Monte Carlo calculated photon interaction coefficients for several body tissues.

Absorption of energy in body tissues because of radiation interactions may induce harmful outcomes such as cancer and hereditary effects due to a variety of damages in the integrity and activity of the cells. This study presents Monte Carlo calculated $\boldsymbol{\mu} /\boldsymbol{\rho}$, ${\boldsymbol{\mu}}_{\boldsymbol{en}}/\boldsymbol{\rho}$ and ${\boldsymbol{\mu}}_{\boldsymbol{tr}}/\boldsymbol{\rho}$ values of some common tissues and organs found in the human body (namely, adipose tissue, blood, bone-cortical, brain-grey/white matter, breast tissue, eye lens, lung tissue, muscle-skeletal, ovary, soft tissue and testes) as well as water for comparison purposes. The simulation model involves a monoenergetic point source producing a pencil beam where, depending on the parameter under study, particle flux, energy flux or absorbed dose from photon interactions are scored in the range of 10 keV to 20 MeV energy. The simulations were performed using the Monte Carlo package MCNP6.1 and provided $\boldsymbol{\mu} /\boldsymbol{\rho}$, ${\boldsymbol{\mu}}_{\boldsymbol{en}}/\boldsymbol{\rho}$ and ${\boldsymbol{\mu}}_{\boldsymbol{tr}}/\boldsymbol{\rho}$ values. The data produced in this study were compared with theoretical photon attenuation data from the XMUDAT database and demonstrated good agreement. The results, which are based on a simple model geometry and pure elemental compositions, indicate that this approach can be applied to evaluate $\boldsymbol{\mu} /\boldsymbol{\rho}$, ${\boldsymbol{\mu}}_{\boldsymbol{en}}/\boldsymbol{\rho}$ and ${\boldsymbol{\mu}}_{\boldsymbol{tr}}/\boldsymbol{\rho}$ in a broad energy range for any element, compound or mixture.

Dosimetric comparison of different treatment planning techniques with International Commission on Radiation Units and Measurements Report-83 recommendations in adjuvant pelvic radiotherapy of gynecological malignancies.

AIM: The study evaluates the different treatment planning techniques according to three recommendation levels of the International Commission on Radiation Units and Measurements Report-83 in gynecologic cancer patients treated with adjuvant pelvic radiotherapy (APR). MATERIALS AND METHODS: Computerized tomography images of ten endometrial and cervical cancer patients who were treated with APR were assessed. For each patient, five different treatment plans were created. One homogeneity index and four different conformity indexes (CIs) were calculated for three-dimensional conformal radiotherapy (3D-CRT), field-in-field (FIF), seven-field intensity modulated radiotherapy (7-IMRT) with two different degrees beginning (7A-IMRT, 7B-IMRT) and 9-IMRT treatment plans. Dose volume histogram parameters and normal tissue complication probability (NTCP) were compared for organs at risk (OAR). RESULTS: The CI values of the IMRT were closer to 1 with respect to other plans (P < 0.05). The rectum and the bladder volumes which received more than 40 Gy were decreased with IMRT compared to 3D-CRT (P < 0.05). Doses received by the 195 cc volume of the small intestine and NTCP values were significantly decreased with IMRT (P < 0.05). CONCLUSION: IMRT provided more protection than FIF plans at high dose volumes of the OAR; however, it did not show any superiority at low-dose volumes. The NTCP results supported IMRT for only small intestine protection. Because IMRT is increasingly used clinically, the comparison of NTCP will become more common in the near future. Therefore, new prospective studies with sufficient number of patients and appropriate NTCP models are needed for this treatment modality.