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Paediatric radiotherapy comes at the expense of increased risk of late effects due to out-of-field dose caused not only by the treatment itself but also by image guidance. This study examined how the out-of-field dose to selected radiosensitive organs was affected by applying a 1 mm lead shielding during delivery of volumetric-modulated arc therapy (VMAT) for paediatric brain cancer. The study also investigated how the out-of-field dose to the same organs was affected by the use of flattening-filter free (FFF) beams. Out-of-field doses to the thyroid, breast and testes were measured using thermoluminescence dosimeters inserted in two anthropomorphic phantoms equivalent to a 1-year and 5-year old child. Coplanar VMAT plans were prepared for 6 MV and 6 MV FFF photon beams and delivered using a Varian TrueBeam linear accelerator, with and without lead shielding applied to the phantoms. The measured out-of-field doses were as large as 200,9 cGy for the whole treatment, with associated secondary cancer risk being as large as 1,1%. Shielding of the phantoms was found to decrease the out-of-field dose by up to 24%. The use of 6 MV FFF beams yielded a decrease in the dose to the testes by 21–42% compared to 6 MV, while in one case increasing the dose to the thyroid by 18%. The observation that only doses to organs distant to the primary irradiated volume were significantly decreased for FFF can be explained by an increase in internal scatter caused by the softer energy spectrum of the Varian FFF beam.

BACKGROUND AND PURPOSE: Chemoradiotherapy (CRT) is the standard therapy for localized anal cancer (AC), but this treatment is associated with substantial toxicity. However, there is a lack of prospectively collected toxicity and patient reported outcome (PRO) data from larger cohorts. The purpose was to prospectively collect and determine agreement between physician assessed toxicity (CTCAE) and PRO during and after CRT and to compare IMRT, VMAT and proton-based planning in a subgroup of patients.MATERIAL AND METHODS: Patients, treated with CRT for AC, were included between 2015 and 2017. NCI-CTCAE v.4.0, EORTC QLQ-C30 and CR29 data were collected baseline, mid-therapy, end-of therapy and 2-4 weeks posttherapy. Treatment planning with 5- or 6-fixed field IMRT, 2 and 3 arc VMAT, and 3- and 4-field proton plans were compared.RESULTS: One-hundred patients were included. Both CTCAE and PROs related to acute toxicity reached a maximum at end of therapy. Incidences of PROs were markedly higher with only slight to fair agreement to CTCAE, (κ 13-37). Comparative planning revealed dosimetric equality of IMRT and VMAT plans, but superiority of proton plans.CONCLUSIONS: The high incidence of PRO scores and weak agreement to CTCAE suggest that PROs are important tools complementary to CTCAE in evaluating patient symptoms during and after CRT. Proton therapy has the potential to lower radiation doses to most organs at risk.

Purpose Radiotherapy of paediatric patients comes at the expense of increased secondary cancer risk. This study examines whether the use of a 1 mm lead shielding during volumetric-modulated arc therapy (VMAT) for paediatric brain cancer can reduce the secondary cancer risk for the thyroid and breast. Methods Coplanar 6 MV VMAT plans were prepared for two anthropomorphic phantoms resembling a 1-year and 5-year old girl, for two different PTV sizes (2 cm and 5 cm diameter), simulating post-operative radiotherapy of an ependymoma in the posterior fossa. Out-of-field doses to the thyroid and breast were measured using thermoluminescence dosimeters. The phantoms were subject to three fractions (1,8 Gy each), with and without 1 mm lead shielding of the torso. The measured doses were used to calculate lifetime attributable risks for cancer incidence, for the total treatment dose of 54 Gy, in accordance with the BEIR VII report. 1 Results Applying lead shielding yielded dose reductions of 8–18% for the thyroid and 12–18% for the breast. The results were statistically significant (Student’s t-test, significance level p Conclusions Lead shielding of the phantoms resulted in a systematic decrease in the measured doses to the thyroid and breast, reducing the lifetime attributable risks for cancer incidence. The results hereby suggest that a 1 mm thick lead rubber blanket might be a clinically feasible solution for reducing the risk of secondary cancer in paediatric radiotherapy patients.

