Evaluating the accuracy of planar gated blood pool processing software using simulated patient studies.

Planar gated blood pool (GBP-P) radionuclide imaging is a valuable non-invasive technique for assessing left ventricular ejection fraction (LVEF). Serial cardiac imaging can be performed to monitor the potential decline in LVEF among patients undergoing cardiotoxic chemotherapy. Consequently, accurate LVEF determination becomes paramount. While commercial software programs have enhanced the LVEF values' reproducibility, concerns remain regarding their accuracy. This study aimed to generate a database of GBP-P studies with known LVEF values using Monte Carlo simulations and to assess LVEF values' accuracy using four commercial software programs. We utilised anthropomorphic 4D-XCAT models to generate 64 clinically realistic GBP-P studies with Monte Carlo simulations. Four commercial software programs (Alfanuclear, Siemens, General Electric Xeleris, and Mediso Tera-Tomo) were used to process these simulated studies. The accuracy and reproducibility of the LVEF values determined with these software programs and the intra- and inter-observer reproducibility of the LVEF values were assessed. Our study revealed a strong correlation between LVEF values calculated by the software programs and the true LVEF values derived from the 4D-XCAT models. However, all the software programs slightly underestimated LVEF at lower LVEF values. Intra- and inter-observer reliability for LVEF measurements was excellent. Accurate LVEF assessment is crucial for determining the patient's cardiac function before initiating and during chemotherapy treatment. The observed underestimation, particularly at lower LVEF values, emphasises the need for the accurate and reproducible determination of these values to avoid excluding suitable candidates for chemotherapy. The software programs' excellent intra- and inter-observer reliability highlights their potential to reduce subjectivity when using the semi-automatic processing option. This study confirms the accuracy and reliability of these commercial software programs in determining LVEF values from simulated GBP-P studies. Future research should investigate strategies to mitigate the underestimation biases and extend findings to diverse patient populations. Gated blood pool studies, left ventricular ejection fraction, Monte Carlo simulations, 4D-XCAT models.

Validation of a Monte Carlo modelled gamma camera for Lutetium-177 imaging.

This study validated a model of the Siemens Symbia T16 dual-head SPECT/CT gamma camera created using the Monte Carlo program SIMIND for 177Lu. The validation was done by comparing experimental and simulated gamma camera performance criteria tests for the 177Lu 208 keV photopeak with a medium-energy collimator. Results showed good agreement between the experimental and simulated values. These results illustrated that SIMIND could emulate the Symbia T16 successfully and therefore, can be used with confidence to model 177Lu images.

Evaluation of an uncollimated printed paper transmission source used under scatter limiting conditions.

Transmission sources used for image attenuation correction, allowing image quantification, are collimated to reduce scatter. We propose the same effect can be achieved for an uncollimated source by increasing source to patient distance. The aim was to compare planar image performance characteristics and absorbed doses of uncollimated and collimated radioactive printed paper transmission sources. The scatter contribution to the uncollimated (99m)Tc source data was evaluated for different combinations of detector phantom distance, detector source distance and phantom source distance. Measurements were performed by increasing the Lucite phantom thickness in 1cm steps to 20 cm. Spatial resolution, detection efficiency and entrance absorbed dose rate were measured for the uncollimated and collimated transmission source images. Results derived from the energy spectra, obtained with the uncollimated transmission source indicate that scatter contribution increases with decreasing detector source distance. The scatter component in the uncollimated transmission images (detector source distances ≥ 60 cm; phantom source distances ≥ 40 cm) was comparable to that obtained with collimated transmission images. Attenuation coefficients obtained compared well (0.168 cm⁻¹ vs. 0.171 cm⁻¹). The full widths at half maxima differed by less than 0.9 mm. The detection efficiency of the uncollimated source was 2.5 times higher than obtained with the collimated source. The entrance absorbed dose obtained from an uncollimated source was 3.75 times larger than that obtained from the collimated source. An uncollimated transmission source (detector source distance ≥ 60 cm) results in acceptable image characteristics and presents a low cost, low dose, high efficiency option for transmission imaging.

