Conditions for the determination of intrinsic uniformity and intrinsic spatial linearity of SPECT / 中国辐射卫生

Objective To address the absence of matrix specified for the determination of intrinsic uniformity in the current standard, and to investigate the effect of source distances on intrinsic spatial linearity, the intrinsic uniformity and intrinsic spatial linearity of 16 probes in eight SPECT devices were measured and analyzed with different matrices and source distances, in order to determine the optimal measurement conditions. Methods According to the standard Specification for Testing of Quality Control in Gamma Cameras and Single Photon Emission Computed Tomograph (SPECT) (WS 523—2019), the intrinsic uniformity was measured using 64 × 64 and 256 × 256 matrices and the intrinsic spatial linearity was measured using of 1.7 and 3 m source distances. Results When intrinsic uniformity was measured with the 64 × 64 matrix, more than 50% of the probes showed lower values. When intrinsic spatial linearity was measured with the 3 m source distance, more probes showed lower values. Conclusion The 64 × 64 matrix is recommended for the determination of intrinsic uniformity and a source distance of ＞5 FOV is recommended for the measurement of intrinsic spatial linearity.

Test and discussion on SPECT performance under the Chinese health industry standard WS523-2019 / 中华放射医学与防护杂志

Objective:To discuss the problems existing in the implementation of the Chinese health industry standard WS 523-2019 by testing SPECT device.Methods:Under the WS 523-2019 standards, a total of 10 SPECT devices were tested with regard to their SPECT reconstructed spatial resolution (SRSR), system planar sensitivity (SPS), system spatial resolution (SSR), whole body system spatial resolution (WSSR), intrinsic uniformity (IU), intrinsic count rate performance (ICR), intrinsic spatial resolution (ISR) and intrinsic spatial linearity(ISL).Result:Under the requirements of WS 523-2019 standards for qualified limits, there are 3 devices with ISL unqualified and the rest of the performances qualified. The new standards basically can meet the clinical requirements and reflected the overall performance of SPECT.Conclusions:The distance between the radiation source and the surface of the detector has great influence on the spatial resolution.In the measurement of ISL, there must be a lead grid separately in the x and y directions. The lead grids with the parallel slits shall be positioned on the detector with the center slit centered on the detector. It is suggested to add rotation center in the new standards.

Comparison of partial intrinsic performance of SPECT with two different crystal thickness / 中华放射医学与防护杂志

Objective To explore the influence of changing probe crystal thickness on the performance of single photon emission computed tomography (SPECT),so as to achieve quantitative improvements and in-depth analyses of the related reasons and to provide effective measures in improving the image quality of SPECTs.Methods Both 12 SPECT units each of 1 inch (1 inch =2.54 cm) thick crystal and 35 SPECT units each of 3/8 inch thick crystal were chosen.Both intrinsic uniformity and intrinsic spatial resolution were measured according to the National Electrical Manufacturers Association (NEMA) standard.The performance was compared between SPECT units with 1 inch thick probe and 3/8 inch thick crystal.Results The intrinsic uniformity measured for 1 inch thick probe and 3/8 inch thick crystal were (3.22 ± 0.83)％ and (2.51 ± 0.65)％.The difference between the two groups was statistically significant (t =-3.601,P ＜ 0.05).Intrinsic spatial resolutions of 1 inch thick probe and 3/8 inch thick crystal were (4.60± 0.14) and (3.70 ± 0.35) mm,with statistical significance between the two groups (t =-13.03,P ＜ 0.05).Conclusions The crystal thickness is a significant factor influencing SPECT's intrinsic uniformity and intrinsic spatial resolution.It is recommended that effective measures be taken to compensate the declined image quality due to crystal thickness change,to make sure the equipment is qualified for clinical use.

The investigation on equipment (SPECT) performance in nuclear medicine / 中国医学装备

Objective:Through 51 SPECT and SPECT/CT systems for performance test results of the collation and analysis, to understand the status of the operation of the SPECT and SPECT/CT systems, and in-depth analysis of indicators and find out the weak links and puts forward suggestions for improvement. Methods:According to the NEMA standards and requirements of the manufacturer, the systems have been tested on intrinsic uniformity, intrinsic spatial linearity, intrinsic spatial resolution, maximum count rate, system sensitivity, system spatial resolution and tomographic spatial resolution. Results:The results show that the majority of SPECT or SPECT/CT systems can pass the test;the failure rate is 9.80%. And the failures mainly show intrinsic uniformity and intrinsic spatial linearity. Conclusion:It is effective to improve the equipment performance by doing well in the daily quality control, regular maintenance and calibration, reducing factors that influence the inherent uniformity and inherent linear.