ITV

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).

AAPM task group report on respiratory motion in thoracic, abdominal and pelvic treatment. It groups management approaches into motion-encompassing methods, respiratory gating, breath-hold techniques, forced shallow breathing (such as abdominal compression) and respiration-synchronized (tracking) techniques. Read in the AAPM report PDF (Report No. 91, July 2006): using ICRU Report 62 nomenclature, the PTV adds margins to the CTV for respiratory (intrafraction) motion, interfraction motion and set-up error; without a respiratory management device the entire range of motion should be considered in the internal margin; and for lung tumors a maximum intensity projection (MIP) can give the motion-encompassing volume, provided there is no mediastinal involvement.

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 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.

The NRG Oncology template for the radiation section of a conventionally fractionated lung trial. Its imaging section allows PET/CT or MRI for structure definition but asks that the final contours be confirmed on the planning CT, follows AAPM TG-132 for deformable registration, and notes that PET can help separate tumor from atelectasis. For plan evaluation it defines the prescription as the dose covering 95% of the PTV, with a protocol-specific D99% requirement, and asks that any dose above 105% of the prescription fall within the PTV rather than in normal tissue outside it.

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).