Purpose Removal of the flattening filter has been shown to alter the out-of-field dose during radiotherapy. In this study, the dose to selected out-of-field organs is compared for conventional flattened and flattening filter free (FFF) volumetric-modulated arc therapy (VMAT) of paediatric brain cancer. Methods Out-of-field doses to the thyroid, breast and testes were measured using thermoluminescence dosimeters inserted in two anthropomorphic phantoms resembling a 1-year and 5-year old child. Coplanar VMAT plans were prepared for 6 MV and 6 MV FFF photon beams, for two different PTV sizes (2 cm and 5 cm diameter), simulating post-operative radiotherapy of an ependymoma in the posterior fossa. The phantoms were subject to three VMAT fractions of 1,8 Gy each, delivered using a Varian TrueBeam linear accelerator. Some additional irradiations were performed for the 1-year phantom with the head of the phantom removed, to investigate the contribution from internal scatter to the total out-of-field dose. Results For the testes, measured doses showed a statistically significant decrease (Student’s t-test, significance level p 0,05) of 21–42% for FFF compared with conventional plans, for both phantoms as well as both PTV sizes. Doses to the breast showed a significant decrease of approximately 12% for the 5-year phantom for the small PTV, but other breast doses did not show a significant difference with and without the flattening filter. Doses to the thyroid showed a significant increase of approximately 18% for the 1-year phantom for the small PTV, with other dose differences being insignificant. However, doses to all three organs were significantly reduced (19–37%) when removing the head of the 1-year phantom, minimizing the contribution from internal scatter. Conclusions The results show that FFF VMAT of paediatric brain cancer leads to reduced doses to organs far from the field compared to VMAT with conventional flattened beams, while doses to organs close to the field seem to increase. The latter finding can be explained by an increase in internal scatter, which is possibly caused by the softer energy spectrum of the 6 MV FFF beam for the investigated linear accelerator model compared to conventional 6 MV.

Purpose:In most departments CT has replaced special radiographic projections with regard to classification of pelvic fractures. This change of procedure calls for analysis in terms of dosimetry.Methods:The total effective radiation doses given with spiral CT and conventional 5 projection radiography were determined according to ICRP 60 by measuring organ doses with an anthropomorphic Rando Alderson phantom packed with thermoluminescence dosimeters. For comparison, easily obtainable calculated effective doses were also determined, based on the CT dose index (CTDI), measured free-in-air and as entrance surface dose using organ conversion factors according to NRPB-R250 and NRPB-R262.Results:The total effective radiation dose was lower in spiral CT than in conventional 5 projection radiography, 4.4 and 5.0 mSv, respectively. In spiral CT the calculated effective dose was 11% lower and in conventional radiography 68% higher than the dose obtained by actual measurement using the Alderson phantom.Conclusion:As CT gives important diagnostic information with regard to classification of pelvic fractures, and without a greater radiation risk than impacted by 5 projection conventional radiography, we recommend the performance of spiral CT instead of special projections.

Medical physics as a separate profession developed from both theoretical and experimental physics. In the current understanding of the scope of the medical physics domain, the field is usually considered to be born with Rontgen’s discovery of x-rays in 1895. However, physical laws and relationships are also underpinning other biomedical applications and techniques that have a longer history, such as hyperthermia. The majority of medical physicists today still work in the fields of radiotherapy, medical imaging and nuclear medicine, in which use of highenergy ionising radiation is the common component. Rontgen’s x-rays, Marie and Pierre Curie’s gamma rays and the other radiation modalities that have followed represent the essence of the medical physics profession’s existence. As mentioned by Steve Webb in his combined historic and futuristic outlook paper published in this issue, most of the early achievements within the field of medical physics were performed by physicists and engineers that did not consider themselves as being medical physicists [1]. This was also the case for the Nordic scientists who earned a place in the medical physics history books for their scientific achievements in the early part of last century. Gustaf Ising, Rolf Sievert and Lars Leksell from Sweden as well as Rolf Wideroe from Norway are among those mentioned in Webb’s overview in this issue. Readers are referred to Webb’s paper for further details of the achievement of these early Nordic scientists from which our profession has developed. The first Nordic medical physics meeting was held in 1962 (in Orebro, Sweden) while the Nordic Association of Clinical Physics (NACP) was formally founded in 1965, only a few years later than e.g. the American Association of Physicists in Medicine (AAPM) that has celebrated its 50 anniversary in 2008. This reflects the strong dedication and professionalism of the scientists involved in these early days of Nordic medical physics. Already in 1965 1966, NACP had formed eight different working groups, within the topics dosimetry, radiation protection, treatment planning data, education, betatron dosimetry, simulation techniques, isotope techniques and electronic data management/treatment planning. At this time, NACP had 81 regular members (41 from Sweden, 21 from Denmark, 11 from Finland and 8 from Norway) in addition to its first honorary member, Rolf Sievert. The NACP meeting in 1966 (in Hango, Finland) attracted more than 100 participants, the majority from outside of the Nordic countries; proceedings from this meeting were also published. It is also interesting to note that NACP was formed before several of the Nordic national societies that it now acts as an umbrella organisation for, i.e., the Norwegian Society for Medical Physics was formed in 1976, the Danish Society for Medical Physics in 1981 while the Icelandic Society for Biomedical Engineering and Medical Physics was formed in 2000. In Finland, the hospital physicist branch of the Finnish Society for Mathematicians and Physicists was founded in the

