A Monte Carlo study of arms effect in myocardial perfusion of normal and abnormal cases utilizing STL heart shape

Arms influence in myocardial perfusion single photon emission computed tomography (SPECT) imaging has been studied for the last two decades. These studies suggested that arms positioning next to the patient would not show cardiac abnormalities or perfusion defects in SPECT imaging while it would not affect the scan during positron emission tomography (PET) scans. As a recent improvement in Geant4 Application for Tomographic Emission (GATE), -a Monte Carlo simulation toolkit- a new feature was added to enable the use of STereoLithography (STL). STL files are implanted as an input geometry for most human organs, which would give superior advantages in details compared to analytical geometry shapes. This study is adopting this recent improvement in GATE to study arms effect in SPECT imaging with the consideration of four scenarios; normal heart perfusion imaging with and without arms positioned next to the patient and two of the same scenarios with a perfusion myocardial defected. The results showed that perfusion defect could be observed with arms next to the patient. For image reconstruction, both filtered backprojection (FBP) and iterative technique – maximum likelihood expectation maximization (MLEM) were used. The MLEM was performed to analyse the four different patient scenarios. The difference in counts between arms-up and arms-down position for the abnormal case was shown to be less than 6%. The conclusion from this paper is that arm influence during abnormal heart SPECT imaging can be measured and has a minimal contribution to the reconstructed images. Keywords: GATE, Reconstruction, SPECT, Arms, Heart, Myocardial, Perfusion, ST

Endometrial Cancer: Combined MR Volumetry and Diffusion-weighted Imaging for Assessment of Myometrial and Lymphovascular Invasion and Tumor Grade

International audiencePURPOSE:To investigate magnetic resonance (MR) volumetry of endometrial tumors and its association with deep myometrial invasion, tumor grade, and lymphovascular invasion and to assess the value of apparent diffusion coefficient (ADC) histographic analysis of the whole tumor volume for prediction of tumor grade and lymphovascular invasion.MATERIALS AND METHODS:The institutional review board approved this retrospective study; patient consent was not required. Between May 2010 and May 2012, 70 women (mean age, 64 years; range, 24-91 years) with endometrial cancer underwent preoperative MR imaging, including axial oblique and sagittal T2-weighted, dynamic contrast material-enhanced, and diffusion-weighted imaging. Volumetry of the tumor and uterus was performed during the six sequences, with manual tracing of each section, and the tumor volume ratio (TVR) was calculated. ADC histograms were generated from pixel ADCs from the whole tumor volume. The threshold of TVR associated with myometrial invasion was assessed by using receiver operating characteristic curves. An independent sample Mann Whitney U test was used to compare differences in ADCs, skewness, and kurtosis between tumor grade and the presence of lymphovascular invasion.RESULTS:No significant difference in tumor volume and TVR was found among the six MR imaging sequences (P = .95 and .86, respectively). A TVR greater than or equal to 25% allowed prediction of deep myometrial invasion with sensitivity of 100% and specificity of 93% (area under the curve, 0.96; 95% confidence interval: 0.86, 0.99) at axial oblique diffusion-weighted imaging. A TVR of greater than or equal to 25% was associated with grade 3 tumors (P = .0007) and with lymphovascular invasion (P .05). The minimum, 10th, 25th, 50th, 75th, and 90th percentile ADCs were significantly lower in grade 3 tumors than in grades 1 and 2 tumors (P < .02).CONCLUSION:The combination of whole tumor volume and ADC can be used for prediction of tumor grade, lymphovascular invasion, and depth of myometrial invasion