Keith Wachowicz

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The work presented herein describes our methods and results for predicting, measuring and correcting geometric distortions in a 3 T clinical magnetic resonance (MR) scanner for the purpose of image guidance in radiation treatment planning. Geometric inaccuracies due to both inhomogeneities in the background field and nonlinearities in the applied gradients(More)
Reporter genes are useful scientific tools for analyzing promoter activity, transfection efficiency, and cell migration. The current study has validated the use of tyrosinase (involved in melanin production) as a dual reporter gene for magnetic resonance and photoacoustic imaging. MCF-7 cells expressing tyrosinase appear brown due to melanin. Magnetic(More)
The aim of this work is to demonstrate a complete, robust, and time-efficient method for distortion correction of magnetic resonance (MR) images. It is well known that MR images suffer from both machine-related spatial distortions [gradient nonlinearity and main field (B0) inhomogeneity] and patient-related spatial distortions (susceptibility and chemical(More)
The proton transverse-relaxation spectrum of peripheral nerve has been reported to consist of three components arising from microanatomical water compartments within the nerve. The component with the shortest decay time has been consistently seen to be a result of the myelin. In this study, experiments were performed to reveal the microanatomical sources of(More)
Interest has been growing in recent years in the development of radiation treatment planning (RTP) techniques based solely on Magnetic Resonance (MR) images. However, it is recognized that MR images suffer from scanner-related and object-induced distortions that may lead to an incorrect placement of anatomical structures. This subsequently may result in a(More)
Photoacoustic imaging is an emerging hybrid imaging technology capable of breaking through resolution limits of pure optical imaging technologies imposed by optical-scattering to provide fine-resolution optical contrast information in deep tissues. We demonstrate the ability of multi-wavelength photoacoustic imaging to estimate relative gene expression(More)
PURPOSE MR image geometric integrity is one of the building blocks of MRI-guided radiotherapy. In particular, tissue magnetic susceptibility-induced effects are patient-dependent and their behavior is difficult to assess and predict. In this study, the authors investigated in detail the characteristics of susceptibility (χ) distortions in the context of(More)
PURPOSE One of the recently published concepts that combine the soft-tissue imaging capabilities of MRI with external beam radiotherapy involves the rigid coupling of a linac with a rotating biplanar low-field MR imaging system. While such a system would prevent possible image distortion resulting from relative motion between the magnet and the linac, the(More)
PURPOSE DESPOT2 is a single-component T2 mapping technique based on bSSFP imaging. It has seen limited application because of banding artifacts and magnetization transfer (MT) effects. In this work, acquisitions are optimized to minimize MT effects, while exact and approximate analytical equations enable automatic correction of banding artifacts within the(More)
PURPOSE To develop a neural-network based autocontouring algorithm for intrafractional lung-tumor tracking using Linac-MR and evaluate its performance with phantom and in-vivo MR images. METHODS An autocontouring algorithm was developed to determine both the shape and position of a lung tumor from each intrafractional MR image. A pulse-coupled neural(More)