A new dose-volume-based Plan Quality Index for IMRT plan comparison.
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.
Leung
Lucullus Hing Tong
LH
Department of Oncology, Princess Margaret Hospital, Hong Kong SAR, China. leunght@ha.org.hk
Kan
Monica Wai Kwan
MW
Cheng
Ashley Chi Kin
AC
Wong
Wicger King Hang
WK
Yau
Chun Chung
CC
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