MRIgRT is widely applicable within the field of radiation oncology and new clinical uses continue to emerge. At our institution to date, applications such as ART for gastrointestinal cancers and accelerated partial breast irradiation (APBI) for breast cancer have become dominant indications, although this is likely to continue to evolve.

To study the dosimetric effect of Qfix kVue Calypso-compatible couch top and rails for spine stereotactic body radiation therapy (SBRT) patients treated with intensity modulated radiation therapy (IMRT) and volumetric modulated arc therapy (VMAT) techniques. Materials/Methods: The computed tomography (CT) dataset for Qfix kVue Calypso-compatible couch top with rails were imported into the treatment planning system (TPS). Ten patients who underwent spine SBRT at our institution were selected for this study. The patients were treated initially on a stereotactic linear accelerator without the couch being part of the dose calculation. Eight patients were treated with static IMRT posterior fields and 2 patients were treated using the VMAT technique. Couch top and rails were added to the structures as support devices and the dose was recalculated for (a) couch top and rails (CR) (b) couch-top and no rails (CNR), then the results were compared the results to no couch-top no-rails (NCNR). Dose covering 100% of the target volume (D100%), dose covering 99% of the target volume (D99%), dose covering 95% of the target volume (D95%), dose covering 90% of the target volume (D90%), volume receiving 100% of the prescription dose (V100%), conformal index (CI), dose gradient index (DGI), and spinal cord threshold and maximum doses were compared to the initial plan with NCNR.

Purpose/Objective(s): Stereotactic body radiation therapy (SBRT) has emerged as an effective treatment modality for locally advanced pancreatic cancer. However, success can be dependent on the definition of local progression (LP). Evaluation of local tumor response has typically been defined by computed tomography (CT) imaging, which is often subject to post-radiation inflammatory changes that limit response assessment. The purpose of this study is to determine the benefit of adding 18 F-fluorodeoxyglucose-positron emission tomography (PET) imaging to CT, using validated objective criteria, for LP assessment of pancreatic adenocarcinoma after SBRT. Materials/Methods: We retrospectively reviewed the pretreatment, follow-up images and outcomes of all patients treated with definitive SBRT for unresectable pancreatic adenocarcinoma between December 2002 and December 2015 at our institution. A pancreas protocol CT consisting of biphasic intravenous contrast and 1-2 mm slice thickness was used for CT images. For each patient, we independently analyzed LP both by CT and by PET criteria, using the Response Evaluation Criteria in Solid Tumors (RECIST) version 1.1 and the PET Response Evaluation Criteria in Solid Tumors (PERCIST) version 1.0, respectively. Results: Among 206 patients treated with definitive SBRT for unresectable pancreatic adenocarcinoma, we identified 31 patients considered to have LP by imaging. Four of them did not undergo follow-up PET. For the 27 patients with LP who had both PET and CT, the median follow-up time was 11.3 months (2-35 months). Median age was 69 years (49-87 years). Median SBRT total dose was 25 Gy (12.5-40 Gy) with a median of one fraction (1-5). Median time to LP after SBRT was 7.3 months (1-25 months). Thirteen LP (42%) occurred concurrently with distant recurrences. The majority of LP occurred on patients treated with a single fraction SBRT schedule. Of the 27 patients who had follow-up PET, there were 21 LP diagnosed by PET (sensitivity Z 81.8%) and 17 diagnosed by CT (sensitivity Z 72.9%), with 11 LP diagnosed both by PET and CT. The combined use of PET and CT result in a 27.1% absolute increase of sensitivity for the diagnosis of LP. The addition of PET to CT for diagnosis of LP was significantly correlated with higher distant recurrence rate (P Z 0.0363). The cumulative incidence of LP, using competing risk of death, at 1 and 2 years after SBRT was 7.6% and 9.3% by CT, and 11.8% and 15.1% by adding PET to CT, respectively. Conclusion: The use of PET increases the sensitivity of detecting LP of unresectable pancreatic adenocarcinoma after SBRT. Follow-up PET imaging is therefore recommended to assess treatment response when evaluating the efficacy of SBRT.

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