disk source were determined. The effects of the geometric conditions of the source-to-camera distance (SCD) and lateral distance on the CCF were investigated by moving the camera or source away from the origin. The system planar sensitivity of NEMA incorporated into a Symbia Intevo SPECT/CT device (Siemens®) was defined as reference values. Results: The temporal variation in CCF using the ⁵⁷Co source was relatively stable within the range of 0.7% to 2.3%, whereas the ^99mTc source ranged from 2.7% to 7.3%. In terms of source shape, the ⁵⁷Co standard point source was the most stable. Both SCD and lateral distance decreased as a function of distance from the origin. Errors in the geometric condition were higher for the ⁵⁷Co standard point source than the ^99mTc disk source. Conclusions: Different calibration schemes influenced the reliability of quantitative values. The ⁵⁷Co standard point source was stable over a long period, and this helped to maintain the quality of quantitative SPECT/CT imaging data. The CCF accuracy of the ^99mTc source decreased depending on the preparative method. The method of calibration for quantitative SPECT should be immediately standardized to eliminate uncertainty.

The aim of this study is to establish radiation exposure dose reduction protocols during cardiac intervention by decreasing the entrance dose at flat panel detector (FPD) with image quality evaluations. For measuring entrance surface dose (ESD), we have used a Radical 9015 dosimeter (6 cc ion chamber) placed under 20 cm thick acrylic plates at the patient’s entrance reference point. We performed an image quality assessment based on quantitative as well as visual evaluation of the images obtained via current and dose reduction protocols. The visual evaluation was performed by measuring the signal to noise ratio and contrast using a cine/digital angiography cardiac phantom. The quantitative evaluation was performed by cardiologists and radiological technologists using the five-point scale method. For the dose reduction protocol, we used an image noise reduction technique to prevent the deterioration of image quality. The ESDs for the fluoroscopy and digital cine in the dose reduction protocol were 18.0 mGy/min and 0.18 mGy/frame, respectively, which corresponded to 81% and 49% of the ESD in the current protocol. Our results reveal that the ESD for fluoroscopy was lower than the diagnostic reference level (20 mGy/min) for interventional radiology. We recommend a lower dose setting and the maintenance of image quality using noise reduction techniques. This will ensure use of a lower FPD entrance dose compared to the initial dose setting currently recommended by manufacturers.

Background: Coronary computed tomography angiography (CCTA) in patients with pacemaker suffers from metallic lead-induced artifacts, which often interfere with accurate assessment of coronary luminal stenosis. The purpose of this study was to assess a frequency of the lead-induced artifacts and artifact-suppression effect by the single energy metal artifact reduction (SEMAR) technique. Methods: Forty-one patients with a dual-chamber pacemaker were evaluated using a 320 multi-detector row CT (MDCT). Among them, 22 patients with motion-free full data reconstruction images were the final candidates. Images with and without the SMEAR technique were subjectively compared, and the degree of metallic artifacts was compared. Results: On images without SEMAR, severe metallic artifacts were often observed in the right coronary artery (#1, #2, #3) and distal anterior descending branch (#8). These artifacts were effectively suppressed by SEMAR, and the luminal accessibility was significantly improved in #3 and #8. Conclusion: While pacemaker leads often cause metallic-induced artifacts, SEMAR technique reduced the artifacts and significantly improved the accessibility of coronary lumen in #3 and #8.