Standardized flattening filter free volumetric modulated arc therapy plans based on anteroposterior width for total body irradiation.

In this work, the feasibility of using flattening filter free (FFF) beams in volumetric modulated arc therapy (VMAT) total body irradiation (TBI) treatment planning to decrease protracted beam-on times for these treatments was investigated. In addition, a methodology was developed to generate standardized VMAT TBI treatment plans based on patient physical dimensions to eliminate plan optimization time. A planning study cohort of 47 TBI patients previously treated with optimized VMAT ARC 6 MV beams was retrospectively examined. These patients were sorted into six categories depending on height and anteroposterior (AP) width at the umbilicus. Using Varian Eclipse, clinical 40 cm × 10 cm open field arcs were substituted with 6 MV FFF. Mid-plane lateral dose profiles in conjunction with relative arc output factors (RAOF) yielded how far a given multileaf collimator (MLC) leaf must move in order to achieve a mid-plane 100% isodose for a specific control point. Linear interpolation gave the dynamic MLC aperture for the entire arc for each patient AP width category, which was subsequently applied through Python scripting. All FFF VMAT TBI plans were then evaluated by two radiation oncologists and deemed clinically acceptable. The FFF and clinical VMAT TBI plans had similar Body-5 mm D98% distributions, but overall the FFF plans had statistically significantly increased or broader Body-5 mm D2% and mean lung dose distributions. These differences are not considered clinically significant. Median beam-on times for the FFF and clinical VMAT TBI plans were 11.07 and 18.06 min, respectively, and planning time for the FFF VMAT TBI plans was reduced by 34.1 min. In conclusion, use of FFF beams in VMAT TBI treatment planning resulted in dose homogeneity similar to our current VMAT TBI technique. Clinical dosimetric criteria were achieved for a majority of patients while planning and calculated beam-on times were reduced, offering the possibility of improved patient experience.

Calculation of midplane dose for total body irradiation from entrance and exit dose MOSFET measurements.

This work is the development of a MOSFET based surface in vivo dosimetry system for total body irradiation patients treated with bilateral extended SSD beams using PMMA missing tissue compensators adjacent to the patient. An empirical formula to calculate midplane dose from MOSFET measured entrance and exit doses has been derived. The dependency of surface dose on the air-gap between the spoiler and the surface was investigated by suspending a spoiler above a water phantom, and taking percentage depth dose measurements (PDD). Exit and entrances doses were measured with MOSFETs in conjunction with midplane doses measured with an ion chamber. The entrance and exit doses were combined using an exponential attenuation formula to give an estimate of midplane dose and were compared to the midplane ion chamber measurement for a range of phantom thicknesses. Having a maximum PDD at the surface simplifies the prediction of midplane dose, which is achieved by ensuring that the air gap between the compensator and the surface is less than 10 cm. The comparison of estimated midplane dose and measured midplane dose showed no dependence on phantom thickness and an average correction factor of 0.88 was found. If the missing tissue compensators are kept within 10 cm of the patient then MOSFET measurements of entrance and exit dose can predict the midplane dose for the patient.

Comparison of the effects of osmotic pump implantation with subcutaneous injection for administration of drugs after total body irradiation in mice.

The increasing potential for radiation exposure from nuclear accidents or terrorist activities has intensified the need to develop pharmacologic countermeasures against injury from total body irradiation (TBI). Many initial experiments to develop and test these countermeasures utilize murine irradiation models. Yet, the route of drug administration can alter the response to irradiation injury. Studies have demonstrated that cutaneous injuries can exacerbate damage from radiation, and thus surgical implantation of osmotic pumps for drug delivery could adversely affect the survival of mice following TBI. However, daily handling and injections to administer drugs could also have negative consequences. This study compared the effects of subcutaneous needlesticks with surgical implantation of osmotic pumps on morbidity and mortality in a murine model of hematopoietic acute radiation syndrome (H-ARS). C57BL/6 mice were sham irradiated or exposed to a single dose of 7.7 Gy 60Co TBI. Mice were implanted with osmotic pumps containing sterile saline seven days prior to irradiation or received needlesticks for 14 days following irradiation or received no treatment. All irradiated groups exhibited weight loss. Fewer mice with osmotic pumps survived to 30 days post irradiation (37.5%) than mice receiving needlesticks or no treatment (70% and 80%, respectively), although this difference was not statistically significant. However, mice implanted with the pump lost significantly more weight than mice that received needlesticks or no treatment. These data suggest that surgical implantation of a drug-delivery device can adversely affect the outcome in a murine model of H-ARS.

