Purpose: A 1.5 T MR Linac (MRL) has recently become available. MRL treatment workflows (WF) include online plan adaptation based on daily MR images (MRI). This study reports initial clinical experiences after five months of use in terms of patient compliance, cases, WF timings, and dosimetric accuracy. Method and materials: Two different WF were used dependent on the clinical situation of the day; Adapt To Position WF (ATP) where the reference plan position is adjusted rigidly to match the position of the targets and the OARs, and Adapt To Shape WF (ATS), where a new plan is created to match the anatomy of the day, using deformable image registration. Both WFs included three 3D MRI scans for plan adaptation, verification before beam on, and validation during IMRT delivery. Patient compliance and WF timings were recorded. Accuracy in dose delivery was assessed using a cylindrical diode phantom. Results: 19 patients have completed their treatment receiving a total of 176 fractions. Cases vary from prostate treatments (60 Gy/20F) to SBRT treatments of lymph nodes (45 Gy/3F) and castration by ovarian irradiation (15 Gy/3F). The median session time (patient in to patient out) for 127 ATPs was 26[21-78] min, four fractions lasted more than 45 minutes due to additional plan adaptation. For the 49 ATSs a median time of 12[1-24] min was used for contouring resulting in a total median session time of 42[29-91] min. Three SBRT fractions lasted more than an hour. The time on the MRL couch was well tolerated by the patients. The median gamma pass rate (2mm,2% global max) for the adapted plans was 99.2[93.4-100]%, showing good agreement between planned and delivered dose. Conclusion: MRL treatments, including daily MRIs, plan adaptation and accurate dose delivery is possible within a clinically acceptable timeframe and is well tolerated by the patients.

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(2013) Stereotactic body radiation therapy versus conventional radiation therapy in patients with early stage non-small cell lung cancer: An updated retrospective study on local failure and survival rates,

The frequency of malignant neoplasms was studied in 248 psoriatics treated with a single, weekly, oral dose of methotrexate ranging from 5 to 25 mg. The follow-up period ranged from 5 to 14 years with a median of 7 years. The following 10 malignant neoplasms were found: ovarian cancer 3, breast cancer 2, esophageal cancer in 1 male, pancreatic cancer in 1 female, malignant lymphoma in 1 female and 1 male and 1 squamous cell carcinoma of the scrotal skin. As the observed number of malignant neoplasms was considerably smaller than the expected number, it is concluded that methotrexate therapy as used in the treatment of psoriasis does not seem to contribute to the development of malignant neoplasms.

Median gamma pass rates were high for pseudo CT and proved superior to uniform density. Local differences in dose calculations were concluded not to have clinical relevance. Feasibility of the MR-only workflow was demonstrated through successful delivery of a treatment course planned based on MR alone.