PubMed Health⌕ Search

Biomedical subjects

Anders Brahme

Publications and source records attributed to Anders Brahme.

18 recordsLinked to original sources
PubMed2006

Three-dimensional atlas of lymph node topography based on the visible human data set.

Comprehensive atlases of lymph node topography are necessary tools to provide a detailed description of the lymphatic distribution in relation to other organs and structures. Despite the recent developments of atlases and guidelines focusing on definitions of lymphatic regions, a comprehensive and detailed description of the three-dimensional (3D) nodal distribution is lacking. This article describes a new 3D atlas of lymph node topography based on the digital images of the Visible Human Male Anatomical (VHMA) data set. About 1,200 lymph nodes were localized in the data set and their distribution was compared with data from current cross-sectional lymphatic atlases. The identified nodes were delineated and then labeled with different colors that corresponded to their anatomical locations. A series of 2D illustrations, showing discrete locations, description, and distribution of major lymph nodes, was compiled to form a cross-sectional atlas. The resultant contours of all localized nodes in the VHMA data set were superimposed to develop a volumetric model. A 3D reconstruction was generated for the lymph nodes and surrounding structures. The volumetric lymph node topography was also integrated into the existing VOXEL-MAN digital atlas to obtain an interactive and photo-realistic visualization of the lymph nodes showing their proximity to blood vessels and surrounding organs. The lymph node topography forms part of our whole body atlas database, which includes organs, definitions, and parameters that are related to radiation therapy. The lymph node topography atlas could be utilized for visualization and exploration of the 3D lymphatic distribution to assist in defining the target volume for treatment based on the lymphatic spread surrounding the primary tumor.

Anatomy, Cross-Sectional↗
PubMed2005

Dose-response relations for anal sphincter regarding fecal leakage and blood or phlegm in stools after radiotherapy for prostate cancer. Radiobiological study of 65 consecutive patients.

BACKGROUND: The estimation of the parameters that describe the dose-response relations of anal sphincter regarding the clinical endpoints of fecal leakage and blood or phlegm in stools is important in the optimization of prostate cancer radiotherapy. Also, the validity of the relative seriality model for this clinical case needs to be examined by associating the clinical follow-up results with the predicted complication rates. PATIENTS AND METHODS: In this study, 65 patients who received radiation therapy for clinically localized prostate adenocarcinoma are analyzed. The clinical treatment outcome and the three-dimensional dose distribution delivered to anal sphincter were available for each patient. A questionnaire was used for assessing the clinical bowel and urinary symptoms. A maximum likelihood fitting was performed to calculate the best estimates of the parameters used by the relative seriality model. The clinical utilization of the calculated parameters in predicting anal sphincter complication probabilities was illustrated by applying the best estimate of the parameters to a subset of the patient population. RESULTS: The estimated values of the parameters for the two clinical endpoints are D (50) = 70.2 Gy, gamma = 1.22, s = 0.35 for fecal leakage and D (50) = 74.0 Gy, gamma = 0.75, s approximately 0 for blood or phlegm in stools. The standard deviations of the parameters were also calculated together with the confidence intervals of the dose-response curves. The analysis proved that the treatment outcome pattern of the patient material can suitably be reproduced by the relative seriality model (probability of finding a worse fit = 60.2%, the area under the receiver operating characteristic curve = 0.72 and 0.69 and chi(2)-test = 0.97 and 0.86, respectively). CONCLUSION: Fecal leakage is characterized by a medium relative seriality whereas blood or phlegm in stools was found to have strong volume dependence (low relative seriality). Diminishing the biologically effective uniform dose to anal sphincter < 40-45 Gy may significantly reduce the risk of fecal leakage or blood or phlegm in stools for patients irradiated for prostate cancer.

Aged↗
PubMed2005

Radiation transport calculations for 50 MV photon therapy beam using the Monte Carlo code GEANT4.

