Treatment planning algorithms for use in the radiotherapeutic treatment of cancer have progressively evolved since the earliest attempts to develop automated dose calculation software in the mid-1950s. Modern algorithms use advanced techniques such as convolution superposition or grid-based Boltzmann solvers to perform external beam radiotherapy calculations. A new method of dose calculation was developed at the Georgia Institute of Technology based on transport theory called COMET-PE. The method combines stochastic pre-computation with a deterministic solver to achieve high accuracy and precision. For the COMET-PE method to be implemented clinically it needs a practical source model that closely mimics the physical characteristics of a typical radiation beam from a linear particle accelerator. The COMET-PE method should also be validated against a known benchmark. A novel linear accelerator source model is presented that models the geometry, angular distribution, spectrum, energy, and electron contamination of a 6 MV photon beam from a Varian c-series clinac. Of note is the use of a hemispherical harmonic expansion with the functional expansion tally method to model photonic fluence. The source was implemented in the COMET-PE radiation transport code and calculations performed with various field sizes and phantoms. The results are benchmarked against Monte Carlo reference solutions and compared with calculations performed with two popular commercially available treatment planning algorithms. The results indicate that the proposed source model when coupled with the COMET-PE method is capable of dosimetric calculations that in many cases more closely match Monte Carlo solutions than the commercially available options.

IINTRODUCTION: This study’s aims were to: 1) evaluate whether or not there was a treat- ment plan change, if CBCT is used; and 2) evaluate if the use of CBCT as diagnostic tool improves the treatment outcome. We hypothesized that 1. the use of CBCT as diagnostic tool changes the treatment plan; and 2. improves the treatment outcome MATERIALS AND METHODS: This was an IRB approved retrospective study of all the conventional re-treatments and surgical RCT performed at Boston University Post-doctoral clinic from 2009 - 2015. Of 10,836 cases completed, 674 cases had a CBCT on file and 31 had a pre- and post-CBCT treatment plan with at least 3 months follow up. Cases with CBCT were matched (2 to 1) with cases without CBCT based on patients’ sex, age, tooth type, diagnosis, procedure performed, and insurance type. Chart notes and treatments were reviewed to identifytreatment plan changes. The investigator evaluated outcome as either Success/Survive/ Failure. Statistical Analyses tested for differences in treatment plan and Success/Survive/ Failure rates at minimum 3 months. RESULT: 31 cases and 49 controls were evaluated. There were no differences in mean age (46) or insurance between cases and controls. In over half of the cases (54.8%) the treatment plan changed when CBCT was used. Cases with CBCT had 32% success rate, 60% sur- vival rate and 8% failure rate at minimum 3 months whereas cases without CBCT had 22.4% success rate, 53.1% survival rate and 24.5% failure rate, p-value = 0.21. CONCLUSION: The use of CBCT as diagnostic tool affected more than half of the treatment plans. While CBCT appeared to improve the treatment outcomes, the difference in this small sample is not statistically significant. Future research will require larger sample sizes to test whether CBCT improves treatment efficacy in endodontics.

Abstract In New Zealand there are currently no regular external audits to verify the full treatment chain in radiotherapy. This thesis reports on a project to devise such an audit procedure suitable to assess the accuracy of the delivery of prescribed radiotherapy doses to patients over the full treatment process. The National Radiation Laboratory (NRL), regulatory authority, will use the method developed to conduct biennial audits of all radiotherapy centres. A commercial chest phantom with a MOSFET dosimetry system was provided for this project. The MOSFETs were commissioned and their characteristics determined, namely reproducibility, energy dependence and angular dependence. The MOSFETs were also tested in a clinical environment with the phantom. Measurements were carried out to test the MOSFET capabilities in both lung and soft tissue in the phantom. Two plans were devised for the audit process, a straightforward one with two parallel opposed beams and a more complex one involving lung tissue and wedges. These plans were designed to test the entire treatment planning and delivery process. It was found that each MOSFET detector needed to be individually calibrated. Reproducibility was found to have an average standard deviation of 2% on standard sensitivity and 1.2% on high sensitivity. The angular dependence of the detectors showed that when the MOSFET was rotated by 90 degrees to the beam axis a drop in response of 3% was observed with 6 MV. The energy dependence factor was constant within uncertainty for all MOSFETs. Overall, the MOSFET and phantom dosimetry system was determined to be suitable for the audit. The measurements with phantom showed that doses in high dose regions could be determined accurately. The greatest variation from the Treatment Planning system dose to the measured dose was 6%. The trial runs of the audit in two New Zealand radiotherapy centres showed that the procedure created is able to find discrepancies within the desired 5%, recommended by the ICRU, in the prescribed dose to the phantom.

