BackgroundA novel CT-linac (kilovolt fan-beam CT-linac) has been introduced into total marrow and lymphoid irradiation (TMLI) treatment. Its integrated kilovolt fan-beam CT (kV FBCT) can be used not only for image guidance (IGRT) but also to re-calculate the dose.PurposeThis study reported our clinical routine on performing TMIL treatment on the CT-linac, as well as dose distribution comparison between planned and re-calculated based on IGRT FBCT image sets.Methods11 sets of data from 5 male and 6 female patients who had underwent the TMLI treatment with uRT-linac 506c were selected for this study. The planning target volumes consist of all skeletal bones exclusion of the mandible and lymphatic sanctuary sites. A planned dose of 10 Gy was prescribed to all skeletal bones exclusion of the mandible in two fractions and 12 Gy in two fractions was prescribed to lymphatic sanctuary sites. Each TMLI plan contained two sub-plans, one dynamic IMRT for the upper body and the other VMAT for the lower extremity. Two attempts were made to obtain homogeneous dose in the overlapping region, i.e., applying two plans with different isocenters for the treatment of two fractions, and using a dose gradient matching scheme. The CT scans, including planning CT and IGRT FBCT, were stitched to a whole body CT scan for dose distribution evaluation.ResultsThe average beam-on time of Planupper is 30.6 min, ranging from 24.9 to 37.5 min, and the average beam-on time of Planlower is 6.3 min, ranging from 5.7 to 8.2 min. For the planned dose distribution, the 94.79% of the PTVbone is covered by the prescription dose of 10 Gy (V10), and the 94.68% of the PTVlymph is covered by the prescription dose of 12 Gy (V12). For the re-calculated dose distribution, the 92.17% of the PTVbone is covered by the prescription dose of 10 Gy (V10), and the 90.07% of the PTVlymph is covered by the prescription dose of 12 Gy (V12). The results showed that there is a significant difference (p < 0.05) between planning V10, V12 and delivery V10, V12. There is no significant difference (p > 0.05) between planned dose and re-calculated dose on selected organs, except for right lens (p < 0.05, Dmax). The actual delivered maximum dose of right lens is apparently larger than the planned dose of it.ConclusionTMLI treatment can be performed on the CT-linac with clinical acceptable quality and high efficiency. Evaluation of the recalculated dose on IGRT FBCT suggests the treatment was delivered with adequate target coverage.

Abstract Background: A novel CT-linac (kilovolt fan-beam CT-linac) has been introduced into total marrow and lymphoid irradiation (TMLI) treatment. Its integrated kilovolt fan-beam CT scanner enables accurate evaluation of the dose distribution difference between plan and delivery, which is crucial for the TMLI treatment improvement for the future. Purpose: This study evaluated the technical feasibility of kilovolt fan-beam CT-linacfor TMLI treatment and investigated the true dose distribution of the delivery. Methods: 11 sets of data from 5 male and 6 female patients who had underwent the TMLI treatment with uRT-linac 506c were selected for this study. The planning target volumes consist of all skeletal bones exclusion of the mandible and lymphatic sanctuary sites. A planned dose of 10Gy was prescribed to all skeletal bones exclusion of the mandible in two fractions and 12Gy in two fractions was prescribed to lymphatic sanctuary sites. Each TMLI plan contained two sub-plans, one dynamic IMRT for the upper body and the other VMAT for the lower extremity. Two attempts were made to obtain homogeneous dose in the overlapping region, i.e., applying two plans with different isocenters for the treatment of two fractions, and using a dose gradient matching scheme. The CT scans, including planning CT and fan-beam CT (obtained during image-guided radiation therapy) were stitched to a whole body CT scan for dose distribution evaluation. Results: Firstly, the kilovolt fan-beam CT-linac can provide the adequate target dose coverage (90% for planning and delivery) and critical organ sparing that satisfied the clinical requirements. Secondly, the beam-on time of kilovolt fan-beam CT-linac is apparently shorter than helical tomotherapy for the TMLI treatment. Thirdly, there exists the dose distribution difference of PTVs between plan and delivery (p<0.05, Wilcoxon signed-rank test), but the PTV coverage of delivery is clinically acceptable (larger than 90%). There is no significant difference (p>0.05) between the dose distribution of the plan and delivery for most organs at risk, except for right len. Fourthly, for the treatment delivery, applying two plans with different isocenters for one patient in two fractions performed better than employing only one plan for one patient in two fractions on PTV coverage for PTVbone, maximum dose for small bowel, heart, and liver. Conclusion: This radiation therapy treatment planning has proved to be effective. This research first exhibited that the dose difference between planning and delivery was evaluated, which is important for treatment evaluation and plan improvement for the future studies.

