Feasibility of Applying a Single Treatment Plan for Fractions in HDR Image Guided Brachytherapy in Cervix Cancer PDF Download
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Author: 何鎵浠
Publisher:
ISBN:
Category : Cervix uteri
Languages : en
Pages : 71
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Book Description
Author: 何鎵浠
Publisher:
ISBN:
Category : Cervix uteri
Languages : en
Pages : 71
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Book Description
Author: Björn Morén
Publisher: Linköping University Electronic Press
ISBN: 9179297382
Category : Electronic books
Languages : en
Pages : 53
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Book Description
Cancer is a widespread class of diseases that each year affects millions of people. It is mostly treated with chemotherapy, surgery, radiation therapy, or combinations thereof. High doserate (HDR) brachytherapy (BT) is one modality of radiation therapy, which is used to treat for example prostate cancer and gynecologic cancer. In BT, catheters (i.e., hollow needles) or applicators are used to place a single, small, but highly radioactive source of ionizing radiation close to or within a tumour, at dwell positions. An emerging technique for HDR BT treatment is intensity modulated brachytherapy (IMBT), in which static or dynamic shields are used to further shape the dose distribution, by hindering the radiation in certain directions. The topic of this thesis is the application of mathematical optimization to model and solve the treatment planning problem. The treatment planning includes decisions on catheter placement, that is, how many catheters to use and where to place them, as well as decisions for dwell times. Our focus is on the latter decisions. The primary treatment goals are to give the tumour a sufficiently high radiation dose while limiting the dose to the surrounding healthy organs, to avoid severe side effects. Because these aims are typically in conflict, optimization models of the treatment planning problem are inherently multiobjective. Compared to manual treatment planning, there are several advantages of using mathematical optimization for treatment planning. First, the optimization of treatment plans requires less time, compared to the time-consuming manual planning. Secondly, treatment plan quality can be improved by using optimization models and algorithms. Finally, with the use of sophisticated optimization models and algorithms the requirements of experience and skill level for the planners are lower. The use of optimization for treatment planning of IMBT is especially important because the degrees of freedom are too many for manual planning. The contributions of this thesis include the study of properties of treatment planning models, suggestions for extensions and improvements of proposed models, and the development of new optimization models that take clinically relevant, but uncustomary aspects, into account in the treatment planning. A common theme is the modelling of constraints on dosimetric indices, each of which is a restriction on the portion of a volume that receives at least a specified dose, or on the lowest dose that is received by a portion of a volume. Modelling dosimetric indices explicitly yields mixed-integer programs which are computationally demanding to solve. We have therefore investigated approximations of dosimetric indices, for example using smooth non-linear functions or convex functions. Contributions of this thesis are also a literature review of proposed treatment planning models for HDR BT, including mathematical analyses and comparisons of models, and a study of treatment planning for IMBT, which shows how robust optimization can be used to mitigate the risks from rotational errors in the shield placement. Cancer är en grupp av sjukdomar som varje år drabbar miljontals människor. De vanligaste behandlingsformerna är cellgifter, kirurgi, strålbehandling eller en kombination av dessa. I denna avhandling studeras högdosrat brachyterapi (HDR BT), vilket är en form av strålbehandling som till exempel används vid behandling av prostatacancer och gynekologisk cancer. Vid brachyterapibehandling används ihåliga nålar eller applikatorer för att placera en millimeterstor strålkälla antingen inuti eller intill en tumör. I varje nål finns det ett antal så kallade dröjpositioner där strålkällan kan stanna en viss tid för att bestråla den omkringliggande vävnaden, i alla riktningar. Genom att välja lämpliga tider för dröjpositionerna kan dosfördelningen formas efter patientens anatomi. Utöver HDR BT studeras också den nya tekniken intensitetsmodulerad brachyterapi (IMBT) vilket är en variation på HDR BT där skärmning används för att minska strålningen i vissa riktningar vilket gör det möjligt att forma dosfördelningen bättre. Planeringen av en behandling med HDR BT omfattar hur många nålar som ska användas, var de ska placeras samt hur länge strålkällan ska stanna i de olika dröjpositionerna. För HDR BT kan dessa vara flera hundra stycken medan det för IMBT snarare handlar om tusentals möjliga kombinationer av dröjpositioner och inställningar av skärmarna. Planeringen resulterar i en dosplan som beskriver hur hög stråldos som tumören och intilliggande frisk vävnad och riskorgan utsätts för. Dosplaneringen kan formuleras som ett matematiskt optimeringsproblem vilket är ämnet för avhandlingen. De övergripande målsättningarna för behandlingen