Feasibility of ultra low-dose thallium stress-redistribution protocol including prone imaging in obese patients using CZT camera

Abstract

High efficiency cadmium-zinc-telluride (CZT) cameras provide an opportunity to lower the injected activities of radiopharmaceuticals for single photon emission tomography (SPECT) myocardial perfusion imaging (MPI). The limits for reducing activities of thallium have not been determined, particularly in obese patients. After an injection of 0.7 megabecquerel (MBq) of thallium/kg, we collected an average 1.5 million counts for the 10-min acquisition in a pilot cohort of ten patients. After extrapolation, we reduced the administered activity to 0.5 MBq/kg to obtain the expected 1 million counts. We studied the image quality in 124 patients (86 men, 43 obese with body mass index over 30 kg/m) referred for MPI. The quality of images was assessed by a number of recorded counts and visually by a four-grade scale (one-poor quality, four-excellent quality). In non-obese and obese patients, the average number of recorded counts was 1.1 vs. 1.07 million counts for the 10-min stress acquisition, 1.04 vs. 1.06 million counts for the 13-min rest acquisition, and the average quality score was 3.97 vs. 3.90, respectively (p = NS).The mean administered activity was 39.2 ± 7 MBq for non-obese and 48.7 ± 6 for obese patients (p < 0.0001), and the calculated effective dose was 4.0 ± 0.7 and 4.9 ± 0.6 mSv respectively (p < 0.0001). The ultra-low-dose thallium stress-redistribution protocol, including post-stress prone imaging, provides good quality of images with a low radiation burden, even in obese patients.

EANM procedural guidelines for myocardial perfusion scintigraphy using cardiac-centered gamma cameras

“…CT-based attenuation correction of MPS allowed for a reduction in the rate of non-diagnostic images down to 55% in this cohort. Kincl et al ( 2016 ) tested the feasibility of an ultra-low-dose 201 Tl protocol (injected activity reduced to 0.5 MBq/kg of 201 Tl) using GE camera with Alcyone technology in 124 patients. Using 10-min gated acquisitions in the supine position image quality, image quality was preserved even in obese patients and radiation exposure of patients was significantly reduced (4–5 mSv).…”

“…In addition, the redistribution of 201 Tl in the myocardium allows for a more sensitive detection of viability, in particular in myocardial territory with chronic occlusion of coronary arteries. The higher tomographic sensitivity of cardiac-centered cameras allows for a reduction of injected activities of 201 Tl of about 30% with preserved high image quality (Kincl et al 2016 ; Songy et al 2012 ). Nevertheless, the radiation exposure of patients for the acquisition of MPS with 201 Tl is 2 to 3 times higher than with 99m Tc-labeled agents.…”

Cardiovascular imaging 2016 in the International Journal of Cardiovascular Imaging

“…Kincl et al [9] evaluated the feasibility of ultra-low dose Thallium stress-redistribution including prone imaging in obese patients using a CZT camera. They studied 124 patients with an ultra-low dose Thallium of 0.5 MBq/kg.…”

Tl-201 dosing for CZT SPECT: More new information

“…In one study of a little over 100 patients, administered activity of 40-50 MBq (roughly 1/2 to 1/3 of the dose used in the current paper) achieved acceptable results even in obese patients with imaging times of 10 and 13 minutes. 9 Songy et al compared images with similar standard doses of Tl-201 on a high-efficiency camera with 5-minute acquisition and a conventional SPECT camera with 10-to 15-minute acquisition. 10 Other previous work has raised concerns about the accuracy of gated images with lower dose of Tl-201 on high-efficiency cameras.…”