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Purpose To develop an infrastructure for structured and automated collection of interoperable radiation therapy (RT) data into a national clinical quality registry. Materials and methods The present study was initiated in 2012 with the participation of seven of the 15 hospital departments delivering RT in Sweden. A national RT nomenclature and a database for structured unified storage of RT data at each site (Medical Information Quality Archive, MIQA) have been developed. Aggregated data from the MIQA databases are sent to a national RT registry located on the same IT platform (INCA) as the national clinical cancer registries. Results The suggested naming convention has to date been integrated into the clinical workflow at 12 of 15 sites, and MIQA is installed at six of these. Involvement of the remaining 3/15 RT departments is ongoing, and they are expected to be part of the infrastructure by 2016. RT data collection from ARIA®, Mosaiq®, Eclipse™, and Oncentra® is supported. Manual curation of RT-structure information is needed for approximately 10% of target volumes, but rarely for normal tissue structures, demonstrating a good compliance to the RT nomenclature. Aggregated dose/volume descriptors are calculated based on the information in MIQA and sent to INCA using a dedicated service (MIQA2INCA). Correct linkage of data for each patient to the clinical cancer registries on the INCA platform is assured by the unique Swedish personal identity number. Conclusions An infrastructure for structured and automated prospective collection of syntactically interoperable RT data into a national clinical quality registry for RT data is under implementation. Future developments include adapting MIQA to other treatment modalities (e.g. proton therapy and brachytherapy) and finding strategies to harmonize structure delineations. How the RT registry should comply with domain-specific ontologies such as the Radiation Oncology Ontology (ROO) is under discussion.

To determine if (11)C-L-methionine PET is a useful tool in the evaluation of the long-term effect of proton beam treatment in patients with meningioma remnant.Included in the study were 19 patients (4 men, 15 women) with intracranial meningioma remnants who received hypofractionated high-energy proton beam treatment. Patients were examined with (11)C-L-methionine PET and MRI prior to treatment and after 6 months, and 1, 2, 3, 5, 7 and 10 years. Temporal changes in methionine uptake ratio, meningioma volume, meningioma regrowth and clinical symptoms throughout the follow-up period were evaluated.In 17 patients the tumour volume was unchanged throughout the follow-up. The methionine uptake ratio on PET decreased over the years in most patients. In two patients the tumour remnant showed progression on MRI. In these patients, prior to the volume increase on MRI, the methionine uptake ratio increased. One patient experienced transient clinical symptoms and showed radiological evidence of a radiation-induced reaction close to the irradiated field.Proton beam treatment is a safe and effective treatment for achieving long-term growth arrest in meningioma remnants. Follow-up with (11)C-L-methionine PET may be a valuable adjunct to, but not a replacement for, standard radiological follow-up.

Background Radiation treatment is commonly employed in the treatment of meningiomas. The aim of this study was to evaluate the effectiveness and safety of hypofractionated high-energy proton therapy as adjuvant or primary treatment for WHO grade I meningiomas. Method A total of 170 patients who received irradiation with protons for grade I meningiomas between 1994 and 2007 were included in the study. The majority of the tumours were located at the skull base (n = 155). Eighty-four patients were treated post subtotal resection, 42 at tumour relapse and 44 with upfront radiotherapy after diagnosis based on the typical radiological image. Irradiation was given in a hypofractionated fashion (3–8 fractions, usually 5 or 6 Gy) with a mean dose of 21.9 Gy (range, 14–46 Gy). All patients were planned for follow-up with clinical controls and magnetic resonance imaging scans at 6 months and 1, 2, 3, 5, 7 and 10 years after treatment. The median follow-up time was 84 months. Age, gender, tumour location, Simpson resection grade and target volume were assessed as possible prognostic factors for post-irradiation tumour progression and radiation related complications. Results The actuarial 5- and 10-year progression-free survival rates were 93% and 85% respectively. Overall mortality rate was 13.5%, while disease-specific mortality was 1.7% (3/170 patients). Older patients and patients with tumours located in the middle cranial fossa had a lower risk for tumour progression. Radiation-related complications were seen in 16 patients (9.4%), with pituitary insufficiency being the most common. Tumour location in the anterior cranial fossa was the only factor that significantly increased the risk of complications. Conclusions Hypofractionated proton-beam radiation therapy may be used particularly in the treatment of larger World Health Organisation grade I meningiomas not amenable to total surgical resection. Treatment is associated with high rates of long-term tumour growth control and acceptable risk for complications.

Background and purpose: The aim of this study is to derive "dose painting by numbers" prescriptions from retrospectively observed recurrence volumes in a patient group treated with conventional radiotherapy for head and neck squamous cell carcinoma. Materials and methods: The spatial relation between retrospectively observed recurrence volumes and pre-treatment standardized uptake values (SUV) from fluorodeoxyglucose positron emission tomography (FDG-PET) imaging was determined. Based on this information we derived SUV driven dose-response functions and used these to optimize ideal dose redistributions under the constraint of equal average dose to the tumor volumes as for a conventional treatment. The response functions were also implemented into a treatment planning system for realistic dose optimization. Results: The calculated tumor control probabilities (TCP) increased between 0.1-14.6% by the ideal dose redistributions for all included patients, where patients with larger and more heterogeneous tumors got greater increases than smaller and more homogeneous tumors. Conclusions: Dose painting prescriptions can be derived from retrospectively observed recurrence volumes spatial relation to pre-treatment FDG-PET image data. The ideal dose redistributions could significantly increase the TCP for patients with large tumor volumes and large spread in SUV from FDG-PET. The results yield a basis for prospective studies to determine the clinical value for dose painting of head and neck squamous cell carcinomas. Correction in: RADIOTHERAPY AND ONCOLOGY, Volume: 131, Pages: 243-243, DOI: 10.1016/j.radonc.2018.11.004

Corrigendum to ‘‘Dose painting by numbers based on retrospectively determined recurrence probabilities” : [Radiother Oncol 122 (2017)236–241]

The use of protons for curative treatment of prostate cancer is increasing, either as a single treatment modality or in combination with conventional radiotherapy. The proximity between prostate (target) and rectum (organ at risk) often leads to a compromise between dose to target and organ at risk.The present study describes a method where the distance between prostate and rectum is increased by retraction of the rectum in dorsal direction. Comparative treatment plans with and without retraction of the rectum in the same patients have been studied. Nine patients with biopsy proven, localised adenocarcinoma of the prostate were studied. A cylindrical rod of Perspex was inserted into the rectum. This device allows the rectum to be retracted posteriorly. The patients were given a proton boost of 20 Gy in four fractions of 5 Gy in addition to a conventional photon beam treatment to a dose of 50 Gy in 25 fractions of 2 Gy.Comparative treatment planning shows that the treatment plan with rectal retraction significantly reduces (p0.01) the volume of the rectal wall receiving high doses (equal to 70 Gy in 2 Gy fractions) in all patients.The proton boost treatment with retraction of rectum during treatment decreases the rectal dose substantially. This is expected to reduce rectal side effects.

