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Dosimetric impact of rotational set‑up errors in high-risk prostate cancer

Poncyljusz Maria, Bulski Wojciech

Polish Journal of Medical Physics and Engineering

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2022

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Vol. 28, Iss. 4

200--206

EN

Introduction: Cone-beam computed tomography (CBCT) provides an excellent solution to quantitative assessment and correction of patient set-up errors during radiotherapy. However, most linear accelerators are equipped with conventional therapy tables that can be moved in three translational directions and perform only yaw rotation. Uncorrected roll and pitch result in rotational set-up errors, particularly when the distance from the isocenter to the target border is large. The aim of this study was to investigate the impact of rotational errors on the dose delivered to the clinical target volume (CTV), the planning target volume (PTV) and organs at risk (OAR). Material and methods: 30 patients with prostate cancer treated with VMAT technique had daily CBCT scans (840 CBCTs in total) prior to treatment delivery. The rotational errors remaining after on-line correction were retrospectively analysed. The sum plans simulating the dose distribution during the treatment course were calculated for selected patients with significant rotational errors. Results: The dose delivered to the prostate bed CTV reported in the sum plan was not lower than in the original plan for all selected patients. For four patients from the selected group, the D98% for prostate bed PTV was less than 95%. The V47.88Gy for pelvic lymph nodes PTV was less than 98% for two of the selected patients. Conclusions: The analysis of the dosimetric parameters showed that the impact of uncorrected rotations is not clinically significant in terms of the dose delivered to OAR and the dose coverage of CTV. However, the PTV dose coverage is correlated with distance away from the isocenter and is smaller than planned.

2

Dosimetry audit of the CyberKnife accelerator with the SHANE phantom

Szymański Marcin, Piziorska Maria, Madetko Oskar, Ślusarczyk-Kacprzyk Wioletta, Bulski Wojciech

Polish Journal of Medical Physics and Engineering

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2021

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Vol. 27, Iss. 3

207--212

EN

Introduction: The aim of this study was to propose a dosimetric audit of the CyberKnife system. Dosimetry audit is an important part of the quality assurance process in radiotherapy. Most of the proposed dosimetric audits are dedicated to classical medical accelerators. Currently, there is no commonly implemented scheme for conducting a dosimetric audit of the CyberKnife accelerator. Material and methods: To verify the dosimetric and geometric parameters of the entire radiotherapy process, as is required in E2E test procedure, the CIRS SHANE anthropomorphic phantom was used. A tomography with a resolution of 1.5 mm was prepared, five PTVs (Planning Target Volume) of different volumes were drawn; approximately: 88 cm3, 44 cm3, 15 cm3, 7 cm3, 1.5 cm3. Five treatment plans were made using the 6D Skull tracking method, FIXED collimators, RayTracing algorithm. Each treatment plan was verified in a slab Phantom, with a PinPoint chamber. The dose was measured by an ionization chamber type TM31010 Semiflex, placed in the center area of the target. Results: The result of the QA verification in slab phantom was up to 5,0%. The percentage difference for the measurement in the SHANE phantom was: 4.29%, -1.42%, -0.70%, 1.37%, -1.88% respectively for the targets: 88 cm3, 44 cm3, 15 cm3, 7 cm3, 1.5 cm3. Conclusions: By analyzing various approaches to small-field dosimetry audits in the literature, it can be assumed that the proposed CyberKnife dosimetric audit using the SHANE phantom is an appropriate method of verification of the radiotherapy process. Particular attention should be paid to the target volume, adjusting it to the system capabilities.

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Adaptacyjna radioterapia u chorych z powodu raka pęcherza moczowego

Poncyljusz Maria, Bulski Wojciech

Inżynier i Fizyk Medyczny

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2020

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Vol. 9, nr 6

441--444

PL

Strategia adaptacyjnej radioterapii stosowana w grupie pacjentów chorych z powodu raka pęcherza moczowego polega na przygotowaniu biblioteki planów leczenia. Przed napromienianiem wykonywane jest badanie obrazowe tomografii komputerowej wiązką stożkową, a następnie wybierany jest odpowiedni plan. Metoda ta zapewnia podwyższenie precyzji w dostarczeniu przepisanej dawki do obszaru leczonego i poprawę ochrony organów krytycznych, w szczególności jelit. Przed wprowadzeniem adaptacyjnej radioterapii konieczne jest wybranie odpowiedniej techniki przygotowania biblioteki planów, która będzie możliwa do zrealizowania w ośrodku. Niezbędne jest również przeszkolenie personelu i przygotowanie procedur minimalizujących ryzyko wystąpienia błędu.

EN

The strategy of adaptive radiotherapy for bladder cancer patients consists in preparing treatment plan library. After performing the cone beam CT imaging preceding the irradiation, an appropriate plan is selected. This method results in an improvement in the clinical target volume coverage and a dose reduction to the organs at risk, particularly the small bowel. Before introducing adaptive radiotherapy it is necessary to select the appropriate technique for preparing treatment plan library that will be possible to implement in the clinic. It is also crucial to train personnel and prepare procedures for minimizing the risk of error.

4

Modern external beam radiotherapy of prostate cancer

Kukołowicz Paweł, Bulski Wojciech, Pęczkowski Piotr, Pilichowska Małgorzata, Dąbkowski Mateusz

Inżynier i Fizyk Medyczny

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2019

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Vol. 8, nr 3

173--177

EN

Prostate cancer is the most commonly diagnosed cancer in modern societies. There are three methods of prostate cancer treatment: surgery and radiotherapy (either external radiotherapy or brachytherapy). Last 10 years radiotherapy developed very much. New methods of treatment allow for diminishing the total treatment time, making the irradiation almost fully safe. The results treatment of surgery and radiotherapy are very similar. The choice of treatment method dependence on the decision of a patient. In this paper new achievements in external radiotherapy are presented.

PL

Nowotwór gruczołu krokowego jest najczęściej diagnozowanym nowotworem w populacji mężczyzn w krajach rozwiniętych. Obecnie u pacjentów z nowotworem gruczołu krokowego można zastosować chirurgię, radioterapię wiązkami zewnętrznymi i brachyterapię. W ciągu ostatnich 10 lat nastąpił bardzo szybki rozwój leczenia z użyciem promieniowania jonizującego. Najnowsze metody umożliwiają skrócenie całkowitego czasu leczenia i zapewniają niemal w pełni bezpieczne leczenie. Wyniki chirurgii i radioterapii są bardzo podobne. Wybór metody leczenia zależy od preferencji pacjenta. W tym artykule zostały przedstawione osiągnięcia radioterapii wiązkami zewnętrznymi w zastosowaniu u pacjentów z nowotworem gruczołu krokowego.