The role of whole brain radiation therapy in the management of newly diagnosed brain metastases: a systematic review and evidence-based clinical practice guideline.

QUESTION: Should patients with newly-diagnosed metastatic brain tumors undergo open surgical resection versus whole brain radiation therapy (WBRT) and/or other treatment modalities such as radiosurgery, and in what clinical settings? TARGET POPULATION: These recommendations apply to adults with a newly diagnosed single brain metastasis amenable to surgical resection. RECOMMENDATIONS: Surgical resection plus WBRT versus surgical resection alone Level 1 Surgical resection followed by WBRT represents a superior treatment modality, in terms of improving tumor control at the original site of the metastasis and in the brain overall, when compared to surgical resection alone. Surgical resection plus WBRT versus SRS + or - WBRT Level 2 Surgical resection plus WBRT, versus stereotactic radiosurgery (SRS) plus WBRT, both represent effective treatment strategies, resulting in relatively equal survival rates. SRS has not been assessed from an evidence-based standpoint for larger lesions (>3 cm) or for those causing significant mass effect (>1 cm midline shift). Level 3 Underpowered class I evidence along with the preponderance of conflicting class II evidence suggests that SRS alone may provide equivalent functional and survival outcomes compared with resection + WBRT for patients with single brain metastases, so long as ready detection of distant site failure and salvage SRS are possible. Note The following question is fully addressed in the WBRT guideline paper within this series by Gaspar et al. Given that the recommendation resulting from the systematic review of the literature on this topic is also highly relevant to the discussion of the role of surgical resection in the management of brain metastases, this recommendation has been included below.

[The dose-response of unstable chromosome exchanges in lymphocytes of cancer patients undergone whole-body fractionated gamma-rays exposure at the total dose 1.15 Gy].

The dose-response of unstable chromosome exchanges (UCE) in lymphocytes of 4 cancer patients undergone whole-body fractionated gamma-rays exposure (at the daily dose of 0.115 Gy up to the total dose 1.15 Gy) was compared with corresponding dose-response for lymphocytes of the same patients, irradiated in vitro at the same dose range. In vivo irradiation yielded lower frequency of UCE on the dose unit than in vitro irradiation. It was shown that the in vivo dose-response curve gives more adequate dose estimation than in vitro one. This curve could be used for reconstruction of absorbed dose in the cases of analogous character of in-controlled irradiation of people.

Identification of critical factors that significantly affect the dose-response in mosquitoes irradiated as pupae.