A new thin transmission target technique for fast dose delivery using narrow scanned photon beams has been developed. High-energy, 50-100 MeV, electron beams of low emittance incident on thin low-Z targets produce narrow and intense high-energy bremsstrahlung beams. However, electrons transmitted through the target are bent from the therapeutic beam by a purging magnet and have to be effectively absorbed in a dedicated electron collector. The electron-photon transport through a treatment head has been studied using the Monte Carlo simulation toolkit Geant4. The Geant4 electromagnetic physics processes have been compared with experimental data of radial dose profiles. The differences between calculated and measured radial dose distributions are approximately 2-10%. Preliminary investigations of the collector design have been carried out in order to minimise secondary electron and photon contamination of the therapeutic beam. The toolkit presented here is promising for further development of narrow photon beam therapy.

Computer Simulation↗
PubMed2004

Statistical methods for clinical verification of dose-response parameters related to esophageal stricture and AVM obliteration from radiotherapy.

The purpose of this work is to provide some statistical methods for evaluating the predictive strength of radiobiological models and the validity of dose-response parameters for tumour control and normal tissue complications. This is accomplished by associating the expected complication rates, which are calculated using different models, with the clinical follow-up records. These methods are applied to 77 patients who received radiation treatment for head and neck cancer and 85 patients who were treated for arteriovenous malformation (AVM). The three-dimensional dose distribution delivered to esophagus and AVM nidus and the clinical follow-up results were available for each patient. Dose-response parameters derived by a maximum likelihood fitting were used as a reference to evaluate their compatibility with the examined treatment methodologies. The impact of the parameter uncertainties on the dose-response curves is demonstrated. The clinical utilization of the radiobiological parameters is illustrated. The radiobiological models (relative seriality and linear Poisson) and the reference parameters are validated to prove their suitability in reproducing the treatment outcome pattern of the patient material studied (through the probability of finding a worse fit, area under the ROC curve and chi2 test). The analysis was carried out for the upper 5 cm of the esophagus (proximal esophagus) where all the strictures are formed, and the total volume of AVM. The estimated confidence intervals of the dose-response curves appear to have a significant supporting role on their clinical implementation and use.

Angiography↗
PubMed2004

Ion beam transport in tissue-like media using the Monte Carlo code SHIELD-HIT.

The development of the Monte Carlo code SHIELD-HIT (heavy ion transport) for the simulation of the transport of protons and heavier ions in tissue-like media is described. The code SHIELD-HIT, a spin-off of SHIELD (available as RSICC CCC-667), extends the transport of hadron cascades from standard targets to that of ions in arbitrary tissue-like materials, taking into account ionization energy-loss straggling and multiple Coulomb scattering effects. The consistency of the results obtained with SHIELD-HIT has been verified against experimental data and other existing Monte Carlo codes (PTRAN, PETRA), as well as with deterministic models for ion transport, comparing depth distributions of energy deposition by protons, 12C and 20Ne ions impinging on water. The SHIELD-HIT code yields distributions consistent with a proper treatment of nuclear inelastic collisions. Energy depositions up to and well beyond the Bragg peak due to nuclear fragmentations are well predicted. Satisfactory agreement is also found with experimental determinations of the number of fragments of a given type, as a function of depth in water, produced by 12C and 14N ions of 670 MeV u(-1), although less favourable agreement is observed for heavier projectiles such as 16O ions of the same energy. The calculated neutron spectra differential in energy and angle produced in a mimic of a Martian rock by irradiation with 12C ions of 290 MeV u(-1) also shows good agreement with experimental data. It is concluded that a careful analysis of stopping power data for different tissues is necessary for radiation therapy applications, since an incorrect estimation of the position of the Bragg peak might lead to a significant deviation from the prescribed dose in small target volumes. The results presented in this study indicate the usefulness of the SHIELD-HIT code for Monte Carlo simulations in the field of light ion radiation therapy.

Algorithms↗
PubMed2004

Recent advances in light ion radiation therapy.

