Effect of intra-fraction motion on the accumulated dose for free-breathing MR-guided stereotactic body radiation therapy of renal-cell carcinoma.

Stereotactic body radiation therapy (SBRT) has shown great promise in increasing local control rates for renal-cell carcinoma (RCC). Characterized by steep dose gradients and high fraction doses, these hypo-fractionated treatments are, however, prone to dosimetric errors as a result of variations in intra-fraction respiratory-induced motion, such as drifts and amplitude alterations. This may lead to significant variations in the deposited dose.

Consensus opinion on MRI simulation for external beam radiation treatment planning.

Aim: To determine the levels at which consensus could be reached regarding general and site-specific principles of MRI simulation for offline MRI-aided external beam radiation treatment planning.

Methods: A process inspired by the Delphi method was employed to determine levels of consensus using a series of questionnaires interspersed with controlled opinion feedback.

Results: In general, full consensus was reached regarding general principles of MRI simulation.

An optimization framework to maximize signal-to-noise ratio in simultaneous multi-slice body imaging.

Parallel imaging is essential for the acceleration of abdominal and pelvic 2D multi-slice imaging, in order to reduce scan time and mitigate motion artifacts. Controlled Aliasing In Parallel Imaging Results IN Higher Acceleration (CAIPIRINHA) accelerated imaging has been shown to increase the signal-to-noise ratio (SNR) significantly compared with in-plane parallel imaging with similar acceleration. We hypothesize that for CAIPIRINHA-accelerated abdominal imaging the consistency of image quality and SNR is more difficult to achieve due to the subject-specific coil sensitivity profiles, caused by (1) flexible coil placement; (2) variations in anatomy; and (3) variations in scan coverage along the superior-inferior direction.

MRI-based tumor motion characterization and gating schemes for radiation therapy of pancreatic cancer.

Background And Purpose: To characterize pancreatic tumor motion and to develop a gating scheme for radiotherapy in pancreatic cancer.

Materials And Methods: Two cine MRIs of 60s each were performed in fifteen pancreatic cancer patients, one in sagittal direction and one in coronal direction. A Minimum Output Sum of Squared Error (MOSSE) adaptive correlation filter was used to quantify tumor motion in craniocaudal, lateral and anteroposterior directions.

Quantification of esophageal tumor motion on cine-magnetic resonance imaging.

Purpose: To quantify the movement of esophageal tumors noninvasively on cine-magnetic resonance imaging (MRI) by use of a semiautomatic method to visualize tumor movement directly throughout multiple breathing cycles.

Methods And Materials: Thirty-six patients with esophageal tumors underwent MRI. Tumors were located in the upper (8), middle (7), and lower (21) esophagus.

Dosimetric feasibility of MRI-guided external beam radiotherapy of the kidney.

At our institution a treatment for kidney tumours with an MRI-Linac is under development. In order to set inclusion criteria for this treatment the anatomical eligibility criteria and the influence of the motion compensation strategy on the delivered dose should be known. Twenty patients with a renal lesion underwent an MR-scan to image the kidney.

The feasibility of using a conventional flexible RF coil for an online MR-guided radiotherapy treatment.

The purpose of this paper is to evaluate the impact of a flexible radiofrequency coil on the treatment delivery of an online MR-guided radiotherapy treatment. For this study, we used a Synergy MR body coil (Philips, Best) in combination with the current MRL prototype of the UMC Utrecht. The compatibility of the coil is evaluated in two steps.

Navigators for motion detection during real-time MRI-guided radiotherapy.

An MRI-linac system provides direct MRI feedback and with that the possibility of adapting radiation treatments to the actual tumour position. This paper addresses the use of fast 1D MRI, pencil-beam navigators, for this feedback. The accuracy of using navigators was determined on a moving phantom.