Background & purpose Helical tomotherapy has been applied to total marrow irradiation (HT-TMI). Our objective was to apply failure mode and effects analysis (FMEA) two times separated by 1 year to evaluate and improve the safety of HT-TMI. Materials and methods A multidisciplinary team was created. FMEA consists of 4 main steps: (1) Creation of a process map; (2) Identification of all potential failure mode (FM) in the process; (3) Evaluation of the occurrence (O), detectability (D) and severity of impact (S) of each FM according to a scoring criteria (1-10), with the subsequent calculation of the risk priority number (RPN=O*D*S) and (4) Identification of the feasible and effective quality control (QC) methods for the highest risks. A second FMEA was performed for the high-risk FMs based on the same risk analysis team in 1 year later. Results A total of 39 subprocesses and 122 FMs were derived. First time RPN ranged from 3 to 264.3. Twenty-five FMs were defined as being high-risk, with the top 5 FMs (first RPN/ second RPN): (1) treatment couch movement failure (264.3/102.8); (2) section plan dose junction error in delivery (236.7/110.4); (3) setup check by megavoltage computed tomography (MVCT) failure (216.8/94.6); (4) patient immobilization error (212.5/90.2) and (5) treatment interruption (204.8/134.2). A total of 20 staff members participated in the study. The second RPN value of the top 5 high-risk FMs were all decreased. Conclusion QC interventions were implemented based on the FMEA results. HT-TMI specific treatment couch tests; the arms immobilization methods and strategy of section plan dose junction in delivery were proved to be effective in the improvement of the safety.

Objective To evaluate the clinical application value of a novel immobilization system in total marrow irradiation ( TMI) with MVCT image. Methods From 2016 to 2017, a retrospective analysis of the setup errors of 22 patients receiving TMI in two groups ( twelve patients were immobilized with the novel immobilization system in group 1, ten patients were immobilized with the combinatorial immobilization devices in group 2) was performed in this study on Zhongnan Hospital of Wuhan University. Two-sample t-test was used to analyze the differences of setup errors and the consistency of setup between two groups. Results In group 1, the setup errors on left-right, superior-inferior, anterior-posterior and rotation directions were ( 1.06±0.79) , ( 1.34±0.66) , ( 2.45±1.48) mm and ( 0.63°±0.65°) for the head and neck position, ( 1.58±1.13) , ( 2.38±1.99) , ( 2.05± 1.68) mm and ( 0.31°± 0.32°) for the chest position, ( 1.67± 1.24) , ( 3.88±2.20) , ( 1.96± 1.32) mm and ( 0.48°± 0.53°) for the pelvis position, and ( 0.95± 0.73) , ( 1.99± 1.35) , ( 3.66±2.13) mm and ( 0.24°±0.31°) for the lower limb, respectively. In group 2, the setup errors were ( 2.59±2.58) , ( 3.28±1.85) , ( 3.71±2.43) mm and ( 1.15°±1.18°) for the head and neck position, ( 4.38±3.69) , ( 5.64±3.78) , ( 2.72± 1.91) mm and ( 1.55°± 0.86°) for the chest position, ( 4.14± 2.97) , ( 6.97±3.68) , ( 2.21±2.26) mm and ( 1.23°±0.74°) for the pelvis position, ( 2.28± 1.15) , ( 5.97± 3.00) , ( 3.44±1.93) mm and ( 1.09°±0.94°) for the lower limb, respectively. The setup errors significantly differed between two groups on the left-right, superior-inferior and rotation directions for all positions ( all P<0.05) . The setup consistency significantly differed between two groups on the left-right, superior-inferior and rotation directions for the chest and pelvis positions ( all P<0.05) . Conclusion The novel immobilization system can significantly improve the setup accuracy and setup consistency, and enhance the precision of treatment for patients.

To report our experience in planning and delivering total marrow irradiation (TMI) and total marrow and lymphatic irradiation (TMLI) in patients with hematologic malignancies.