Cone beam computed tomography (CBCT) is the recommended imaging modality of choice for evaluating previous endodontic treatment (1). The aim of this study was to compare treatment planning decisions made when evaluating previous endodontic treatment to determine if treatment planned and projected prognosis differs when digital radiography is used alone or in combination with CBCT. A retrospective chart review was conducted. Patients for whom a CBCT was taken were included in the study. Twenty-eight patients qualified. Patient’s periapical digital radiographs (Dexis©) were evaluated by 2 calibrated endodontists, a treatment plan was identified and a prognosis was projected. Later the same radiographs were viewed with CBCT scan. The CBCT provided significant information 75% of the time. CBCT provided the only information for an accurate diagnosis 17% of the time. Prognosis changed 38% of the time when CBCT was added. An unfavorable or questionable prognosis changed to favorable 30% of the time.

Total body irradiation (TBI) is often used as part of the conditioning process prior to bone marrow transplants for diseases such as leukemia. By delivering radiation to the entire body, together with chemotherapy, tumour cells are killed and the patient is also immunosupressed. This reduces the risk of disease relapse and increases the chances of a successful implant respectively. TBI requires a large flat field of radiation to cover the entire body with a uniform dose. However, dose uniformity is a major challenge in TBI. (AAPM Report 17) The ICRU report 50 recommends that the dose range within the target volume remain in the range of -5% to +7%. Whilst it is generally accepted that this is not possible for TBI, it is normally clinically acceptable that ±10% of the prescribed dose to the whole body is sufficiently uniform, unless critical structures are being shielded. TBI involves complex dosimetry due to the large source to treatment axis distance (SAD), dose uniformity and flatness over the large field, bolus requirements, extra scatter from the bunker walls and floor and large field overshoot. There is also a lack of specialised treatment planning systems for TBI planning at extended SAD. TBI doses at Westmead Hospital are prescribed to midline. Corrections are made for variations in body contour and tissue density heterogeneity in the lungs using bolus material to increase dose uniformity along midline. Computed tomography (CT) data is imported into a treatment planning system. The CT gives information regarding tissue heterogeneity and patient contour. The treatment planning system uses this information to determine the dose distribution. Using the dose ratio between plans with and without heterogeneity correction the effective chest width can be calculated. The effective chest width is then used for calculating the treatment monitor units and bolus requirements. In this project the tissue heterogeneity corrections from two different treatment planning systems are compared for calculating the effective chest width. The treatment planning systems used were PinnacleTM, a 3D system that uses a convolution method to correct for tissue heterogeneity and calculate dose. The other system, RadplanTM, is a 2D algorithm that corrects for tissue heterogeneity using a modified Batho method and calculates dose using the Bentley - Milan Algorithm. Other possible differences between the treatment planning systems are also discussed. An anthropomorphic phantom was modified during this project. The chest slices were replaced with PerspexTM slices that had different sized cork and PerspexTM inserts to simulate different lung sizes. This allowed the effects of different lung size on the heterogeneity correction to be analysed. The phantom was CT scanned and the information used for the treatment plans. For each treatment planning system and each phantom plans were made with and without heterogeneity corrections. For each phantom the ratio between the plans from each system was used to calculate the effective chest width. The effective chest width was then used to calculate the number of monitor units to be delivered. The calculated dose per monitor unit at the extended TBI distance for the effective chest width from each planning system is then verified using thermoluminescent dosimeters (TLDs) in the unmodified phantom. The original phantom was used for the verification measurements as it had special slots for TLDs. The isodose distributions produced by each planning system are then verified using measurements from Kodak EDR2 radiographic film in the anthropomorphic phantom at isocentre. Further film measurements are made at the extended TBI treatment SAD. It was found that only the width of the lungs made any significant difference to the heterogeneity correction for each treatment planning system. The height and depth of the lungs will affect the dose at the calculation point from changes to the scattered radiation within the volume. However, since the dose from scattered radiation is only a fraction of that from the primary beam, the change in dose was not found to be significant. This is because the calculation point was positioned in the middle of the lungs, so the height and depth of the lungs didn't affect the dose at the calculation point. The dose per monitor unit calculated using the heterogeneity correction for each treatment planning system varied less than the accuracy of the TLD measurements. The isodose distributions measured by film showed reasonable agreement with those calculated by both treatment planning systems at isocentre and a more uniform distribution at the extended TBI treatment distance. The verification measurements showed that either treatment planning system could be used to calculate the heterogeneity correction and hence effective chest width for TBI treatment planning.