BACKGROUND: The fast development of energy- and intensity-modulated radiation therapy during the last two decades using photon and electron beams has when implemented resulted in a considerable improvement of radiation therapy, particularly if combined with radiobiologically based treatment optimization techniques. This has made intensity-modulated electron and photon beams as powerful as today's uniform dose proton therapy. To be able to cure also the most advanced hypoxic and radiation-resistant tumors of complex local spread, intensity-modulated light ion beams are really the ultimate tool and in clinical practice 2 to 3 times less expensive per patient treated than proton therapy. This development and the recent development of advanced tumor diagnostics based on PET-CT imaging of the tumor cell density open the field for new powerful radiobiologically based treatment optimization methods. The ultimate step is to use the unique radiobiologic and dose distributional advantages of light ion beams for truly optimized bioeffect planning where the integral three-dimensional dose delivery and tumor cell survival can be monitored by PET-CT imaging and corrected by biologically based adaptive therapy optimization methods. PURPOSE: The main purpose of the present paper is to discuss the principal areas of development of therapy optimization, by considering the therapy chain from tumor diagnostics and the use of three-dimensional predictive assay to biologically based treatment optimization with special focus on the rapid clinical development of advanced light ion therapy. METHODS: Besides the "classical" approaches using low ionization density hydrogen ions (protons, but also possibly deuterons and tritium nuclei) and high ionization density carbon ions, two new approaches will be discussed. In the first one, lithium or beryllium or boron ions, which induce the least detrimental biologic effect to normal tissues for a given biologic effect in a small volume of the tumor, will be key particles. In the second approach, referred patients will be given a high-dose, high-precision "boost" treatment with carbon or oxygen ions during 1 week preceding the final treatment with conventional radiation in the referring hospital. The rationale behind these approaches is to minimize the high ionization density dose to the normal-tissue stroma outside but sometimes also inside the tumor bed and to ensure a more uniform and optimal biologic effectiveness in the tumor, also on the microscopic scale. The present discussion indicates that BIologically Optimized predictive Assay based light ion Radiation Therapy (Bio-Art) is really the ultimate way to perform high-precision radiation therapy using checkpoints of the integral dose delivery and the tumor response and, based on this information, perform compensating corrections of the dose delivery. By using biologically optimized scanned high-energy photon or ion beams, it is possible to measure in vivo the three-dimensional dose delivery using the same PET-CT camera that was used for diagnosing the tumor spread. This method thus opens up the door for truly three-dimensional biologically optimized adaptive radiation therapy, where the measured dose delivery to the true target tissues can be used to fine-adjust the incoming beams, so that possible errors in the integral therapy process are eliminated toward the end of the treatment. Interestingly enough, practically all major error sources--such as organ motion, treatment planning errors, patient setup errors, and dose delivery problems due to gantry, multileaf, or scanning beam errors--can be corrected for in this way. RESULTS AND CONCLUSIONS: Radiobiologically optimized dose delivery using intensity and radiation quality modulation based on high-resolution PET-CT or Magnetic Resonance Spectroscopic Imaging (MRSI)-based tumor and normal-tissue imaging is probably the ultimate development of radiation therapy, taking the unique physical and biologic advantages of light ions fully into account in truly patient-individualized curative treatment schedules. Using recently available biologically based treatment ilable biologically based treatment optimization algorithms, it is possible to improve the treatment outcome for advanced tumors by as much as 10-40%. The adaptive radiotherapy process based both on three-dimensional tumor cell survival and dose delivery monitoring has the potential of percent accuracy in tumor response and dose delivery monitoring, using two-dimensional, narrow high-energy photon beam scanning and three-dimensional (11)C Bragg peak scanning for radiation quality and intensity-modulated dose delivery. There is no doubt that the future of radiation therapy is very promising, and gradually more and more patients may not even need advanced surgery. Instead, they could be cured by biologically optimized electron, photon, or light ion therapy, where the densely ionizing Bragg peak is placed solely in the gross tumor, and a lower ionization density is used in microscopically invasive tumor volumes.