Background. Proton beam radiotherapy of arteriovenous malformations (AVM) in the brain has been performed in Uppsala since 1991. An earlier study based on the first 26 patients concluded that proton beam can be used for treating large and medium sized AVMs that were considered difficult to treat with photons due to the risk of side effects. In the present study we analyzed the result from treating the subsequent 65 patients. Material and methods. A retrospective review of the patients’ medical records, treatment protocols and radiological results was done. Information about gender, age, presenting symptoms, clinical course, the size of AVM nidus and rate of occlusion was collected. Outcome parameters were the occlusion of the AVM, clinical outcome and side effects. Results. The rate of total occlusion was overall 68%. For target volume 0–2cm3 it was 77%, for 3–10 cm3 80%, for 11–15 cm3 50% and for 16–51 cm3 20%. Those with total regress of the AVM had significantly smaller target volumes (p < 0.009) higher fraction dose (p < 0.001) as well as total dose (p < 0.004) compared to the rest. The target volume was an independent predictor of total occlusion (p = 0.03). There was no difference between those with and without total occlusion regarding mean age, gender distribution or symptoms at diagnosis. Forty-one patients developed a mild radiation-induced brain edema and this was more common in those that had total occlusion of the AVM. Two patients had brain hemorrhages after treatment. One of these had no effect and the other only partial occlusion from proton beams. Two thirds of those presenting with seizures reported an improved seizure situation after treatment. Conclusion. Our observations agree with earlier results and show that proton beam irradiation is a treatment alternative for brain AVMs since it has a high occlusion rate even in larger AVMs.

Objectives – To evaluate the therapeutic efficiency and adverse effects of stereotactic proton beam treatment of cerebral arteriovenous malformations (AVM). Material and methods – Twenty-six patients treated in Uppsala during 1991–97 were included (men = 14, women = 12; mean age = 39, range = 23–64). The nidus volumes ranged from 0.3 to 102 ml (mean = 24, median = 13). The follow-up included clinical evaluation, magnetic resonance imaging (and/or computed tomography) every 6–12 months for 3 years and final angiography. Results – The volume changes at final follow-up in AVMs >25 ml were −89, −85, −44, −29, −7, 0, 0, +5 and +18 (%); in AVMs 11–24 ml, −100, −100, −97, −92 and 0 (%); and in AVMs

Purpose : To determine how much proton and intensity modulated photon radiotherapy (IMRT) can improve treatment results of node-positive left-sided breast cancer compared to conventional radiation qualities (X-rays and electrons) after breast-conserving surgery in terms of lower complication risks for cardiac mortality and radiation pneumonitis. Methods and material : For each of 11 patient studies, one proton plan, one IMRT, and two conventional (tangential and patched) plans were calculated using a three-dimensional treatment-planning system, Helax-TMS ™ . The evaluation of the different treatment plans was made by applying the normal tissue complication probability model (NTCP) proposed by Kallman (also denoted the relative seriality model) on the dose distributions in terms of dose-volume histograms. The organs at risk are the spinal cord, the left lung, the heart, and the non-critical normal tissues (including the right breast). Results : The comparison demonstrated that the proton treatment plans provide significantly lower NTCP values for the heart and lung when compared to conventional radiation qualities including IMRT for all 11 patients. At a prescribed dose of 50 Gy in the PTV, the calculated mean NTCP value for the patients decreased, on the average, from 14.7 to 0.6% for the lung (radiation pneumonitis) for the proton plans compared with the best plan using conventional radiation qualities. The corresponding figures for the heart (cardiac mortality) were from 2.1 to 0.5%. The figures for cardiac mortality for IMRT, tangential technique and the patched technique were 2.2, 6.7, and 2.1%, respectively. Conclusions : Protons appear to have major advantages in terms of lower complication risks when compared with treatments using conventional radiation qualities for treating node-positive left-sided breast cancer after breast-conserving surgery.

The implementation of two algorithms for calculating dose distributions for radiation therapy treatment planning of intermediate energy proton beams is described. A pencil kernel algorithm and a depth penetration algorithm have been incorporated into a commercial three dimensional treatment planning system (Helax-TMS, Helax AB, Sweden) to allow conformal planning techniques using irregularly shaped fields, proton range modulation, range modification and dose calculation for non-coplanar beams. The pencil kernel algorithm is developed from the Fermi Eyges formalism and Molière multiple-scattering theory with range straggling corrections applied. The depth penetration algorithm is based on the energy loss in the continuous slowing down approximation with simple correction factors applied to the beam penumbra region and has been implemented for fast, interactive treatment planning. Modelling of the effects of air gaps and range modifying device thickness and position are implicit to both algorithms. Measured and calculated dose values are compared for a therapeutic proton beam in both homogeneous and heterogeneous phantoms of varying complexity. Both algorithms model the beam penumbra as a function of depth in a homogeneous phantom with acceptable accuracy. Results show that the pencil kernel algorithm is required for modelling the dose perturbation effects from scattering in heterogeneous media.

Nineteen patients with inextirpable skull base meningioma with involvement of neurovascular structures were given irradiation with a 180 MeV proton beam at the The Svedberg Laboratory, Uppsala, Sweden. The patients were treated seated in a fixed position with a stereotactic approach. Titanium-markers to the outer table served for identification and verification of the target positioning for dose planning and irradiation. The patients were given a total dose of 24 Gy in four consecutive daily 6 Gy fractions. All patients have been followed for at least 36 months. So far no meningiomas have progressed after treatment. Two patients have developed corticosteroid responsive oedema in the target area 6 moths after treatment. Late, but not serious, symptoms of side effects have been observed in one patient.

High-energy protons have physical properties that virtually always will result in geometrically better dose distributions than can be achieved using photons or electrons. The clinical gains in terms of the probability of higher tumour control and/or the reduced probability of normal tissue complications are, however, not completely known. Comparative model dose planning studies using real patients offer the possibility of estimating the potential gains using a new technique. Several recently completed model studies, including clinically relevant endpoints, indicate that protons may have advantages, even when compared with the conventional treatment that is likely to be introduced at the most advanced hospitals world-wide within the next decade. These advantages can be seen not only in well-demarcated targets close to risk organs, but also when irradiating extended irregular tissue volumes at risk of containing tumour cells.

