Introduction to suspension levels: radiotherapy.

In 2007, the European Commission (EC) commissioned a group of experts to undertake the revision of Report Radiation Protection (RP 91) 'Criteria for acceptability of radiological (including radiotherapy) and nuclear medicine installations' written in 1997. The revised draft report was submitted to the EC in 2010, who issued it for public consultation. The EC has commissioned the same group of experts to consider the comments of the public consultation for further improvement of the revised report. The EC intends to publish the final report under its Radiation Report Series as RP 162. This paper describes the background to the selection of the key performance parameters for radiotherapy equipment and sets out the sources of their criteria of acceptability including suspension levels for a wide range of radiotherapy equipment.

Practical application of suspension criteria scenarios: radiotherapy.

In 2007, the European Commission (EC) commissioned a group of experts to undertake the revision of Report RP91 'Criteria for Acceptability of Radiological (including Radiotherapy) and Nuclear Medicine Installations' written in 1997. The revised draft report was submitted to the EC in 2010, which issued it for public consultation. The EC commissioned the same group of experts to consider the comments of the public consultation for further improvement of the revised report. The EC intends to publish the final report under its Radiation Report Series as RP162. This paper presents a selection of practical applications of suspension criteria scenarios in radiotherapy, mostly in brachytherapy, with special emphasis on the critical roles and responsibilities of qualified radiotherapy staff (radiation oncologists, medical physicists and radiotherapy technicians).

Development of educational image databases and e-books for medical physics training.

Medical physics education and training requires the use of extensive imaging material and specific explanations. These requirements provide an excellent background for application of e-Learning. The EU projects Consortia EMERALD and EMIT developed five volumes of such materials, now used in 65 countries. EMERALD developed e-Learning materials in three areas of medical physics (X-ray diagnostic radiology, nuclear medicine and radiotherapy). EMIT developed e-Learning materials in two further areas: ultrasound and magnetic resonance imaging. This paper describes the development of these e-Learning materials (consisting of e-books and educational image databases). The e-books include tasks helping studying of various equipment and methods. The text of these PDF e-books is hyperlinked with respective images. The e-books are used through the readers' own Internet browser. Each Image Database (IDB) includes a browser, which displays hundreds of images of equipment, block diagrams and graphs, image quality examples, artefacts, etc. Both the e-books and IDB are engraved on five separate CD-ROMs. Demo of these materials can be taken from www.emerald2.net.

Quality assurance in radiotherapy: the importance of medical physics staffing levels. Recommendations from an ESTRO/EFOMP joint task group.

The safe application of ionising radiation for diagnosis and therapy requires a high level of knowledge of the underlying processes and of quality assurance. Sophisticated modern equipment can be used effectively for complicated diagnostic and therapeutic techniques only with adequate physics support. In the light of recent analyses and recommendations by national and international societies a joint working group of representatives from ESTRO (European Society for Therapeutic Radiology and Oncology) and from EFOMP (European Federation of Organisations for Medical Physics) was set up to assess the necessary staffing levels for physics support to radiotherapy. The method used to assess the staffing levels, the resulting recommendations and examples of their practical application are described.

Electrolysis with different electrode materials and combined with irradiation for treatment of experimental rat tumors.

In order to make electrolytic tumor destruction more effective new electrode materials were tested (Part I) as well as a combination of electrolysis and megavolt therapy (Part II). All tests were performed in experimental tumors implanted subcutaneously in rats. Altogether in 41 rats in 5 series (Part I) electrodes made of rhodium (Rh), copper (Cu), or brass (Zn-Cu alloy) were investigated but the effect was not found to be better than that of the previously tested platinum (Pt). Oxidation and corrosion made Rh and Cu electrodes less suitable for electrolysis compared to Pt, while brass electrodes became isolated through zinc-salt-formation and performed unsatisfactorily. The radiosensitizing properties of electrolysis were tested in 55 rats with experimental tumors (Part II). One control group had only Co-irradiation, while in 2 other groups Cu- or Pt-electrolysis of the tumors was carried out before irradiation. The combined treatment resulted in a significantly better effect on the tumors, registered as inhibition of tumor growth or disappearance of tumor. As the electrolyzed, necrotic tissue remained in the tumor the effect might not be mediated through diminished target volume. An inflammatory reaction around the electrolytic lesion with increased blood flow and higher oxygenation of the tumor could cause a more positive response to megavolt treatment.

Prognostic factors influencing survival in combined radiotherapy and surgery of squamous cell carcinoma of the esophagus with special reference to a histopathologic grading system.