BACKGROUND: The sterile insect technique (SIT) for use against mosquitoes consists of several steps including the production of the target species in large numbers, the separation of males and females, the sterilization of the males, and the packing, transport and release of the sterile males at the target site. The sterility of the males is the basis of the technique; for this, efficient and standardized irradiation methods are needed to ensure that the required level of sterility is reliably and reproducibly achieved. While several reports have found that certain biological factors, handling methods and varying irradiation procedures can alter the level of induced sterility in insects, few studies exist in which the methodologies are adequately described and discussed for the reproductive sterilization of mosquitoes. Numerous irradiation studies on mosquito pupae have resulted in varying levels of sterility. Therefore, we initiated a series of small-scale experiments to first investigate variable parameters that may influence dose-response in mosquito pupae, and secondly, identify those factors that potentially have a significantly large effect and need further attention. METHODS: In this study, we compiled the results of a series of experiments investigating variable parameters such as pupal age (Aedes aegypti), pupal size (Ae. aegypti), geographical origin of mosquito strains (Ae. aegypti and Ae. albopictus), exposure methods (in wet versus dry conditions, Ae. albopictus) and subsequently in low versus high oxygen environments [submerged in water (low O2 (< 5 %)] and in air [high O2 (~ 21 %)] on the radiosensitivity of male pupae (Ae. aegypti, Ae. albopictus and Anopheles arabiensis). RESULTS: Results indicate that radiosensitvity of Ae. aegypti decreases with increasing pupal age (99% induced sterility in youngest pupae, compared to 93% in oldest pupae), but does not change with differences in pupal size (P = 0.94). Differing geographical origin of the same mosquito species did not result in variations in radiosensitivity in Ae. aegypti pupae [Brazil, Indonesia, France (La Reunion), Thailand] or Ae. albopictus [Italy, France (La Reunion)]. Differences in induced sterility were seen following irradiation of pupae that were in wet versus dry conditions, which led to further tests showing significant radioprotective effects of oxygen depletion during irradiation procedures in three tested mosquito species, as seen in other insects. CONCLUSIONS: These findings infer the necessity to further evaluate significant factors and reassess dose-response for mosquitoes with controlled variables to be able to formulate protocols to achieve reliable and reproducible levels of sterility for application in the frame of the SIT.

[Certification of an in-house manufactured translational couch unit for total body irradiation in accordance with the medical devices act]. / Zertifizierung einer Translationsliege zur Ganzkörperbestrahlung aus In-Haus-Herstellung gemäss dem Medizinproduktegesetz.

UNLABELLED: A new translational couch unit with extended potentials of dose optimization by variable velocity and a comfortable user interface with integrated patient administration was developed at the university clinic of Regensburg. MATERIALS AND METHODS: The concept and construction were elaborated in legal accordance with the in-house manufacture conditions mentioned in the German Medical Devices Act. In particular we have implemented a concept of functional safety based on a controller unit, an independent monitoring unit and self-testing procedures. Redundant safety relevant hard- and software components are continuously checked against each other. In case of any malfunction the translation movement and the linear accelerator are stopped. Gap-free continuation of the treatment will be possible after elimination of the cause of the interrupt. RESULTS AND CONCLUSION: After the testing of the implemented functional safety features including the risk assessment and management, electrical safety, electromagnetic compatibility by accredited technical experts the translational couch system complies with the requirements of the Medical Devices Act and can be operated in terms of in-house application. The presented certification procedure can motivate other radiation departments to develop own systems for in-house usage.

Whole-body voxel phantoms of paediatric patients--UF Series B.

Following the previous development of the head and torso voxel phantoms of paediatric patients for use in medical radiation protection (UF Series A), a set of whole-body voxel phantoms of paediatric patients (9-month male, 4-year female, 8-year female, 11-year male and 14-year male) has been developed through the attachment of arms and legs from segmented CT images of a healthy Korean adult (UF Series B). Even though partial-body phantoms (head-torso) may be used in a variety of medical dose reconstruction studies where the extremities are out-of-field or receive only very low levels of scatter radiation, whole-body phantoms play important roles in general radiation protection and in nuclear medicine dosimetry. Inclusion of the arms and legs is critical for dosimetry studies of paediatric patients due to the presence of active bone marrow within the extremities of children. While the UF Series A phantoms preserved the body dimensions and organ masses as seen in the original patients who were scanned, comprehensive adjustments were made for the Series B phantoms to better match International Commission on Radiological Protection (ICRP) age-interpolated reference body masses, body heights, sitting heights and internal organ masses. The CT images of arms and legs of a Korean adult were digitally rescaled and attached to each phantom of the UF series. After completion, the resolutions of the phantoms for the 9-month, 4-year, 8-year, 11-year and 14-year were set at 0.86 mm x 0.86 mm x 3.0 mm, 0.90 mm x 0.90 mm x 5.0 mm, 1.16 mm x 1.16 mm x 6.0 mm, 0.94 mm x 0.94 mm x 6.00 mm and 1.18 mm x 1.18 mm x 6.72 mm, respectively.

