Effect of photon-beam energy on VMAT and IMRT treatment plan quality and dosimetric accuracy for advanced prostate cancer.

PURPOSE: The goal of the research was to evaluate treatment plan quality and dosimetric accuracy of volumetric modulated arc therapy (VMAT) and intensity-modulated radiotherapy (IMRT) plans using 6, 10, and 15 MV photon beams for prostate cancer including lymph nodes. METHODS: In this retrospective study, VMAT and IMRT plans were generated with the Pinnacle© treatment planning system (TPS) (V9.0) for 10 prostate cancer cases. Each plan consisted of two target volumes: PTV(B) included the prostate bed, PTV(PC+LN) contained PTV(B) and lymph nodes. For plan evaluation statistics, the homogeneity index, conformity index, mean doses, and near-max doses to organs at risk (OAR) were analyzed. Treatment time and number of monitor units were assessed to compare delivery efficiency. Dosimetric plan verification was performed with a 2D ionization chamber array placed in a full scatter phantom. RESULTS: No differences were found for target and OAR parameters in low and high energy photon beam plans for both VMAT and IMRT. A slightly higher low dose volume was detected for 6 MV VMAT plans (normal tissue: D(mean) = 16.47 Gy) compared to 10 and 15 MV VMAT plans (D(mean) = 15.90 Gy and 15.74 Gy, respectively), similar to the findings in IMRT. In VMAT, > 96% of detector points passed the 3%/ 3 mm γ criterion; marginally better accuracy was found in IMRT (> 97%). CONCLUSION: For static and rotational IMRT, 15 MV photons did not show advantages over 6 and 10 MV high energy photon beams in large volume pelvic plans. For the investigated TPS and linac combination, 10 MV photon beams can be used as the general purpose energy for intensity modulation.

Impact of gantry rotation time on plan quality and dosimetric verification--volumetric modulated arc therapy (VMAT) vs. intensity modulated radiotherapy (IMRT).

BACKGROUND AND PURPOSE: To compare plan quality criteria and dosimetric accuracy of step-and-shoot intensity-modulated radiotherapy (ss-IMRT) and volumetric modulated arc radiotherapy (VMAT) using two different gantry rotation times. PATIENTS AND METHODS: This retrospective planning study based on 20 patients was comprised of 10 prostate cancer (PC) and 10 head and neck (HN) cancer cases. Each plan contained two target volumes: a primary planning target volume (PTV) and a boost volume. For each patient, one ss-IMRT plan and two VMAT plans at 90 s (VMAT90) and 120 s (VMAT120) per arc were generated with the Pinnacle© planning system. Two arcs were provided for the PTV plans and a single arc for boost volumes. Dosimetric verification of the plans was performed using a 2D ionization chamber array placed in a full scatter phantom. RESULTS: VMAT reduced delivery time and monitor units for both treatment sites compared to IMRT. VMAT120 vs. VMAT90 increased delivery time and monitor units in PC plans without improving plan quality. For HN cases, VMAT120 provided comparable organs at risk sparing and better target coverage and conformity than VMAT90. In the VMAT plan verification, an average of 97.1% of the detector points passed the 3 mm, 3% γ criterion, while in IMRT verification it was 98.8%. CONCLUSION: VMAT90, VMAT120, and IMRT achieved comparable treatment plans. Slower gantry movement in VMAT120 plans only improves dosimetric quality for highly complex targets.

Mobilising stakeholders to improve access to state-of-the-art radiotherapy in low- and middle-income countries.

In an ongoing effort to improve access to state-of-the-art radiotherapy in low- and middle-income countries (LMICs), a joint symposium was organised by the non-governmental, non-profit organisation Medical physicists in diaspora for Africa e.V. (MephidA e.V.) in collaboration with the Germany-based Cameroon-German medical doctor's association (Camfomedics e.V.) and the Harvard-based Global Health Catalyst summit. The goal of the symposium was to discuss the technical and structural challenges faced in African LMIC settings, re-evaluate strategies to overcome the shortfall of radiotherapy services and ameliorate the situation. The meeting brought together industry partners, including radiotherapy machine vendors and dosimetry solution providers, alongside public health, oncology and medical physics experts. This paper summarises the deliberations and recommendations based on the ongoing efforts including the use of information and communication technologies towards the provision of expert knowledge and telemedicine, the use of solar energy to avoid power outages and the use of high-end technology for enhanced quality assurance. We also present the experiences on the first linac installation at the Rwanda Military Hospital, the challenges faced in this LMIC as well as the patient's demography, reflecting the reality in most sub-Saharan LMICs.

Influence of the pandemic dissemination of COVID-19 on radiotherapy practice: A flash survey in Germany, Austria and Switzerland.

BACKGROUND: The COVID-19 pandemic has already changed our globalised world and its long-term impact is not yet known. It is apparent that businesses and institutions are increasingly affected. COVID-19 discussions often focus on intensive care units in hospitals. However, COVID-19 also effects life-saving and -prolonging radiotherapy for patients suffering from cancer. METHOD: We have conducted a structured online survey among medical physicists in Germany, Austria and Switzerland from March 23rd to 26th 2020. In total 154 responses (82 completed, 72 partially completed) were analysed in the context of the COVID-19 dissemination. RESULTS: 72.4% of the respondent's state that their processes are affected due to COVID-19, while the top three answers are longer processing times (54.2%), patient no-shows (42.5%) and staff reduction (36.7%). 75.8% expect further unavailability of their personnel in the upcoming weeks. All participants have already taken several measures, especially providing information for patients at the entrance (89.6%) or over the phone (73.6%), restricting access for accompanying persons (77.4%) and providing disinfectant at the entrance (72.6%). DISCUSSION: The results presented in this article aim to support business continuity and risk management for radiotherapy centres to prepare for future challenges. The results show that most radiotherapy centres has implemented initial contingency measures, applying them pragmatically. The main problem however remains, that is the high risk of infection both for patients and medical personnel along with the associated risk of temporarily loss of personnel and ordered closure of business.

Report of a study on IMRT planning strategies for ethmoid sinus cancer.

AIM: This communication reviews the planning strategies and dose statistics of nine IMRT plans generated for a complex head and neck case. PATIENT AND METHOD: An ethmoid sinus cancer case was sent as an IMRT planning task to all participants of the ESTRO course on "IMRT and Other Conformal Techniques in Practice", held in Amsterdam in June 2001. RESULTS: Nine IMRT plans were generated for the case, the majority of the plans generated with commercial planning systems. The number of beam incidences ranged between four and eleven, while five of the nine beam setups were coplanar. The planning target volume dose homogeneity was inversely correlated with the degree of sparing of the surrounding organs at risk. CONCLUSION: IMRT strategies for complex head and neck cases, such as ethmoid sinus cancer, can be strikingly different in various aspects, such as beam setup, total number of segments, PTV dose coverage and dose statistics for organs at risks.