Laura M. Fayad

Contrast enhancement by multi-scale adaptive histogram equalization

An approach for contrast enhancement utilizing multi-scale analysis is introduced. Sub-band coefficients were modified by the method of adaptive histogram equalization. To achieve optimal contrast enhancement, the sizes of sub-regions were chosen with consideration to the support of the analysis filters. The enhanced images provided subtle details of tissues that are only visible with tedious contrast/brightness windowing methods currently used in clinical reading. We present results on chest CT data, which shows significant improvement over existing state-of-the-art methods: unsharp masking, adaptive histogram equalization (AHE), and the contrast limited adaptive histogram equalization (CLAHE). A systematic study on 109 clinical chest CT images by three radiologists suggests the promise of this method in terms of both interpretation time and diagnostic performance on different pathological cases. In addition, radiologists observed no noticeable artifacts or amplification of noise that usually appears in traditional adaptive histogram equalization and its variations.

Can MR Imaging Be Used to Predict Tumor Grade in Soft-Tissue Sarcoma?

PURPOSEnTo identify the magnetic resonance (MR) imaging features that can be used to differentiate high-grade from low-grade soft-tissue sarcoma (STS).nnnMATERIALS AND METHODSnInstitutional review board approval was obtained, and informed consent was waived. Patients with STS who had undergone MR imaging with T1-weighted, T2-weighted, and contrast material-enhanced sequences prior to neoadjuvant therapy and surgery were included retrospectively. Tumor grade (grades 1-3) was recorded from the histologic specimen for each STS. Images were evaluated by two observers for tumor size and MR features (signal intensity, heterogeneity, margin, and perilesional characteristics) on images obtained with each sequence. Descriptive statistics for low-grade (grade 1) and high-grade (grades 2 and 3) STS were recorded, and the accuracy of individual features was determined. A multivariate logistic regression model was developed to identify features that were independently predictive of a high-grade tumor.nnnRESULTSnNinety-five patients (48 female [mean age, 55.8 years; age range, 7-96 years] and 47 male [mean age, 55.3 years; age range, 1-87 years]) with STS (16 patients with grade 1 STS, 34 patients with grade 2 STS, and 45 patients with grade 3 STS) were included. High-grade STS differed from low-grade STS in size (>5 cm, P = .004), tumor margin (partly or poorly defined margin on T1-weighted images, P = .002; with other sequences, P < .001), internal signal intensity composition (heterogeneous signal intensity on T2-weighted images, P = .009), and peritumoral characteristics (peritumoral high signal intensity on T2-weighted images, P = .025; peritumoral enhancement on contrast-enhanced T1-weighted images, P < .001). The logistic regression model showed that peritumoral contrast enhancement is the strongest independent indicator of high-grade status (odds ratio, 13.6; 95% confidence interval: 2.9, 64.6).nnnCONCLUSIONnAmong several MR imaging features that aid in the discrimination of high-grade from low-grade sarcomas, the presence of peritumoral contrast enhancement is a feature that may be solely used to diagnose high-grade STS.

Multiparametric Assessment of Treatment Response in High-Grade Soft-Tissue Sarcomas with Anatomic and Functional MR Imaging Sequences

PURPOSEnTo determine the added value of quantitative diffusion-weighted and dynamic contrast material-enhanced imaging to conventional magnetic resonance (MR) imaging for assessment of the response of soft-tissue sarcomas to neoadjuvant therapy.nnnMATERIALS AND METHODSnMR imaging examinations in 23 patients with soft-tissue sarcomas who had undergone neoadjuvant therapy were reviewed by two readers during three sessions: conventional imaging (T1-weighted, fluid-sensitive, static postcontrast T1-weighted), conventional with diffusion-weighted imaging, and conventional with diffusion-weighted and dynamic contrast-enhanced imaging. For each session, readers recorded imaging features and determined treatment response. Interobserver agreement was assessed and receiver operating characteristic analysis was performed to evaluate the accuracy of each session for determining response by using results of the histologic analysis as the reference standard. Good response was defined as less than or equal to 5% residual viable tumor.nnnRESULTSnOf the 23 sarcomas, four (17.4%) showed good histologic response (three of four with >95% granulation tissue and <5% necrosis, one of four with 95% necrosis and <5% viable tumor) and 19 (82.6%) showed poor response (viable tumor range, 10%-100%). Interobserver agreement was substantial or excellent for imaging features in all sequences (k = 0.789-1.000). Receiver operating characteristic analysis showed an increase in diagnostic performance with the addition of diffusion-weighted and dynamic contrast-enhanced MR imaging for prediction of response compared with that for conventional imaging alone (areas under the curve, 0.500, 0.676, 0.821 [reader 1] and 0.506, 0.704, 0.833 [reader 2], respectively).nnnCONCLUSIONnAdding functional sequences to the conventional MR imaging protocol increases the sensitivity of MR imaging for determining treatment response in soft-tissue sarcomas.

