PRV

ICRU supplement to Report 50 that refined the PTV concept: an internal margin for variations in the CTV's size, shape and position, a set-up margin for planning and positioning uncertainties, and a planning organ at risk volume (PRV) around organs at risk. DoseLab has not read the report itself (it is sold by the ICRU); these points are checked as summarized in the open-access Burnet 2004 review. Citation as given in the DEGRO/DGMP statement on ICRU Report 91 (Wilke 2019).

Review of the ICRU target-volume concepts. It summarizes ICRU Report 62's internal margin (for variations in the size, shape and position of the CTV, for example from organ filling or respiration) and set-up margin, and its planning organ at risk volume (PRV): a margin around an organ at risk, analogous to the PTV margin, because systematic and random errors apply to organs at risk as much as to the CTV. It notes that a PRV substantially enlarges the organ and may create dilemmas with target dose, so it is needed only in certain circumstances — around organs whose damage is especially dangerous, such as the spinal cord, a "serial" tissue. Full text read in Europe PMC (PMC1434601).

Recommendations for standardized naming of targets, organs at risk and dose-volume metrics. Section 9 sets out the DVH-metric nomenclature DoseLab follows: Vx (volume receiving at least dose x), Dx (minimum dose to the hottest sub-volume x), CVx and DCx (the "cold" complements), output units in square brackets (Gy or % of prescription; cc or % of the structure), and an EQD2Gy unit with the α/β written in parentheses — for example D90%(10)[EQD2Gy]. Section 10 asks that DVH metrics say whether a lower-dose PTV is segmented (excludes the higher-dose PTV) or not. Read in the AAPM report PDF.

The NRG Oncology template for the radiation section of a head and neck trial. Its simulation section asks for planning images in the treatment position with slices of 3 mm or less, uses MRI and/or PET to aid delineation (MRI especially near the skull base), asks for the MRI to be taken as close as possible to the treatment position with distortion correction applied, and recommends PET/CT and MRI fusion when IV contrast can't be given.

The NRG Oncology template for the radiation section of a brain tumor trial. It strongly encourages MRI for target delineation (contrast T1, T2/FLAIR and a 3D gradient-echo sequence), recommends fusing FDG-PET/CT when available, and asks that the fusion be done by a medical physicist or a dosimetrist under physicist supervision and reviewed by the attending physician.

The template NRG Oncology gives investigators for writing the radiation section of a lung SBRT trial. Its imaging section allows PET/CT or MRI for structure definition, asks that the images be registered accurately to the planning scan (following AAPM TG-132 for deformable registration), notes that PET may be needed to separate tumor from atelectasis or fibrosis, and suggests an extra margin when a fused image is the primary image for the GTV. Its target and planning sections (5.2.4 and 5.2.6–5.2.8) define the plan-quality measures for lung SBRT trials: the prescription as the dose covering 95% of the PTV, a D99% requirement, R100% (prescription isodose volume ÷ PTV), R50% (50% prescription isodose volume ÷ PTV) and D2cm (maximum dose at 2 cm from the PTV in any direction, as a percentage of the prescription), with a table of allowable dose spillage by PTV volume. It describes a 20 mm PTV expansion structure used to control intermediate dose spillage, asks that dose above 105% of prescription be avoided outside the PTV, describes a deliberately heterogeneous dose with the hotspot in the central GTV, defines the maximum dose on a 0.03 cc volume, and ranks planning priorities when target coverage and organ limits conflict.

DEGRO working-group statement defining SBRT for stage I NSCLC. It lists the motion-management approaches in routine use — free-breathing delivery with the internal target volume concept (described as the most commonly practiced), the mean target position concept or real-time tracking, and delivery in specific breathing phases by gating or breath hold — and names safety margins for critical organs (the PRV concept), repositioning or replanning as ways to avoid organ overdose. Full text read in Europe PMC (PMC3889283).