Purpose: Conformal treatment planning with megavoltage x-rays and protons for five patients with esophageal cancer has been studied in an attempt to determine if there are advantages of using protons instead of x-rays. Methods and Materials: For each of the five patients, two different proton plans, one x-ray plan, and one mixed plan with x-rays and protons were made. A three-dimensional treatment planning system, TMS™, was used. The evaluation of the different plans was made by applying the tumor control probability (TCP) model proposed by Nahum and Webb and the normal tissue complication (NTCP) model proposed by Lyman on the dose distributions in terms of dose–volume histograms (DVHs). Results: The comparison shows advantages of using protons instead of x-rays for all five patients. The dose-limiting organs at risk are the spinal cord, the lungs, and the heart, but the proton plans also spare the kidneys better than the x-ray plan does. At 5% NTCP in any risk organ, the calculated mean TCP value for the five patients is increased by an average of 20%-units (from 2 to 23%-units) with the best proton plan compared with x-rays only. However, if we assume maximally a 1% risk in the spinal cord and a total NTCP for the two lungs of 100%, the mean TCP value for the five patients is increased from 6 to 49% with the best proton plan compared with x-rays only. The corresponding figure for the mixed plan is 27%. These gains are relatively insensitive to variations within reasonable limits in the biological parameters. Conclusions: Protons appear to have clear therapeutic advantages over conventional external radiotherapy when treating esophageal carcinoma.

Background and purpose : Loco-regional radiotherapy after breast cancer surgery significantly reduces the risk of recurrences. An increase of cardiac deaths for irradiated breast cancer patients has been reported in some studies, especially for women with tumours in the left breast. The aim of this study was to compare retrospectively the conventionally used technique using two opposed tangential photon beams with a modified technique using a combination of photon and electron beams to find an optimal technique with respect to dose homogeneity in the breast and surrounding regional lymph nodes and a minimal dose in the organs at risk. Materials and methods : Thirty patients with stage II breast cancer who received different types of adjuvant systemic therapy were included in the investigation. Comparative dose planning of two techniques was performed, i.e. an isocentric technique with two photon beams with coplanar medial beam edges and a technique with one electron and three photon beams with a common isocentre for all beams aided by a multileaf collimator. Results : The mixed technique was selected for eight of 12 patients with left-sided breast cancers because of significantly lower doses to the heart. However, the decision-making was influenced by many factors such as dose coverage of the target volume combined with minimizing of the doses to the organs at risk and the contralateral breast. Conclusion : The use of the mixed technique will optimize the loco-regional radiotherapy after breast-conserving surgery for many left-sided breast cancers.

In electron beam dosimetry using parallel-plate chambers solid phantoms are sometimes necessary. To obtain the dose to water from the ionization obtained in the solid phantom, fluence correction factors and perturbation factors have to be applied. In this study fluence factors in a perturbation free geometry have been determined experimentally for common phantom materials. Wall perturbation factors for simulated Attix, NACP, and Roos chambers have also been determined for the same materials. Comparative Monte Carlo calculations have been performed using the EGS4 Monte Carlo code. Comparison with data in newly published protocols such as IAEA and IPEMB shows an agreement with the results obtained in this paper to within 1%, demonstrating that the data published in these protocols may be used with reasonable accuracy if recommended phantoms are used. The results also show that if unsuitable phantom materials are used, the wall perturbation factors may differ for different chambers and for different phantom materials by more than 3% and perturbation factors have to be considered in order to obtain a high accuracy in the dose determination.

A dosimeter gel, based on an agarose gel infused with a ferrous sulphate solution and evaluated in a magnetic resonance scanner, was used for complete verification of calculated dose distributions. Two standard treatment procedures, treatment of cancer in the urinary bladder and treatment of breast cancer after modified radical mastectomy, were examined using pixel-by-pixel and dose volume histogram comparison. The dose distributions calculated with the dose planning system was in very good agreement with the measured ones. However, in the case of the more complicated breast cancer treatment, some discrepancies were found, mainly at the beam abutment region. This may be explained by field displacements errors and by a small limitation of the dose planning utilising small electron beams in this region. The dosimeter gel system have proven to be a useful tool for dosimetry in clinical radiation therapy applications.

Background: Semi-automated segmentation using deformable registration of selected atlas cases consisting of expert segmented patient images has been proposed to facilitate the delineation of lymph node regions for three-dimensional conformal and intensity-modulated radiotherapy planning of head and neck and prostate tumours. Our aim is to investigate if fusion of multiple atlases will lead to clinical workload reductions and more accurate segmentation proposals compared to the use of a single atlas segmentation, due to a more complete representation of the anatomical variations. Methods: Atlases for lymph node regions were constructed using 11 head and neck patients and 15 prostate patients based on published recommendations for segmentations. A commercial registration software (Velocity AI) was used to create individual segmentations through deformable registration. Ten head and neck patients, and ten prostate patients, all different from the atlas patients, were randomly chosen for the study from retrospective data. Each patient was first delineated three times, (a) manually by a radiation oncologist, (b) automatically using a single atlas segmentation proposal from a chosen atlas and (c) automatically by fusing the atlas proposals from all cases in the database using the probabilistic weighting fusion algorithm. In a subsequent step a radiation oncologist corrected the segmentation proposals achieved from step (b) and (c) without using the result from method (a) as reference. The time spent for editing the segmentations was recorded separately for each method and for each individual structure. Finally, the Dice Similarity Coefficient and the volume of the structures were used to evaluate the similarity between the structures delineated with the different methods. Results: For the single atlas method, the time reduction compared to manual segmentation was 29% and 23% for head and neck and pelvis lymph nodes, respectively, while editing the fused atlas proposal resulted in time reductions of 49% and 34%. The average volume of the fused atlas proposals was only 74% of the manual segmentation for the head and neck cases and 82% for the prostate cases due to a blurring effect from the fusion process. After editing of the proposals the resulting volume differences were no longer statistically significant, although a slight influence by the proposals could be noticed since the average edited volume was still slightly smaller than the manual segmentation, 9% and 5%, respectively. Conclusions: Segmentation based on fusion of multiple atlases reduces the time needed for delineation of lymph node regions compared to the use of a single atlas segmentation. Even though the time saving is large, the quality of the segmentation is maintained compared to manual segmentation.

