Suresh K. Mukherji

Diffusion Tensor Imaging of the Brain. Review of clinical applications

We review the theoretical background to diffusion tensor imaging (DTI) and some of its commoner clinical applications, such as cerebral ischemia, brain maturation and traumatic brain injury. We also review its potential use in diseases such as epilepsy, multiple sclerosis, and Alzheimer’s disease. The value of DTI in the investigation of brain tumors and metabolic disorders is assessed.

Clinical applications of diffusion tensor imaging.

Directionally‐ordered cellular structures that impede water motion, such as cell membranes and myelin, result in water mobility that is also directionally‐dependent. Diffusion tensor imaging characterizes this directional nature of water motion and thereby provides structural information that cannot be obtained by standard anatomic imaging. Quantitative apparent diffusion coefficients and fractional anisotropy have emerged from being primarily research tools to methods enabling valuable clinical applications. This review describes the clinical utility of diffusion tensor imaging, including the basic principles of the technique, acquisition, data analysis, and the major clinical applications. J. Magn. Reson. Imaging 2004;19:6–18.

Preradiotherapy computed tomography as a predictor of local control in supraglottic carcinoma

PURPOSE To determine the utility of pretreatment computed tomography (CT) for predicting primary site control in patients with supraglottic squamous cell carcinoma (SCC) treated with definitive radiotherapy (RT). MATERIALS AND METHODS Pretreatment CT studies in 63 patients were reviewed. Minimum length of follow-up was 2 years. Local recurrence and treatment complications resulting in permanent loss of laryngeal function were documented. Tumor volume was calculated using a computer digitizer, and pre-epiglottic space (PES) spread was estimated. The data were analyzed using a combination of Fishers exact test, logistic regression modeling, and multivariate analyses. Five-year local control rates were calculated using the product-limit method. RESULTS Local control rates were inversely and roughly linearly related to tumor volume, although there seemed to be a threshold volume at which primary site prognosis diminished. Local control was 89% in tumors less than 6 cm3 and 52% when volumes were > or =6 cm3 (P = .0012). The likelihood of maintaining laryngeal function also varied with tumor volume: 89% for tumors less than 6 cm3 and 40% for tumors > or =6 cm3 (P = .00004). Pre-epiglottic space involvement by tumor of > or =25% was associated with a reduced chance of saving the larynx (P = .0076). Multivariate analyses revealed that only tumor volume independently altered these end points. CONCLUSION Pretreatment CT measurements of tumor volume permits stratification of patients with supraglottic SCC treated with RT alone (which allows preservation of laryngeal function) into groups in which local control is more likely and less likely. Pre-epiglottic space spread is not a contraindication to using RT as the primary treatment for supraglottic SCC.

Differentiation of benign and malignant pathology in the head and neck using 3T apparent diffusion coefficient values: early experience.

BACKGROUND AND PURPOSE: The purpose of this work was to study differences in apparent diffusion coefficient (ADC) values between benign and malignant head and neck lesions at 3T field strength imaging. MATERIALS AND METHODS: Our study population in this retrospective study was derived from the patient population who had undergone routine neck 3T MR imaging (for clinical indications) from December 2005 to December 2006. There were 33 patients identified: 17 with benign and 16 with malignant pathologies. In all of the subjects, conventional MR imaging sequences were performed apart from diffusion-weighted sequences. The mean ADC values in the benign and malignant groups were compared using an unpaired t test with unequal variance with a P < 0.05 considered statistically significant. RESULTS: There was a statistically significant difference (P = .004) between the mean ADC values (in 10−3 mm2/s) in the benign and malignant lesions (1.505 ± 0.487; 95% confidence interval, 1.305–1.706, and 1.071 ± 0.293; 95% confidence interval, 0.864–1.277, respectively). There were 2 malignant lesions with ADC values higher than 1.3 × 10−3 mm2/s and 5 benign lesions with ADC values less than 1.3 × 10−3 mm2/s. The lack of overlap of ADC values within 95% confidence limits suggests that a 3T ADC value of 1.3 × 10−3 mm2/s may be the threshold value for differentiation between benign and malignant head and neck lesions. CONCLUSION: ADC values of benign and malignant neck pathologies are significantly different at 3T imaging, though larger studies are required to establish threshold ADC values that can applied in daily clinical practice.

