Comparison between the prone and upright imaging for inferior wall in 201TlCl myocardial perfusion SPECT

Objectives In obese patients, the prone imaging method is suitable for inferior wall evaluation to suppress attenuation artifacts from the diaphragm. Imaging position of the solid-state dedicated cardiac camera is an upright position, and there is evidence that upright imaging can also be used as control the attenuation artifacts from the diaphragm. The author compared between the prone and upright imaging for inferior wall evaluation in ²⁰¹TlCl myocardial perfusion SPECT.

Methods Prone imaging group was 30 subjects with additional prone imaging because it had reduced uptake for the inferior wall in the supine imaging, and upright imaging group was 30 subjects with upright imaging in patients who reduced uptake for the inferior wall in the supine imaging in the past. Subjects for visual evaluation were 5 who were performed both of the prone and upright imaging. Using 42 regions of interest (ROI) on a polar map, and we compared the coefficient of variation (CV) for %uptake between the two groups, and examined the correlation between the CV and the variation of body mass index (BMI). In addition, five raters were visually evaluated the uniformity for the inferior wall in the prone and upright imaging.

Results CV for %uptake in the upright position (10.05±1.56%) was significantly lower than those in the prone position (11.39±2.42%; P<0.05). Prone imaging was not correlated with the CV and BMI. On the other hand, upright imaging had a weak positive correlation to the CV and BMI. There was no difference in rater evaluation or in visual assessment of the inferior wall between the prone and upright imaging groups. Conclusions: Upright imaging is superior to prone imaging for image quality in inferior wall. Uniformity for inferior wall was similar with both of imaging. Therefore, upright imaging is excellent in image quality than that in prone imaging, but both of imaging can be equivalent in the inferior wall evaluation.