A comparison between 64-projection and 32-projection myocardial perfusion scintigraphy

While most clinical guidelines recommend using a 64-projection view technique, some protocols do not specify a preference between 32-projection and 64-projection methods for conducting myocardial perfusion scintigraphy (MPS), which shows the lack of consensus in this matter. Nevertheless, these guidelines and protocols have not provided us with compelling evidence to support why the 64-projection technique is usually chosen. Thus, we aimed to determine if there is a significant difference between them in the assessment of cardiac perfusion and functional indices.

Sixty-nine patients were included in this pilot prospective, cross-sectional, cross-over, same patient control protocol study and underwent 32- and 64-projection MPS at both stress and rest phases after injecting 740-925 MBq of 99mTc-MIBI for every patient. Then, cardiac indices, including summed stress, rest, and difference scores, extent-stress and rest, left ventricular volumes and ejection-fraction, peak filling rate (PFR), and time to peak filling rate (TTPF) were recorded. Lin's concordance correlation coefficient was used to assess the agreement between protocols, and a paired sample t-test was used to compare the means of variables where appropriate. Findings revealed no significant difference as well as excellent/good agreement between the two methods in either the stress or rest state, except for the TTPF and PFR.

The findings suggest that lower-projection techniques could be adequate for routine clinical assessments without sacrificing diagnostic accuracy. However, the poor agreement for PFR and TTPF indicates that the 32-projection method may not reliably assess diastolic function, implying that the 64-projection protocol is preferable when precise evaluations are necessary.