Total body irradiation with volumetric modulated arc therapy: Dosimetric data and first clinical experience

A study was undertaken to explore the use of volumetric modulated arc therapy (VMAT) for total body irradiation (TBI). Five patient plans were created in Pinnacle3 using nine 6 MV photon dynamic arcs. A dose of 12 Gy in six fractions was prescribed. The planning target volume (PTV) was split into four subsections for the head, chest, abdomen, and pelvis. The head and chest beams were optimized together, followed by the abdomen and pelvis beams. The last stage of the planning process involved turning all beams on and performing a final optimization to achieve a clinically acceptable plan. Beam isocenters were shifted by 3 or 5 mm in the left–right, anterior–posterior, and superior–inferior directions to simulate the effect of setup errors on the dose distribution. Treatment plan verification consisted of ArcCheck measurements compared to calculated doses using a global 3%/3 mm gamma analysis. All five patient plans achieved the planning aim of delivering 12 Gy to at least 90% of the target. The mean dose in the PTV was 12.7 Gy. Mean lung dose was restricted to 8 Gy, and a dose reduction of up to 40% for organs such as the liver and kidneys proved feasible. The VMAT technique was found to be sensitive to patient setup errors particularly in the superior–inferior direction. The dose predicted by the planning system agreed with measured doses and had an average pass rate of 99.2% for all arcs. VMAT was found to be a viable treatment technique for total body irradiation.

Section: Discussionsupporting

confidence: 84%

“…Previous studies have demonstrated the use of Varian RapidArc in combination with the Eclipse TPS23 with promising results in the first clinical cases 24. A VMAT approach to TBI treatments has the potential to make TBI accessible to more clinical departments where equipment limitations or bunker size has restricted implementation.…”

Section: Introductionmentioning

confidence: 99%

Volumetric modulated arc therapy for total body irradiation: A feasibility study using Pinnacle³ treatment planning system and Elekta Agility™ linac

Symons

Morrison

Parry

et al. 2018

“…This includes the use of volumetric modulated arc therapy (VMAT), which has shown promise in improving dose homogeneity and reducing the dose to organs at risk (OAR). Springer et al developed a 9‐15 isocenter VMAT technique where the patient is longitudinally translated to capture the entire planning target volume (PTV) in eight segments . Smooth junctions between segments were achieved using inverse planning, resulting in a homogeneous dose delivery.…”

Section: Introductionmentioning

confidence: 99%

Standardized flattening filter free volumetric modulated arc therapy plans based on anteroposterior width for total body irradiation

Frederick

Hudson

Balogh

et al. 2020

In this work, the feasibility of using flattening filter free (FFF) beams in volumetric modulated arc therapy (VMAT) total body irradiation (TBI) treatment planning to decrease protracted beam‐on times for these treatments was investigated. In addition, a methodology was developed to generate standardized VMAT TBI treatment plans based on patient physical dimensions to eliminate plan optimization time. A planning study cohort of 47 TBI patients previously treated with optimized VMAT ARC 6 MV beams was retrospectively examined. These patients were sorted into six categories depending on height and anteroposterior (AP) width at the umbilicus. Using Varian Eclipse, clinical 40 cm × 10 cm open field arcs were substituted with 6 MV FFF. Mid‐plane lateral dose profiles in conjunction with relative arc output factors (RAOF) yielded how far a given multileaf collimator (MLC) leaf must move in order to achieve a mid‐plane 100% isodose for a specific control point. Linear interpolation gave the dynamic MLC aperture for the entire arc for each patient AP width category, which was subsequently applied through Python scripting. All FFF VMAT TBI plans were then evaluated by two radiation oncologists and deemed clinically acceptable. The FFF and clinical VMAT TBI plans had similar Body–5 mm D98% distributions, but overall the FFF plans had statistically significantly increased or broader Body–5 mm D2% and mean lung dose distributions. These differences are not considered clinically significant. Median beam‐on times for the FFF and clinical VMAT TBI plans were 11.07 and 18.06 min, respectively, and planning time for the FFF VMAT TBI plans was reduced by 34.1 min. In conclusion, use of FFF beams in VMAT TBI treatment planning resulted in dose homogeneity similar to our current VMAT TBI technique. Clinical dosimetric criteria were achieved for a majority of patients while planning and calculated beam‐on times were reduced, offering the possibility of improved patient experience.

“…Helical tomotherapy (HT) based methods have been used for TMI/TMLI2, 3, 4, 5 as well as TBI 5, 6, 7. Using conventional linacs, intensity modulated radiotherapy (IMRT) TMI delivery proved feasible,8, 9 however, the predominant linac approach utilizes volumetric modulated arc therapy (VMAT) using Varian RapidArc (Varian Medical Systems, Palo Alto, CA, USA) 10, 11, 12, 13, 14, 15, 16, 17…”

Section: Introductionmentioning

confidence: 99%

“…Previous VMAT TBI and TMI/TMLI studies have utilized a variety of dose verification techniques. Portal imaging,13 Mapcheck,14 thermoluminescent dosimeters (TLDs) in an anthropomorphic phantom,15 ionization chamber array (Octavius)16 and diode array (ArcCHECK) 17. Junction measurements are seldom reported on.…”

Section: Introductionmentioning

confidence: 99%

Verification of junction dose between VMAT arcs of total body irradiation using a Sun Nuclear ArcCHECK phantom

Morrison

Symons

Woodings

et al. 2017

A volumetric modulated arc therapy (VMAT) approach to total body irradiation (TBI) has recently been introduced at our institution. The planning target volume (PTV) is divided into separate sub‐volumes, each being treated with 2 arcs with their own isocentre. Pre‐treatment quality assurance of beams is performed on a Sun Nuclear ArcCHECK diode array. Measurement of junction regions between VMAT arcs with separate isocentres has previously been performed with point dose ionization chamber measurements, or with films. Translations of the ArcCHECK with respect to a known distance between the adjacent isocentres of two arcs, which are repeated with the ArcCHECK in an inverted position, allows the recording of a junction dose map. A 3%/3 mm global gamma analysis (10% threshold) pass rate for arc junctions were comparable to their component arcs. Dose maps of junction regions between adjacent arcs with different isocentres can be readily measured on a Sun Nuclear ArcCHECK diode array.