ACPSEM ROSG TBI working group recommendations for quality assurance in total body irradiation.

The Australasian College of Physical Scientists and Engineers in Medicine (ACPSEM) radiation oncology specialty group (ROSG) formed a series of working groups in 2011 to develop recommendations for guidance of radiation oncology medical physics practice within the Australasian setting. These recommendations are intended to provide guidance for safe work practices and a suitable level of quality control without detailed work instructions. It is the responsibility of the medical physicist to ensure that locally available equipment and procedures are sufficiently sensitive to establish compliance to these recommendations. The recommendations are endorsed by the ROSG, and have been subject to independent expert reviews. For the Australian audience, these recommendations should be read in conjunction with the tripartite radiation oncology practice standards [1, 2]. This publication presents the recommendations of the ACPSEM total body irradiation working group (TBIWG) and has been developed in alignment with other international associations. However, these recommendations should be read in conjunction with relevant national, state or territory legislation and local requirements, which take precedence over the ACPSEM recommendations. It is hoped that the users of this and other ACPSEM recommendations will contribute to the development of future versions through the ROSG of the ACPSEM. This document serves as a guideline for calibration and quality assurance of equipment used for TBI in Australasia.

ACPSEM ROSG TBE working group recommendations for quality assurance in total body electron irradiation.

The Australasian College of Physical Scientists and Engineers in Medicine (ACPSEM) Radiation Oncology Specialty Group (ROSG) formed a series of working groups in 2011 to develop recommendations for guidance of radiation oncology medical physics practice within the Australasian setting. These recommendations are intended to provide guidance for safe work practices and a suitable level of quality control without detailed work instructions. It is the responsibility of the medical physicist to ensure that locally available equipment and procedures are sufficiently sensitive to establish compliance to these recommendations. The recommendations are endorsed by the ROSG, and have been subject to independent expert reviews. For the Australian readers, these recommendations should be read in conjunction with the Tripartite Radiation Oncology Reform Implementation Committee Quality Working Group: Radiation Oncology Practice Standards (2011), and Radiation Oncology Practice Standards Supplementary Guide (2011). This publication presents the recommendations of the ACPSEM ROSG Total Body Electron Irradiation Working Group and has been developed in alignment with other international associations. However, these recommendations should be read in conjunction with relevant national, state or territory legislation and local requirements, which take precedence over the ACPSEM recommendations. It is hoped that the users of this and other ACPSEM recommendations will contribute to the development of future versions through the Radiation Oncology Specialty Group of the ACPSEM. This document serves as a guideline for calibration and quality assurance of equipment used for TBE in Australasia.

An Interlaboratory Validation of the Radiation Dose Response Relationship (DRR) for H-ARS in the Rhesus Macaque.

The Medical Countermeasures against Radiological Threats (MCART) consortium has established a dose response relationship for the hematopoietic acute radiation syndrome (HARS) in the rhesus macaque conducted under an individualized supportive care protocol, including blood transfusions. Application of this animal model as a platform for demonstrating efficacy of candidate medical countermeasures is significantly strengthened when the model is independently validated at multiple institutions. The study reported here describes implementation of standard operating procedures at an institute outside the consortium in order to evaluate the ability to establish an equivalent radiation dose response relationship in a selected species. Validation of the animal model is a significant component for consideration of the model protocol as an FDA-recommended drug development tool in the context of the "Animal Rule." In the current study, 48 male rhesus macaques (4-8 kg) were exposed to total-body irradiation (TBI) using 6 MV photon energy at a dose rate of approximately 0.8 Gy min. Results show that onset and duration of the hematological response, including anemia, neutropenia, and thrombocytopenia, following TBI ranging from 6.25 to 8.75 Gy correlate well with previously reported findings. The lethality values at 60 d following TBI were estimated to be 6.88 Gy (LD30/60), 7.43 Gy (LD50/60), and 7.98 Gy (LD70/60). These values are equivalent to those published previously of 7.06 Gy (LD30/60), 7.52 Gy (LD50/60), and 7.99 Gy (LD70/60); the DRR slope (p = 0.68) and y-intercepts show agreement along the complete dose range for HARS. The ability to replicate the previously established institutional lethality profile (PROBIT) and model outcomes through careful implementation of defined procedures is a testament to the robustness of the model and highlights the need for consistency in procedures.

