Artefacts and False Positive Results of Myocardial Perfusion SPECT with CZT D-SPECT Camera.

Introduction: The artifacts occurring during myocardial perfusion SPECT acquisition with a CZT camera potentially reduce the specificity of the results and are poorly documented. The aim of our study was to analyze the relationship between these artefacts and the occurrence of false-positive myocardial SPECT examinations.

Methods: Quality control of myocardial SPECT images from 60 consecutive patients with a True Positive (TP) (n=30) or False Positive (FP) (n=30) perfusion SPECT was retrospectively analyzed. All examinations were performed with a D-SPECT camera (Spectrum dynamics, Caesarea, Il), using a 99mTc-labeled radiopharmaceutical and a 1-day stress/rest protocol. All patients had coronary angiography within 3 months after myocardial perfusion SPECT. Artefacts were considered and classified as follows: (1) inadequate positioning of the heart within the cardio-focal area (0%, 30%, 60%, or 100% outside), (2) nonidentical patient positioning during stress and rest acquisition, (3) number of patient movements during stress and rest acquisition (graded as 0 [no movement], 1 [single movement], to 2 [more than 1 movement]), (4) quality of ECG-gating (good or poor), and (5) stress and rest myocardial count statistics (<500 kcts or ≥500 kcts).

Results: Our study revealed that there was a majority of men in both groups (n=21, 70% for TP and n=22, 73% for FP). In the FP group, the main indication for SPECT was diagnostic SPECT for suspected coronary artery disease (n=25, 83%), whereas in the TP group, the main indication was risk assessment in patients with documented coronary artery disease (n=16, 53%). Patients considered FP were younger (mean age = 64±11 vs. 69±10 y/o in VP, p< 0.05) with an increased BMI (32±8.6 vs. 27±5.3 kg/m² in VP, p=0.02). Among the quality control characteristics, the occurrence of a false-positive SPECT examination was significantly associated with the inadequate position of the heart in the cardio-focal area (p < 0.05), non-identical patient positioning during stress and rest imaging (p < 0.05), number of patient movements (p < 0.05), and low count statistics at rest (p < 0.05). The number of artefacts was strongly associated with the occurrence of false-positive examinations, with an 80% false-positive rate in patients with at least 2 artefacts (p = 0.0003).

Conclusions: In this retrospective study, the false-positive rate dramatically increased with the number of artefacts, which shows the importance of having a robust quality control.