Detection and characterization of tendon abnormalities with multidetector computed tomography.

Abstract With recent advances in multidetector computed tomography (MDCT) acquisition and reconstruction options, MDCT can now be used successfully for evaluating tendon abnormalities. In this article, MDCT protocol optimization for the imaging of tendons is underscored, and applications of MDCT for assessing tendon pathology are highlighted. Although our retrospective experience of CT imaging with 2-dimensional multiplanar reconstructions and 3-dimensional postprocessing techniques is reviewed, potential applications for newer CT technologies, including dual-energy CT and 4-dimensional CT imaging of the peripheral tendons, are also discussed.

Chemical shift imaging: preliminary experience as an alternative sequence for defining the extent of a bone tumor.

OBJECTIVEnTo investigate chemical shift imaging (CSI) with in-phase and opposed-phase (OP) gradient-echo sequences as an alternative sequence to spin-echo T1 imaging for defining intra-medullary skeletal tumor extent.nnnMETHODS AND MATERIALSnThis retrospective HIPAA-compliant study was approved by our institutional institutional review board (IRB). Twenty-three subjects with histologically-proven tumors (17 appendicular, 6 axial) underwent magnetic resonance imaging (MRI) with T1-weighted spin echo (T1SE), fluid-sensitive, CSI, and contrast-enhanced T1 sequences. One observer recorded intra-medullary tumor extent (millimeters), with 153 total measurements on each sequence. Red marrow grade [0 (none), 1 (<50%), 2 (50-75%) and 3 (>75%)] in each bone was recorded. Tumor extent on different sequences was compared (Students t-test); the impact of red marrow grade on measurements was assessed (Spearmans correlation coefficient).nnnRESULTSnThere was good agreement between measurements of tumor extent on T1SE and CSI sequences in all cases (T1SE-CSI measurement difference range 0-13.2 mm, P>0.05). Measurements from other sequences were significantly different from those of T1SE (P<0.05). As red marrow grade in the bone increased, a significant increase in measurement difference obtained on T1SE and CSI sequences was observed (P<0.001).nnnCONCLUSIONSnCSI is a potential alternative technique to T1SE imaging for defining the intra-medullary extent of a bone tumor, possibly especially useful in regions with abundant red marrow.nnnADVANCE IN KNOWLEDGEnCSI could be an alternative technique to T1SE imaging for defining the intra-medullary extent of bone tumor by abundant red marrow in the surrounding bone.

Advanced Imaging of the Scapula: What Every Radiologist Needs to Know.

The scapula plays a central role in shoulder motion and stability. A wide variety of anatomic variants as well as traumatic, neoplastic, and infectious pathologies can involve the scapula. Detection of scapular lesions using radiography can be challenging because of the obscuration by the overlying structures or incomplete imaging during shoulder magnetic resonance imaging or computed tomography examinations. Familiarity with imaging characteristics of these abnormalities will allow radiologists to better diagnose and characterize scapular disorders.

Multiparametric MR Imaging of Benign and Malignant Bone Lesions

Although radiography is a first-line test for the assessment of bone lesions, MR imaging is needed for defining the extent of a bone tumor. In addition, MR imaging provides features and metrics for the characterization of bone lesions as well as for the evaluation a tumor following treatment. There are several noncontrast and contrast-enhanced sequences available for clinical use that collectively provide valuable information for tumor evaluation, and include conventional T1-weighted imaging, fluid-sensitive sequences, chemical shift imaging, and diffusion-weighted imaging with ADC mapping, as well as postcontrast sequences, including static postcontrast imaging and dynamic contrast-enhanced MR imaging.