Setup Management for Stereotactic Body Radiation Therapy of Patients With Pancreatic Cancer Treated via the Breath-Hold Technique.

Purpose: Active Breathing Coordinator (Elekta AB, Crawley, UK) is a motion management strategy for radiation treatment. During setup, aligning the patient to the bony spine alone does not necessarily lead to an accurate alignment to soft tissue targets, and further adjustment is necessary. Determining a safe range of values for such adjustments is an important quality assurance measure and was the purpose of this study, with focus on stereotactic body radiation therapy in patients with pancreatic cancer.

4D tumor centroid tracking using orthogonal 2D dynamic MRI: implications for radiotherapy planning.

Purpose: Current pretreatment, 4D imaging techniques are suboptimal in that they sample breathing motion over a very limited "snapshot" in time. Heretofore, long-duration, 4D motion characterization for radiotherapy planning, margin optimization, and validation have been impractical for safety reasons, requiring invasive markers imaged under x-ray fluoroscopy. To characterize 3D tumor motion and associated variability over durations more consistent with treatments, the authors have developed a practical dynamic MRI (dMRI) technique employing two orthogonal planes acquired in a continuous, interleaved fashion.

Respiration-based sorting of dynamic MRI to derive representative 4D-MRI for radiotherapy planning.

Purpose: Current pretreatment, 4D imaging techniques are suboptimal in that they sample breathing motion over a very limited "snap-shot" in time. To potentially address this, the authors have developed a longer-duration MRI and postprocessing technique to derive the average or most-probable state of mobile anatomy and meanwhile capture and convey the observed motion variability.

Methods: Sagittal and coronal multislice, 2D dynamic MRI was acquired in a sequential fashion over extended durations in two abdominal and four lung studies involving healthy volunteers.

Comparative analysis of traditional and coiled fiducials implanted during EUS for pancreatic cancer patients receiving stereotactic body radiation therapy.

Background: EUS-guided fiducial placement facilitates image-guided radiation therapy (IGRT).

Objective: To compare 2 types of commercially available fiducials for technical success, complications, visibility, and migration.

Design: Retrospective, single-center, comparative study.

The radiobiological P(+) index for pretreatment plan assessment with emphasis on four-dimensional radiotherapy modalities.

Purpose: Radiation treatment modalities will continue to emerge that promise better clinical outcomes albeit technologically challenging to implement. An important question facing the radiotherapy community then is the need to justify the added technological effort for the clinical return. Mobile tumor radiotherapy is a typical example, where 4D tumor tracking radiotherapy (4DTRT) has been proposed over the simpler conventional modality for better results.

A method for deriving a 4D-interpolated balanced planning target for mobile tumor radiotherapy.

Purpose: Tumor control and normal tissue toxicity are strongly correlated to the tumor and normal tissue volumes receiving high prescribed dose levels in the course of radiotherapy. Planning target definition is, therefore, crucial to ensure favorable clinical outcomes. This is especially important for stereotactic body radiation therapy of lung cancers, characterized by high fractional doses and steep dose gradients.

Incorporating system latency associated with real-time target tracking radiotherapy in the dose prediction step.

System latency introduces geometric errors in the course of real-time target tracking radiotherapy. This effect can be minimized, for example by the use of predictive filters, but cannot be completely avoided. In this work, we present a convolution technique that can incorporate the effect as part of the treatment planning process.

A radiobiological analysis of the effect of 3D versus 4D image-based planning in lung cancer radiotherapy.

Dose distributions generated on a static anatomy may differ significantly from those delivered to temporally varying anatomy such as for abdominal and thoracic tumors, due largely in part to the unavoidable organ motion and deformation effects stemming from respiration. In this work, the degree of such variation for three treatment techniques, namely static conventional, gating and target tracking radiotherapy, was investigated. The actual delivered dose was approximated by planning all the phases of a 4DCT image set.

A prediction study on radiation-induced second malignancies for IMRT treatment delivery.

Low-level peripheral organ dose and its effect on second malignancies for patients undergoing radiation therapy have been reported in the literature. However, a comprehensive database outlining the treatment modalities, the tumor location, and a quantification of the overall relative risk of second malignancies is rather limited. In this work, we quantify the relative risks or percent likelihood of second malignancies for patients undergoing IMRT and conventional radiotherapy for four different tumor sites: breast, head and neck, lung, and prostate.

Measurement and comparison of skin dose for prostate and head-and-neck patients treated on various IMRT delivery systems.

Treatment planning systems inaccurately quantify dose deposited to the skin in the course of radiotherapy owing to their inability to properly account for all the surface dose contributing factors. In this work, we describe a technique for accurately measuring skin dose using ultra-thin thermoluminescent dosimeters and EBT gafchromic films. We investigated the variation in average skin dose for prostate and head-and-neck patients undergoing radiotherapy on three IMRT systems including serial/helical tomotherapy, and IMRT-step and shoot system.