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The influence of the used applicators on organ and target doses for cervical cancer patients treated with HDR brachytherapy

100%

Pszczółkowska B. , Bijok M. , Brzozowska B.

Polish Journal of Medical Physics and Engineering

2022

tom Vol. 28, Iss. 3

139--149

Introduction: The aim of this work was to study the influence of the applicators used for cervical cancer patients treated with high dose-rate brachytherapy (HDR-BT) in the Maria Sklodowska-Curie National Research Institute of Oncology in Warsaw, Poland on doses in the tumour volumes and organs at risk. Material and methods: The treatment was carried out using Iridium-192 in 4 fractions (7.5 Gy each) given in weekly intervals. Two types of applicators were used for comparison: fletcher and ring. The standard dose distribution parameters, read from the system Oncentra Brachy (version 4.5, Elekta), for bladder, rectum, and sigmoid (D2 cc) and tumour (HR-CTV D100, D98, D90) were studied. Patients were divided into two groups (240 treatment plans) depending on the type of applicator used and into four groups according to the tumour volumes (HR-CTV < 25 cm3 or HR-CTV ≥ 25 cm3). The collected data were analysed using the PQStatSoftware (version 1.8.2). Results: The treatment plans prepared with all types of applicators fulfil the dose distribution requirements, however, the dose delivered to the tumour using the ring applicator was found to be the highest. For the bladder and sigmoid the optimal dose distribution was obtained when using the fletcher applicator, while for the rectum the ring applicator gave the smallest dose value. The D2 cc parameter for sigmoid obtained for fletcher treatment has smaller values in the case of patients with small tumour volume and for this type of applicator was observed a statistically significant difference when compared with the ring. Conclusions: The ring applicator gives the optimal parameters of the dose distribution independently on the tumour volume with respect to the fletcher applicator, which is however more often used in clinical practice.

Measurement of Transit Time of a Gammamed-Plus Remote Afterloading High Dose Rate Brachytherapy Source

88%

Supe S. , Shwetha B. , Bijina T. , Varatharaj C. , Sathiyan S. , Ganesh K. , Arunkumar T. , Ravikumar M.

Polish Journal of Medical Physics And Engineering

2007

tom 13

nr 2

55-63

Accurate measurement of transit time of the HDR brachytherapy source of a remote after-loading unit is necessary to calculate the total radiation dose given to the treatment volume. Presently, most of the HDR brachytherapy treatment planning systems neglect the transit time in the computation of dose. The aim of this investigation is to use a well type ionization chamber to measure the transit time during the source movement between two dwell positions. As well type ionization chamber and a precision electrometer (manufacturer CD instruments, Bangalore) were used to measure the charge generated during the movement of the Ir-192 source of a Gammamed HDR brachytherapy unit with an interstitial needle. Effective transit time and effective speed were determined on the basis of methodology described by Sahoo [2]. Corrections were done on the basis of relative sensitivity values for varaious dwell position in the ionization chamber. In the present study the variation of effective speed with interdwell distance was minimal as compared with that of Sahoo [2]. The effective transit times were 0.129, 0.182, 0.301, 0.402, 0.701, and 0.993 seconds for 1, 2, 4, 6, 8 and 10 cm interdwell separations respectively. The effective transit times in the present study were higher than those of Sahoo [2]. Software modification accounting for the dynamic dose should be incorporated into all HDR planning systems. Such an improvement would enhance the safety and accuracy of HDR brachytherapy.

Brachyterapia o wysokiej mocy dawki u chorych na raka szyjki macicy

51%

Żółciak-Siwińska A. , Jońska-Gmyrek J. , Staniaszek J. , Kawczyńska M. , Kulik A.

Current Gynecologic Oncology

2011

tom 9

nr 4

264-271

Selection of optimal treatment modality in a patient with cervical cancer depends on FIGO clinical stage. At stages IB2-IVA, the cornerstone of treatment is radiochemotherapy. As first step, patients undergo irradiation from external fields combined with chemotherapy (cisplatin, 40 mg/m2, QW). Brachytherapy is used as second-line treatment – an essential component thereof – enabling delivery of high dose of radiation to both genital organs and tumor. Quality of this treatment directly correlates with local control of the disease, long-term overall survival and quality of life of patients after completion of therapy. The paper presents current principles of high dose rate (HDR) brachytherapy in cervical cancer patients. Discussed are principles of two-dimensional (2D) planning, used to date in about 50% of brachytherapy centers worldwide, as well as three-dimensional (3D) magnetic resonance (MR)-based planning. As availability of MR in ours and many other oncology centers is limited, a computed tomography-based modification of gynecologic recommendations GIN GEC ESTRO has been suggested. Therapeutic areas are defined: high-risk clinical target volume (HR CTV) and intermediate risk clinical target volume (IR CTV) which may be safely contoured based on clinical exam and CT study, when no MRI is available. Acceptable doses for critical organs are listed. Based on own experience, indications and limitations for use of intraparenchymal (interstitial) and intracavitary applications were developed.

Wybór metody leczenia chorych na raka szyjki macicy jest uzależniony od stopnia zaawansowania, ocenionego według klasyfikacji FIGO (International Federation of Gynecology and Obstetrics). Zasadniczą metodą leczenia chorych na raka szyjki macicy w stopniach zaawansowania IB2-IVA jest radiochemioterapia. W pierwszym etapie przeprowadzane jest napromienianie z pól zewnętrznych wraz z chemioterapią z zastosowaniem cisplatyny w dawce 40 mg/m2, raz w tygodniu. W kolejnym etapie leczenia stosuje się brachyterapię. Brachyterapia jest istotną częścią leczenia, umożliwiającą podanie wysokiej dawki na narząd rodny wraz z guzem, a jakość tego leczenia ma wpływ na kontrolę miejscową nowotworu (LC), przeżycia odległe (OS), jak również na jakość życia chorych po zakończeniu terapii. W pracy przedstawiono zasady obowiązujące współcześnie podczas leczenia brachyterapią o wysokiej mocy dawki (high dose rate brachytherapy, HDR) u chorych na raka szyjki macicy. Opisano zasady planowania w systemie dwuwymiarowym (2D), stosowanym do dzisiaj mniej więcej w połowie ośrodków brachyterapii na świecie, oraz planowania w systemie trójwymiarowym (3D) na podstawie rezonansu magnetycznego (MR). Ponieważ dostępność MR w naszym i wielu ośrodkach onkologicznych jest utrudniona, zaproponowano modyfikację rekomendacji GIN (Gynaecological) GEC ESTRO dla potrzeb planowania, opierając się na tomografii komputerowej. Zdefiniowano obszary terapeutyczne: HR CTV (high-risk clinical target volume), IR CTV (intermediate risk clinical target volume), jakie można bezpiecznie konturować, opierając się na badaniu klinicznym i TK, przy braku MR. Opisano dopuszczalne dawki dla narządów krytycznych. Na podstawie własnych doświadczeń opracowano wskazania i ograniczenia w zastosowaniu aplikacji śródtkankowych i śródjamowych.