Diffusion MRI: A new strategy for assessment of cancer therapeutic efficacy

The use of anatomical imaging in clinical oncology practice traditionally relies on comparison of patient scans acquired before and following completion of therapeutic intervention. Therapeutic success is typically determined from inspection of gross anatomical images to assess changes in tumor size. Imaging could provide significant additional insight into therapeutic impact if a specific parameter or combination of parameters could be identified which reflect tissue changes at the cellular or physiologic level. This would provide an early indicator or treatment response/outcome in an individual patient before completion of therapy. Moreover, response of a tumor to therapeutic intervention may be heterogeneous. The use of imaging could assist in delineating therapeutic-induced spatial heterogeneity within a tumor mass by providing information related to specific regions that are resistant or responsive to treatment. Largely untapped potential resides in exploratory methods such as diffusion MRI, which is a nonvolumetric intravoxel measure of tumor response based upon water molecular mobility. Alterations in water mobility reflect changes in tissue structure at the cellular level. While the clinical utility of diffusion MRI for oncologic practice is still under active investigation, this overview on the use of diffusion MRI for the evaluation of brain tumors will serve to introduce how this approach may be applied in the future for the management of patients with solid tumors.

Nephrogenic Systemic Fibrosis: A Report of 29 Cases

OBJECTIVE The purpose of this study was to determine the incidence of nephrogenic systemic fibrosis and its relation to renal failure and the administration of gadolinium-based contrast material at an academic medical center. MATERIALS AND METHODS A dermatopathology database was searched to identify patients in whom nephrogenic systemic fibrosis was diagnosed. The medical records of these patients were reviewed. Renal function concurrent with any administration of gadolinium-based contrast material was assessed, as was patient outcome. A database of patients undergoing long-term dialysis was reviewed separately to determine how many had received gadolinium and the frequency of nephrogenic systemic fibrosis among these patients. RESULTS Twenty-nine patients were found to have had nephrogenic systemic fibrosis between November 15, 1999, and December 31, 2006. It was known that gadolinium-based contrast material had been administered to 25 of these patients before diagnosis. All 29 patients had compromised renal function (27 had chronic renal failure, and two had acute renal failure). Determination of the temporal relation between gadolinium-based contrast administration and symptom onset often was difficult. Only eight patients had severe morbidity. Nephrogenic systemic fibrosis developed in 12 (2.9%) of 414 patients undergoing long-term dialysis who received gadolinium-based contrast material. CONCLUSION We confirm the strong association between nephrogenic systemic fibrosis and gadolinium-based contrast administration. Although the use of high doses of gadolinium and the occurrence of chronic renal failure have been implicated in other reports, several of our patients received standard doses of gadolinium, and two had transient acute renal failure before diagnosis. Most patients had mild or moderate symptoms. Nephrogenic systemic fibrosis developed in 2.9% of patients undergoing long-term dialysis who received gadolinium-based contrast material but in none of the long-term dialysis patients who did not receive gadolinium-based contrast material.

Computed tomography Perfusion of squamous cell carcinoma of the upper aerodigestive tract: Initial results

Objective To define the computed tomography (CT) perfusion characteristics of head and neck squamous cell carcinoma. Methods Fourteen consecutive patients with untreated squamous cell cancers of head and neck underwent CT of the head and neck along with CT perfusion imaging through the primary site. For the perfusion studies, CT density changes in blood and tissues were kinetically analyzed using the commercially available CT Perfusion 2 software (General Electric Medical Systems. Milwaukee, WI) on a GE Advantage Windows workstation. This yielded parameter maps of fractional tissue blood volume (mL/100 g), blood flow (mL · 100 g−1 · min−1), mean transit time (s), and microvascular permeability surface area product (mL · 100 g−1 · min−1). One head and neck radiologist analyzed perfusion data. Regions of interest (ROI) were placed over the primary tumor site, tongue base, and adjacent muscle groups. The average values of tissue blood volume (BV), blood flow (BF), mean transit time (MTT), and capillary permeability surface area product (CP) were then calculated for the tumor and compared with the average values for the tongue base and adjacent musculature. To determine a statistically significant difference between the tumor and muscle parameters, the Wilcoxon sign test, a nonparametric test for paired data, was employed. Results The average values of CP, BF, and BV were higher in primary tumor (41.9, 132.9, 6.2, respectively) than in tongue base or adjacent muscular structures. The MTT was reduced in primary tumors (4.0) compared with adjacent normal structures. The above differences were statistically significant (P < 0.05). Conclusions We obtained baseline perfusion data for head and neck squamous cell cancers and compared it with adjacent normal structures. Our initial results suggest that CT perfusion parameters (CP, BF, BV, and MTT) can be used to help differentiate head and neck squamous cell carcinoma (SCCA) from adjacent normal tissue.

