Application of deformable image registration in radiotherapy dose accumulation of helical tomotherapy combined with brachytherapy for cervical cancer / 中华放射肿瘤学杂志

ABSTRACT

Objective:To assess the feasibility of deformable image registration (DIR) in evaluating cumulative dose distribution of bladder and rectum of cervical cancer patients during helical tomotherapy (HT)-based intensity-modulated radiotherapy (IMRT) and high-dose-rate(HDR) brachytherapy.Methods:Clinical data of 18 patients were retrospectively analyzed. Cumulative bladder/rectum D 2cm 3 and high-risk clinical target volume (HR-CTV) D 90% parameters were calculated and compared to two direct parameter-adding methods with two registration-adding methods. Equivalent uniform dose (EUD group) and overlapping high dose (OHD group) methods were employed as parameter-adding methods. The registration-adding methods including rigid image registration (RIR group) and deformable image registration (DIR group) were adopted based on a commercial image registration software (MIM Maestro ?). The dice similarity coefficient (DSC) and mean distance to agreement (MDA) were measured to assess the accuracy of RIR and DIR. Results:In the EUD, OHD, RIR and DIR groups, the cumulative doses of bladder/rectum D 2cm 3 and HR-CTV D 90% were (80.11±3.59) Gy (EQD 2Gy), (82.23±3.46) Gy (EQD 2Gy), (80.99±6.01) Gy (EQD 2Gy) and (81.19±3.11) Gy (EQD 2Gy)( P=0.516); (72.90±3.58) Gy (EQD 2Gy), (73.83±4.28) Gy (EQD 2Gy), (72.45±6.05) Gy (EQD 2Gy) and (71.98±2.89) Gy (EQD 2Gy)( P=0.625), and (85.51±2.91) Gy (EQD 2Gy), (87.65±3.46) Gy (EQD 2Gy), (81.53±3.63) Gy (EQD 2Gy) and (85.81±3.30) Gy (EQD 2Gy)( P<0.001), respectively. The mean DSC of the bladder, rectum and HR-CTV were 0.69, 0.65 and 0.63 with RIR; and 0.85, 0.81 and 0.78 with DIR ( P<0.001), respectively. In DIR, the average MDA of bladder, rectum, and HR-CTV were 2.88, 2.48 and 2.66 mm, respectively. Conclusions:The cumulative DVH parameters among 4 groups show no significant difference in the bladder/rectum D 2cm 3/D 0.2cm 3. Since the DIR group achieves satisfactory volume matching of greater than 0.8 with DSC analysis, it can yield acceptable results for clinical application between HT IMRT and HDR BT for cervical cancer.