Comparison of dose calculation algorithms model: convolution, superposition, and fast superposition in 3-D Conformal Radiotherapy (3D-CRT) treatment plan

The important task of radiotherapy is to make sure that the radiation dose to the target tumour is accurate as prescribed and the dose to the organ at risk is minimized. Therefore, the aim of this study is to compare and evaluate the efficiency of the dose calculation algorithms: namely convolution, superposition, and fast superposition which installed in Treatment Planning System (TPS) (CMS XiO, USA). In this study, we modified protocols described in IAEATecdoc-1583, where four typical treatment techniques such as single field, multiple field, wedge field, and multi-leaf collimated (MLC) field were analysed from the system. The measurement data for calculated dose and measured dose were taken from thorax CIRS anthropomorphic phantom. The assessment of algorithms was done by comparing the point dose calculated with the measured dose. The study shows that the superposition algorithm produced relative error less than ±3% which passed 100% of all reference points, whilst the convolution algorithm and fast superposition presented relative error more than ±3% which passed 82% and 91% of reference points, respectively. In conclusion, the evaluation of radiotherapy treatment plan shall take into account the type of dose calculation algorithm model in order to optimize radiotherapy treatment and ensure the radiation safety to the patient

Evaluation of organ dose and image quality metrics of pediatric CT Chest-Abdomen-Pelvis (CAP) examination: an anthropomorphic phantom study

The aim of this study is to investigate the impact of CT acquisition parameter setting on organ dose and its influence on image quality metrics in pediatric phantom during CT examination. The study was performed on 64-slice multidetector CT scanner (MDCT) Siemens Definition AS (Siemens Sector Healthcare, Forchheim, Germany) using various CT CAP protocols (P1–P9). Tube potential for P1, P2, and P3 protocols were fixed at 100 kVp while P4, P5, and P6 were fixed at 80 kVp with used of various reference noise values. P7, P8, and P9 were the modification of P1 with changes on slice collimation, pitch factor, and tube current modulation (TCM), respectively. TLD-100 chips were inserted into the phantom slab number 7, 9, 10, 12, 13, and 14 to represent thyroid, lung, liver, stomach, gonads, and skin, respectively. The image quality metrics, signal to noise ratio (SNR) and contrast to noise ratio (CNR) values were obtained from the CT console. As a result, this study indicates a potential reduction in the absorbed dose up to 20% to 50% along with reducing tube voltage, tube current, and increasing the slice collimation. There is no significant difference (p > 0.05) observed between the protocols and image metrics

Paediatric radiation dose and cancer risk associated with body effective diameter during CT thorax examination

Paediatric patients are considered vulnerable to radiation exposure and have a greater risk of developing radiation-induced cancers due to active growth cells. Radiation dose from a CT examination is the highest among other imaging modalities and can become harmful if unoptimised. Thus, the aim of this study is to evaluate the influence of paediatric size on SSDE value and to estimate cancer risk occurrence in specific organs of paediatric patients receiving CT chest examination. Data such as volume-weighted CT dose index (CTDIvol), dose length product (DLP) and patient's demography were retrospectively collected from a 64-slice CT scanner (Siemens Somatom Definition AS+) at University Malaya Medical Centre. A total of 120 patients were categorised into four age groups: G1 (0 – 0.05) was observed between the SSDEAAPM and SSDENCICT across all age groups. The cancer risk estimated shows thyroid organs receives the highest probability of cancer incidence in both the genders, which was calculated to be 2.1 for males and 3.9 for females per 100,000 procedures, respectively. Nevertheless, adequate justification of paediatric CT scans and dose optimisation are required to reduce unnecessary exposure and radiation-induced risks