Sixty-six patients with squamous cell carcinoma of the esophagus were treated with combined surgery and radiotherapy, mostly in a sandwich fashion. Fourteen patients received misonidazole during preoperative radiotherapy. Prospective cumulative survival at 1, 2, and 5 years was 60%, 35%, and 17%, respectively. Original biopsy specimens and operation specimens were evaluated according to a histopathologic grading system based on an evaluation of the tumor cell population in terms of cell differentiation, structure, nuclear polymorphism, and the frequency of mitotic figures. The tumor-host relationship was also estimated by the mode of invasion, stage of invasion, vascular invasion, and degree of lymphocytic infiltration. A multivariate regression analysis according to Cox and actuarial survival were used to determine the relative contributions of the clinical and histopathologic parameters to patient outcome. The major results were as follows: (1) patients who were old (70 to 80 years) fared as well as younger patients (P = 0.9198); (2) tumor site did not influence therapeutic outcome (P = 0.1100); (3) there was an insignificant difference in survival between patients with M0 and M1 disease (P = 0.7130); (4) radical surgery gave better survival; (5) misonidazole administered preoperatively was associated with worse survival (P = 0.0147); and (6) the histopathologic malignancy grading score system was very useful for prognostication--the tumor-host score in the operative specimen was the strongest of all analyzed predictive parameters. Since palliation was excellent in all patients treated in the combined fashion, selection criteria should be wide for such a program, not the least since long-term survival is possible also for patients with very advanced tumors.

Electrolytic tissue destruction and external beam irradiation of the lung. An experimental and clinical investigation.

In order to evaluate possible benefits of local therapy of lung tumors--electrolysis at Pt-electrodes percutaneously inserted in the tumor, followed by radiation therapy--6 pigs were used as test objects. Two died of lung hemorrhage due to too fast electrolysis causing lung rupture but the other 4 survived when electrolysis was performed at a lower speed. No complication was observed of the combination of electrolysis and external beam irradiation. One human primary lung tumor was treated and probably destroyed by two electrolytic procedures and irradiation to 64 Gy. The evidence of the limited series of animal experiments and of single human tumor case would indicate that further investigations seem worthwhile.

Radiation therapy and surgery in the treatment of regional lymph nodes in squamous cell carcinoma of the vulva.

A series of 244 patients with vulvar squamous cell carcinomas was analyzed with regard to treatment of the regional lymph nodes. In 144 patients, groin dissection was performed, supplemented in 24 cases by pelvic lymphadenectomy. Preoperative irradiation was given and in cases with positive nodes postoperative irradiation as well. Patients in whom lymph node dissection was not performed received irradiation. Treatment failures in the regional lymph node regions were analyzed and the policy concerning treatment of the regional lymph nodes is discussed.

User requirements on CT-based computed dose planning systems in radiation therapy. Presentation of 'check lists'.

The expanding use of computers in radiation therapy procedures, especially the rapidly increasing use of digital CT-information, necessitates the coordination of the different systems in order to facilitate their developments. In order to define necessary demands for tomorrow a Nordic cooperation was initiated 1981 by NORDFORSK (Nordic co-operative organization for applied research), and a group of physicians and physicists having their daily work in this field of medicine and physics was invited to produce a report on 'User requirements on CT-based computed dose planning systems on radiation therapy'. The work has been done within the frame of NORDFORSK's activities and has been independent of the existing commissions and associations in the radiology field, but it has taken into consideration recommendations that have been given by or are being produced by other organizations. This report is a short summary of the complete paper which will be published in Acta Radiologica. The aim of this short version is to get an early presentation of the 'requirement lists' (see Appendix) which we think are of immediate importance.

User requirements on CT-based computed dose planning systems in radiation therapy.

The expanding use of computers in radiation therapy procedures, especially the rapidly increasing use of digital CT information, necessitates the coordination of the different systems in order to facilitate their developments. In order to define necessary demands for tomorrow a Nordic cooperation was initiated 1981 by NORDFORSK (Nordic co-operative organization for applied research), and a group of physicians and physicists having their daily work in this field of medicine and physics was invited to produce a report on 'User requirements on CT-based computerized dose planning systems in radiotherapy'. The work has been done within the frame of NORDFORSK's activities. The working group has been independent of the existing commissions and associations in the radiology field, but it has taken into consideration recommendations that have been given by or are being produced by other organizations.

Theoretical studies of image artifacts and counting losses for different photon fluence rates and pulse-height distributions in single-crystal NaI(T1) scintillation cameras.

Using computer simulations, we have developed a theoretical model to explain the correlation between counting losses and image artifacts in single-crystal NaI(T1) scintillation cameras. The theory, valid for scintillation cameras of the Anger type, is based on the physical properties of the NaI(T1) crystal. Based on a statistical model using random numbers, pulse trains of the light pulses from scintillations were simulated. Pulse-height distributions for different event rates were calculated, with various Compton distributions. Images of point sources and line sources were generated. Counting losses and image artifacts were dependent on the shape of the pulse-height distribution. The calculated counting losses decreased with larger Compton distributions, due to increasing numbers of pileup events in the energy window; this also caused severe image distortion. The improvement of the spatial resolution with pileup rejection was demonstrated. The theoretical results are in good agreement with experimental results obtained previously. It is concluded that, in modern cameras, the decay time of the scintillation determines the amount of pileup, and the resolving time of the electronics governs the count rates. The results indicate that in some modern cameras the limits of the count-rate capacity in Anger cameras may be reached.

Effect of different radiation fractionation schedules on metastases from an oesophageal carcinoma.

Subcutaneous metastases from an oesophageal carcinoma were irradiated using different schedules. The results have to be evaluated with greatest caution but indicate that with the same CRE value, few fractions caused less skin reactions than several, and the size of the shoulder of the cell survival curve was of the order of 0.7 Gy.