Calculation and prescription of dose for total body irradiation.

The use of large total body fields creates a unique set of problems that stress the accuracy of techniques routinely used for dose calculation. This paper discusses an approach suggested by the Children's Cancer Study Group (CCSG) for both prescribing the total body irradiation (TBI) dose and calculating the beam-on time or meter set needed to deliver it. It is aimed at guaranteeing the accuracy of the calculations, while at the same time ensuring a high degree of compliance for the various CCSG protocols using TBI. Data supporting the various CCSG recommendations are presented.

In vivo dosimetry during external photon beam radiotherapy.

In this critical review of the current practice of patient dose verification, we first demonstrate that a high accuracy (about 1-2%, 1 SD) can be obtained. Accurate in vivo dosimetry is possible if diodes and thermoluminescence dosimeters (TLDs), the main detector types in use for in vivo dosimetry, are carefully calibrated and the factors influencing their sensitivity are taken into account. Various methods and philosophies for applying patient dose verification are then evaluated: the measurement of each field for each fraction of each patient, a limited number of checks for all patients, or measurements of specific patient groups, for example, during total body irradiation (TBI) or conformal radiotherapy. The experience of a number of centers is then presented, providing information on the various types of errors detected by in vivo dosimetry, including their frequency and magnitude. From the results of recent studies it can be concluded that in centers having modern equipment with verification systems as well as comprehensive quality assurance (QA) programs, a systematic error larger than 5% in dose delivery is still present for 0.5-1% of the patient treatments. In other studies, a frequency of 3-10% of errors was observed for specific patient groups or when no verification system was present at the accelerator. These results were balanced against the additional manpower and other resources required for such a QA program. It could be concluded that patient dose verification should be an essential part of a QA program in a radiotherapy department, and plays a complementary role to treatment-sheet double checking. As the radiotherapy community makes the transition from the conventional two-dimensional (2D) to three-dimensional (3D) conformal and intensity modulated dose delivery, it is recommended that new treatment techniques be checked systematically for a few patients, and to perform in vivo dosimetry a few times for each patient for situations where errors in dose delivery should be minimized.

A dose escalation study of total body irradiation followed by high-dose etoposide and allogeneic blood stem cell transplantation for the treatment of advanced hematologic malignancies.

Since approximately 30% of leukemia patients relapse after allogeneic BMT using total body irradiation (TBI)-based preparative regimens, treatment intensity may be suboptimal. The killing of leukemia cells is proportional to the radiation absorbed dose. We studied the feasibility and toxicity of escalating the doses of fractionated TBI above our previous prescription of 13.5 Gy. Sixteen evaluable patients with advanced hematologic malignancies were treated with twice daily TBI using a high-energy source (18-24 MV). The first patient cohort (n = 11) received a total dose of 14.4 Gy in nine fractions, and the second cohort (n = 5) received doses escalated to 15.3 Gy. All patients received high-dose etoposide (60 mg/kg) and allogeneic stem cell transplantation following the TBI. All patients had HLA-identical sibling donors. The median times for neutrophil and platelet engraftment were 13.5 and 12 days, respectively, and did not differ between the two cohorts. All but one patient developed treatment-related grade 3 or 4 mucositis. There were three cases of grade 4 pulmonary toxicity and three cases of grade 4 hepatic toxicity among the 14.4 Gy cohort, and one case each of grade 4 pulmonary and hepatic toxicities among the 15.3 Gy cohort. In most cases comorbid conditions contributed to these toxicities. Two patients had significant GVHD of the GI tract. Six relapses occurred, five (45%) in the 14.4 Gy cohort and one (20%) in the 15.3 Gy cohort. The 100-day treatment-related mortality rates were 9% and 20% for the 14.4 Gy and 15.3 Gy cohorts, respectively, and the median survivals were 226 and 201 days, respectively. We conclude that TBI dose escalation above the previously used 13.5 Gy dose is feasible using a high-energy source and high-dose etoposide. Acute and chronic toxicities were primarily related to GVHD, infection and relapse rather than to TBI.

