Prostate cancer is the most common cancer in men. One type of treatment is internal radiation therapy, brachytherapy. This treatment requires the patient to lie completely motionless and in lithotomy position. The purpose of this study was to investigate the prevalence of pressure ulcers associated with brachytherapy in prostate cancer at the UniversityHospitalin Uppsala. Furthermore, the purpose was to identify the most common location of pressure ulcer and to examine whether there were any connection between risk factors and possible pressure ulcers. Thirty patients participated in the study. The data collection was carried out partly by the nurse anesthetist and partly by the nurse in the oncology ward in fall 2009 to spring 2010. The study showed that seven of thirty patients (23.3%) developed pressure ulcers after brachytherapy. All of these were stage 1 according to EPUAP's pressure ulcer scale. Only one of the patients (3.3%) had remaining pressure ulcer the day after treatment. The most common location were lower legs/calves (16.7%). No statistically significant relationship was found between risk factors and the development of pressure ulcers. The results of this study showed a relatively high incidence of pressure ulcers (23.3%). All of stage 1 and only one of the pressure ulcers were remaining the day after brachytherapy. This indicates a good pressure-relieving measures and equipment, and that the patients in this study have a relatively good general          condition.Keywords: brachytherapy, pressure ulcers, lithotomy position, risk factors / Prostatacancer är den vanligast förekommande cancersjukdomen hos män. En av behandlingsformerna är intern strålbehandling, brachyterapi. Denna behandling kräver att patienten ligger helt stilla och i gynekologiskt läge. Syftet med studien var att undersöka förekomsten av trycksår i samband med brachyterapi vid prostatacancer på Akademiska sjukhuset i Uppsala. Vidare var syftet med studien att kartlägga de vanligaste lokalisationerna samt att undersöka om de fanns några samband mellan riskfaktorer och eventuella trycksår. Trettio patienter deltog i studien. Datainsamlingen utfördes dels av anestesisjuksköterskan och dels av patientansvarig sjuksköterska på onkologavdelningen under hösten 2009 till våren 2010. Resultatet av studien visade att sju av trettio patienter (23,3 %) utvecklade trycksår efter behandlingen. Alla dessa var av grad 1 enligt EPUAP:s trycksårsskala. Endast en av patienterna (3,3 %) hade kvar trycksåret dagen efter behandlingen. Den vanligaste lokalisationen för trycksår var underben/vader (16,7 %). Inga statistiskt säkra samband kunde ses mellan riskfaktorerna och utvecklandet av trycksår. Studien visade en relativt hög frekvens av trycksår (23,3 %). Dock var samtliga av grad 1 och endast ett trycksår var kvarstående till dagen efter brachybehandlingen. Detta tyder på bra tryckavlastande åtgärder och utrustning samt att patienterna i den aktuella undersökningsgruppen har relativt gott allmäntillstånd.   Nyckelord: brachyterapi, trycksår, gynekologiskt läge, riskfaktorer

A new generation of medical grade Cf-252 sources was developed in 2002 at the Oak Ridge National Laboratory (ORNL). The combination of small size and large activity of these Cf-252 sources makes them suitable to be used with the conventional high-dose-rate (HDR) remote afterloading systems for interstitial brachytherapy. A recent in-water calibration experiment showed that the measured gamma dose rates near the new source are slightly greater than the neutron dose rates; contradicting the well established neutron-to-gamma dose ratio of approximately 2:1 at locations near a Cf-252 brachytherapy source. Specifically, the MCNP-predicted gamma dose rate is a factor of two higher than the measured gamma dose rate at the distance of 1 cm, and the differences between the two results gradually diminish at distances farther away from the source. To resolve this discrepancy, we updated the source gamma spectrum by including in the ORIGEN-S data library the experimentally measured Cf-252 prompt gamma spectrum as well as the true Cf-252 spontaneous fission yield data to explicitly model delayed gamma emissions from fission products. We also investigated the bremsstrahlung x-rays produced by the beta particles emitted from fission-product decays. The results show that the discrepancy of gamma dose rates is mainly caused by the omission of the bremsstrahlung x-rays in the MCNP runs. By including the bremsstrahlung x-rays, the MCNP results show that the gamma dose rates near a new Cf-252 source agree well with the measured results and that the gamma dose rates are indeed greater than the neutron dose rates. The calibration experiment also showed discrepancies between the experimental and computational neutron dose profiles obtained. Specifically the MCNP-predicted neutron dose rates were ~25% higher than the measured neutron dose rates at all distances. In attempting to resolve this discrepancy the neutron emission rate was verified by the National Institute of Standards and Technology (NIST) and an experiment was performed to explore the effects of bias voltage on ion chamber charge collection. So far the discrepancies between the computational and experimental neutron dose profiles have not been resolved. Further study is needed to completely resolve this issue and some suggestions on how to move forward are given.