Background and purpose : Conformal treatment planning with megavoltage X-rays and protons for medically inoperable patients with a large rectal cancer has been studied in an attempt to determine if there are advantages of using protons instead of X-rays. Material and methods : Three dose plans were made for each of the six patients: one proton plan, including three beams covering the primary tumour and adjacent lymph nodes and three boost beams covering the primary tumour; one X-ray plan, eight beams including a boost with four beams and one mixed plan with four X-ray beams and a boost with three proton beams. A three-dimensional treatment-planning system, TMS TM , was used. The evaluation of the different plans was made by applying the biological models TCP and NTCP on the dose distributions in terms of dose-volume histograms. Results : The comparison shows advantages of using protons instead of X-rays for all six patients, but in three of them, the advantage is only marginal. The dose-limiting organ at risk is the small bowel, but the proton plan and the mixed plan also spare the bladder and the femoral heads better. At 5% NTCP in any risk organ, the calculated mean TCP value for the six patients is increased by 14%-units with the proton plan and 8%-units with the mixed plan compared to X-rays only. Conclusions : Proton beam therapy has potential advantages when treating medically inoperable patients with a large rectal cancer over conventional X-ray therapy. Since the benefits are comparatively small, although clinically worthwhile, large randomised studies are needed.

To explain a possible association between treatment technique and postoperative mortality after preoperative radiotherapy of rectal carcinoma, the dose distributions were compared in model experiments.Preoperative radiotherapy with a three-beam technique delivered in five fractions to 25 Gy (5 Gy/daily for 5 or 7 days) was given to patients with primary resectable rectal carcinoma. The adverse effects of this treatment, both acute and late, have been low. In a parallel trial using an identical fractionation schedule and total dose but with a two-beam technique, the postoperative mortality was higher. Two-, three-, and four-beam techniques were analyzed in 20 patients with computed tomography based, three-dimensional dose planning. Dose distributions and dose-volume histograms in the planning target volume (PTV) and in the organs at risk were considered. A numerical "biological" model was used to compare the techniques.The two-beam and the four-beam box techniques give the most homogeneous dose distributions in the PTV, although all techniques result in dose distributions that would be considered adequate, provided 16 MV or higher photon energies are used. Three- and four-beam techniques show advantages over the two-beam technique with respect to organs at risk, particularly the small bowel. With the two-beam technique and the upper beam limit at mid-L4, the volume of the bowel that receives95% of the prescribed dose, and hence, is included in the treated volume (TV), is more than twice as large as that with three- and four-beam techniques, and that of the total body between 1.5 and 2 times as large. The results of the analyses using the biological model indicate that the three- and four-beam techniques result in less small bowel complication rates than the two-beam technique. The integral energy to the total body is similar for all treatment modalities compared.The volume of bowel included in the TV, rather than the energy imparted to the body, influences postoperative mortality, and emphasizes the importance of precise radiotherapy planning to minimize normal tissue toxicity.

All dosimetry protocols recommend the use of plane-parallel chambers for dose determination in electron beams with energies below 10-15 MeV. The protocols have assumed chamber perturbation effects to be negligible. The new AAPM Protocol (TG39) includes a cavity replacement factor prepl that differs from unity for some chambers, but assumes that the wall perturbation factor, pwall, may be taken as unity. In this paper the perturbation of the wall has been determined, using a large plane-parallel ionization chamber with exchangeable front and back walls. The results show that in many commercial chambers there is an energy dependent pwall factor, mainly due to differences in backscatter from the often thick chamber body as compared to the phantom material. Backscatter in common phantom and chamber materials may differ by as much as 2% at low electron energies (Plastic Water as compared to polystyrene). The front walls are often thin, resulting in negligible perturbation, but the 0.5 mm front wall of graphite in the NACP chamber was found to increase the response by 0.7% in a PMMA phantom. The experimental results have been compared with EGS4 Monte Carlo calculations using the DOSRZ code. There is an agreement within statistical and experimental uncertainties (0.5%) indicating that it is possible to use Monte Carlo calculations to calculate perturbation factors with good accuracy.

The benefit of preoperative radiotherapy of adenocarcinoma of the rectum with respect to a reduced local recurrence rate and an improved survival should be weighed against adverse effects. For 14 years a three-beam, isocentric technique was employed at our hospital to deliver five fractions (5.0 or 5.1 Gy), over 5 or 7 days preoperatively, to patients with rectal cancer which was considered primarily resectable. The adverse effects of the radiotherapy were few, but acute pain and subacute neurological symptoms and signs did occur. An apparent increase in the frequency of these symptoms/signs was noted during 1993. The pain and neurological symptoms are described in case reports and the individual treatments are reviewed. The three-beam technique was analyzed in detail with individual, CT-based, three-dimensional dose-planning and dose distributions in the vicinity of the lumbar nerve plexus are presented. The major result of this analysis showed that technical errors could be excluded, that human errors were unlikely, and that the culprit probably was an unexpected sensitivity to marginal changes in the daily dose and unknown or unexpected radiosensitizing effects of concurrent diseases or medication.

Three-dimensional dose planning systems employing accurate proton transport algorithms are essential for calculating absorbed dose distributions in proton therapy. In this paper, a pencil beam algorithm for the transport of protons in materials of interest for radiation therapy is developed. The Fermi-Eyges multiple-scattering theory is used to derive transport equations for calculating proton fluence and absorbed dose distributions. The multiple-scattering theory of Molière is used to predict mean square scattering angles and to develop an expression for calculating the root mean square (RMS) radial spread of a proton pencil beam, as a function of depth, in an arbitrary scattering material. A correction factor is suggested to account for the decrease in the radial spread at the end of the range due to range straggling. The effects of neglecting large-angle scattering events and the possibility of incorporating such events into the pencil beam algorithm are discussed. An energy scaling technique for determining the water-equivalent surface energy at a given depth in a heterogeneous scattering medium is developed. The water-equivalent energy, giving the same Molière scattering parameter B in water, is determined and the 1/e angle in water is scaled to the appropriate width in the scattering material. By using stored analytically or Monte Carlo calculated pencil beam distributions in water, the large-angle single-scattering events may be incorporated by approximating the scattering in an arbitrary material by the scattering in water for protons of the appropriate water-equivalent surface energy.

Proton boost of 20 Gy in daily 5 Gy fractions followed by external beam radiotherapy (EBRT) of 50 Gy in daily 2 Gy fractions were given to 278 patients with prostate cancer with T1b to T4N0M0 disease. Fifty-three percent of the patients received neoadjuvant androgen deprivation therapy (N-ADT). The medium followup was 57 months. The 5-year PSA progression-free survival was 100%, 95%, and 74% for low-, intermediate-, and high-risk patients, respectively. The toxicity evaluation was supported by a patient-reported questionnaire before every consultant visit. Cumulative probability and actuarial prevalence of genitourinary (GU) and gastrointestinal (GI) toxicities are presented according to the RTOG classification. N-ADT did not influence curability. Mild pretreatment GU-symptoms were found to be a strong predictive factor for GU-toxicity attributable to treatment. The actuarial prevalence declined over 3 to 5 years for both GU and GI toxicities, indicating slow resolution of epithelial damage to the genitourinary and gastrointestinal tract. Bladder toxicities rather than gastrointestinal toxicities seem to be dose limiting. More than 5-year followup is necessary to reveal any sign of true progressive late side effects of the given treatment. Hypofractionated proton-boost combined with EBRT is associated with excellent curability of localized PC and acceptable frequencies of treatment toxicity.