Cell Cycle↗
PubMed2004

Development of light ion therapy at the Karolinska Hospital and Institute.

Recent developments in radiation therapy have made it possible to optimize the high dose region to cover almost any target volume and shape at the same time as the dose level to adjacent organs at risk is acceptable. Further implementations of IMRT (Intensity Modulated Radiation Therapy), and inverse treatment planning using already available technologies but also foreseeable improved design of therapy accelerators delivering electron- and photon beams, will bring these advances to the benefit of a broad population of cancer patients. Protons will therefore generally not be needed since in most situations the improvement will be insignificant or moderate due to the large lateral penumbra with deep proton therapy. A further step would be to use He-ions, which have only half the penumbra width of protons and still a fairly low-LET in the spread-out Bragg peak. There is however still a group of patients that cannot be helped by these advances as the tumor might be radioresistant for the presently utilized low ionization density beam qualities. The ultimate step in the therapy development process should therefore be to optimize the beam quality for each tumor-normal tissue situation. To facilitate beam quality optimization light ions are needed. It is argued that in many radioresistant tumors a dose-mean LET of 25-50 eV/nm in the target would be optimum as then tumor cells will be lost in the highest proportion through apoptotic cell kill and the superficial tissues will still be irradiated with a fairly low LET. Light ions using Li, Be, B, and C would then be the ideal choice. In this paper a light ion facility is outlined for the Karolinska University Hospital facilitating both dose distribution and beam quality optimization.

Humans↗
PubMed2003

Radiation therapy dose delivery.

In an investigation by the Swedish Cancer Society, the present status critical issues and future aspects and potentials in each of nine major areas of radiation therapy research were described by an expert group. The report presented here deals with radiation therapy dose delivery. dose distributions, beam shaping and intensity modulation.

Humans↗
PubMed2003

Biological response to radiation therapy.

In an investigation by the Swedish Cancer Society, the present status, critical issues and future aspects and potentials were described by an expert group for each of nine major areas of radiation therapy research. This article deals with biological response to radiation. Separate sections deal with molecular responses to radiation, the stem cell and clonogenic cell concepts and the importance of cell proliferation, cell and tissue responses to doses above and below 1 Gy, respectively, the potential role of intercellular signalling pathways, the so-called bystander effect and radiation biology-based therapy planning and treatment optimization.

Bystander Effect↗
PubMed2003

Biologically optimized 3-dimensional in vivo predictive assay-based radiation therapy using positron emission tomography-computerized tomography imaging.

PET-CT is probably the ultimate tool for accurate tumor imaging and 3-dimensional in vivo predictive assay of radiation sensitivity. By imaging the tumor twice during the early course of therapy, it should be possible to quantify both the tumor responsiveness to therapy and the rate of loss of functional tumor cells using the presently derived equations. This new information is ideal for use together with biologically based therapy optimization and makes it possible accurately to quantitate the dose-response relation, at least for the bulk of the tumor cells. Since the tumor responsiveness is available after about one and a half weeks of therapy, the information is also ideal for use with adaptive therapy where all forms of deviations from the original treatment plan can be accurately corrected for since they generally influence the still functional, but mainly doomed tumor cell compartment. Thus, uncertainties such as: 1) the geometric misalignment of the therapeutic beam with the tumor, 2) deviations of the delivered dose distribution from the planned delivery whether due to 3) an erroneous treatment planning algorithm or 4) treatment equipment uncertainties and 5) deviations in the anticipated responsiveness of the tumor of the patient based on historical response data, can all be taken into account. Fortunately, when a larger tumor cell compartment than expected is seen an increased dose during the remainder of the treatment should always be delivered independently on whichever combination of the above deviations was the true reason. With high-energy photon and hadron therapy it is even possible to image the integral dose delivery in vivo during or after a treatment using PET-CT imaging. The high-energy photons above about 20 MeV produce positron emitters through photonuclear reactions in tissue which are proportional to the photon fluence and thus approximately also to the absorbed dose. Light ion beams, the ultimate radiation modality with regard to physical and biological selectivity, instead produce PET emitters through direct nuclear interactions in tissue, but can also be used as radioactive beams consisting of intrinsic PET emitters such as 8B, 11C, 13N and 15O. These radioactive beams allow more accurate imaging of the Bragg peak distribution and thus indirectly the absorbed dose. The most universal feedback for adaptive radiation therapy would then be to use the measured image of mean dose delivery during the early part of the treatment while revising the treatment plan based on the initially planned dose distribution and the radiation responsiveness of the tumor as seen after the first week or two of therapy. By this so-called BIO-ART approach (Biologically Optimized 3D in vivo predictive Assay-based Radiation Therapy) radiation therapy optimization may become an almost exact science, where the patient's true individual radiation response, considering hypoxia and general radiation resistance as well as possible dose delivery and planning errors, is taken into account.

