Papers by Charles Mistretta
Medical Imaging 2018: Image Processing
Biomedical Physics & Engineering Express
Journal of medical imaging (Bellingham, Wash.), 2017
A conventional three-dimensional/four-dimensional (3D/4D) digital subtraction angiogram (DSA) req... more A conventional three-dimensional/four-dimensional (3D/4D) digital subtraction angiogram (DSA) requires two rotational acquisitions (mask and fill) to compute the log-subtracted projections that are used to reconstruct a 3D/4D volume. Since all of the vascular information is contained in the fill acquisition, it is hypothesized that it is possible to reduce the x-ray dose of the mask acquisition substantially and still obtain subtracted projections adequate to reconstruct a 3D/4D volume with noise level comparable to a full-dose acquisition. A full-dose mask and fill acquisition were acquired from a clinical study to provide a known full-dose reference reconstruction. Gaussian noise was added to the mask acquisition to simulate a mask acquisition acquired at 10% relative dose. Noise in the low-dose mask projections was reduced with a weighted edge preserving filter designed to preserve bony edges while suppressing noise. Two-dimensional (2D) log-subtracted projections were computed f...
Investigative radiology, Nov 1, 2016
Time-of-arrival (TOA) maps can be derived from high-resolution 4-dimensional (4D) contrast-enhanc... more Time-of-arrival (TOA) maps can be derived from high-resolution 4-dimensional (4D) contrast-enhanced magnetic resonance angiography (MRA) data sets to provide a quantitative description of contrast material arrival time in each voxel. This information can further be processed to create a compressed time evolution curve that virtually shortens the contrast bolus (virtual bolus [VB]). The purpose of this project was to determine whether TOA-enhanced 4D MRA and/or VB imaging improve the display of contrast kinetics in patients with vascular disease. High-resolution whole-brain contrast-enhanced 4D MRA examinations with 1.2-second temporal reconstruction were acquired by using radial acquisition and highly constrained projection reconstruction (radial 4D contrast-enhanced HYPRFlow, abbreviated as HFMRA in this article) in 10 patients (8 patients with arteriovenous malformations [AVM], 1 patient with an arteriovenous fistula, and 1 patient with a high-grade intracranial stenosis). The TOA...
Radiology, Oct 1, 2002
To compare the diagnostic accuracy of time-resolved three-dimensional contrast material-enhanced ... more To compare the diagnostic accuracy of time-resolved three-dimensional contrast material-enhanced magnetic resonance (MR) angiography with that of conventional angiography for imaging the lower extremity vasculature. Sixty-nine patients who were evaluated for possible surgical intervention underwent conventional angiography (ie, digital subtraction angiography [DSA]) and contrast-enhanced MR angiography (ie, time-resolved imaging of contrast kinetics [TRICKS]). Two independent, blinded readers evaluated vessel stenosis and occlusion at DSA and MR angiographic image readings. Sensitivity, specificity, positive and negative predictive values, and area under the receiver operating characteristic curve were analyzed with repeated-measures analysis of variance. The Cohen kappa test was performed to examine interreader variability. At pooled readings, contrast-enhanced MR angiography had a sensitivity of 78% and a specificity of 98% for detection of occlusion. For detection of significant stenosis (at least one > or = 50% stenosis), sensitivity and specificity were 77% and 91%, respectively. Interreader agreement was high for detection of both occlusion (kappa = 0.76) and significant stenosis (kappa = 0.68). Sensitivity increased as MR angiographic technical parameters were optimized. When improvements resulting from coil type and injection protocol were considered, the sensitivity and specificity of TRICKS MR angiography were 89% and 97%, respectively, for occlusion detection and 87% and 90%, respectively, for significant stenosis detection. Contrast-enhanced TRICKS MR angiography is a feasible and minimally invasive means of acquiring angiograms of the peripheral vasculature with high sensitivity and specificity.
Society of Nuclear Medicine Annual Meeting Abstracts, May 1, 2008
ABSTRACT PURPOSE The lack of a ubiquitous and effective intra-procedural imaging technique is a c... more ABSTRACT PURPOSE The lack of a ubiquitous and effective intra-procedural imaging technique is a critical limitation to the field of thermal tumor ablation. Ultrasound imaging can be obscured by bubbles formed while heating, and contrast-enhanced CT is typically limited to one scan with a large injection of contrast material. The purpose of this study was to assess the feasibility of using small, periodic injections of iodinated contrast material over the course of the ablation with HYPR reconstruction to improve visualization of thermal ablation zone growth while reducing contrast material required. METHOD AND MATERIALS Female domestic swine were prepared and anesthetized. RF ablation was performed for 20 min using three internally-cooled, switched electrodes. During ablation, 15 ml iodinated contrast material (300 mg/ml) was delivered every 2 min and an abdominal CT collected at the pre-determined liver enhancement time following each injection (90 s) . The CT time-series was later reconstructed offline using HighlY-constrained backPRojection (HYPR). Conventional and HYPR-reconstructed images were compared for imaging contrast between the ablation zone and background liver and signal to noise ratios. Contrast uptake inside and outside the ablation zone was also quantified on excised specimens using microCT and gross imaging. RESULTS Periodic injections of contrast material allowed ablation zone growth to be visualized with 2 min temporal resolution. The ablation zone became obvious in 2-6 min with a cumulative contrast dose of 15-45 ml. Image quality improved with cumulative contrast dose. SNR in HYPR-reconstructed images was ~3-4x better than standard reconstructions and, importantly, HYPR improved signal contrast between the ablation zone and background liver by 2-3x. CONCLUSION Small, periodic doses of contrast material combined with HYPR reconstruction is a promising technique to monitor ablation zone growth intra-procedurally. Optimization of scanning protocol and injection dose and timing parameters should improve these results and further reduce the amount of contrast material and/or x-ray dose required. CLINICAL RELEVANCE/APPLICATION Effective intra-procedural imaging techniques that provide information about ablation zone growth, not just the resulting ablation, may increase treatment efficacy and safety.
