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Background: In planning radiotherapy treatments, computed tomography (CT) has become a crucial tool. CT scans involve exposure to ionizing radiation, which can increase the risk of cancer and other adverse health effects in patients. Ionizing radiation doses for medical exposure must be kept "As Low As Reasonably Achievable". Very few articles on guidelines for radiotherapy-computed tomography scans are available. This paper reviews the current literature on radiation dose optimization based on the effective dose and diagnostic reference level (DRL) for head, neck, and pelvic CT procedures used in radiation therapy planning. This paper explores the strategies used to optimize radiation doses, and high-quality images for diagnosis and treatment planning. Methods: A cross-sectional study was conducted on 300 patients with head, neck, and pelvic region cancer in our institution. The DRL, effective dose, volumetric CT dose index (CTDIvol), and dose-length product (DLP) for the present and optimized protocol were calculated. DRLs were proposed for the DLP using the 75th percentile of the distribution. The DLP is a measure of the radiation dose received by a patient during a CT scan and is calculated by multiplying the CT dose index (CTDI) by the scan length. To calculate a DRL from a DLP, a large dataset of DLP values obtained from a specific imaging procedure must be collected and can be used to determine the median or 75th-percentile DLP value for each imaging procedure. Results: Significant variations were found in the DLP, CTDIvol, and effective dose when we compared both the standard protocol and the optimized protocol. Also, the optimized protocol was compared with other diagnostic and radiotherapy CT scan studies conducted by other centers. As a result, we found that our institution's DRL was significantly low. The optimized dose protocol showed a reduction in the CTDIvol (70% and 63%), DLP (60% and 61%), and effective dose (67% and 62%) for both head, neck, and pelvic scans. Conclusions: Optimized protocol DRLs were proposed for comparison purposes. [ABSTRACT FROM AUTHOR]

Introduction: The anatomy of the chest wall is curved which makes it quite complicated to plan radiation therapy for breast cancer. There are different techniques for delivering external beam radiation therapy. Therefore, it is essential to know the technique by which we can render a better treatment. Aim: To compare and analyse three different planning techniques namely Three Dimensional Conformal Radiation Therapy (3DCRT), two field Intensity Modulated Radiation Therapy (IMRT) and multiple field IMRT using dosimetric parameters. Materials and Methods: In this retrospective dosimetric study, we evaluated 10 breast cancer patients. For each patient, three plans namely 3DCRT, two field IMRT and multiple field IMRT (7 beams) were generated on the computed tomographic images using Oncentra Treatment Planning system. A dose of 50Gy in 25 fractions was prescribed to the Planning Target Volume (PTV). The plans were compared with each other on volume coverage (conformity and homogeneity) and organ-at-risk sparing. Paired t-test was used for identifying statistical differences between the plans. A significance level, p=5% or 0.05 was chosen. Results: The dose conformity was best by multiple field IMRT (p=0.0001). Both two field IMRT and multiple field IMRT provided more homogenous dose distribution with homogeneity index of 1.09±0.01 and 1.08±0.01 respectively when compared to 1.11±0.01 by 3DCRT (p=0.001 and 0.0001, respectively). D2 (dose received by 2% of the tumour volume), a measure of maximum dose was greater in 3DCRT. While dose to the critical organs was considerably less in both two field IMRT and 3DCRT than in multiple field IMRT, two field IMRT achieved lowest doses. Moreover, there was a substantial increase in the Monitor Units (MUs) for multiple field IMRT when compared with the other two techniques. Conclusion: Two field IMRT have the features intermediate of 3DCRT and multiple field IMRT. The two field IMRT is on the beneficial side with homogenous dose distribution in the target and less dose to the critical organs. [ABSTRACT FROM AUTHOR]