When irradiating targets in the brain, an accurately localised dose is often needed. One crucial moment to achieve this is the positioning of the patient. We have developed a positioning method where the patient is immobilised with a bite block and a head mould, and where the position of the target is determined by X-ray imaging of fiducial markers that are placed in the patient's skull. A method for computing the transformation needed to move the target from the observed to the prescribed position and orientation is described. This method uses the information from two orthogonal X-ray images and takes measurement errors and data from three or more markers into account. Results from using the method clinically in proton beam therapy are given.

Acta Oncologica has for more than two decades spon-sored scientifi c symposia on emerging issues in all fi elds of oncology. The most recent symposia within radiation oncology have addressed stereotactic body radiotherapy in 2006 [1], image-guided radiotherapy in 2008 [2] and biology-guided adaptive radiotherapy in 2010 [3]. Following the experience from 2008 with an Acta Oncologica symposium co-localised with a sympo-sium of the Nordic Association for Clinical Physics (NACP) [4], the present issue contains publications presented at the Acta Oncologica Symposium on Particle Therapy as well as at the back-to-back event of the NACP 2011 symposium [5], both held in Uppsala, Sweden, on April 13 – 15, 2011. The choice of topic this time came from the broad introduction of new particle therapy facilities around the globe, in particular proton therapy clinics. Although proton therapy was suggested as early as 1946 [6] and the fi rst proton treatment worldwide of a cancer patient was performed in Uppsala already in 1957 [7], par-ticle therapy has not become widely available and the capacity in the existing particle therapy facilities has been limited. This situation is however about to change and there is an almost exponential growth in the number of planned facilities. Presently, the fi rst hospital-based particle therapy facility in the Nordic countries is being established in Uppsala; the Skandion clinic. This facility is a national centre, designed to serve the whole popula-tion of Sweden. Still it is expected that at least for the fi rst few years of operation, some capacity can also be offered to neighbouring countries, for exam-ple in the Nordic region. What makes this project unique, also in an international context, is the con-cept of cooperation between the seven academic oncology departments of the country [8]. Rather than referring patients to Uppsala for treatment, pre-scription, planning and all preparations will be made at the university clinics and patients will thereafter be treated at the Skandion clinic in Uppsala. Beside the opportunity to gather competence from a num-ber of academic clinics into one single proton facil-ity, this collaborative approach also offers a unique possibility for sharing experiences, not only between the cooperating clinics, but also with interested regional centres or even international partners, since a signifi cant fraction of the collaboration will be conducted via teleconferencing [9]. In addition, the model is designed to promote scientifi c activities and to constitute a ground for extensive collaboration in clinical trials. With the increased accessibility of particle ther-apy follows the challenge of distributing and sharing the proton-specifi c knowledge and expertise among all potential actors in radiation oncology, who are or will be considering treating patients that might bene-fi t from proton therapy. To make a contribution in this direction, the organisers of this symposium invited some of the most distinguished and experi-enced actors on the particle therapy arena to share their most recent experiences. In addition, a large number of abstracts, mostly from the Nordic coun-tries, were submitted for the proffered sessions and

A large plane-parallel ionization chamber has been constructed to investigate interface effects in 60Co beam. The designed geometry yields negligible perturbation from the side walls, as opposed to the large effects existing in commercially available plane-parallel chambers. The chamber has been used to investigate interface phenomena in transition zones using a wide range of elements (Z = 4-82) as front- and back-scattering media and a clinically relevant 60Co gamma-ray field size. The effects of varying the chamber height discretely (0.5-11 mm) and increasing the wall thickness (1-9 mg/cm2) have been investigated. The variation of the measured ionization with the experimental setup (air gap between backscatter material and chamber wall, measurements at dmax and at 5-cm depth, varying the material both in front of and behind the chamber, etc.) has also been investigated. The simple geometry of the ion chamber has been found optimum for benchmark studies of Monte Carlo calculations. The ion chamber is suited for investigating experimentally the effects of varying transport parameters used in Monte Carlo simulations. The results presented show that the complex physical mechanisms governing 60Co interface dosimetry still make Monte Carlo condensed-history (macroscopic) techniques uncertain. It has been found that the EGS4 Monte Carlo system, together with the user code DOSRZ V4.0 and the PRESTA algorithm, yields good agreement with experiments for low and medium Z (main interest in dosimetry and radiotherapy), but may underestimate up to 10% the backscatter from high-Z materials even when transport parameters are optimized.

The increased interest in high precision radiation therapy is to a large extent driven by the potential of modern imaging technology. The aim of this project was to analyse how an expensive proton facility best could support a multi-centre health care system. We have developed a model for distributed expert collaboration where all clinical experts will work close to their patients in regional centres. Patients who are candidates for proton therapy will be examined and dose-planned at their regional clinic, discussed in a fully information supported video conference and digitally made available at the proton treatment facility. The proton facility itself will be placed near a communication centre easily reached by all patients where they will be treated under full responsibility of their own physician at the home clinic. This concept has been analysed in detail both with respect to the overall functionality and with respect to possible weaknesses. It was found that the concept of distributed radiation therapy, as proposed here, will offer a stable clinical solution for advanced radiation therapy. It will support the spread of knowledge, serve as a fully developed backup system and the concept will further serve as an efficient base for clinical research.

The techniques and procedures for intensity-modulated radiation therapy (IMRT) are reviewed in the context of the information process central to treatment planning and delivery of IMRT. A presentation is given of the evolution of the information based radiotherapy workflow and dose delivery techniques, as well as the volume and planning concepts for relating the dose information to image based patient representations. The formulation of the dose shaping process as an optimization problem is described. The different steps in the calculation flow for determination of machine parameters for dose delivery are described starting from the formulation of optimization objectives over dose calculation to optimization procedures. Finally, the main elements of the quality assurance procedure necessary for implementing IMRT clinically are reviewed.