Production of radioactive quality assurance phantoms using a standard inkjet printer.

This note proposes the use of a standard inkjet printer to produce radioactive (99m)Tc phantoms that can be used for routine quality control of gamma cameras. The amount of activity that will be deposited on paper per unit area was predicted and compared to the measured activity. The uniformity of the printouts was compared to the uniformity obtained with a standard (57)Co flood source. A scintillation detector connected to a multi-channel analyzer was used to evaluate the uniformity of the printout independently from the gamma camera. Joining two A4 size printed phantoms to create larger sources was evaluated. The spatial resolution obtained with printed sources was compared to that obtained using standard line source techniques. The results indicated that the uniformity of the printed phantoms compared well with those obtained with the (57)Co flood source (integral uniformity 2.29% (printed source) and 2.10% ((57)Co flood source)). There was no difference in the resolution measurements obtained with the printed sources and those obtained with the standard methods. This study demonstrates that affordable phantoms can easily be created to evaluate system uniformity and resolution in any department where a standard PC and inkjet printer are available.

Left ventricular ejection fraction calculated from gated technetium-99-sestamibi SPECT.

BACKGROUND: The accuracy of the left ventricular ejection fraction (LVEF) calculated from gated single photon emission computed tomography (GSPECT) studies is dependent on the accuracy of the determination of the end-diastolic volume (EDV) and end-systolic volume (ESV) of the left ventricle (LV). In this study we evaluated the feasibility of calculating the EDV, ESV and LVEF from the area under the polar graph (APC) of the edges of the LV image determined by a first derivative edge-detection method. METHODS AND RESULTS: Technetium-99m ((99m)Tc) sestamibi GSPECT studies and planar equilibrium radionuclide ventriculography (ERNV) were performed on 15 male subjects in whom the LVEF ranged from 19% to 75%. Images were reconstructed to obtain short axis slices of the LV spanning the cardiac cycle. On each slice the LV edge points were determined at 10 degrees intervals using the APC method. The area of each short axis slice was determined by conversion to polar co-ordinates, interpolation and numerical integration of the graphs and multiplication by a pre-determined conversion factor. RESULTS: Edges were successfully determined in all 15 patients using the APC method. The LVEF results correlate well with conventional planar ERNV studies (r = 0.96, LVEF(GSPECT) = 8.80 + 0.66 LVEF( ERNV)). The absolute difference between the LVEF for ERNV and for the APC method was 6.1% with a standard deviation of 7.6%. The reproducibility of SPECT LVEF using the APC method was good (intra-observer r = 0.99, inter-observer r = 0.99). CONCLUSIONS: The APC method provides for easy and accurate ejection fraction determination with limited underlying mathematical assumptions. The ability to interpolate the edge points provides for stable edge detection even in hypoperfused myocardium.

Biodistribution and absorbed radiation dose estimates of 99mTc-labeled dimercaptopropionyl human serum albumin.

UNLABELLED: The use of 99mTc-labeled red blood cells (RBC) for the evaluation of left ventricular function using equilibrium-gated blood-pool imaging suffers from several problems and potential risks. In this study, we estimated the absorbed radiation dose of 99mTc-labeled dimercaptopropionyl human serum albumin (DMP-HSA) as a potential alternative to 99mTc-RBC. METHODS: After the administration of 99mTc-DMP-HSA, whole-body imaging was performed up to 48 h after injection in five volunteers. The heart contents, liver and remainder of the body were used as source organs. Multicompartment modeling of the biodistribution was performed and absorbed radiation dose estimates for 99mTc-DMP-HSA were obtained using the Medical Internal Radiation Dose (MIRD) calculation. RESULTS: Residence times of 0.62 and 0.43 h were obtained for the heart contents and liver, respectively. Radiation dose estimates yielded an effective dose of 0.0055 mSv/MBq. CONCLUSION: 99MTC-DMP-HSA yielded absorbed radiation doses comparable with those of 99mTc-RBC. Therefore, the radiation properties of 99mTc-DMP-HSA are such that it can be used for clinical diagnostic studies.