är att ge en tillräckligt hög stråldos till tumören, för att döda alla cancerceller, samt att undvika att bestråla riskorgan eftersom det kan ge allvarliga biverkningar. Då alla målsättningarna inte samtidigt kan uppnås fullt ut så fås optimeringsproblem där flera målsättningar behöver prioriteras mot varandra. Utöver att dosplanen uppfyller kliniska behandlingsriktlinjer så är också tidsaspekten av planeringen viktig eftersom det är vanligt att den görs medan patienten är bedövad eller sövd. Vid utvärdering av en dosplan används dos-volymmått. För en tumör anger ett dosvolymmått hur stor andel av tumören som får en stråldos som är högre än en specificerad nivå. Dos-volymmått utgör en viktig del av målen för dosplaner som tas upp i kliniska behandlingsriktlinjer och ett exempel på ett sådant mål vid behandling av prostatacancer är att 95% av prostatans volym ska få en stråldos som är minst den föreskrivna dosen. Dos-volymmått utläses ur de kliniskt betydelsefulla dos-volym histogrammen som för varje stråldosnivå anger motsvarande volym som erhåller den dosen. En fördel med att använda matematisk optimering för dosplanering är att det kan spara tid jämfört med manuell planering. Med väl utvecklade modeller så finns det också möjlighet att skapa bättre dosplaner, till exempel genom att riskorganen nås av en lägre dos men med bibehållen dos till tumören. Vidare så finns det även fördelar med en process som inte är lika personberoende och som inte kräver erfarenhet i lika stor utsträckning som manuell dosplanering i dagsläget gör. Vid IMBT är det dessutom så många frihetsgrader att manuell planering i stort sett blir omöjligt. I avhandlingen ligger fokus på hur dos-volymmått kan användas och modelleras explicit i optimeringsmodeller, så kallade dos-volymmodeller. Detta omfattar såväl analys av egenskaper hos befintliga modeller, utvidgningar av tidigare använda modeller samt utveckling av nya optimeringsmodeller. Eftersom dos-volymmodeller modelleras som heltalsproblem, vilka är beräkningskrävande att lösa, så är det också viktigt att utveckla algoritmer som kan lösa dem tillräckligt snabbt för klinisk användning. Ett annat mål för modellutvecklingen är att kunna ta hänsyn till fler kriterier som är kliniskt relevanta men som inte ingår i dos-volymmodeller. En sådan kategori av mått är hur dosen är fördelad rumsligt, exempelvis att volymen av sammanhängande områden som får en alldeles för hög dos ska vara liten. Sådana områden går dock inte att undvika helt eftersom det är typiskt för dosplaner för brachyterapi att stråldosen fördelar sig ojämnt, med väldigt höga doser till små volymer precis intill strålkällorna. Vidare studeras hur små fel i inställningarna av skärmningen i IMBT påverkar dosplanens kvalitet och de olika utvärderingsmått som används kliniskt. Robust optimering har använts för att säkerställa att en dosplan tas fram som är robust sett till dessa möjliga fel i hur skärmningen är placerad. Slutligen ges en omfattande översikt över optimeringsmodeller för dosplanering av HDR BT och speciellt hur optimeringsmodellerna hanterar de motstridiga målsättningarna.
Author: Dae Yup Han
Publisher:
ISBN: 9781321891836
Category :
Languages : en
Pages : 72
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Book Description
To achieve most effective cervical cancer breachytherapy treatment quality with image guided brachytherapy (IGBT), we propose a directional intensity modulate-available applicator. The direction modulate brachytherapy (DMBT) cervical cancer tandem applicator was designed to create non-isotropic dose distribution using tungsten alloy shielding in a tandem for an isotropic 192-Ir HDR radiation source. Conventional tandem has 6 mm in outer diameter with 1 channel, however, the DMBT tandem has 6 channels, which is 1.3 mm in diameter, on a surface of the tungsten alloy shield. Prototypes of the DMBT tandem was manufactured to prove of compatibilities with conventional clinical treatment systems such as MR image test, 192-Ir afterloader source delivering test, and so on. The Monte Calro code was used to calculate the non-isotropic 192-Ir dose distributions and in-house developed brachytherapy planning platform were used for plan re-optimizaiton. To evaluate a potential of the DMBT tandem, 3 different clinical treated patients group were re-optimized with DMBT tandem. The conventional tandem was replaced to the DMBT tandem for comparing differences while the ovoid or ring was kept in the same position. For comparing plan quality, HRCTV coverage was matched to each the clinical treated plans. The D2cc to OARs such as bladder, rectum, and sigmoid was recorded and compared. The first group was 75 clinical cases, which treated with the conventional tandem and ovoids (T&O) applicator. In the second group, a patient case with 5 brachytherapy fractions course was evaluated. From the 3rd to 5th fraction, supplementary free loaded needles were used. To evaluate the DMBT tandem potential of covering irregular HRCTV growth patters, the clinical plans were compared with DMBT and ovoid (without supplement needles) plans. The last group was clinical treated patient cases treated with T&R with combined intracavitary- interstitial applicator with PDR brachytherapy afterloader. The free loaded needles and the attached to ring applicator needles were modified to investigate the DMBT tandem covering availability of an irregular growth pattern of the HRCTV.