Low-dose hyperradiosensitivity (HRS) has been found for several cell types after exposure to low doses,0.5 Gy, of high dose-rate (typically 50-150 Gy/h) low-LET radiation. HRS precedes the occurrence of a relative resistance for doses above 0.5-1 Gy. A critical question is whether HRS is of importance in radionuclide therapy where the dose-rate is low but the total dose might be high. An indication that cells exposed to low dose-rate can be kept hyperradiosensitive has recently been published. We have in the present study applied cells without (glioma U373MG) and with (glioma U118MG and colon carcinoma HT29) HRS and studied early effects, up to one week, during low dose-rate (LDR), 0.05-0.09 Gy/hours, exposure (total dose after one week: 11.8 +/- 1.5 Gy). The cells were grown on thin foils above a (32)P source placed in a cell culture chamber. Cell number reductions, cell-cycle disturbances, and changed numbers of apoptotic cells were analyzed after continuous LDR exposures. There seemed to be no relation with HRS when the cell number reduction was considered. The U373MG cells, lacking HRS, had the strongest cell number reduction due to a combination of a G(2) block and increased apoptosis. The U118MG and HT29 cells, both having HRS, had surprisingly low cell number reductions. U118MG had only a G(2) block but no increase in apoptosis. HT29 had both a G(2) block and an increase in apoptosis but the apoptosis change was somewhat smaller than for U373MG. Thus, there seemed to be no obvious relation between HRS and early cellular effects when the cells were analyzed after continuous LDR exposure.

To determine potential improvements in treatment outcome for patients with hypopharyngeal carcinoma, T4N0M0, using proton and intensity modulated photon radiotherapy (IMRT) compared to a standard 3D conformal radiotherapy treatment (3D-CRT) in terms of local tumour control probability, TCP, and normal tissue complication probability (NTCP) for the spinal cord and the parotid glands using.Using the three-dimensional treatment-planning system, Helax-TMS, 5 patients were planned with protons, IMRT, and 3D-CRT plans. The prescribed dose used was 30 fractions x 2.39 Gy for the protons and IMRT and 35 fractions x 2.00 Gy for 3D-CRT. The treatment plans were evaluated using dose volume data and dose response models were used to calculate TCP and NTCP. The target volumes were delineated to spare the parotid glands. A dose escalation was made for protons and IMRT using NTCP constraints to the spinal cord.On average, protons and IMRT increase TCP by 17% compared to 3D-CRT. For the spinal cord NTCP values are zero for all methods and patients. Average NTCP values for the parotid glands were90% for 3D-CRT and significantly lower for protons and IMRT varying from 43-65%. The average parotid gland dose was 33 Gy for the protons, 38 Gy for IMRT and 48 Gy for 3D-CRT.Protons and IMRT gave a significant TCP increase compared to 3D-CRT while no significant difference between protons and IMRT was found. Protons generally show lower non-target tissue doses, which indicates a possibility for further dose escalation. Large individual dose differences between protons and IMRT for parotid glands indicate that some patients may benefit more from protons and others from IMRT.

A formalism tailored for portal dose image verification is proposed to facilitate the comparison of calculated and measured portal dose distributions. Each portal image is converted into a dose proportional image and normalized to the reference beam calibration dose per monitor unit. The calculated or measured dose to a detector phantom is accordingly normalized so as to enable direct comparison. The collapsed cone kernel superposition method is adapted and evaluated for calculation of portal dose distributions in a water-equivalent detector phantom through comparisons with Monte Carlo calculations and with measurements. The deviation compared with Monte Carlo calculations for 6 and 15 MV was between +0.9% (the 0.9 quantile) and −2.1% (the 0.1 quantile) for a range of investigated geometries. Collapsed cone calculations compared with measurements for clinical fields agreed within [−1.9%, +2.4%] for 15 MV and [−0.9%, +3.2%] for 6 MV for the 0.1 and 0.9 quantiles, respectively. Hence, the absolute portal dose to a detector phantom could be calculated and verified well within the present accuracy requirements for clinical dose calculations.

We investigated the use of unencapsulated silicon semiconductor detectors for backscatter radiation detection. The results were compared with Monte Carlo (MC) calculations modelling the experimental set-up. A special diode was manufactured, which was designed so that it allowed the positioning of different materials in close contact with the detector surface. Polymethylmethacrylate (PMMA), Pb, Ti and Fe (stainless steel) were used as backscatter materials. The diode signal was measured by integrating the current when irradiating the diode with an equal photon fluence obtained from a medical Co-60 source. When compared to the signal with PMMA as backscatter material the increase in signal was 21%, 27% and 73% for Ti, Fe and Pb, respectively. This is in reasonable agreement with the MC calculations, when taking the effective measurement depth in the Si diode detector into account.

A ferrous gel, based on ferrous (Fe) sulphate and agarose, was used with a clinical magnetic resonance imaging (MRI) scanner to obtain relative dose distribution data from therapeutic photon and electron beams. The FeMRI gel was scanned using a new MRI acquisition protocol optimized for T1 measurements. Thorough comparisons with silicon semiconductor detector and ionization chamber measurements, as well as with Monte Carlo calculations, were performed in order to quantify the improvements obtained using FeMRI for dose estimations. Most of the relative doses measured with FeMRI were within 2% of the doses measured with other methods. The larger discrepancies (2-4%) found at shallow depths are discussed. The uncertainty in relative dose measurements using FeMRI was significantly improved compared with previously reported results (5-10%, one standard deviation, 1 SD), and is today between 1.6% and 3.3% (depending on dose level, 2 SD). This corresponds to an improvement in the minimum detectable dose (3 SD above background) from approximately 2 Gy to better than 0.6 Gy. The results obtained in this study emphasize the importance of obtaining basic FeMRI dose data before the method is extended to complicated treatment regimes.

Background and purpose: Conformal treatment planning with megavoltage X-rays and protons was studied in an attempt to determine if there are advantages of boost therapy with protons instead of X-rays for a patient with a tumour growing around the cervical spinal cord. Materials and methods: A patient with a Ewing sarcoma was selected for the model study. The proton boost plan was realised with a six beam patched technique. Several X-ray boost techniques were planned, some not yet practically realisable. The techniques giving the best dose distributions and the best tumour control probabilities in the absence of significant late toxicity were looked for. The boost techniques were added to two large lateral X-ray beams covering the planning target volume (PTV) and the main risk organ, the spinal cord. The evaluation was made with two biological models, i.e. the tumour control probability (TCP) model, proposed by Webb and Nahum (Webb, S. and Nahum, A.E. A model for calculating tumour control probability in radiotherapy including the effect of inhomogeneous distributions of dose and clonogenic cell density. Phys. Med. Biol. 38: 653–666, 1993), and the normal tissue complication probability (NTCP) model, first derived by Lyman (Lyman, J.T. Complication probability as assessed from dose-volume histograms. Radiat. Res. 104: s13–s19, 1985). Results: The comparison showed small but clear advantages of protons for the boost. At 1% NTCP in the spinal cord, the calculated TCP was on average 5% higher. However, depending on the values of the parameters chosen in the biological models, the gain for protons varied from 0–10%. The smallest gains were seen in radiosensitive tumours for which the TCP was close to 100% with any of the techniques and in radioresistant tumours for which neither technique resulted in any appreciable probability of local cure. Conclusion: Protons appear to have therapeutic advantages over conventional radiotherapy in tumours with relatively high radiosensitivity situated close to the spinal cord.

