Papers by Keyvan Farahani
Journal of Medical Imaging, 2015
Medical Imaging 1999: Physics of Medical Imaging, 1999
Image quality characteristics of spiral CT are similar to conventional CT except for image noise ... more Image quality characteristics of spiral CT are similar to conventional CT except for image noise and slice sensitivity profile. While these factors have been studied for high contrast, low contrast detectability in spiral CT has not yet been fully explored. Low contrast simulations that have been performed demonstrate the behavior of contrast sensitivity as related to the parameters of pitch,
Translational oncology, 2014
The purpose of this editorial is to provide a brief history of National Institutes of Health Nati... more The purpose of this editorial is to provide a brief history of National Institutes of Health National Cancer Institute (NCI) workshops as related to quantitative imaging within the oncology setting. The editorial will then focus on the recently supported NCI initiatives, including the Quantitative Imaging Network (QIN) initiative and its organizational structure, including planned research goals and deliverables. The publications in this issue of Translational Oncology come from many of the current members of this QIN research network.
Neurosurgery, 2000
We describe the development of an alternative approach to intraoperative magnetic resonance imagi... more We describe the development of an alternative approach to intraoperative magnetic resonance imaging (iMR)-guided neurosurgery and report our initial experience with 22 craniotomies and 16 brain biopsies. The advantages and disadvantages of each approach are examined. An iMR suite houses a 0.2-T open configuration system (Siemens Medical Systems, Erlangen, Germany) and is equipped with anesthetic gases and a magnetic resonance imaging (MRI)-compatible anesthesia machine and monitor. Standard operating instruments and equipment were tested for safety and compatibility in the magnetic fringe fields surrounding the open MRI system. We then performed brain biopsies and craniotomies in the iMR suite. Standard operating equipment functioned properly in the 0.5- to 10-mT zone and was not affected by the magnet's attractive force. Twenty-two craniotomies and 16 brain biopsies were performed in the interventional suite, using serial intraoperative MRI guidance, without injury to patients ...
Ophthalmic plastic and reconstructive surgery, 1994
Although the histologic anatomy of the lower eyelid retractors is well defined, the physiology of... more Although the histologic anatomy of the lower eyelid retractors is well defined, the physiology of the lower retractors has been determined only by interference based on anatomic and clinical findings. In this study, in five normal subjects we investigated the physiology of the lower eyelid retractors utilizing dynamic high resolution magnetic resonance imaging (MRI) with a custom designed surface coil. Measurements of the excursion of the cornea, lower eyelid margin, and anterior edge of the inferior oblique muscle were made from scans taken in upgaze and downgaze. We found that the corneal movement was substantially greater than the movement of the eyelid margin, a finding that can readily be made clinically. A more important result was that the movement of the eyelid margin and the movement of the inferior oblique margin were similar in all cases. Thus, the length of the anterior capsulopalpebral fascia between the tarsus and inferior oblique muscle remains constant in downgaze, a...
AJNR. American journal of neuroradiology, 1995
To evaluate the feasibility of a technique of MR-guided stereotactic radio frequency ablation, wh... more To evaluate the feasibility of a technique of MR-guided stereotactic radio frequency ablation, which was developed as a minimally invasive treatment for brain tumors, and to determine MR characteristics and sequential evolution of radio frequency lesions created to ablate brain tumors. Fourteen lesions in 12 patients with primary and metastatic brain tumors were treated with this technique and followed for up to 10 months. The stereotactic coordinates of the tumor and the angle of the radio frequency probe were calculated on MR imaging. The radio frequency lesion was generated in the awake patient by increasing the temperature to 80 degrees C within the tumor for 1 minute. This was repeated until the entire tumor volume was destroyed. MR imaging was performed before, during, and immediately after the radio frequency procedure, and sequential MR was obtained during clinical follow-up. MR imaging clearly showed well-defined radio frequency lesions and provided feedback for treatment p...
Radiology, 1995
To determine the natural time course of development of hyperacute thermal lesions in the brain. T... more To determine the natural time course of development of hyperacute thermal lesions in the brain. Ten interstitial lesions were created in five rabbit brains with a radio-frequency probe; an electrode-tip temperature of 80 degrees C was maintained for 60 seconds. Continuous fast spin-echo magnetic resonance (MR) imaging was used to follow lesion development for a minimum of 30 minutes. Temporal variations in lesion size and signal intensity were examined. Findings in final images were correlated with histologic findings. Images demonstrated a focal hyperintense zone, which developed into an expanding ring of edema surrounding a necrotic center in about 10 minutes. Quantitative analysis revealed a 23% +/- 6 (standard deviation) increase in average signal intensity of the edema layer and a 152% +/- 41 increase in overall lesion size. Full development of a thermal lesion is delayed for a period of minutes. Clinical implications of this effect should be considered when MR imaging-guided t...
Medical Imaging 2001: Visualization, Display, and Image-Guided Procedures, 2001
ABSTRACT MR-guided neurosurgery may offer greater accuracy in surgical localization and resection... more ABSTRACT MR-guided neurosurgery may offer greater accuracy in surgical localization and resection of brain tumors. Proper utilization of MRI for surgical guidance requires real-time consultation with a neuroradiologist during typically lengthy procedures. We sought to build a system that allows fast and efficient tele-radiologic consultation in the MR- surgical suite. We modeled the imaging tasks and data flow for representative MR-guided neurosurgical procedures. Customized viewing modes, which associate specific data and tasks, were designed accordingly. We implemented application sharing in order to allow teleconsultation between the surgeon and a remotely located radiologist during a case. The system described here provides an effective and efficient method for expert tele-consultation during MR-guided neurosurgery.
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Papers by Keyvan Farahani