Sanaz Arkani

University of Chicago, Chicago, Illinois, United States

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Publications (7)8.51 Total impact

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    ABSTRACT: To determine relative diagnostic value of MR diffusion and perfusion parameters in detection of active small bowel inflammation in patients with Crohn's disease (CD). We reviewed 18 patients with active CD of terminal ileum (TI) who underwent MR enterography (MRE; including dynamic contrast enhanced MRI and diffusion-weighted MRI). Conventional MRI findings of TI were recorded. Regions of interest were drawn over TI and normal ileum to calculate apparent diffusion coefficient (ADC), the volume transfer constant (K(trans)) and the contrast media distribution volume (v(e)). Receiver operating characteristic analysis was used to determine their diagnostic performance. Among conventional MR findings, mural thickening and increased enhancement were present in all actively inflamed small bowel. K(trans), v(e), and ADC values differed significantly between actively inflamed TI and normal ileum (0.92 s(-1) versus 0.36 s(-1); 0.31 versus 0.15 ± 0.08; 0.00198 mm(2)/s versus 0.00311 mm(2)/s; P < 0.001). Area under the curve (AUC) for K(trans), v(e), and ADC values ranged from 0.88 to 0.92 for detection of active inflammation. Combining K(trans) and ADC data provided an AUC value of 0.95. Dynamic contrast-enhanced MRI (DCE-MRI) and diffusion-weighted imaging (DWI) provide quantitative measures of small bowel inflammation that can differentiate actively inflamed small bowel segments from normal small bowel in CD. DWI provides better sensitivity compared with DCE-MRI and combination of ADC and K(trans) parameters for analysis can potentially improve specificity.
    No preview · Article · Mar 2011 · Journal of Magnetic Resonance Imaging
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    ABSTRACT: The purpose of this study was to test whether an empirical mathematical model (EMM) of dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI) can distinguish between benign and malignant breast lesions. A modified clinical protocol was used to improve the sampling of contrast medium uptake and washout. T(1)-weighted DCE magnetic resonance images were acquired at 1.5 T for 22 patients before and after injection of Gd-DTPA. Contrast medium concentration as a function of time was calculated over a small region of interest containing the most rapidly enhancing pixels. Then the curves were fitted with the EMM, which accurately described contrast agent uptake and washout. Results demonstrate that benign lesions had uptake (P<2.0 x 10(-5)) and washout (P<.01) rates of contrast agent significantly slower than those of malignant lesions. In addition, secondary diagnostic parameters, such as time to peak of enhancement, enhancement slope at the peak and curvature at the peak of enhancement, were derived mathematically from the EMM and expressed in terms of primary parameters. These diagnostic parameters also effectively differentiated benign from malignant lesions (P<.03). Conventional analysis of contrast medium dynamics, using a subjective classification of contrast medium kinetics in lesions as "washout," "plateau" or "persistent" (sensitivity=83%, specificity=50% and diagnostic accuracy=72%), was less effective than the EMM (sensitivity=100%, specificity=83% and diagnostic accuracy=94%) for the separation of benign and malignant lesions. In summary, the present research suggests that the EMM is a promising alternative method for evaluating DCE-MRI data with improved diagnostic accuracy.
    Full-text · Article · Jul 2007 · Magnetic Resonance Imaging
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    ABSTRACT: To compare conventional fat-suppressed MR images of the breast to images derived from high spectral and spatial resolution MR data. Image quality and the level of fat suppression are compared qualitatively and quantitatively. Women with suspicious breast lesions found on X-ray mammography were imaged on 1.5 Tesla GE SIGNA scanners. High spectral and spatial resolution (HiSS) data were acquired using echo-planar spectroscopic imaging. Images with intensity proportional to the water signal peak height in each voxel were synthesized. Conventional fat-suppressed images were acquired using a frequency selective inversion method. The experimental (HiSS) and conventional images were compared by experienced radiologists to evaluate the quality of fat suppression. In addition, fat suppression and image quality were evaluated quantitatively. Fat suppression, tumor edge delineation, lesion conspicuity, and image texture were improved in the peak height images derived from HiSS data. The results demonstrate that the water peak height images obtained from HiSS data potentially could improve the quality of fat suppression, detection and diagnosis of breast cancer. HiSS allowed detection of lesions and evaluation of lesion morphology prior to contrast media injection. J. Magn. Reson. Imaging 2006. (c) 2006 Wiley-Liss, Inc.