A Faraday cup in a proton beam can give an accurate measurement of the number of protons collected by the cup. It is shown that the collection efficiency with a proper design can be close to unity. To be able to calibrate an ionization chamber from such a measurement, as is recommended in some dosimetry protocols, the energy spectrum of the proton beam must be accurately known. This is normally not the case when the lateral beam extension is defined by collimators. Therefore a method for relating an ionization chamber measurement in an uncollimated beam to the total number of protons in the beam has been developed and is described together with experimental results from calibrating an ionization chamber using this method in the therapeutic beam in Uppsala. This method is applicable to ionization chambers of any shape and the accuracy is estimated to be 1.6% (1 SD).

Determinations of the absorbed dose in a 170 MeV proton beam have been performed using seven ionization chambers of different types: five cylindrical (two FWT IC-18 and three NE-2571, of which one was modified to have the central electrode made of graphite) and two plane parallel (NACP-02 and Roos FK-6). The ionization was converted into absorbed dose in the proton beam according to the generalization of the formalism provided by the IAEA Code of Practice (TRS 277), which enables the use of the same equations for all kinds of beam used in radiotherapy. The absorbed dose obtained with the two IC-18 chambers, a chamber type commonly used as a reference in proton beams, was up to 1.5% lower than that obtained with the Farmer NE-2571 chamber, which was used as the reference in this work when calibration factors in terms of NK were used. To investigate this difference, experimental ND factors for six chambers (the two IC-18 chambers, the NACP-02, the FK-6 and two of the NE-2571 chambers) were determined in a high-energy electron beam. The procedure commonly recommended for plane parallel ion chambers was used for all the chambers, using the same reference chamber, a Farmer NE-2571. In the 170 MeV proton beam all the ND factors yielded consistent absorbed dose determinations within the estimated experimental uncertainties. This finding calls into question the value of the product kattkm for the IC-18 chamber given by the IAEA Code of Practice used in this comparison, and points at possible chamber to chamber variations that theoretical kattkm factors cannot predict. The investigations enabled the determination of the Pwall(60Co) factor of the Roos FK-6 plane parallel chamber, yielding 1.003 +/- 0.5%, and a correction for the effect of the aluminium central electrode of NE-2571 chambers in proton beams, equal to 1.003 +/- 0.4%. Two of the chambers (the plane parallel FK-6 and the modified cylindrical NE-2571) were provided with calibration factors in terms of absorbed dose to water, Nw, at the quality of 60Co by the Primary Standard Dosimetry Laboratory in Germany (PTB). Using the Nw formalism excellent agreement was found with the determination based on the experimental ND, giving support to the implementation of the NW procedure in therapeutic proton beams.

This paper describes a dual-scattering-foil technique for flattening of radiotherapeutic charged particle beams. A theory for optimization of shapes and thicknesses of the scattering foils is presented. The result is a universal optimal secondary-scatterer profile, which can be adapted to any charged particle beam by a simple scaling procedure. The calculation of the mean square scattering angle of the beam after passing through the scattering foils is done using the generalized Fermi-Eyges model for charged particle transport. It is shown that the fluence profile in the plane of interest can be made flat to better than 1% inside a predefined beam radius provided the shaped secondary scatterer has the universal radial thickness profile. The thicknesses of the two foils are optimized to minimize the total energy loss. The theory has been tested experimentally in an 180 MeV clinical proton beam. The measured distributions agree well with the calculations.

Range modulated proton beams are used for radiotherapy of malignant tumours at several accelerator laboratories with the aim of introducing proton therapy as a clinical hospital-based therapy modality. Due to the finite range and the sharpness of the dose gradients, the dose to well defined target volumes can be raised without excessive irradiation of non-target tissue. The prescribed proton doses are determined in part on the basis of the relative biological effectiveness (RBE) of the particular radiation quality. In this study, RBE values were determined for a proton beam with a maximal range of 33 mm, which corresponds to an energy of ∼67 MeV. The range modulated depth-dose distribution, with a 20 mm extended Bragg peak, was mainly designed for high precision treatment of small targets such as uveal melanomas. The tested cell lines, LS-174T and V79-379A, were chosen because of their suitability for clonogenic assays. The cells were irradiated with single doses in the range 2–10 Gy at different depths in the extended peak region of the range modulated proton beam. RBE values were determined by comparing the doses needed to obtain the same reduction in colony formation (0.5, 0.1 and 0.01) as with the reference 60 Co gamma source. The mean RBE value was1.22 with a standard deviation of 0.08. The variations depended on both cell type and on the survival levels considered. The clonogenic cell survival showed only a very small decrease with depth when cells were placed in different positions, along the central axis of the range modulated depth-dose distribution, indicating only a small increase in RBE with depth. The RBE of the proton beam was greater than unity indicating that proton doses should be somewhat reduced in comparison with conventional radiation when irradiation of critical normal tissues is unavoidable.

The induced secondary electrons from a metal surface by diagnostic x-rays are thought to contribute to cell damage near the tissue-metal boundaries of metal implants. Titanium implants are becoming increasingly more popular for tissue reconstructions and it is rather often desirable to take radiographs of the operated area. In this study we compared the biological effects of radiation on cultured mammalian test cells grown on titanium plates with the radiation effects on cells that were grown on plastic control plates. In order to study the acute radiation effects on cell growth it was necessary to work with rather high radiation doses (0.7-5 Gy). Photon energies, suitable for diagnostic radiography in odontology, 65 kV, were applied. We found that the cells grown on titanium plates were, in terms of the applied dose in the surrounding culture medium, more sensitive to the irradiations than the cells growing on plastic plates. The survival curve for the cells on titanium had a steeper slope, showed no shoulder in the low-dose region and looked like curves normally obtained for high LET radiation. It was not possible to resolve to what degree the titanium-dependent changes were due to an increased dose near the titanium surface or to a change in the radiobiological effectiveness. Although there was a significant decrease in cellular survival near the metal, postoperative intraoral radiography after titanium implantations need not be excluded. The maximal doses given in odontological x-ray examinations are less than 1 mGy and, if the results in this study are applied, the biological effects near the titanium implant will correspond to biological effects in soft tissue of doses less than 20 mGy which is lower than the doses that give acute effects. The risk of acute healing disturbances are significant only at much higher radiation doses.