Comparison of total body irradiation vs busulfan in combination with cyclophosphamide as conditioning for unrelated stem cell transplantation in CML patients.

We compared fractionated total body irradiation (12 Gy)/cyclophosphamide (120 mg/kg) with busulfan (16 mg/kg)/cyclophosphamide (120 mg/kg) as preparative therapy in unrelated donor stem cell transplantation of CML patients. Fifty patients with CML (1.CP = 46; aP = 4) and a median age of 36 years (range 16-52) were enrolled in this sequential trial between 1994 and 1999. In both groups patients were well balanced with respect to age, disease status, stem cell source and CMV status. All patients received standard doses of cyclosporin A, methotrexate and anti-thymocyte globulin (ATG) as GVHD prophylaxis. No graft failures occurred in either group. The median day of leukocyte engraftment was earlier in the Bu/Cy than in the TBI/Cy group (day 15 vs 17; P = 0.006). The incidence of grade II-IV GVHD was 40% in the TBI/Cy and 36% in the Bu/Cy group, whereas severe grade III/IV GVHD was only observed in 12% of patients in both groups. The incidence of chronic GVHD (limited and extensive) at 1 year was higher in the Bu/Cy arm (65% vs 30%; P = 0.02). More toxicity grade I/II of the liver (88% vs 44%; P = 0.002) and more hemorrhagic cystitis (32% vs 8%; P = 0.02) were observed in the Bu/Cy regimen. Seven relapses in the TBI and no relapse in the Bu/Cy group were observed after a median follow-up of 44 and 15 months, respectively. The estimated 3 year OS and DFS was 72% (95% CI: 55-98%) and 58% (95% CI: 39-77%) in the TBI and 70% (95% CI: 51-89%) for DFS and OS in the Bu/Cy group. We conclude that the anti-leukemic effect of the Bu/Cy regimen seems to be at least as effective as the TBI/Cy combination in unrelated stem cell transplantation of CML patients, with no graft failures, but that it correlates with a higher incidence of liver toxicity, hemorrhagic cystitis and chronic GVHD. Longer follow-up is necessary to determine the late relapse rate and late toxicity.

CD34+-selected autologous peripheral blood stem cell transplantation conditioned with total body irradiation for malignant lymphoma: increased risk of infectious complications.

Although high-dose chemotherapy with autologous peripheral blood stem cell transplantation (autoPBSCT) has been shown or confirmed to be an effective treatment for high-risk and relapsed non-Hodgkin's lymphoma (NHL), relapse after autoPBSCT remains a serious problem. In a clinical trial to overcome relapse, we adopted a treatment plan in which PBSCs purified in vitro to CD34+ cells to deplete tumor cells (CD34+ autoPBSCT), total body irradiation (TBI) of 1200 cGy, and melphalan, 180 mg/m2, were used as a preconditioning regimen. Eighteen patients with relapsed or high-risk NHL participated in the study. This study compared the incidence of complications following CD34+ autoPBSCT preconditioned with the TBI regimen (n = 10): the TBI group; CD34+ autoPBSCT with the non-TBI regimen (n = 8): the non-TBI group; and unselected autoPBSCT with the non-TBI regimen (n = 19): the unselected autoPBSCT control group. After day 30 posttransplantation, 6 of 10 patients treated with the TBI regimen developed 11 infectious complications in total, compared with only 1 of 8 patients treated with the non-TBI regimen and 4 of 19 patients given unselected autoPBSCT. Two fatal complications occurred in the TBI group, but none occurred in the other 2 groups. The CD4+ lymphocyte count at 1 month posttransplantation was significantly lower in the TBI group than in the unselected autoPBSCT group. These findings suggest that the addition of TBI to the preconditioning regimen for CD34+ autoPBSCT is associated with an increased incidence of severe infectious complications after transplantation.