A novel optical calorimetry approach is proposed for the dosimetry of therapeutic radiation, based on the optical technique of Digital Holographic Interferometry (DHI). This detector determines the radiation absorbed dose to water by measurement of the refractive index variations arising from radiation induced temperature increases. The output consists of a time series of high resolution, two dimensional images of the spatial distribution of the projected dose map across the water sample. This absorbed dose to water is measured directly, independently of radiation type, dose rate and energy, and without perturbation of the beam. These are key features which make DHI a promising technique for radiation dosimetry. A prototype DHI detector was developed, with the aim of providing proof-of-principle of the approach. The detector consists of an optical laser interferometer based on a lensless Fourier transform digital holography (LFTDH) system, and the associated mathematical reconstruction of the absorbed dose. The conceptual basis was introduced, and a full framework was established for the measurement and analysis of the results. Methods were developed for mathematical correction of the distortions introduced by heat di usion within the system. Pilot studies of the dosimetry of a high dose rate Ir-192 brachytherapy source and a small eld proton beam were conducted in order to investigate the dosimetric potential of the technique. Results were validated against independent models of the expected radiation dose distributions. Initial measurements of absorbed dose demonstrated the ability of the DHI detector to resolve the minuscule temperature changes produced by radiation in water to within experimental uncertainty. Spatial resolution of approximately 0.03 mm/pixel was achieved, and the dose distribution around the brachytherapy source was accurately measured for short irradiation times, to within the experimental uncertainty. The experimental noise for the prototype detector was relatively large and combined with the occurrence of heat di usion, means that the method is predominantly suitable for high dose rate applications. The initial proof-of-principle results con rm that DHI dosimetry is a promising technique, with a range of potential bene ts. Further development of the technique is warranted, to improve on the limitations of the current prototype. A comprehensive analysis of the system was conducted to determine key requirements for future development of the DHI detector to be a useful contribution to the dosimetric toolbox of a range of current and emerging applications. The sources of measurement uncertainty are considered, and methods suggested to mitigate these. Improvement of the signal-to-noise ratio, and further development of the heat transport corrections for high dose gradient regions are key areas of focus highlighted for future development.

The TG-43 dosimetry parameters of the AdvantageTM 125I model IAI-125A brachytherapy seed were studied. An investigation using modern MCNP radiation transport code with updated cross-section libraries was performed. Twelve different simulation conditions were studied for a single seed by varying the coating thickness, mass density, photon energy spectrum and cross-section library. The dose rate was found to be 6.3% lower at 1 cm in comparison to published results. New TG-43 dosimetry parameters are proposed. The dose distribution for a brachytherapy eye plaque, model EP917, was investigated, including the effects of collimation from high-Z slots. Dose distributions for 26 slot designs were determined using Monte Carlo methods and compared between the published literature, a clinical treatment planning system, and physical measurements. The dosimetric effect of the composition and mass density of the gold backing was shown to be less than 3%. Slot depth, width, and length changed the central axis (CAX) dose distributions by < 1% per 0.1 mm in design variation. Seed shifts in the slot towards the eye and shifts of the 125I-laden silver rod within the seed had the greatest impact on the CAX dose distribution, changing it by 14%, 9%, 4.3%, and 2.7% at 1, 2, 5, and 10 mm, respectively, from the inner scleral surface. The measured, full plaque slot geometry delivered 2.4% ± 1.1% higher dose along the plaque’s CAX than the geometry provided by the manufacturer and 2.2%±2.3% higher than Plaque SimulatorTM (PS) treatment planning software (version 5.7.6). The D10 for the simulated tumor, inner sclera, and outer sclera for the measured slot plaque to manufacturer provided slot design was 9%, 10%, and 19% higher, respectively. In comparison to the measured plaque design, a theoretical plaque having narrow and deep slots delivered 30%, 37%, and 62% lower D10 doses to the tumor, inner sclera, and outer sclera, respectively. CAX doses at –1, 0, 1, and 2 mm were also lower by a factor of 2.6, 1.72, 1.50, and 1.39, respectively. The study identified substantial sensitivity of the EP917 plaque dose distributions to slot design.

Dieser Beitrag ist mit Zustimmung des Rechteinhabers aufgrund einer (DFG-geförderten) Allianz- bzw. Nationallizenz frei zugänglich.

