Optimization of CT protocols for thyroid and parathyroid SPECT/CT imaging
- Shalamanov, S. Avramova-Cholakova, I. Kostadinova, I. Dyakov
The first national survey of patient exposures from hybrid imaging in Nuclear Medicine, performed in Bulgaria in 2014, revealed that SPECT/CT imaging of either thyroid or parathyroid glands was performed by applying a CT scan of the whole anatomical region, neck and chest, subject to SPECT. In most cases it was not necessary to perform a CT scan matching the whole SPECT region. The aim of this study is to propose an optimized CT protocol by reducing the CT scan length. The standard CT protocols for both types of examinations included neck and chest scan with the same exposure data. After the optimization the CT scan was restricted to the region of radiopharmaceutical uptake. Comparison of scan length, dose-length product (DLP) and effective dose from the old and the new protocols was performed. Software was used to estimate effective dose from the CT scan separately for males and females. A total of 17 patients undergoing either thyroid or parathyroid examination received CT of the neck and chest before the optimization. After the introduction of the optimized protocol, data were collected for a total of 70 patients. The mean scan length for males was reduced from 39 to 22 cm (42% reduction) and for females the reduction was from 44 to 22 cm (50%). The mean DLP was decreased by about 34% (from 138 to 91 mGy.cm) for males and 48% (from 147 to 77 mGy.cm) for females respectively. The effective dose was reduced by 67 % (from 1.8 to 0.6 mSv) for males and 79% (from 2.8 to 0.6 mSv) for females. The introduction of the optimized CT protocol for hybrid SPECT/CT imaging of the thyroid or parathyroid glands led to significant decrease of the total effective dose of the patients from these examinations.
Key words: SPECT-CT. OPTIMIZATION, THYROID IMAGING, PARATHYROID IMAGING