Publications by authors named "Vladimir Vondracek"

Artificial intelligence (AI) has made a tremendous impact in the space of healthcare, and proton therapy is not an exception. Proton therapy has witnessed growing popularity in oncology over recent decades, and researchers are increasingly looking to develop AI and machine learning tools to aid in various steps of the treatment planning and delivery processes. This review delves into the emergent role of AI in proton therapy, evaluating its development, advantages, intended clinical contexts, and areas of application.

View Article and Find Full Text PDF

Purpose: Patients with p16 positive tonsillar cancer (p16 + TC) have an excellent prognosis and long-life expectancy. Deintensification of therapy is a prevalent topic of discussion. Proton radiotherapy is one way to reduce radiation exposure and thus reduce acute and late toxicity.

View Article and Find Full Text PDF
Article Synopsis
  • - Boron may improve the effectiveness of proton beam therapy in cancer treatment by enhancing cell damage in the targeted Bragg peak region through a specific nuclear reaction, although some studies have questioned this claim.
  • - Experiments with prostate cancer and glioblastoma cells using 190 MeV proton beams showed that boron (from sodium mercaptododecaborate) significantly increased cell killing, especially at low concentrations and in the Bragg peak area.
  • - The beneficial effects of boron occur through rare proton-boron reactions generating alpha particles, which lead to enhanced cell death, and this response seems to be amplified through interactions between cells, highlighting its potential for clinical use in treating certain tumors.
View Article and Find Full Text PDF

Background And Purpose: As no guidelines for pencil beam scanning (PBS) proton therapy (PT) of paediatric posterior fossa (PF) tumours exist to date, this study investigated planning techniques across European PT centres, with special considerations for brainstem and spinal cord sparing.

Materials And Methods: A survey and a treatment planning comparison were initiated across nineteen European PBS-PT centres treating paediatric patients. The survey assessed all aspects of the treatment chain, including but not limited to delineations, dose constraints and treatment planning.

View Article and Find Full Text PDF

Background: We retrospectively analyzed the 5-year biochemical disease-free survival (bDFS) and occurrence of late toxicity in prostate cancer patients treated with pencil beam scanning (PBS) proton radiotherapy.

Methodology: In the period from January 2013 to June 2018, 853 patients with prostate cancer were treated with an ultra-hypofractionated schedule (36.25 GyE/five fractions).

View Article and Find Full Text PDF

Introduction: Glomus jugulare tumours (GJT) are benign tumours that arise locally and destructively in the base of the skull and can be successfully treated with radiotherapy. Patients have a long-life expectancy and the late effects of radiotherapy can be serious. Proton radiotherapy reduces doses to critical organs and can reduce late side effects of radiotherapy.

View Article and Find Full Text PDF

A favourable dose distribution has been described for proton beam therapy (PBT) of anal cancer in dosimetric studies. The relationship between dosimetric parameters in bone marrow and haematologic toxicity, treatment interruptions, and treatment efficacy has also been documented. There are only few references on clinical results of PBT for anal cancer.

View Article and Find Full Text PDF

Few studies have directly compared passive scattering (PS) to intensity-modulated proton therapy (IMPT) in the delivery of ultra-hypofractionated proton beams to the localized prostate cancer (PCa). In this preliminary study involving five patients previously treated with CyberKnife, treatment plans were created for PS and IMPT (36.25 CGE in five fractions with two opposing fields) to compare the dosimetric parameters to the planning target volume (PTV) and organs-at-risk (OAR: rectum, bladder, femoral heads).

View Article and Find Full Text PDF

Purpose: To analyze the 5-year biochemical disease-free survival (bDFS) and late toxicity profile in patients with prostate cancer treated with pencil beam scanning (PBS) proton radiation therapy.

Methods And Materials: Between January 2013 and March 2016, 284 patients with prostate cancer were treated using intensity modulated proton therapy (IMPT), with an ultrahypofractionated schedule (36.25 GyE in 5 fractions).

View Article and Find Full Text PDF

Nowadays, the irradiation methodology in proton therapy is switching from the use of passively scattered beams to active pencil beams due to the possibility of more conformal dose distributions. The dose rates of active pencil beams are much higher than those of passive beams. The purpose of this study was to investigate whether there is any difference in the biological effectiveness of these passive and active irradiation modes.

View Article and Find Full Text PDF

Objectives:  Patients with nasopharyngeal cancer are candidates for proton radiotherapy due to large and comprehensive target volumes, and the necessity for sparing of healthy tissues. The aim of this work is to evaluate treatment outcome and toxicity profile of patients treated with proton pencil-beam scanning radiotherapy.

Materials And Methods:  Between Jan 2013 and June 2018, 40 patients were treated for nasopharyngeal cancer (NPC) with IMPT (proton radiotherapy with modulated intensity).