Abstract In New Zealand there are currently no regular external audits to verify the full treatment chain in radiotherapy. This thesis reports on a project to devise such an audit procedure suitable to assess the accuracy of the delivery of prescribed radiotherapy doses to patients over the full treatment process. The National Radiation Laboratory (NRL), regulatory authority, will use the method developed to conduct biennial audits of all radiotherapy centres. A commercial chest phantom with a MOSFET dosimetry system was provided for this project. The MOSFETs were commissioned and their characteristics determined, namely reproducibility, energy dependence and angular dependence. The MOSFETs were also tested in a clinical environment with the phantom. Measurements were carried out to test the MOSFET capabilities in both lung and soft tissue in the phantom. Two plans were devised for the audit process, a straightforward one with two parallel opposed beams and a more complex one involving lung tissue and wedges. These plans were designed to test the entire treatment planning and delivery process. It was found that each MOSFET detector needed to be individually calibrated. Reproducibility was found to have an average standard deviation of 2% on standard sensitivity and 1.2% on high sensitivity. The angular dependence of the detectors showed that when the MOSFET was rotated by 90 degrees to the beam axis a drop in response of 3% was observed with 6 MV. The energy dependence factor was constant within uncertainty for all MOSFETs. Overall, the MOSFET and phantom dosimetry system was determined to be suitable for the audit. The measurements with phantom showed that doses in high dose regions could be determined accurately. The greatest variation from the Treatment Planning system dose to the measured dose was 6%. The trial runs of the audit in two New Zealand radiotherapy centres showed that the procedure created is able to find discrepancies within the desired 5%, recommended by the ICRU, in the prescribed dose to the phantom.

京都大学 / 0048 / 新制・課程博士 / 博士(医学) / 甲第20222号 / 医博第4181号 / 新制||医||1019(附属図書館) / 京都大学大学院医学研究科医学専攻 / (主査)教授 鈴木 実, 教授 高田 穣, 教授 武藤 学 / 学位規則第4条第1項該当 / Doctor of Medical Science / Kyoto University / DFAM

"The thesis includes fundamental work in the following, · Development of materials database which includes the main parameters of the various heat transfer models · Validation and testing of the system capability and accuracy by means of various case studies A computer aided heat treatment planning system (CAHTPS) is developed to assist the heat treatment process. The temperature distribution inside the furnace and the temperature of the various parts in the load can be determined. The various models for the heat treatment are analyzed and the various parameters in the equations are classified. The majority of the equations parameters were properties of various metals and non metals. Hence an extensive database is developed so as to assist the models. The remaining physical conditions dependent parameters of the models were analyzed and the effects due to change in the conditions and these parameters are tested and studied by various case studies. The change in the loading pattern effects and change in the load quantity effects for the various cases are presented. The thesis work establishes the system’s application scope and the accuracy to be used in the current heat treatment industries."

The use of treatment support tools to enhance client outcomes is not well understood in the youth treatment literature. Adult outcome researchers have found that the use of Clinical Support Tools (CST) leads to improved outcomes with clients identified as at risk for treatment failure. However, the American Psychological Association (APA) has noted that understanding important client factors that influence treatment is critical during the clinical formulation and treatment planning phase of therapy. No studies to date have evaluated the effectiveness of utilizing a CST as a treatment planning tool with youth clients. The purpose of this study was to evaluate the effectiveness of the Treatment Support Measure, a CST, for the purpose of treatment planning rather than as a reaction to clients who became at-risk for treatment failure. Two hundred and eight youth participants and their caregivers from three outpatient community mental health clinics were randomly assigned to a feedback (TSM-FB) or Non-FB condition. All participants completed the Youth Outcome Questionnaire (Y-OQ) at each session. The TSM was administered to clients in the TSM-FB condition during the intake session. Only therapists whose clients were in the TSM-FB condition received TSM and Y-OQ data. A multilevel model was created to evaluate for differences between conditions on the dependent variable. The initial randomization failed to create similar groups at intake and a statistically and clinically significant difference was detected on the Y-OQ at intake. As such, no conclusions can be drawn for hypotheses tied to the primary dependent variable. Premature termination (PT) rates were significantly lower for the TSM-FB condition when defined as attending more than one session. Contrastingly, there was no difference between conditions on PT when defining PT based on the therapist's opinion. A significant minority of therapists (40%) found that the TSM was useful for treatment planning compared to 10% which did not.

