ABSTRACT
@#This systematic review was conducted to evaluate the image quality performance when implementing computed tomography data (CTAC) or magnetic resonance data for attenuation correction (MRAC) on positron emission tomography (PET) images. The CTAC and MRAC were performed on image from PET/CT and PET/MR scanners, respectively. The systematic review was done based on Preferred Reporting Items for Systematic Reviews (PRISMA). In this study, twelve articles were included from six databases. The image performance was evaluated by overall image quality, contrast, spatial resolution, detectability, standardised uptake value (SUV) and acquisition time. Data was shown as mean ± standard deviation and compared between CTAC and MRAC images to determine which attenuation correction method provides better image quality. Results found that PET-CTAC and PET-MRAC have similar image performance in overall image quality (p=0.93), detectabilty (p=0.84), SUVmean (p=0.84) and SUVmax (p=0.81). Meanwhile, PET-CTAC acquisition time is significantly faster than PET-MRAC by approximately two fold (p <0.05). There were no statistical analyses performed for image contrast, spatial resolution and contrast-noise-ratio due to the insufficient data. In conclusion, although PET/CT is faster than PET/MRI procedure, images yielded from CTAC and MRAC are equivalent to each other. Due to the variation of linear attenuation coefficient for each type of tissue, future review of image quality comparison can be done focusing on specific tissue or region such as soft tissue, bone and lungs to reflect the real impact of CTAC and MRAC on PET image.
ABSTRACT
Thyroid and gonads are radiosensitive organs which requires radiation shield to reduce the dose received. However, radiation shielding is not widely used in radionuclide imaging because it is heavy, uncomfortable and can cause pain in the spine. Therefore, a research was carried out to determine the ability of thyroid and gonad radiation shield which is thinner and lighter in reducing radiation dose. A study was conducted in Hospital Putrajaya to determine the radiation dose received by the thyroid and gonads during a complete Positron Emission Tomography-Computed Tomography (PET-CT) procedure with and without radiation shield. A total of six male staffs have been chosen as subject and data from 33 complete PET-CT procedures have been collected. For every PET-CT procedure, the subject’s thyroid and gonad were shielded using 0.5-mm thick radiation shielded, model Mavig 615 (USA) and Shielding International (USA) respectively. Thermal luminescent dosimeter (TLD) chips were used as radiation dose detector. The average 18FFDG radioactivity administered to the patient was 387 MBq and the average scan time is 9.224 ± 1.797 minutes. The results showed that the mean equivalent dose received by the thyroid with and without shielding were 0.080 ± 0.033 mSv and 0.078 ± 0.039 mSv respectively. The mean equivalent dose received by gonad with and without shielding were 0.059 ± 0.040 mSv and 0.061 ± 0.030 mSv respectively. Radiation shield with 0.5 mm thickness is unable to reduce radiation dose received by the thyroid (p = 0.76) and gonads (p = 0.79) because it is too thin to resist the high-energy radiation during PET-CT procedures. Thyroid receive higher radiation dose of 0.016 m Sv compared to the gonads (p < 0.05) because the thyroid’s position is more exposed to radiation sources which are 18F-FDG during radiopharmaceutical preparation and patients after administered with 18F-FDG during PET-CT procedure.