Early Prediction of Outcome in Advanced Head-and-Neck Cancer Based on Tumor Blood Volume Alterations During Therapy: A Prospective Study

PURPOSE To assess whether alterations in tumor blood volume (BV) and blood flow (BF) during the early course of chemo-radiotherapy (chemo-RT) for head-and-neck cancer (HNC) predict treatment outcome. METHODS AND MATERIALS Fourteen patients receiving concomitant chemo-RT for nonresectable, locally advanced HNC underwent dynamic contrast-enhanced (DCE) MRI scans before therapy and 2 weeks after initiation of chemo-RT. The BV and BF were quantified from DCE MRI. Preradiotherapy BV and BF, as well as their changes during RT, were evaluated separately in the primary gross tumor volume (GTV) and nodal GTV for association with outcomes. RESULTS At a median follow-up of 10 months (range, 5-27 months), 9 patients had local-regional controlled disease. One patient had regional failure, 3 had local failures, and 1 had local-regional failure. Reduction in tumor volume after 2 weeks of chemo-RT did not predict for local control. In contrast, the BV in the primary GTV after 2 weeks of chemo-RT was increased significantly in the local control patients compared with the local failure patients (p < 0.03). CONCLUSIONS Our data suggest that an increase in available primary tumor blood for oxygen extraction during the early course of RT is associated with local control, thus yielding a predictor with potential to modify treatment. These findings require validation in larger studies.

Congenital aplasia of the semicircular canals.

Objective To describe the underrecognized inner ear malformation characterized by complete aplasia of the labyrinthine semicircular canals associated with a relatively well-formed cochlea, to investigate its relationship with known syndromic forms of hearing loss, and to hypothesize regarding the potential embryopathogenesis of this anomaly. Study Design A retrospective case review consisting of cases of sensorineural hearing loss with radiographic evidence demonstrating agenesis of the semicircular canals associated with a cochlea that was either morphologically normal or sufficiently well developed to accommodate the full insertion of a cochlear implant electrode. Cases were identified by computerized tomography findings that identified the anomaly under study. Setting Departments of otolaryngology and radiology in a tertiary referral center, with a large cochlear implant program serving over 800 patients, more than half of whom are children. Patients Fifteen patients with the anomaly under study were identified. Interventions Each patient underwent a complete otologic examination, audiometric studies, and high resolution computerized tomography of the temporal bone in axial and coronal planes. Main Outcome Measures The bony morphology of the cochlea, round and oval windows, vestibule, semicircular canals, and vestibular aqueduct, and the course of the facial nerve were examined. Auditory findings and otologic treatment are presented. Results Of the 15 identified patients, 4 were nonsyndromic, 9 had CHARGE association (Coloboma of the eye, congenital Heart defects, choanal Atresia, mental and/or growth Retardation, Genital hypoplasia, and Ear anomalies and/or deafness), 1 met criteria for Noonans syndrome, and one had features of both these syndromes. Although the cochlea was present in all cases, the cochlear morphology was usually abnormal in the CHARGE association patients. Of the 20 ears in the CHARGE subjects, only 3 ears (15%) were seen to have completely normal development of the cochlea in both the basal and upper turns. The others showed either mild hypoplasia of the upper turns (13 ears, 65%) or an incomplete partition typical of the classic Mondini deformity (4 ears, 20%). In the 4 nonsyndromic cases, one subject had bilateral Mondini dysplasia and the other three had normal cochleae. In the entire group, abnormalities of oval window development were common (20 of 30 ears, 67%), especially in the syndromic cases (18/22, 81%), but the round window was normal in the majority of cases (73%). Seven patients in the CHARGE association group had an anomalous course of the facial nerve, which was particularly severe in three. Four patients had congenital unilateral facial paralysis, although two of these children had normal radiographic anatomy of the facial nerve. One patient had bilateral facial weakness. Conclusions Syndromic and nonsyndromic cases of isolated semicircular canal aplasia were identified. Except for mild to moderate cochlear dysplasia, and the anomalous course of the facial nerve in some CHARGE association patients, both groups of patients were generally suitable for cochlear implantation if indicated. A high incidence of oval window aplasia with normal round window development may help to explain the embryopathogenesis of this anomaly, considering the sequence of inner ear development.

Diffusion-weighted magnetic resonance imaging

Diffusion-weighted magnetic resonance imaging is a specialized technique that measures the degree of diffusion of water molecules within extracellular space and between intracellular and extracellular space. Diffusion-weighted imaging signal is high (bright) when diffusion is restricted, as occurs in cytotoxic damage from ischemia, inflammation, trauma, or tumor. This technique, now available on most magnetic resonance imaging units, is especially helpful in detecting early ischemic stroke and multiple sclerosis and in differentiating arachnoid cyst from epidermoid tumor and brain abscess from neoplasm.