Quantification of myocardial blood flow using (201)Tl SPECT and population-based input function.

Area of Science:

• Nuclear Cardiology
• Cardiovascular Imaging
• Myocardial Perfusion Assessment

Background:

• Thallium-201 ((201)Tl) single photon emission computed tomography (SPECT) is crucial for diagnosing ischemic heart disease.
• Absolute quantification of myocardial blood flow (MBF) offers superior diagnostic information compared to semi-quantitative methods.
• Accurate MBF quantification requires reliable input function data, typically derived from arterial blood sampling.

Purpose of the Study:

• To validate the quantification of MBF using (201)Tl cardiac SPECT.
• To assess a novel technique employing a population-averaged input function (STD-IF) and a one-point blood sample.
• To compare MBF results obtained with the STD-IF method against those derived from individual input functions (IND-IFs).

Main Methods:

• 11 healthy volunteers underwent resting (201)Tl SPECT/CT scans.
• Individual input functions (IND-IFs) were established using arterial blood samples.
• A population-averaged input function (STD-IF) was calibrated at an optimal time (20 min post-injection) to minimize discrepancies with IND-IFs. MBF was estimated using a single-tissue compartment model and an autoradiography method with pseudo-STD-IFs and an optimal mid-scan time (MST) of 20 min.

Main Results:

• Optimal calibration time and MST were determined to be 20 minutes post-(201)Tl injection.
• Global MBF correlated significantly with rate-pressure products for both IND-IFs (R²=0.645, p<0.01) and STD-IFs (R²=0.303, p<0.05).
• The mean percent error for regional MBF using STD-IFs was minimal (0.69 ± 7.80%), with no significant difference compared to IND-IFs.

Conclusions:

• The proposed STD-IF technique with a single blood sample provides hemodynamically valid global MBF measurements.
• Regional MBF quantification using the STD-IF method is comparable to the gold standard IND-IF approach.
• This simplified method enhances the clinical utility of (201)Tl SPECT for accurate myocardial perfusion assessment.