Author: B.R. Thomadsen
Publisher: CRC Press
ISBN: 1482268574
Category : Medical
Languages : en
Pages : 267
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Book Description
Achieving Quality in Brachytherapy addresses the main issues that often prevent correct delivery of brachytherapy treatment. The book explains how to set up a functional quality assurance program in brachytherapy and covers all the steps needed to undertake particular treatment plans, from the initial planning required to the detailed specification
Author: Peng Yin
Publisher:
ISBN:
Category :
Languages : en
Pages : 214
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Author:
Publisher:
ISBN:
Category : Electronic books
Languages : en
Pages : 43
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Purpose: To validate and an automated deformable image registration (DIR) algorithm for dose accumulation in organs at risk (OARs) in HDR brachytherapy for cervical cancer. Methods: Image and plan data were collected from 15 patients who underwent 3-5 fractions of HDR brachytherapy to treat cervical cancer. The images were pre-processed to perform a hybrid intensity-based and contour-based DIR: the applicator region and bones were auto-segmented, and together with bladder, rectum/sigmoid and uterus, were automatically masked with a different uniform intensity for each structure. Dice Similarity Coefficient (DSC) and cumulative D2cc of OARs using different fractions as reference were used to assess the accuracy of DIR. The total organ D2cc is averaged considering each fraction as the reference and compared to the total D2cc found by simple DVH addition (clinical method). All DIR steps were done automatically. Results: The average DSC between deformed and reference bladder is 0.93±0.03; and for the rectum the DSC figure is 0.851±0.03. Changes in organ volume as high as 223% still resulted in a DSC of 0.946. On average, the total D2cc using DIR and DVH-based addition differ by 1.918 ± 2.066% for the bladder and 2.257 ± 2.524% for the rectum. However, differences as large as 13.35% in the bladder and 14.46% in the rectum when considering pairs of fractions were observed. The masking and DIR process takes a matter of minutes to complete. Conclusion: We have validated a quick, efficient, and automated DIR algorithm for dose accumulation of multiple fractions for cervical cancer HDR brachytherapy. The algorithm is accurate and simultaneously evaluates all OAR doses. Contour consistency plays an important role in the assessment of the cumulative dose, especially in the rectum. Although the average differences between cumulative D2cc by DIR and simple DVH addition are small, they were found to be significantly high in some patients. In these cases, a more accurate dose calculation is important and can be achieved using our method. More accurate dose calculations lead to the possibility of dose escalation, which could be clinically significant.
Author:
Publisher:
ISBN:
Category : Electronic books
Languages : en
Pages : 54
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Book Description
he purpose of this study is to optimize Deformable Image Registration (DIR) and dose accumulation in High-Dose-Rate (HDR) cervical brachytherapy. The conventional brachytherapy dose accumulation relies on the assumption that the hot spot region of the Organs At Risk (OAR) remain anatomically consistent each fraction. However, two sources of uncertainty introduce inaccuracies: 1) inter-fractional shifts in patient organ geometry and brachytherapy applicator placements; 2) inconsistencies in OAR contouring in the high dose regions. Although DIR has been considered as a tool to correct the fluctuations, the intensity-based algorithm is prone to errors if high-intensity structures, such as the brachytherapy Applicator Region (AR), are involved. In this study, 23 HDR cervical brachytherapy fractions from 6 patients treated with Tandem & Ovoids applicator were included. Firstly, a 3D random walks-based Matlab algorithm was used to semi-automatically segment the AR from all images. Subsequently, artificial intensity masks were applied on the OAR, AR, skeleton, and treatment couch, to prioritize the OAR and minimize the influence of high-intensity structures during DIR. It should be noted that inter-fractional inconsistencies in OAR contouring act as a major limiting factor in this method, since masking removes indications of inconsistency within contours. Cumulative OAR dose was calculated from Dose-Volume Histograms, generated from: 1) the reference contours; 2) each fraction’s deformed contours. AR segmentation produced consistent results for differently sized ARs. Contour masking was utilized in cases where nearby high intensity structures interfered with the algorithm. After DIR, each image and contour was cropped to better represent only the high-dose regions of the OAR. Compared to regular DIR, intensity-masked DIR resulted in increased Dice Similarity Coefficient (DSC) values in all patients, ranging: 0.067(s=0.021)~0.416(s=0.226) for bladder, and 0.046(s=0.014)~0.321(s=0.170) for rectum. Dose accumulation results were inconclusive due to dose uncertainties introduced by high-dose-region OAR contouring inconsistencies. The DSC analyses indicate that intensity mask-guided DIR results in optimized deformable registration in high-dose regions. However, inconsistencies in OAR contouring is a major source of uncertainty in dose accumulation and image registration. Root Mean Square Distance (RMSD) analysis suggests a positive correlation between contouring inconsistency and image registration inaccuracy.