American Journal of Neuroradiology, Apr 1, 2005
Three-dimensional phase-contrast (3DPC) is limited by long imaging times, limited coverage, flow ... more Three-dimensional phase-contrast (3DPC) is limited by long imaging times, limited coverage, flow artifacts, and the need to perform multiple additional 2D examinations (2DPC) to measure flow. A highly undersampled 3D radial acquisition (isotropic-voxel radial projection imaging [PCVIPR]) makes it possible to increase the product of volume coverage and spatial resolution by a factor of 30 for the same imaging time as conventional Cartesian 3DPC. This provides anatomic information over a large volume with high isotropic resolution and permits retrospective measurement of average flow rates throughout the volume. METHODS: PCVIPR acquires a reference and three flow-encoded acquisitions for each VIPR projection. Complex difference images were formed by combining information from all flow directions. Following retrospective definition of planes perpendicular to selected vessels, volume flow rates were determined by using phase-difference information. The accuracy of average flow measurement was investigated in a phantom and in six volunteers. Anatomic PCVIPR images acquired in three patients and three volunteers by using a 384 3 matrix were compared with conventional Cartesian 3DPC. RESULTS: The flow validation produced R 2 ؍ 0.99 in vitro and R 2 ؍ 0.97 in vivo. PCVIPR produced minimal streak and pulsatile flow artifacts. PCVIPR produced far higher resolution and volume coverage in comparable imaging times. The highest acceleration factors relative to 3DPC were achieved by using gadolinium-contrast material. Ultimately, acceleration factors are limited by signal-to-noise ratio. CONCLUSION: PCVIPR rapidly provides isotropic high-resolution angiographic images and permits retrospective measurement of average flow rate throughout the volume without the need to prescribe multiple 2D acquisition planes.
Proceedings of Spie the International Society For Optical Engineering, Mar 1, 2006
ABSTRACT X-ray cone-beam computed tomography (CBCT) is of importance in image-guided intervention... more ABSTRACT X-ray cone-beam computed tomography (CBCT) is of importance in image-guided intervention (IGI) and image-guided radiation therapy (IGRT). In this paper, we present a cone-beam CT data acquisition system using a GE INNOVA 4100 (GE Healthcare Technologies, Waukesha, Wisconsin) clinical system. This new cone-beam data acquisition mode was developed for research purposes without interfering with any clinical function of the system. It provides us a basic imaging pipeline for more advanced cone-beam data acquisition methods. It also provides us a platform to study and overcome the limiting factors such as cone-beam artifacts and limiting low contrast resolution in current C-arm based cone-beam CT systems. A geometrical calibration method was developed to experimentally determine parameters of the scanning geometry to correct the image reconstruction for geometric non-idealities. Extensive phantom studies and some small animal studies have been conducted to evaluate the performance of our cone-beam CT data acquisition system.
Radiology, Dec 1, 2007
To prospectively evaluate the hypothesis that retrospectively electrocardiographically gated phas... more To prospectively evaluate the hypothesis that retrospectively electrocardiographically gated phase contrast with vastly undersampled isotropic projection reconstruction (VIPR) magnetic resonance (MR) angiography data sets can be used to measure transstenotic pressure gradients (TSPGs) in vivo. TSPGs were calculated by using phase-contrast VIPR MR angiography data sets; measurements obtained with a pair of endovascular pressure-sensing guidewires served as a reference standard. With institutional animal care and use committee approval, 12 swine underwent surgical creation of stenoses at the left common carotid, right renal, and left external iliac arteries. The percentage stenosis and reference diameter of the lesions were calculated from conventional digital subtraction angiograms. A pair of 0.014-inch pressure-sensing guidewires was placed in tandem; sensors 1 cm distal and 1 cm proximal to the lesions measured the mean TSPG. Phase-contrast VIPR phase difference images were analyzed with an iterative technique based on the Navier-Stokes equations to determine the mean TSPG. Pearson product correlation was calculated, and Bland-Altman plots were generated to determine the degree of agreement between the two methods. Twenty-one lesions (12 carotid, nine iliac; mean percentage stenosis, 52.4%; range, 29.8%-64.9%; mean reference diameter, 3.4 mm; range, 2.4-5.6 mm) were analyzed. For carotid and iliac lesions, phase-contrast VIPR and guidewire TSPG measurements were highly correlated (r = 0.952, P < .001). Bland-Altman plots (bias, 0.86 mm Hg; limits of agreement: -6.17 to 7.88 mm Hg) showed good agreement. Measurements in renal lesions (n = 9) were poorly correlated (r = -0.081, P = .835) and were excluded because of image degradation secondary to respiratory motion. Phase-contrast MR angiography with VIPR enables reliable measurements of TSPG in carotid and iliac lesions that are comparable to those obtained with endovascular pressure-sensing guidewires. However, further work to compensate for respiratory motion is required to extend this technique to the renal arteries.
Contrast Media Mol Imaging, 2009
Medical Imaging 2016: Physics of Medical Imaging, 2016
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Papers by Charles Mistretta