Varian Medical Systems (Germany)

BackgroundThe coronavirus disease 2019 (COVID-19) pandemic resulted in more than six million deaths in the first two years, a third of the estimated number of cancer-related deaths during this time. It directly impacted radiotherapy training in Africa.AimThis study evaluated the changes applied to the Access to Care Cape Town Radiotherapy training programme during the pandemic.SettingThe training platform prior to March 2020 was used as a baseline and compared with the programme status in January 2022, representing the emergency teaching model.MethodsFive themes were investigated: computer hardware and software changes; e-Learning resources; programme and curriculum changes; challenges experienced and alignment with modern medical education principles.ResultsReconfiguration of the computer laboratories was required, including additional computer monitors, web cameras and headsets, as well as installation of screen recording and teleconferencing software. The EclipseTM radiotherapy treatment planning laboratory was reconfigured for remote student access, with simultaneous monitoring by local assistants. Online learning was augmented by adding the University of Cape Town VulaTM system as resource, and courses restructured for delivery of short blocks. Five new courses were developed, including collaborations with international training partners, showing good alignment with the principles of modern medical education.ConclusionReconfiguration was performed at a manageable cost but required a high level of information technology support. Connectivity and bandwidth issues remain a challenge, as well as online engagement.ContributionDespite these challenges, the virtualisation allowed for continued training between March 2020 and December 2021, with 18 departments attending remote teaching courses.

PurposeTo develop a method of (a) calculating the dose rate of voxels within a proton field delivered using pencil beam scanning (PBS), and (b) reporting a representative dose rate for the PBS treatment field that enables correspondence between multiple treatment modalities. This method takes into account the unique spatiotemporal delivery patterns of PBS FLASH radiotherapy.MethodsThe dose rate at each voxel of a PBS radiation field is approximately the quotient of the voxel’s dose and “effective” irradiation time. Each voxel’s “effective” irradiation time starts when the cumulative dose rises above a chosen threshold value, and stops when its cumulative dose reaches its total dose minus the same threshold value. The above calculation yields a distribution of dose rates for the voxels within a PBS treatment field. To report a representative dose rate for the PBS field, we propose a user‐selectable parameter of pth percentile of the dose rate distribution, such that (100 − p) % of the field is above the corresponding dose rate. To demonstrate the method described above, we design FLASH transmission fields using 250 MeV protons and calculate the PBS dose rate distributions in both two‐dimensional (2D) and three‐dimensional (3D) models. To further evaluate the formalism, we provide an example of a clinical PBS treatment field.ResultsWith the 2D PBS transmission field, it is demonstrated that the time to accumulate the total dose at a voxel is limited to a fraction of the delivery time of the entire field. In addition, the spatial distributions of dose and dose rate are quite different within the field. For the 10 × 10 cm2 PBS field irradiating a 3D water phantom, the prescribed dose of 10 Gy at 10 cm depth is delivered in 1.0 s. The dose rate decreases in the irradiated volume with increasing depth (until the Bragg peak) due to increase of beam spot size by Coulomb scattering. For example, 95% of the irradiated volume between 0 and 10 cm depth receive >40 Gy/s, whereas between 0–20 cm and 0–30 cm depth, 95% of the irradiated volume received >36 Gy/s and >24 Gy/s, respectively. For the clinical PBS treatment field, the scanning pattern conforms to the PTV. PBS dose rate data are presented for the PTV and adjacent normal organs.ConclusionWe have developed a method of calculating the dose rate distribution of a PBS proton field and have recommended nomenclature for reporting PBS treatment dose rate. We believe that standardizing the method for calculating and reporting PBS treatment dose rates, in a manner that corresponds with other treatment modalities, will advance the research and potential application of PBS FLASH radiotherapy.

pydicom v1.3.0

At KARA, the KArlsruhe Research Accelerator of the KIT synchrotron, the so called short bunch operation mode allows the reduction of the bunch length down to a few picoseconds. The micro- bunching instability resulting from the high degree of longitudinal compression leads to fluctuations in the emitted THz radiation, referred to as bursting. For extremely compressed bunches at KARA, bursting occurs not only in one but in two different bunch-current ranges that are separated by a stable region. This work presents measurements of the bursting behavior in both regimes. Good agreement is found between data and numerical solutions of the Vlasov-Fokker-Planck equation.

PurposeRecent guidelines recommend magnetic resonance imaging–based brachytherapy (MRBT) for locally advanced cervical cancer. However, its implementation is challenging within the developing world. This article reports the outcomes of patients with locally advanced cervical cancer treated with chemoradiation and point A–based brachytherapy (BT) using x-ray– or computed tomography–based planning.MethodsPatients treated between January 2014 and December 2015 were included. Patients underwent x-ray– or computed tomography–based BT planning with an aim to deliver equivalent doses in 2 Gy (EQD2) > 84 Gy10 to point A while minimizing maximum dose received by rectum or bladder to a point or 2 cc volume to < 75 Gy EQD2 and < 90 Gy EQD2, respectively. The impact of known prognostic factors was evaluated.ResultsA total of 339 patients were evaluated. Median age was 52 (32 to 81) years; 52% of patients had stage IB2 to IIB and 48% had stage III to IVA disease. There was 85% compliance with chemoradiation, and 87% of patients received four or more cycles. Median point A dose was 84 (64.8 to 89.7) Gy. The median rectal and bladder doses were 73.5 (69.6 to 78.4) Gy3 and 83 (73.2 to 90.0) Gy3, respectively. At a median follow-up of 28 (4 to 45) months, the 3-year local, disease-free, and overall survival for stage IB to IIB disease was 94.1%, 83.3%, and 82.7%, respectively. The corresponding rates for stage III to IVA were 85.1%, 60.7%, and 69.6%. Grade III to IV proctitis and cystitis were observed in 4.7% and 0% of patients, respectively.ConclusionThis audit demonstrates good 3-year outcomes that are comparable to published MRBT series. Conventional BT with selective use of interstitial needles and MRBT should continue as standard procedures until level-I evidence for MRBT becomes available.