Humans↗
PubMed2003

Determination and clinical verification of dose-response parameters for esophageal stricture from head and neck radiotherapy.

The purpose of this work is to determine the parameters and evaluate the predictive strength of the relative seriality model. This is accomplished by associating the calculated complication rates with the clinical follow-up records. The study is based on 82 patients who received radiation treatment for head and neck cancer. For each patient the 3D dose distribution delivered to the esophagus and the clinical treatment outcome were available. Clinical symptoms and radiological findings were used to assess the manifestation of radiation-induced esophageal strictures. These data were introduced into a maximum likelihood fitting to calculate the best estimates of the parameters used by the relative seriality model (D50 = 68.4 Gy, gamma = 6.55, s = 0.22). The uncertainties of these parameters were also calculated and their individual influence on the dose-response curve was demonstrated. The best estimate of the parameters was applied to 58 patients of the study material and their esophageal stricture induction probabilities were calculated to illustrate the clinical utilization of the calculated parameters. The calculation of the biological effective dose (BED) appeared to be significantly sensitive to the applied fractionation correction for complex treatment plans. The relative seriality model was proved suitable in reproducing the treatment outcome pattern of the patient material studied (probability of finding a worse fit = 61.0%, the area under the ROC curve = 0.84 and chi2 test = 0.95). The analysis was carried out for the upper 5 cm of the esophagus (proximal esophagus) where all the strictures are formed. Radiation-induced strictures were found to have a strong volume dependence (low relative seriality). The uncertainties of the parameters appear to have a significant supporting role on the estimated dose-response curve.

Adolescent↗
PubMed2003

The clinical value of non-coplanar photon beams in biologically optimized intensity modulated dose delivery on deep-seated tumours.

The aim of the present study is to compare the merits of different radiobiologically optimized treatment techniques using few-field planar and non-coplanar dose delivery on an advanced cancer of the cervix, with rectum and bladder as principal organs at risk. Classically, the rational for using non-coplanar beams is to minimize the overlap of beam entrance and exit regions and to find new beam directions avoiding organs at risk, in order to reduce damage to sensitive normal tissues. Two four-beam configurations have been extensively studied. The first consists of three evenly spaced coplanar beams and a fourth non-coplanar beam. A second tetrahedral-like configuration, with two symmetric non-coplanar beams at the same gantry angle and two coplanar beams, with optimized beam directions, was also tested. The present study shows that when radiobiologically optimized intensity modulated beams are applied to such a geometry, only a marginal increase in the treatment outcome can be achieved by non-coplanar beams compared to the optimal coplanar treatment. The main reason for this result is that the high dose in the beam-overlap regions is already optimally reduced by biologically optimized intensity modulation in the plane. The large number of degrees of freedom already incorporated in the treatment by the use of intensity modulation and radiobiological optimization, leads to the saturation of the benefit acquired by a further increase in the degrees of freedom with non-coplanar beams. In conclusion, the use of coplanar radiobiologically optimized intensity modulation simplifies the dose delivery, reducing the need for non-coplanar beam portals.