Is total body irradiation a necessary component of preparative therapy for autologous transplantation in non-Hodgkin's lymphoma.

Between September 1986 and June 1998, 157 patients with low grade, intermediate grade, or high grade lymphoma underwent autologous transplantation at a single institution. Two preparative regimens were used: cyclophosphamide, etoposide, total body irradiation (CY-VP-TBI) (N=110) and cyclophosphamide, BCNU, etoposide (CBV) (N=47). The two groups were not significantly different with respect to source of stem cells, gender, stage at presentation, incidence of prior bone marrow involvement, sensitivity to salvage therapy, or histologic grade of lymphoma. The CBV group was significantly older, 49% of patients over age 50, as compared to 26% of patients over age 50 for the CY-VP-TBI group. Response rates and the incidence of fatal toxicity were similar for the two groups. Five year actuarial survival was 31% +/- 9% for CBV and 38% +/- 5% for CY-VP-TBI, p =.85. In a multivariate analysis, in which preparative regimen, age, histologic grade of lymphoma, and sensitivity to salvage therapy were the independent variables, TBI was not significantly associated with survival, and the direction of the trend was for TBI to be less effective than CBV. TBI does not appear to be an essential component of preparative therapy for autologous transplantation in patients with lymphoma.

All about FAX: a Female Adult voXel phantom for Monte Carlo calculation in radiation protection dosimetry.

The International Commission on Radiological Protection (ICRP) has created a task group on dose calculations, which, among other objectives, should replace the currently used mathematical MIRD phantoms by voxel phantoms. Voxel phantoms are based on digital images recorded from scanning of real persons by computed tomography or magnetic resonance imaging (MRI). Compared to the mathematical MIRD phantoms, voxel phantoms are true to the natural representations of a human body. Connected to a radiation transport code, voxel phantoms serve as virtual humans for which equivalent dose to organs and tissues from exposure to ionizing radiation can be calculated. The principal database for the construction of the FAX (Female Adult voXel) phantom consisted of 151 CT images recorded from scanning of trunk and head of a female patient, whose body weight and height were close to the corresponding data recommended by the ICRP in Publication 89. All 22 organs and tissues at risk, except for the red bone marrow and the osteogenic cells on the endosteal surface of bone ('bone surface'), have been segmented manually with a technique recently developed at the Departamento de Energia Nuclear of the UFPE in Recife, Brazil. After segmentation the volumes of the organs and tissues have been adjusted to agree with the organ and tissue masses recommended by ICRP for the Reference Adult Female in Publication 89. Comparisons have been made with the organ and tissue masses of the mathematical EVA phantom, as well as with the corresponding data for other female voxel phantoms. The three-dimensional matrix of the segmented images has eventually been connected to the EGS4 Monte Carlo code. Effective dose conversion coefficients have been calculated for exposures to photons, and compared to data determined for the mathematical MIRD-type phantoms, as well as for other voxel phantoms.

The validation of organ dose calculations using voxel phantoms and Monte Carlo methods applied to point and water immersion sources.

The Monte Carlo program 'Visual Monte Carlo-dose calculation' (VMC-dc) uses a voxel phantom to simulate the body organs and tissues, transports photons through this phantom and reports the absorbed dose received by each organ and tissue relevant to the calculation of effective dose as defined in ICRP Publication 60. This paper shows the validation of VMC-dc by comparison with EGSnrc and with a physical phantom containing TLDs. The validation of VMC-dc by comparison with EGSnrc was made for a collimated beam of 0.662 MeV photons irradiating a cube of water. For the validation by comparison with the physical phantom, the case considered was a whole body irradiation with a point 137Cs source placed at a distance of 1 m from the thorax of an Alderson-RANDO phantom. The validation results show good agreement for the doses obtained using VMC-dc and EGSnrc calculations, and from VMC-dc and TLD measurements. The program VMC-dc was then applied to the calculation of doses due to immersion in water containing gamma emitters. The dose conversion coefficients for water immersion are compared with their equivalents in the literature.