Purpose: Proton's physical properties offer the maximum radiationdose to the target volume, which is an advantage in the radiotherapy development. The aim of this study is the clinical derivation of the dose‐response relations regarding urinary complications from combined photon and proton prostate radiotherapy.Material and Methods: 189 patients were treated for prostate cancer at Uppsala's Academic Hospital, Sweden from 2002 to 2006. The patients were treated with a proton boost of 20 Gy given in 5 Gy, followed by a X‐ray treatment of 50 Gy in 2 Gy fractions. The dose distribution delivered to the organs of interest and the clinical treatment outcomes (24 months follow‐up time) were available for 72 patients. The delineated regions of interest were the urinary bladder and the region of the lower 3 cm part of the bladder. The photon and protondoses were calculated with the BED (biologically effective dose) concept. Additionally, an RBE of 1.1 was used for protons. The radiobiological parameter acquisition of D 50 and γ was performed for the Poisson, Binomial and Probit models applying the Maximum Likelihood method. Results: Of the 72 patients, 15 (21%) showed urinary complications, whereas 57 (79%) didn't. The best estimated values of the parameters for the whole bladder and bladder 3 cm are D 50=104.0 Gy, γ =0.7 and D 50=88.4 Gy, γ =1.3 for Poisson,D 50=108.0 Gy, γ=0.6 and D 50=88.6 Gy, γ=1.3 for Binomial, whereas for Probit are D 50=97.0 Gy, γ=1.0 and D 50=85.6 Gy, γ=1.8, respectively. The analysis of the mean cumulative DVHs proves that the urinary complications were mainly due to the photontreatment.Conclusions: The dose‐response relations are described well by the estimated parameters of the Poisson, Binomial and Probit models. The results are necessary for a prospective estimation of the clinical effectiveness of radiation therapy using combinations of different radiation modalities.

Purpose Recent advances in radiation therapy have provided the possibility of combining different modalities in different parts of the treatment. The purpose of this study was the determination of the parameters D 50 and γ for the prostate adenocarcinoma using different radiobiological models, when proton and photon beams are combined. Material and Methods In this study 100 patients, who were treated for prostate cancer at the Academic Hospital in Uppsala, Sweden from 2002 to 2006, were used. The patients were treated with a conventional photon beam configuration to a dose of 50 Gy in 2 Gy fractions. Additionally, a proton boost of 20 Gy in 5 Gy fractions was applied. The photon and protondoses were corrected for the fractionation effects using the BED (biologically effective dose) concept. In the calculation of the protondose, we considered RBE=1.1. For each patient, the clinical treatment outcome (follow‐up of 24 months) and the 3D dose distribution delivered to the target were available. The best estimates of the parameters D 50 and γ of the Binomial, Poisson and Probit models were determined by applying a maximum likelihood fitting. Results Of the 100 patients, 94 had tumor control (94.0%) whereas 6 patients had treatment failure (6.0%). The mean doses in the prostate in these two groups of patients were 72.97Gy and 62.60Gy, respectively. The estimated values of the parameters for the Poisson and Binomial models are D 50=49.6Gy (68%CI=47.1–51.9Gy) and γ=2.25 (68%CI=1.83–2.75), whereas for the Probit model they are D 50=47.3Gy (68%CI=45.1–49.4Gy) and γ=1.31 (68%CI=1.11–1.52). Conclusions The estimated parameters are able to describe the dose‐response relation of prostate adenocarcinoma. Since there are very limited data on radiation therapy using combinations of photon and proton beams, the determined parameters can be useful in estimating the expected clinical outcome during treatment planning and perform optimization of the delivered treatment.

Purpose The purpose of this study was the determination of the parameters D 50 and γ for the rectum and penile bulb using different radiobiological models, when proton and photon beams are combined. Material and Methods In this study, 98 patients were included with localized adenocarcinoma of the prostate. The patients were treated with a conventional photon beam configuration to a dose of 50 Gy in 2 Gy fractions. Additionally, a proton boost of 20 Gy in 5 Gy fractions was applied. In some patients, the distance between prostate and rectum was increased during proton therapy by retraction of the rectum in the dorsal direction by the use of a cylindrical rod of Perspex inside the rectum. In the calculation of the protondose, we considered RBE=1.1. The best estimates of the parameters D 50 and γ of the Binomial, Poisson and Probit models were determined by applying a maximum likelihood fitting. Results 33 of the patients produced rectal dysfunction (33.7%). The analysis shows that the treatment plans with rectal retraction significantly reduces the dose in the rectum and as a consequence the responders of the treatment (27.3% vs. 36.9% with and without the rod, respectively). The estimated parameters values for the Poisson and Binomial models are D 50=61.2Gy (68%CI=57.5–65.2Gy) and γ =0.8 (68%CI=0.6–1.0) for the rectum. The estimated values for the Probit model are D 50=60.5Gy (68%CI=56.9–64.1Gy) and γ=1.0 (68%CI=0.7–1.3) for the rectum. Of the 89 patients used in the penile bulb analysis, 25 had sexual dysfunction (28.1%) with mean doses for the responders and non‐responders of 55.5 Gy and 54.2 Gy, respectively. Conclusions The additional use of the cylindrical rod in the protontreatment appears to reduce rectal side effects. The determined parameters can be useful in estimating the expected clinical outcome during treatment planning and perform optimization of the delivered treatment.

The output factor for a therapy photon beam is defined as the dose per monitor unit relative to the dose per monitor unit in a reference field. Convolution models for photon dose calculations yield the dose in units normalized to the incident energy fluence with phantom scatter intrinsically modeled. Output factors calculated with the convolution method as the dose per unit energy fluence relative to the calculated dose per unit energy fluence in a reference field could deviate as much as 5% if corrections are not made for perturbations due to treatment head scatter. Significant perturbations are particles backscattered from the collimators to the monitor and photons forward scattered from the filter and collimators in the treatment head. The forward scatter adds an "unmonitored" contribution to the total energy fluence of the beam. A model is developed that describes the field size dependence of these perturbations for conversion of output factors, calculated with the convolution method, to machine output factors as an integrated part in treatment planning. The necessary machine characteristics are derived from measurements of the output in air for a limited set of field sizes. The method has been tested using five different multileaf collimated irregular fields at 6 MV and for a large set of rectangular fields at 5, 6, and 18 MV and found to predict output factors with an accuracy better than 1%.

The TMS-Radix treatment planning system by Helax has been used in clinical practice at the University Hospital in Uppsala for more than a year. As Uppsala was one of the two test sites for TMS, an extensive test program was undertaken before the system was used in the clinic. Five different therapy machines are in use at the University Hospital: one 60Co unit, three linear accelerators, and one microtron. The X-ray qualities available are 5, 6, 8, 16, and 21 MV, and the electron energies range from 5 to 22 MeV. All X-ray qualities and a number of electron energies between 8 and 20 MeV are now implemented in TMS and have been subjected to tests. This paper deals with tests of the dose calculation models for photon and electron beams.