    No preview · Article · Dec 2006 · Journal of Magnetic Resonance Imaging
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    ABSTRACT: PURPOSE A transgenic mouse model was serially imaged using a variety of MRI pulse sequences to track the development of prostate cancer. In this model cancer occurs spontaneously and follows a course that is similar to that of human prostate cancer. Imaging of non-invasively induced prostate cancers can provide critical information about its natural history and the effect of experimental therapies. METHOD AND MATERIALS A transgenic mouse model for prostate cancer (SV40 TAg, n=3) was imaged serially at 3 months, 5 months, and beyond - until significant tumor growth was found. The same slices through each mouse prostate gland were imaged at each time point in a small bore 4.7T scanner using gradient echo (GE) imaging, spin echo (SE) imaging, and high resolution EPSI (echo planar spectroscopic imaging). Images were collected with ~117 microns in-plane resolution over 0.5mm slices; EPSI images had a spectral resolution of ~3Hz. The EPSI pulse sequence provided a detailed spectrum of water and fat associated with each image. Water resonance peak height images were produced from EPSI datasets. RESULTS In SE images it is difficult to discriminate between the prostate and the urinary bladder whereas in the GE images there is significant loss of signal at this same junction. PH images showed clear contrast differences between the prostate and the bladder with a much more defined border between the two. PH images showed greater texture across the prostate compared with GE and SE images and had a higher signal to noise ratio. CONCLUSION High spectral and spatial resolution datasets collected with EPSI provided images that were superior to those produced from more conventional non-spectroscopic imaging techniques. Further, because in spectroscopic imaging techniques a water spectrum is produced for each tiny voxel imaged, the details of these spectra can be utilized to produce a variety of images with different contrasts. These novel contrasts provide a unique view of the development of prostate cancer in a transgenic mouse model. CLINICAL RELEVANCE/APPLICATION The results obtained in the mouse model suggest that high resolution EPSI could have clinical applications for detecting and monitoring suspicious lesions in the prostate.
    No preview · Conference Paper · Nov 2006
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    ABSTRACT: PURPOSE To perform a systematic evaluation of the kinetic and morphologic characteristics of 82 pure DCIS lesions on DCEMRI and to classify these characteristics by nuclear grade and x-ray mammographic presentation. METHOD AND MATERIALS 80 patients with 82 histologically proven pure DCIS lesions were selected for review. Nuclear grade classification: 14 low, 25 intermediate and 37 high grade pure DCIS lesions with 6 unclassified. The mammographic findings of 63 lesions were classified as: pleomorphic or linear calcifications (n=32), fine or punctate calcifications (n=14), mass (n=8) and occult (n=9). MR protocol:1 pre and 5 post-contrast 3D SPGR images acquired in the coronal plane with 68 s time resolution. Two experienced radiologists generated signal intensity vs. time curves by manually tracing a region of interest around the most enhancing part of the lesion. Analysis of lesion morphology and kinetic curve shape was made according to the BI-RADS lexicon. Several quantitative parameters were derived from the kinetic curves: initial enhancement percentage (E1), time to peak enhancement (Tpeak) and washout ratio (W). RESULTS The morphology of pure DCIS lesions on MRI was predominantly non-mass, clumped or heterogeneous enhancement in a segmental or linear distribution. There was no correlation between lesion morphology and nuclear grade or mammographic presentation. 45% and 27% of lesions qualitatively showed washout and plateau curves, respectively. The average kinetic parameters were: E1=201 %, Tpeak=230s, and W=1.08 suggesting very slow washout. There was no statistically significant difference in enhancement kinetics across nuclear grade. Lesions with mass-like appearance on x-ray mammography or with pleomorphic calcifications had more suspicious kinetics and strong washout. CONCLUSION Pure DCIS lesions display a slow initial rise and a variety of washout characteristics. Enhancement kinetics correlated with x-ray mammographic appearance rather than nuclear grade. Recognition of the unique morphology and kinetics of pure DCIS may aid in improving the detection of early breast cancer. CLINICAL RELEVANCE/APPLICATION Recognition of the unique morphology and kinetics of pure DCIS may aid in improving the detection of early breast cancer.
