title: A new dose-volume-based Plan Quality Index for IMRT plan comparison.
abstract: OBJECTIVE
  To develop a dose-volume-based Plan Quality Index for IMRT plans.
  
  
  METHODS
  This study used a H(ealthy) Tissue Conformity Index to describe the overall plan conformity, a M(erit) function to describe the target coverage and a P(enalty) function to evaluate doses to critical organs. The Euclidean distance (PQI) between (H, M, P) and (1,1,1) represented the quality of a treatment plan. By checking the polarity of each term in M and P, one might conclude if the plan was satisfied with the given treatment protocol. Ten prostate plans (3-DCRT and IMRT) and 20 NPC IMRT plans were used to test PQI, Conformation Number (CN), COnformal INdex (COIN). EUD was used as a vehicle to explain the results. This study defined the power of a quality index as the ratio of the absolute difference to the mean of the same index of two plans, to compare the discerning power of PQI, CN and COIN.
  
  
  RESULTS
  The plan quality discerning power of PQI, COIN and CN was 20.6%, 8.2% and 5.5%, respectively, in prostate plans.
  
  
  CONCLUSIONS
  PQI improved the plan quality discerning power and was capable of discerning qualified and unqualified treatment plans.
authors.affiliation: Department of Oncology, Princess Margaret Hospital, Hong Kong SAR, China. leunght@ha.org.hk
authors.forename: Lucullus Hing Tong
authors.initials: LH
authors.lastname: Leung
authors.forename: Monica Wai Kwan
authors.initials: MW
authors.lastname: Kan
authors.forename: Ashley Chi Kin
authors.initials: AC
authors.lastname: Cheng
authors.forename: Wicger King Hang
authors.initials: WK
authors.lastname: Wong
authors.forename: Chun Chung
authors.initials: CC
authors.lastname: Yau
mesh_terms: D006801:Humans; D008297:Male; D009303:Nasopharyngeal Neoplasms / Q000532:radiotherapy; D011471:Prostatic Neoplasms / Q000532:radiotherapy; D011879:Radiotherapy Dosage; D011880:Radiotherapy Planning, Computer-Assisted; D050397:Radiotherapy, Intensity-Modulated