View Article and Find Full Text PDF

Twenty (10 intensity-modulated proton therapy (IMPT) and 10 intensity-modulated x-ray therapy (IMXT) treatment plans for patients with advanced prostate carcinoma were compared in this study. All chosen patients were indicated for prostate and pelvic lymph nodes irradiation using simultaneous integrated boost technique. These patients represent typical specimen for this diagnose.

View Article and Find Full Text PDF

Introduction: Extreme hypofractionated radiotherapy for prostate cancer is a common modality in photon therapy. Pencil beam scanning (PBS) in similar fractionation allows better dose distribution and makes proton therapy more available for such patients. The purpose of this study is the feasibility of extreme proton hypofractionated radiotherapy and publication of early clinical results.

View Article and Find Full Text PDF

A collaborative network between proton therapy (PT) centres in Trento in Italy, Poland, Austria, Czech Republic and Sweden (IPACS) was founded to implement trials and harmonize PT. This is the first report of IPACS with the aim to show the level of harmonization that can be achieved for proton therapy planning of head and neck (sino-nasal) cancer. CT-data sets of five patients were included.

View Article and Find Full Text PDF

Background: We performed a survey using the modified EORTC Facility questionnaire (pFQ) to evaluate the human, technical and organizational resources of particle centers in Europe.

Material And Methods: The modified pFQ consisted of 235 questions distributed in 11 sections accessible on line on an EORTC server. Fifteen centers from 8 countries completed the pFQ between May 2015 and December 2015.

View Article and Find Full Text PDF

In recent years, there is an increased interest in using scanning modes in proton therapy, due to the more conformal dose distributions, thanks to the spot-weighted dose delivery. The dose rate in each spot is however much higher than the dose rate when using passive irradiation modes, which could affect the cell response. The purpose of this work was to investigate how the relative biological effectiveness changes along the spread-out Bragg peak created by protons delivered by the pencil beam scanning mode.

View Article and Find Full Text PDF

Purpose: The aim of this study was to determine fluence corrections necessary to convert absorbed dose to graphite, measured by graphite calorimetry, to absorbed dose to water. Fluence corrections were obtained from experiments and Monte Carlo simulations in low- and high-energy proton beams.

Methods: Fluence corrections were calculated to account for the difference in fluence between water and graphite at equivalent depths.

View Article and Find Full Text PDF

Purpose: To investigate the clinical implications of a variable relative biological effectiveness (RBE) on proton dose fractionation. Using acute exposures, the current clinical adoption of a generic, constant cell killing RBE has been shown to underestimate the effect of the sharp increase in linear energy transfer (LET) in the distal regions of the spread-out Bragg peak (SOBP). However, experimental data for the impact of dose fractionation in such scenarios are still limited.

View Article and Find Full Text PDF

Spectral fluences of neutrons generated in the heads of the radiotherapeutic linacs Varian Clinac 2100 C/D and Siemens ARTISTE were measured by means of the Bonner spheres spectrometer whose active detector of thermal neutrons was replaced by an activation detector, i.e. a tablet made of pure manganese.

View Article and Find Full Text PDF

Aim: To evaluate the outcome of prostate cancer patients with initial PSA value >40 ng/ml.

Background: The outcome of prostate cancer patients with very high initial PSA value is not known and patients are frequently treated with palliative intent. We analyzed the outcome of radical combined hormonal treatment and radiotherapy in prostate cancer patients with initial PSA value >40 ng/ml.

View Article and Find Full Text PDF

Background And Purpose: To present the feasibility and results of accelerated radiotherapy with concomitant boost technique (69.5 Gy/5 weeks) in the treatment of locally advanced head and neck cancer.

Patients And Methods: A total of 65 patients were treated between June 2006 and August 2009.

View Article and Find Full Text PDF

We present an alternative way to create a video-assisted port access proximal anastomosis in the ascending aorta with the Symmetry Bypass System Aortic Connector (St. Jude Medical ATG, St. Paul, MN).

View Article and Find Full Text PDF

Objective: We sought to demonstrate the applicability of video-assisted multivessel revascularization through a left anterior small thoracotomy approach with the use of the Symmetry Aortic Connector System (St Jude Medical Anastomotic Technology Group, Inc, St Paul, Minn) as an alternative to the standard median sternotomy approach and to evaluate predischarge angiographically documented graft patency.

Methods: From October 2001 through February 2002, a total of 15 patients with triple-vessel disease were operated on through a left anterior small thoracotomy approach with video-assisted port-access construction of proximal aorta-to-saphenous vein anastomoses with the Symmetry Aortic Connector System and cardiopulmonary bypass with femoral cannulation and without cardioplegic arrest. There were 9 male and 6 female subjects with a mean age of 68.

View Article and Find Full Text PDF