This study was carried out to analyze the effect of varying kilovoltage peak (kVp) on Hounsfield unit (HU) for various tissue substitutes in two different phantoms and their dosimetric impact on dose calculation in Monaco treatment planning system version 5.11.02.

HU for different density materials was obtained from computed tomography images of the phantoms acquired at various kVps (80, 100, and 120). Two different phantoms (CatPhan 503 and CIRS 062 M) were used to construct their suitability for computed tomography. Both scan phantoms were used to perform 30 volumetric modulated arc therapy plans.

No significant variation in the CatPhan phantom was observed for HU of different density materials with various kVp. In contrast, a direct relationship between kVp and HU was observed in the case of CIRS phantom, as increases in the kVp resulted in a corresponding decrease in HU. The maximum HU deviation was found in breast tissue. HU is inversely proportional to the kVp for tissues. There was a difference of ≥22% in HU values between the highest densities in CatPhan and CIRS phantoms.

CIRS 062 M was found more convenient for calibration than CatPhan 503, especially for high-density material.

Breast cancer (BC) is first of the top 10 malignancies in Iraq. Dose-volume histograms (DVHs) are most commonly used as a plan evaluation tool. This study aimed to assess DVH statistics using three-dimensional conformal radiotherapies in BC in an adjuvant setting.

A retrospective study of 70 histologically confirmed women diagnosed with BC was reviewed. The study was conducted between November 2020 and May 2021, planning for treatment with adjuvant three-dimensional conformal radiotherapies. The treatment plan used for each woman was based on an analysis of the volumetric dose, including DVH analysis.

The planning target volume and clinical target volume coverage for tumors at V85% was better than V90% and V95%, with highly significant differences (p < 0.0001). The planning target volume and clinical target volume coverage for lymph nodes at V85% was higher than V90% and V95%, with no significant differences.

This is the only study that has been carried out in Iraq that we are aware of that addresses the evaluation of DVH statistics in BC. V85% produced the best chest wall coverage, and V95% made the worst. With little significance, higher lymph nodes coverage was attained at V85%, whereas the lowest coverage was at V95%.

Dose gradient index (DGI) is a tool used to evaluate radiation dose gradient outside the target. This study aimed to analyze the consistency of this tool through the long course of radiotherapy due to patient anatomical changes, such as body weight loss and tumor shrinkage.

A total of 30 patients diagnosed with different head and neck cancer were treated with the simultaneous integrated boost intensity-modulated radiation therapy technique; the patients underwent new computed tomography (CT) simulations after 10 and 20 treatment sessions. The gradient index was compared for the initial, reconstructed, and adaptive plans.

All patients showed a significant decrease (p < 0.001) in weight at reconstructed CT1 (RCT1) and reconstructed CT2 compared with original CT. Also, primary gross tumor volume was significantly decreased (p < 0.001) at reconstructed CT1 and reconstructed CT2. In the dosimetric part, all organs showed a significant increase in dose delivery at reconstructed plans (Rplans) compared with the original plan (Oplan). Meanwhile, at adaptive plans (Aplans), all organs showed a significant decrease in dose delivery compared with Oplan. The DGI was significantly increased at Rplan1 and Rplan2 compared with Oplan, with a median value of 29 (15.5–41.3) and 30 (15.1–38) at Rplan1 and Rplan2, respectively, and 25.8 (14.9–37.6) at Oplan. Whereas DGI value decreased significantly at Aplan1 compared with Oplan, and then insignificantly increased at Aplan2 compared with Aplan1.

DGI must be evaluated during the intensity-modulated radiation therapy course in the treatment of head and neck cancers, which clearly varies significantly as a result of a patient's anatomical changes during the radiotherapy course, and it can be improved or maintained to its original value by using adaptive planning strategy.