Tyrimo tikslas - išanalizuoti priešinės liaukos vėžiu sergančių pacientų, 2007–2010 metais gydytų brachiterapija, radioaktyviojo Jodo-125 šaltinių implantavimo kokybę ir nepageidaujamą poveikį. Įvade išdėstomi tyrimo tikslai bei uždaviniai, pateikiama literatūros apžvalga, kurioje apibendrinamos pagrindinės su nagrinėjama tema susijusios problemos. Atskirame skyriuje aprašyta tyrimo metodika. Disertacijoje išnagrinėta laisvų ir skirtingais atstumais į grandinėlę sujungtų Jodo-125 šaltinių implantavimo kokybės skirtumais gydant priešinės liaukos vėžį bei dozimetrijos po implantacijos atlikimo laiko įtaką implantacijos rezultatų vertinimui. Atskirai analizuotas nepageidaujamas gydymo poveikis. Įvertinti su priešinės liaukos vėžio gydymu Jodo-125 šaltiniais susiję šlapinimosi sutrikimai, išanalizuoti erekcijos sutrikimai ir juos sukeliančtys veiksniai po Jodo-125 šaltinių implantavimo, nustatytos kraujavimo iš tiesiosios žarnos dažnio sąsajos su klinikiniais ir dozimetriniais parametrais. / Aim of this study - to analyze implant quality and treatment toxicity in prostate cancer patients, treated with Iodine-125 seeds brachytherapy during the perios of 2007 – 2010 years. Initial dissertation chapters covers study aims and objectives. Literature data about prostate brachytherapy with Iodine-125 seeds are analysed. Material and methods are thorougly described. Data about implant quality differences in prostate cancer patients, treated with loose and linked seeds, are presented. Influence of postimplant dosimetry time to evaluation of Iodine-125 implantation results is analysed. Another part of this work is dedicated to toxicity of Iodine-125 seeds brachytherapy. Various aspects of treatment side effects are evaluated urinary disorders and erectile dysfunction. Association of risk of rectal bleeding after Iodine–125 brachytherapy with clinical and dosimetry parameters is assesed.

Brachytherapy is a form of radiotherapy in which radioactive sources are placed at short distances from, or even inside the target volume. The use of high dose rate brachytherapy is a widely accepted and clinically proven treatment for some stages of prostate cancer. The aim of this project was to investigate potential improvements on two of the most important aspects of high dose rate (HDR) and pulsed dose rate (PDR) prostate brachytherapy - prostate definition and treatment delivery verification. The use of magnetic resonance (MR) imaging in addition to the conventional computed tomography (CT) imaging methods currently used routinely for brachytherapy planning may provide some benefit in accurately defining the prostate and surrounding critical structures. The methods used in this project involved analysis of data sets provided by two Radiation Oncologists. The results presented showed inter-observer and intra-observer variations in the size and shape of the prostate, as well as analysis of the dosimetric differences that may be reported due to the differences in prostate size and shape. The results also included analysis of critical structure dosimetry - dose to the surrounding radio-sensitive rectum and urethra. In summary, the results showed that the prostate was defined to be smaller using MR imaging than CT, however the consistency between Oncologists was not significantly improved using MR imaging. MR imaging may be useful in reducing the dose to normal tissue surrounding the prostate and in obtaining better coverage of the smaller target volume, without compromising the critical structures. The use of LiF:Mg,Ti thermoluminescent dosimeters (TLDs) is a potential avenue for in vivo dose verification of an HDR or PDR prostate brachytherapy treatment plan. This project included a phantom study of these TLDs with the aim to determine their feasibility for clinical use. Cylindrical TLD rods (6 mm length x 1 mm diameter) were used, as these fit inside the brachytherapy needles implanted into the prostate, and therefore had potential to be used clinically to verify the dose delivered in the prostate. This study was extended to include determination of a correction factor to allow an independent radiation source (6 MV photon beam from a linear accelerator) to be used to obtain control readings for this relative dosimetric method. The results showed these TLDs to be a promising in vivo dosimeter for prostate brachytherapy with potential errors in the order of 4%. Their potential lies in the fact that they could detect and flag significant calculation errors in treatment plans, and they utilise equipment used routinely for external beam radiotherapy dosimetry in many treatment facilities, reducing the cost of implementing such a procedure.

Diss. (sammanfattning) Stockholm : Karol. inst., 2006. / Härtill 4 uppsatser.

Thesis (M.Sc.). / Written for the Medical Physics Unit. Title from title page of PDF (viewed 2008/05/14). Includes bibliographical references.

Thesis--University of Oklahoma. / Bibliography: leaves 78-79.