Female↗
PubMed2002

Prediction of AVM obliteration after stereotactic radiotherapy using radiobiological modelling.

This study was carried out in order to derive the radiobiological parameters of the dose-response relation for the obliteration of arteriovenous malformation (AVM) following single fraction stereotactic radiotherapy. Furthermore, the accuracy by which the linear Poisson model predicts the probability of obliteration and how the haemorrhage history, location and volume of the AVM influence its radiosensitivity are investigated. The study patient material consists of 85 patients who received radiation for AVM therapy. Radiation-induced AVM obliterations were assessed on the basis of post-irradiation angiographies and other radiological findings. For each patient the dose delivered to the clinical target volume and the clinical treatment outcome were available. These data were used in a maximum likelihood analysis to calculate the best estimates of the parameters of the linear Poisson model. The uncertainties of these parameters were also calculated and their individual influence on the dose-response curve was studied. AVM radiosensitivity was assumed to be the same for all the patients. The radiobiological model used was proved suitable for predicting the treatment outcome pattern of the studied patient material. The radiobiological parameters of the model were calculated for different AVM locations, bleeding histories and AVM sizes. The range of parameter variability had considerable effect on the dose-response curve of AVM. The correlation between the dosimetric data and their corresponding clinical effect could be accurately modelled using the linear Poisson model. The derived response parameters can be introduced into the clinical routine with the calculated accuracy assuming the same methodology in target definition and delineation. The known volume dependence of AVM radiosensitivity was confirmed. Moreover, a trend relating AVM location with its radiosensitivity was observed.

Adolescent↗
PubMed2002

Investigation of the added value of high-energy electrons in intensity-modulated radiotherapy: four clinical cases.

PURPOSE: Intensity-modulated radiotherapy (IMRT) with photon beams is currently pursued in many clinics. Theoretically, inclusion of intensity- and energy-modulated high-energy electron beams (15-50 MeV) offers additional possibilities to improve radiotherapy treatments of deep-seated tumors. In this study the added value of high-energy electron beams in IMRT treatments was investigated. METHODS AND MATERIALS: In a comparative treatment planning study, conventional treatment plans and various types of IMRT plans were constructed for four clinical cases (cancer of the bladder, pancreas, chordoma of the sacrum, and breast). The conventional plans were used for the actual treatment of the patients. The IMRT plans were optimized using the Orbit optimization code (Löf et al., 2000) with a radiobiologic objective function. The IMRT plans were either photon or combined electron and photon beam plans, with or without dose homogeneity constraints assuming standard or increased radiosensitivities of organs at risk. RESULTS: Large improvements in expected treatment outcome are found using IMRT plans compared to conventional plans, but differences in tumor control probability (TCP) and normal tissue complication probabilities (NTCP) values between IMRT plans with and without electrons are small. However, the use of electrons improves the dose-volume histograms for organs at risk, especially at lower dose levels (e.g., 0-40 Gy). CONCLUSIONS: This preliminary study indicates that addition of higher energy electrons to IMRT can only marginally improve treatment outcome for the selected cases. The dose-volume histograms of organs at risk show improvements for IMRT with higher energy electrons, which may reduce tumor induction but does not substantially reduce NTCP.

Aged↗
PubMed2002

Prognostic significance of intratumour microvessel density and haemoglobin level in carcinoma of the uterine cervix.

