PMID- 37285227
OWN - NLM
STAT- MEDLINE
DCOM- 20231023
LR  - 20231023
IS  - 1526-9914 (Electronic)
IS  - 1526-9914 (Linking)
VI  - 24
IP  - 10
DP  - 2023 Oct
TI  - A clinical application of fair value estimate (FVE) for R50%: Separating 
      overlapping 50% isodose volumes in single isocenter multiple targets SRS.
PG  - e14061
LID - 10.1002/acm2.14061 [doi]
LID - e14061
AB  - In the treatment of single isocenter multiple targets (SIMT) stereotactic cranial 
      cases with linac-based, multi-leaf collimated delivery, one encounters cases when 
      the 50% isodose clouds (IDC50%s) of planning target volumes (PTVs) in close 
      proximity overlap and cannot easily be separated. In such cases, it is difficult 
      to assign an IDC50% to each individual PTV, which is necessary to allow 
      evaluation of individual PTV intermediate dose spill for comparison to 
      established intermediate dose spill metrics for plan quality assessment. The Fair 
      Value Estimate (FVE) for R50% (R50%(FVE) ) is a method to unambiguously apportion 
      the overlapping volume of IDC50% to allow calculation of the intermediate dose 
      spill metric R50% (defined as volume of IDC50% / volume of PTV). Full application 
      of R50%(FVE) requires knowing the surface area of the PTVs. Since surface area 
      information is not always available, we develop a spherical PTV approximation to 
      R50%(FVE-sphere) and compare this to R50%(FVE) . Then we apply the 
      R50%(FVE-sphere) to clinical data from the University of Alabama, Birmingham 
      (UAB) that catalogs 68 PTVs from various SIMT plans with overlapping IDC50%. The 
      UAB dataset reports intermediate dose spill as Falloff Index. While Falloff Index 
      looks mathematically equivalent to R50%, the Falloff Index attributes the "entire 
      overlapping IDC50% of PTVs in close proximity" to each individual PTV in the 
      cluster. R50%(FVE-sphere) provides a value that is conceptually correct and 
      numerically smaller relative to the Falloff Index data reported by UAB in all 
      cases. This reprocessing of the UAB data places many of the PTVs with very high 
      intermediate dose spill within recently proposed R50% guidelines.
CI  - (c) 2023 The Authors. Journal of Applied Clinical Medical Physics published by 
      Wiley Periodicals, LLC on behalf of The American Association of Physicists in 
      Medicine.
FAU - Desai, Dharmin D
AU  - Desai DD
AD  - Varian Advanced Oncology Solutions, Palto Alto, California, USA.
FAU - Cordrey, Ivan L
AU  - Cordrey IL
AD  - Regional Cancer Center, Cumberland Medical Center, Crossville, Tennessee, USA.
LA  - eng
PT  - Journal Article
DEP - 20230607
PL  - United States
TA  - J Appl Clin Med Phys
JT  - Journal of applied clinical medical physics
JID - 101089176
SB  - IM
MH  - Humans
MH  - Radiotherapy Dosage
MH  - *Radiosurgery/methods
MH  - Radiotherapy Planning, Computer-Assisted/methods
MH  - *Radiotherapy, Intensity-Modulated/methods
PMC - PMC10562026
OTO - NOTNLM
OT  - FVE
OT  - Fair Value Estimate
OT  - IDC50% overlap
OT  - R50%
OT  - SIMT
OT  - cranial SRS
OT  - cranial SRT
COIS- The authors report no conflicts of interest.
EDAT- 2023/06/07 19:42
MHDA- 2023/10/23 00:44
PMCR- 2023/06/07
CRDT- 2023/06/07 12:13
PHST- 2023/05/02 00:00 [revised]
PHST- 2022/08/31 00:00 [received]
PHST- 2023/05/18 00:00 [accepted]
PHST- 2023/10/23 00:44 [medline]
PHST- 2023/06/07 19:42 [pubmed]
PHST- 2023/06/07 12:13 [entrez]
PHST- 2023/06/07 00:00 [pmc-release]
AID - ACM214061 [pii]
AID - 10.1002/acm2.14061 [doi]
PST - ppublish
SO  - J Appl Clin Med Phys. 2023 Oct;24(10):e14061. doi: 10.1002/acm2.14061. Epub 2023 
      Jun 7.