New SPECT camera technology with low isotope dose significantly reduces ionizing radiation exposure and imaging times compared to traditional protocols while maintaining image quality and diagnostic accuracy.

New SPECT CZT camera technology allows significantly reduced radiation exposure and acquisition time without loss of image quality.

Background Recently introduced high-efficiency (HE) SPECT cameras with solid-state CZT detectors have been shown to decrease imaging time and reduce radiation exposure to patients. An automated, computer derived quantification of HE MPI has been shown to correlate well with coronary angiography on one HE SPECT camera system (D-SPECT), but has not been compared to visual interpretation on any of the HE SPECT platforms. Methods Patients undergoing a clinically indicated Tc-99m sestamibi HE SPECT (GE Discovery 530c with supine and prone imaging) study over a one year period followed by a coronary angiogram within 2 months were included. Only patients with a history of CABG surgery were excluded. Both MPI studies and coronary angiograms were reinterpreted by blinded readers. One hundred and twenty two very low (risk of CAD < 5%) or low (risk of CAD < 10%) likelihood subjects with normal myocardial perfusion were used to create normal reference limits. Computer derived quantification of the total perfusion deficit (TPD) at stress and rest was obtained with QPS software. The visual and automated MPI quantification were compared to coronary angiography (≥ 70% luminal stenosis) by receiver operating curve (ROC) analysis. Results Of the 3,111 patients who underwent HE SPECT over a one year period, 160 patients qualified for the correlation study (66% male, 52% with a history of CAD). The ROC area under the curve (AUC) was similar for both the automated and visual interpretations using both supine only and combined supine and prone images (0.69-0.74). Using thresholds determined from sensitivity and specificity curves, the automated reads showed higher specificity (59-67% versus 27-60%) and lower sensitivity (71-72% versus 79-93%) than the visual reads. By including prone images sensitivity decreased slightly but specificity increased for both. By excluding patients with known CAD and cardiomyopathies, AUC and specificity increased for both techniques (0.72-0.82). The use of a difference score to evaluate ischemic burden resulted in lower sensitivities but higher specificities for both automated and visual quantification. There was good agreement between the visual interpretation and automated quantification in the entire cohort of 160 unselected consecutive patients (r = 0.70-0.81, p < 0.0001). Conclusions Automated and visual quantification of high-efficiency SPECT MPI with the GE Discovery camera provide similar overall diagnostic accuracy when compared to coronary angiography. There was good correlation between the two methods of assessment. Combined supine and prone stress imaging provided the best diagnostic accuracy.

Recently introduced high-efficiency SPECT cameras have demonstrated the ability to reduce radiation exposure to patients undergoing myocardial perfusion imaging studies, especially when combined with stress-only imaging protocols. To date there have been no relevant studies examining the reduced occupational radiation exposure to medical staff. We sought to determine whether changes in stress myocardial perfusion imaging protocols and camera technology can reduce the occupational radiation exposure to the staff of a nuclear cardiology laboratory. Methods: Monthly radiation dosimeter readings from 4 nuclear technologists, 4 nurses, and 2 administrative employees were analyzed from two 12-mo periods: October 2007-September 2008 (period 1), before the use of high-efficiency SPECT, and October 2010-September 2011 (period 2), after high-efficiency SPECT was introduced. The average monthly dose equivalent in millirems (1 mrem 5 0.01 mSv) was recorded from personal dosimeters worn on laboratory coats. The total activity of 99m Tc used per month, mean 99m Tc administered activity per patient, average number of patients per month, patient time spent in the laboratory, and proportion of stress-only studies were determined. Results: There were 3,539 patients in period 1 and 3,898 in period 2. An approximately 40% reduction in the dose equivalent across all staff members occurred during this time (216.9 and 216.2 mrem for nuclear technologists and nurses, respectively; P , 0.0001). During period 2, the total activity of 99m Tc used per month decreased (10,746 vs. 7,174 mCi [1 mCi 5 37 MBq], P , 0.0001), as did the mean 99m Tc administered activity per patient (36.5 vs. 23.8 mCi, P , 0.0001). The percentage of patients having stress-only imaging increased (35% vs. 56%, P , 0.0001), and the total patient time spent in the laboratory decreased. Radiation dose equivalent levels were reduced in period 2 to 1%-7% of the allowed annual occupational dose equivalent. The combination of the use of high-efficiency SPECT technology and stress-only protocols resulted in a 34.7% reduction in mean total 99m Tc administered activity between time periods, with camera technology being responsible for 39.2% of the reduction and stress-only protocols for 60.8%. Conclusion: A combination of high-efficiency SPECT technology and selective use of stress-only protocols significantly reduces the occupational radiation dose equivalent to the staff of a nuclear cardiology laboratory.Key Words: radiation exposure; myocardial perfusion imaging; high-efficiency SPECT; stress-only imaging Radi ation exposure to patients from diagnostic imaging has recently been a prominent topic in the cardiac imaging literature (1), and myocardial perfusion imaging (MPI) has been suggested as one of the larger contributors to a patient's cumulative radiation exposure (2). Much recent effort has been directed toward reducing exposure to the patient (3); however, little attention has been paid to exposure of the medical staff to radiation. There is scant literature on medi...

High-efficiency SPECT technology can reduce radiation exposure to patients during gated blood pool imaging or decrease acquisition time while maintaining diagnostic accuracy. Based on the improved count sensitivity with high-efficiency SPECT, a 50% reduction in injected activity may be achievable while maintaining short imaging times of 5 minutes, with further reduction possible at longer imaging times.