Original Article
Reduced administered activity, reduced acquisition time, and preserved image quality for the new CZT camera

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Abstract

Background

For a 1-day myocardial perfusion SPECT (MPS) the recommendations for administered activity stated in the EANM guidelines results in an effective dose of up to 16 mSv per patient. Recently, a gamma camera system, based on cadmium zinc telluride (CZT) technology, was introduced. This technique has the potential to reduce the effective dose and scan time compared to the conventional NaI gamma camera. The aim of this study was to investigate if the effective dose can be reduced with a preserved image quality using CZT technology in MPS.

Methods

In total, 150 patients were included in the study. All underwent a 1-day 99mTc-tetrofosmin stress-rest protocol and were divided into three subgroups (n = 50 in each group) with 4, 3, and 2.5 MBq/kg body weight of administered activity in the stress examination, respectively. The acquisition time was increased in proportion to the decrease in administered activity. All examinations were analyzed for image quality by visual grading on a 4-point scale (1 = poor, 2 = adequate, 3 = good, 4 = excellent), by two expert readers.

Results

The total effective dose (stress + rest) decreased from 9.3 to 5.8 mSv comparing 4 to 2.5 MBq/kg body weight. For the patients undergoing stress examination only (35%) the effective dose, administrating 2.5 MBq/kg, was 1.4 mSv. The image acquisition times for 2.5 MBq/kg body weight were 475 and 300 seconds (stress and rest) compared to 900 seconds for each when using conventional MPS. The average image quality was 3.7 ± 0.5, 3.8 ± 0.5, and 3.8 ± 0.4 for the stress images and 3.5 ± 0.6, 3.6 ± 0.6, and 3.5 ± 0.6 for the rest images and showed no statistically significant difference (P = .62) among the 4, 3, and 2.5 MBq/kg groups.

Conclusions

The new CZT technology can be used to considerably decrease the effective dose and acquisition time for MPS with preserved high image quality.

Section snippets

Background

Myocardial perfusion single photon emission computed tomography (MPS) is an established non-invasive imaging technique for detection of myocardial perfusion defects. The conventional technology with a NaI-crystal was introduced more than 50 years ago and is the most widely used nuclear medicine imaging technique. Conventional MPS is associated with time-consuming image acquisition and a relatively high administered activity is required to enable adequate image quality.

Recently, a new generation

Study Design

The study group comprised 150 consecutive patients referred for MPS due to known or suspected coronary artery disease. All patients underwent a 1-day 99mTc-tetrofosmin stress protocol according to clinically established protocols. Exclusion criteria were a patient weight more than 100 kg, patients undergoing a 2-day protocol and patients undergoing the rest examination before the stress examination.

The patients were consecutively included into three different subgroups. The first 50 patients

Results

Patient characteristics and MPS study results are shown in Table 1. All 150 patients successfully underwent stress examination with mean activity of 318, 238, and 203 MBq at stress for the 4, 3, and 2.5 MBq/kg protocols, respectively (Table 2). Examination at rest was performed in 97 patients (65%) based on the interpretation of the stress images. The mean duration between stress and rest activity administration was 3.5 ± 1.1 hour resulting in a mean administered activity for the rest

Discussion

This study shows that it is possible to perform MPS with the new CZT technology with both a significantly reduced effective dose and a shorter scan time with a preserved image quality as compared to conventional MPS technology and the EANM guidelines.

There was no statistically significant difference in image quality between the three activity groups. Also, the image quality was graded as “good” or “excellent” in the vast majority of the studies by both expert readers. These results are

Conclusions

The effective radiation dose and the acquisition time can be considerably decreased with preserved high image quality when MPS is performed with the novel CZT technology. A stress and rest examination, using a 1-day protocol, can be performed with an effective dose of 37% compared to the dose recommended in international guidelines.

Acknowledgments

The authors would like to thank Christel Kullberg for excellent technical assistance. This study was supported in part by research funding from Region of Scania, Swedish Research Council, Swedish Heart and Lung Foundation, and Lund University Faculty of Medicine.

Conflict of interest

None.

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