ABSTRACT
Objective:To validate the feasibility of the gamma analysis method in the study of prescription dose conversion between logistic nanodosimetry model (LNDM) and microdosimetric kinetic model (MKM) basing on the Chinese self-developed model LNDM by applying clinical experiences of National Institute of Radiological Science (NIRS).Methods:Physical dose distributions derived from the MKM- and LNDM-based carbon ion treatment plans were compared via the method of gamma analysis under the open-source treatment planning platform matRad. In this way, the prescribed dose conversion factor between the MKM- and LNDM-based treatment plans was obtained. Using water phantoms, the influence of geometric shape, size, depth of target volume (TV), prescribed dose and field setting on the conversion factor was investigated comprehensively. Moreover, preliminary verification of the acquired conversion factor was conducted on the C-shape model and a case of liver cancer patient.Results:The conversion factor depended on the field setting rather than the TV shape. Under the condition of single field, the conversion factor was positively correlated with the size and depth of TV, and the prescribed dose. Moreover, the conversion factor was successfully verified using the C-shape model and the patient with liver cancer, where the gamma passing rates (2%/2 mm) of the physical dose distribution generated by the MKM and LNDM treatment plans were 92.79% and 91.19%, respectively.Conclusions:The conversion factors (f=D LNDM/D MKM) obtained in this study might provide guidance for the prescribed dose setting during the carbon ion treatment planning based on the LNDM. Besides, the gamma analysis method could be used for the study of the prescribed dose conversion between different models.
ABSTRACT
Objective:To compare the adverse reactions, efficacy and survival rate of carbon ion beam irradiation in the elective lymph node (ENI) drainage area of locally advanced non-small cell lung cancer (LA-NSCLC) with relative biological effect (RBE) dose of 48 Gy using 16 and 12 fractions.Methods:A total of 72 patients with pathologically confirmed LA-NSCLC admitted to Wuwei Heavy Ion Center of Gansu Wuwei Tumor Hospital from June 2020 to December 2021 were enrolled and simple randomly divided into groups A and B, with 36 patients in each group. Patients in groups A and B were treated with carbon ion beam irradiation to the lymph node drainage area with 48 Gy (RBE) using 16 and 12 fractions. The acute and chronic adverse reactions, efficacy and survival rate were observed. The survival curve was drawn by Kaplan-Meier method. Difference test was conducted by log-rank test.Results:The median follow-up time was 13.9 (8.8-15.7) months in group A and 14.6 (6.3-15.9) months in group B. Sixteen (44.4%) patients were effectively treated in group A and 9 (25%) patients in group B. Thirty-four (94.4%) cases achieved disease control in group A and 30 (83.3%) cases in group B. Statistical analysis showed that the overall survival rate in group B was similar to that in group A ( χ2=1.192, P=0.275). Comparison of planning parameters between two groups showed CTV volume, D mean, V 5 Gy(RBE), V 20 Gy(RBE) and V 30 Gy(RBE) of the affected lung, cardiac V 20 Gy(RBE), V 30 Gy(RBE) and D mean, esophageal V 30 Gy(RBE), V 50 Gy(RBE), D max and D mean, D max of the trachea and spinal cord had no significant difference (all P>0.05). No grade 3 or 4 adverse reactions occurred in the enrolled patients during treatment and follow-up. No statistical differences were observed in the acute radiation skin reaction ( χ2=5.134, P=0.077), radiation esophagitis ( χ2=1.984, P=0.371), and advanced radiation pneumonia ( χ2=6.185, P=0.103) between two groups. Conclusions:The two dose fractionation modes of carbon ion therapy system are equally safe in the mediastinal lymphatic drainage area of LA-NSCLC, and the adverse reactions are controllable. The long-term efficacy still needs further observation.
ABSTRACT
Objective:A two-dimensional (2D) in-house-built scintillator detection system (SDS) was utilized for quality assurance of the active spot scanning proton and heavy ion accelerator, aiming to establish a rapid detection method and provide reference for the quality of proton and heavy ion beam (spot position, spot size, virtual source-to-axis distance, profile depth dose distribution and beam range).Methods:The SDS consisted of a ceramic gadolinium-sulfoxylate phosphor-scintillating screen, a mirror and a commercial digital camera. The dose distribution image was obtained based on scintillator, mirror reflector and optical signal acquisition device to transform the proton and heavy ion beam into visible light through sulfur gadolinium oxide scintillator and collect visible light information to meet the clinical requirements for the quality of proton and heavy ion beam.Results:The deviation of spot position measured by multifilament proportional chamber and the SDS was less than 1mm. The differences of beam spot size measured by multifilament proportional chamber and the SDS were (1.40±0.59)mm for protons, and (0.5±0.08)mm for carbon ions. For 429.25MeV/u carbon, the virtual source-to-axis distance (V SAD) at the x-and y-axes was 751.8cm and 805.6cm. And difference between physical distance and virtual source-to-axis distance was less than 1%. The range of 287.5MeV/u carbon measured by SDS was 160mm. Conclusions:The in-house-built scintillator detector can measure beam spot position and size, virtual source, depth distribution curve and range, which can be used as an effective tool for quality assurance control of proton and heavy ion therapy.
ABSTRACT
Objective To evaluate the short-term efficacy and adverse events of pencil beam scanning proton and carbon ion therapy in the treatment of chordoma and chondrosarcoma of the head and neck.Methods Between July 2014 and July 31,2017,61 patients with chordoma and chondrosarcoma of the head and neck receiving proton and heavy ion therapy as the first course of radiotherapy were enrolled.Among them,45 patients were diagnosed with chordoma and 16 cases of chondrosarcoma,39 male and 22 female.The median age was 38 years old (range:14-70 years).The median maximum tumor diameter was 4.1 cm (range:0-8.6 cm).The clivus and the cervical spine were the primary tumor sites.Results Eight patients received proton therapy,21 patients were treated with proton combined with carbon ion therapy and 32 patients received carbon ion therapy.All patients successfully completed the planned radiotherapy.The medial follow-up time was 21 months (range:7-47 months).No grade 3-4 acute toxicity was observed.Only one patient suffered from radiation-induced temporal lobe injury.The 2-year progression-free survival (PFS)and overall survival (OS) were 91％ and 100％.Conclusions Pencil beam scanning proton and heavy ion therapy yields relatively favorable short-term outcomes in the treatment of chordoma and chondrosarcoma of the head and neck.Nevertheless,the long-term clinical efficacy and safety remain to be investigated during follow-up.