The prognostic significance of intratumour microvessel density (IMD) and haemoglobin (Hb) level was studied in 152 (FIGO stage IB-IIIB) cervical cancer patients before radiotherapy. Patients' age and tumour stage, grade and degree of keratinization were also studied. IMD measurement expressed as the mean vessel count per 1 mm2 was performed on formalin-fixed, paraffin-embedded tumour biopsies stained with anti-factor VIII antibody (DAKO Ltd.) using immunohistochemistry and the vascular hot-spot technique. The median age of patients was 55 years (29-80). Median values for IMD and Hb level were: 142.5 (range 56.3-476.6) vessels/mm2 and 129 (range 81-160) gil, respectively. The median time of follow-up was 26 months, with a range of 2-145 months. Tumour stage (p = 0.7009), grade (p = 0.6660) and degree of keratinization (0.2669) were not significant in the Kaplan-Meier univariate analysis. However, patients' age > 50 years (p = 0.0079). high vascularity (IMD > 190.0 vessels/mm2, minimal cut-off point, p = 0.0503) and Hb concentration > 116 g/l (p = 0.0213) were favourable prognostic factors for cervical cancer treated with radiotherapy. In the Cox multivariate analysis only higher vascularity (IMD > 190/mm2 and Hb concentration > 116 g/l were favourable prognostic factors in terms of patients' survival. However, when a Cox analysis was done separately for keratinizing and non-keratinizing tumours, it was found that higher vascularity was significant only for keratinizing, and higher Hb level only for non-keratinizing cancers.

Adult↗
PubMed2002

Effects of positioning uncertainty and breathing on dose delivery and radiation pneumonitis prediction in breast cancer.

The quality of the radiation therapy delivered in the treatment of breast cancer is susceptible to setup errors and organ motion uncertainties. For 60 breast cancer patients (24 resected with negative node involvement, 13 resected with positive node involvement and 23 ablated) who were treated with three different irradiation techniques. these uncertainties are simulated. The delivered dose distributions in the lung were recalculated taking positioning uncertainty and breathing effects into account. In this way the real dose distributions delivered to the patients are more closely determined. The positioning uncertainties in the anteroposterior (AP) and the craniocaudal (CC) directions are approximated by Gaussian distributions based on the fact that setup errors are random. Breathing is assumed to have a linear behavior because of the chest wall movement during expiration and inspiration. The combined frequency distribution of the positioning and breathing distributions is obtained by convolution. By integrating the convolved distribution over a number of intervals, the positions and the weights of the fields that simulate the original 'effective fields' are calculated. Opposed tangential fields are simulated by a set of 5 pairs of fields in the AP direction and 3 such sets in the CC direction. Opposed AP + PA fields are simulated by a set of 3 pairs of fields in the AP direction and 3 such sets in the CC direction. Single frontal fields are simulated by a set of 5 fields. In radiotherapy for breast cancer, the lung is often partly within the irradiated volume even though it is a sensitive organ at risk. The influence of the deviation in the dose delivered by the original and the adjusted treatment plans on the clinical outcome is estimated by using the relative seriality model and the biologically effective uniform dose concept. Radiation pneumonitis is used as the clinical endpoint for lung complications. The adjusted treatment plans show larger lung complication probabilities than the original plans. This means that the true expected complications are often underestimated in clinical practice. The lung density variation during breathing is calculated from the maximal change in average density during tidal breathing. The change in density in the lung due to breathing is shown to have almost no influence on the dose distribution in the lung. The proposed treatment-plan adjustments taking positioning uncertainty and breathing effects into account indicate significant deviations in the dose delivery and the predicted lung complications.

Breast Neoplasms↗
PubMed2002

Swedish Cancer Society radiation therapy research investigation.

In an investigation by the Swedish Cancer Society, the present status, critical issues and future aspects and prospects were described by an expert group for each of nine major areas of radiation research. A summary of the investigation is presented in this report. A more extensive summary (in Swedish) can be found at www.Cancerfonden.se. It is concluded that radiation therapy plays an increasingly important role in curative and palliative tumour treatment and presents a considerable challenge to research. Several suggestions are made that could improve the possibilities for high-quality radiation therapy research in Sweden.

Humans↗