    No preview · Conference Paper · Nov 2006
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    ABSTRACT: PURPOSE To compare the qualitative and semi-quantitative enhancement characteristics and morphologic appearance of malignant breast lesions by histologic tumor type and grade. METHOD AND MATERIALS 324 patients with 362 malignant breast lesions were selected in a retrospective review of 1300 examinations performed at our institution between May 1 2002 and Decemebr 31 2004. All patients were imaged with a bilateral 3D dynamic sequence prior to percutaneous or excisional biopsy. Analysis of kinetic and morphologic features of the lesions was performed by two experienced radiologists. Signal intensity vs. time curves following contrast agent injection were obtained by using operator defined region of interest measurements. In addition to a qualitative assessment of the shape of the curve (washout, plateau or persistent), the initial enhancement percentage at 68 s (E_initial), and the time to peak enhancement (T_peak) were also measured. Morphologic assessment of the shape, margin, enhancement pattern and lesion size was recorded. RESULTS Distribution of lesion histology was invasive duct carcinoma (IDC) 71% (grade I 13%, grade II 45%, grade III 34%, unclassified 8%), ductal carcinoma in situ (DCIS) 23% and invasive lobular carcinoma (ILC) 6%. Washout curves were present in 65% of lesions (88% IDC, 40% DCIS and 46% ILC). T_peak was shortest for IDC lesions at 131 +/- 90 s, and longest for ILC lesions at 270 +/- 112 s. E_initial was lowest for DCIS and ILC lesions at 155 +/-94% compared to malignant lesions overall at 273+/-152 %. Mass morphology was found in 76% IDC, 16% DCIS and 55% ILC. Non-mass-like enhancement was found in 33% IDC, 79% DCIS and 45% ILC. A focus was the presentation in 1% IDC and 4% DCIS lesions. T_peak decreased while E_initial and washout increased progressively for IDC lesions, by increasing tumor grade. CONCLUSION The characteristics of DCIS and ILC lesions were significantly different than IDC lesions for all measured parameters (p<0.001). The findings of decreased signal intensity and preponderance of non-mass-like enhancement may contribute to perceptual difficulties in the diagnosis of DCIS and ILC at MR imaging.
    No preview · Conference Paper · Nov 2005
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    ABSTRACT: PURPOSE/AIM Benign breast lesions are frequently encountered on breast MRI. We conducted a retrospective review of 107 lesions detected by MRI and subsequently shown to be benign at histological evaluation. This exhibit provides examples of the usual variety of benign lesions commonly seen on MRI and demonstrates the typical findings. CONTENT ORGANIZATION The study includes 35 (33%) fibroadenomata, 25 (23%) papillomata, 41 (38%) fibrocystic change, 4 (4%) fat necrosis and 2 (2%) lymph nodes. Detailed analysis of both the morphologic and kinetic data and size of each lesion, grouped by histology, will be presented. The imaging component includes examples of each histologic type, and examples of the MR imaging findings. Guidelines for accurate lesion description, according to the BI-RADS lexicon, are provided. SUMMARY Identification and classification of benign lesions found at MR imaging often pose diagnostic problems for the radiologist. Distinct differences in the kinetic and morphologic MR findings associated with various benign histologies will be demonstrated. Our hope is that this exhibit will improve radiologists’ confidence level in the diagnosis of benign lesions encountered on breast MR imaging.
    No preview · Conference Paper ·