In this thesis, we aim to develop fundamentally new techniques and algorithms for efficiently computing rotating-shield brachytherapy (RSBT) treatment plans. We propose that these algorithms will pave the way for making RSBT available in clinical practices. RSBT is an intensity modulated high-dose-rate brachytherapy (HDR-BT) technique. Theoretically, RSBT offers advantages over the conventional HDR-BT. Although this technique is promising in theory, its application in practice is still at an early stage. The RSBT technique entails rotating a radiation-attenuating shield about a brachytherapy source to directionally modulate the radiation in an optimized fashion. The unshielded brachytherapy source used in conventional HDR-BT delivers radially symmetric dose distributions, thus the intensity modulation capability of the conventional HDR-BT is limited. With the capability of making anisotropic radiation, RSBT will revolutionize the brachytherapy technique through superior dose conformity, increased flexibility and inherent accuracy. Due to the enhanced power of intensity-modulation, RSBT will also enable dose escalation without increasing toxicity to the organs-at-risk, thus improving quality of life for millions of cancer patients. Although the first conceptual RSBT method was proposed more than ten years ago, there are still tremendous challenges for applying it in clinical practices. Creating efficient and automated treatment planning system is one of the major technical obstacles for making RSBT deliverable in the clinic. The time-critical nature of the application significantly increases the difficulty of RSBT treatment planning, demanding innovative techniques for information integration. Therefore, we propose that fundamentally novel technology and algorithms for RSBT treatment planning can make RSBT clinically accessible. The fundamental concept used for this thesis is to decompose the dose optimization step for RSBT treatment planning into two steps, namely anchor plan optimization and optimal sequencing. The degree of freedom in anchor plan optimization is controlled at a low level compared to single-step dose optimization, and the optimal sequencing algorithms can efficiently calculate treatment plans by reusing the solutions from anchor plan optimization. Thus, by decomposing the dose optimization, the computational complexity in the two-step method is greatly reduced compared to the single-step method. In the anchor plan optimization, an abstract RSBT delivery model is assumed. The abstract RSBT delivery model assumes that only beams with fixed small azimuthal emission angle, which are called beamlets, will be used during the delivery. An anchor plan is created based on this assumption that only these beamlets will be used. Generally, an anchor plan will be of high quality in the sense of dose distribution, but of low quality in the sense that it has prohibitory long delivery time. In the optimal sequencing step, beamlets will be superposed into beams to reduce the delivery time. By limiting the delivery time to a clinically acceptable level, the anchor plans turn into deliverable plans. Unlike anchor plan optimization, where an abstract RSBT delivery model is assumed, the optimal sequencing step depends on more concrete RSBT delivery models. Specifically, we will study three methods of RSBT, namely the single rotating-shield brachytherapy (S-RSBT), the dynamic rotating-shield brachytherapy (D-RSBT) and the paddle rotating-shield brachytherapy (P-RSBT). We proposed a novel anchor plan dose optimization method as well as novel optimal sequencing methods for each of the RSBT delivery methods studied in this work. We have implemented all the proposed algorithms and experimented with them using real medical data. With the methods proposed in this thesis, the optimization time for creating delivery plans can be controlled within 15 minutes based on the data from our experiments. Compared to the conventional brachytherapy techniques, the three methods studied in this work can produce more conformal dose distributions at an acceptable level of delivery time increase. With 15 min/fx delivery time, S-RSBT, D-RSBT and P-RSBT averagely increased the D90 (the minimum dose received by the hottest 90% of the tumor) by 17, 9 and 5 Gy compared to conventional interstitial plus intracavitary brachytherapy, whose D90 is 79 Gy. The best choice depends on the specified delivery time or quality requirement, as well as the complexity of building the equipment. Roughly speaking, among the three RSBT methods studied in this thesis, P-RSBT has the most complex applicators as well as the highest plan qualities. S-RSBT has the simplest applicators, and its plan qualities is generally better than D-RSBT with limited delivery time (/fx). With sufficient delivery time (~30 min/fx), D-RSBT may be considered as the best solution in the sense of balancing the complexity of applicators and the dose qualities.