Sara St James

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For the radiation treatment of lung cancer patients, four-dimensional computed tomography (4D-CT) is a common practice used clinically to image tumor motion and subsequently determine the internal target volume (ITV) from the maximum intensity projection (MIP) images. ITV, which is derived from short pre-treatment 4D-CT scan (<6 s per couch position), may(More)
UNLABELLED Detectors with depth-encoding allow a PET scanner to simultaneously achieve high sensitivity and high spatial resolution. METHODS A prototype PET scanner, consisting of depth-encoding detectors constructed by dual-ended readout of lutetium oxyorthosilicate (LSO) arrays with 2 position-sensitive avalanche photodiodes (PSAPDs), was developed. The(More)
Improvements to current small animal PET scanners can be made by improving the sensitivity and the spatial resolution of the scanner. In the past, efforts have been made to minimize the crystal dimensions in the axial and transaxial directions to improve the spatial resolution and to increase the crystal length to improve the sensitivity of the scanner. We(More)
Digital phantoms continue to play a significant role in modeling and characterizing medical imaging. The currently available XCAT phantom incorporates both the flexibility of mathematical phantoms and the realistic nature of voxelized phantoms. This phantom generates images based on a regular breathing pattern and can include arbitrary lung tumor(More)
PURPOSE To quantitatively assess the impact of real time tumor tracking on the delivered dose during thoracic radiotherapy in the presence of realistic breathing. METHODS The 4D XCAT digital torso phantom was used in this study. The phantom was created with irregular breathing motion based on observed patient tumor motion. A locally mass-conserving(More)
PURPOSE To develop a method of verifying delivered dose based on time-varying 3D treatment images estimated from single kV projection images and a 4DCT-based patient-specific motion model. METHODS Delivered dose calculation is performed in two steps. In the first step 3D fluoroscopic (time-varying) images are generated from single 2D kV projection images.(More)
Many laboratories develop depth-encoding detectors to improve the trade-off between spatial resolution and sensitivity in positron emission tomography (PET) scanners. One challenge in implementing these detectors is the need to calibrate the depth of interaction (DOI) response for the large numbers of detector elements in a scanner. In this work, we(More)
PURPOSE The XCAT phantom is a realistic 4D digital torso phantom that is widely used in imaging and therapy research. However, lung mass is not conserved between respiratory phases of the phantom, making detailed dosimetric simulations unphysical. A framework is presented for enforcing local mass conservation in the XCAT lung and is combined with a dose(More)
PURPOSE The purpose of this work is to present a framework to evaluate the accuracy of four-dimensional treatment planning in external beam radiation therapy using measured patient data and digital phantoms. METHODS To accomplish this, 4D digital phantoms of two model patients were created using measured patient lung tumor positions. These phantoms were(More)
PURPOSE The internal target volume (ITV) accounts for uncertainties in tumor position and shape and is defined from images acquired with 4DCT. In this work, the locations of gold fiducial markers implanted in lung tumors of seven patients are used to represent tumor motion and investigate the role of the CT scanner geometry and scan duration on ITV(More)