Author: Marcin Sawicki
Publisher:
ISBN:
Category : Medicine
Languages : en
Pages :
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Treatment planning in High Dose Rate (HDR) brachytherapy based on three-dimensional (3D) imaging allows for prearranging and realization optimal treatment process. This process consists of procedure planning, the choice of applicators, adjusting the appropriate implantation technique, and planning of three-dimensional distribution of dose in computerized treatment planning system. 3D images used in treatment planning in HDR brachytherapy allows for choosing the most appropriate application technique. This in turn allows for the best area coverage by reference dose with simultaneous protection of critical organs. Treatment planning on 3D images assures individual planning of dose dispersion in target area. Several techniques will be presented based on 3D imaging in location such as lung, skin cancer, breast, and prostate cancer. For each location, relative cases will be provided where different applicators and techniques were applied. These examples are going to present images from before and after performed application along with the pictures from computer treatment planning system. In each of described locations, relative advice and rules of conducting accurate application will be provided.
Author: Kenji Yoshida
Publisher:
ISBN:
Category : Medicine
Languages : en
Pages :
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Book Description
Image-guided adaptive brachytherapy (IGABT) using magnetic resonance imaging (MRI) has been accepted as a novel treatment technique for cervical cancer. During the development of MRI-based IGABT, a very important concept called "High-risk clinical target volume (HR-CTV)" was introduced. However, computed tomography (CT)-based IGABT is the most common modality in Japan.
Author: Xing Li
Publisher:
ISBN:
Category : Cervix uteri
Languages : en
Pages : 139
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Book Description
Intensity-modulated brachytherapy techniques, compensator-based intensity modulated brachytherapy (CBT) and interstitial rotating shield brachytherapy (I-RSBT), are two novel conceptual radiation therapies for treating cervical and prostate cancer, respectively. Compared to conventional brachytherapy techniques for treating cervical cancer, CBT can potentially improve the dose conformity to the high-risk clinical target volume (CTV) of the cervix in a less invasive approach. I-RSBT can reduce the dose delivered to the prostate organ at risks (OARs) with the same radiation dose delivered to the prostate CTV. In this work, concepts and prototypes for CBT and I-RSBT were introduced and developed. Preliminary dosimetric measurements were performed for CBT and I-RSBT, respectively. A CBT prototype system was constructed and experimentally validated. A prototype cylindrical compensator with eight octants, each with different thicknesses, was designed. Direct metal laser sintering (DMLS) was used to construct CoCr and Ti compensator prototypes, and a 4-D milling technique was used to construct a Ti compensator prototype. Gafchromic EBT2 films, held by an acrylic quality assurance (QA) phantom, were irradiated to approximately 125 cGy with an electronic brachytherapy (eBT) source for both shielded and unshielded cases. The dose at each point on the films were calculated using a TG-43 calculation model that was modified to account for the presence of a compensator prototype by ray-tracing. With I-RSBT, a multi-pass dose delivery mechanism with prototypes was developed. Dosimetric measurements for a Gd-153 radioisotope was performed to demonstrate that using multiple partially shielded Gd-153 sources for I-RSBT is feasible. A treatment planning model was developed for applying I-RSBT clinically. A custom-built, stainless steel encapsulated 150 mCi Gd-153 capsule with an outer length of 12.8 mm, outer diameter of 2.10 mm, active length of 9.8 mm, and active diameter of 1.53 mm was used. A partially shielded catheter was constructed with a 500 micron platinum shield and a 500 micron aluminum emission window, both with 180° azimuthal coverage. An acrylic phantom was constructed to measure the dose distributions from the shielded catheter in the transverse plane using Gafchromic EBT3 films. Film calibration curves were generated from 50, 70, and 100 kVp x-ray beams with NIST-traceable air kerma values to account for energy variation. In conclusion, CBT, which is a non-invasive alternative to supplementary interstitial brachytherapy, is expected to improve dose conformity to bulky cervical tumors relative to conventional intracavitary brachytherapy. However, at the current stage, it would be time-consuming to construct a patient-specific compensator using DMLS, and the quality assurance of the compensator would be difficult. I-RSBT is a promising approach to reducing radiation dose delivered to prostate OARs. The next step in making Gd-153 based I-RSBT feasible in clinic is developing a Gd-153 source that is small enough such that the source, shield, and catheter all fit within a 16 guage needle, which has a 1.65 mm diameter.