Udgivelsesdato: 2009-null BACKGROUND: During a review of the current practice for computer tomography (CT) in 2005 at the Department of Radiology, Aarhus University Hospital, we observed 300 patients with more than six CT examinations during one year. They comprised 8% of the patients and accounted for 27% of all examinations. These patients needed further analysis. MATERIAL AND METHODS: The 300 patients were analyzed concerning age, type of diseases indicating multiple CTs and the CT protocols used. The effective dose and risk of low dose radiation was estimated and survival of the patients after >1.5 year was analyzed. RESULTS: A total of 289 patients had malignancies, the most frequent being lung cancer, bladder cancer and colon cancer. A total of 4.3% of the patients with malignancies were < or =40 year old, 13.3% were 41-50 years old and 62.7% 51-70 years old. The highest average number of CT examinations was observed in patients with sarcomas (11.2 examinations per patient). Eleven patients (aged 15-77 years) had traumatic lesions. Their number of examinations varied from 7 to 20. The total radiation dose for all 300 patients was 21.42 Sv, which may imply induction of a fatal cancer in one of the patients. However, only 102 patients survived their disease. CONCLUSION: A total of 198 patients had serious disease and were not alive 1.5 years after the examinations. The multiple CT examinations were necessary to monitor their treatment. For the surviving 102 patients the use of CT contributed to an optimal therapy, but the examinations implied a risk for radiation induced malignancies.

Udgivelsesdato: 2009-null BACKGROUND: The number of CT examinations performed in Denmark increased from 14,500 examinations in 1979 to 301,617 in 2005. This implies increased radiation dose to the population. On this background, an analysis of the practice for CT examinations including potential limitations of radiation exposure and the associated risk is needed. PURPOSES: To analyse 1) the current use of CT in a university department compared to 1996, 2) the radiation dose and risk associated with the examinations and 3) the use of CT in Denmark since 1979. MATERIAL AND METHODS: The administrative data of CT examinations performed in the Department of Radiology, Aarhus Sygehus, during 2005 and 1996, respectively, were obtained. Additionally national CT data were obtained from the database at the National Board of Health. RESULTS: In 1996 1,840 patients obtained 5,538 CT examinations at Aarhus Sygehus. Their mean age was 46.7 years (0-88). The most frequent referring speciality was oncology followed by abdominal surgery and orthopaedic surgery. In 2005 3,769 patients obtained 11,216 CT examinations. They were generally older with a mean age of 56.9 years (0-97). The most frequent referring speciality was oncology followed by chest medicine and abdominal surgery. In 2005 the total effective dose was 71,043 mSv (mean 18.9 mSv/per patient). According to the BEIR VII model this radiation level corresponded to a risk for inducing a cancer in 7 patients, being fatal in half of them. The national data showed a gradual increase of the number of CT examinations from 1979 to 2005, most pronounced after year 2000 coinciding with the introduction of multi-slice CT (MSCT). CONCLUSION: The number of CT examinations at Aarhus Sygehus doubled during a 9 year period. The increase occured especially in middle and high age groups.

To present results of optimising scoliosis examination by changing from a conventional film/grid (F/G) to air-gap technique using computed radiography (CR), and to evaluate different methods for estimating effective radiation doses. Forty-nine children and adolescents were examined with an F/G technique, and 21 with air-gap and CR techniques. Entrance surface doses (ESD) were determined with lithium fluoride thermoluminescence dosimeters. For all patients, the effective radiation doses were determined using a hermaphrodite PCXMC computer program. For all F/G radiographs, the effective doses were also determined according to the NRPB-R279 report, and for 22 children (>9 years and/or >40 kg) also with the ODS-60 program, which allows separate gender calculations. Accumulated doses for 37 children examined more than once with F/G examinations were assessed. For F/G techniques, the ESDs for both frontal and lateral views varied with age and were significantly correlated to the patients' thickness. The calculated effective doses using the PCXMC program and the NRPB-R279 did not differ significantly for all frontal and lateral radiographs, respectively, but ODS-60 gave significantly higher values in female subjects. With air-gap and CR techniques, the mean effective doses were reduced by a factor over 10. The mean accumulated effective dose for 37 children with a mean of seven F/G examinations was 6.1 mSv, implying a risk of death of about 1:2,000 for boys and at least 1:1,000 for girls. Paediatric scoliosis radiography should be considered a specialised procedure, which has to be optimised using a non-grid technique.

The aim of this study was to evaluate the radiation dose given by semicoronal CT of the sacroiliac joints (SIJs) in comparison with axial CT and conventional radiography. The total effective radiation doses given by serial contiguous semicoronal and axial CT, using 5-mm slices, 120 kV and 330 mAs, were determined by measurement of organ doses using an anthropomorphic Rando Alderson phantom paced with thermoluminescence dosimeters. The doses given by conventional antero-posterior (AP) and oblique projections of the SIJs were determined similarly. In a female the total effective dose by semicoronal CT was found to be more than six times lower than by axial CT and 2.5 times lower than the dose use to obtain a conventional AP radiograph, the values being 102, 678, and 255 micro Sv, respectively. The effective dose by semicoronal CT was only a little higher than the dose given to obtain two oblique radiographs. In a male with lead protection of the gonads the dose by semicoronal CT was four times lower than by axial CT, but higher than by conventional radiography. In conclusion, the effective dose by semicoronal CT of the SIJs is lower than by axial CT, and in females a semicoronal CT implies a lower effective radiation dose that used to obtain an AP radiograph.