Robert B. Lufkin

Evaluation of cervical lymph node metastases in squamous cell carcinoma of the head and neck

Although computed tomography and magnetic resonance imaging have contributed to the ability to identify metastatic disease in head and neck Cancer, inadequacies in evaluating lymphadenopathy still exist. This study was undertaken to estimate the accuracy of radiological criteria used to detect cervical lymph node metastases. The morphological characteristics of 957 lymph nodes from 36 neck dissections from patients with squamous cell Cancer were examined microscopically. A large number of malignant nodes were found to have diameters of less than 10 mm. Extranodal spread also occurred in a substantial percentage of smaller nodes. Because the present radiological criteria for assessing cervical lymph node Status are based largely on size, findings indicate major limitations in the capabilities of detecting metastatic disease. New modalities to improve the Staging of head and neck Cancer are discussed.

Corpus callosum morphometry and dichotic listening performace: Individual differences in functional interhemispheric inhibition?

We examined the relationship between midsagittal corpus callosum area, as seen by magnetic resonance imaging, and behavioral laterality effects from a dichotic listening task requiring cross-callosal relay of an auditory signal, in 60 healthy young adults. Four patients with complete forebrain commissurotomy were also given the dichotic listening task, confirming that in this task, the report of left ear items is dependent on callosal pathways. Contrary to our predictions, callosum measures were unrelated to either a laterality measure or to inferior (typically left) ear performance. Surprisingly, superior (typically right) ear accuracies, which do not depend on cross-callosal sensory transfer, were significantly and negatively correlated with callosum size. These findings show that normal variations in callosum size do not appear to contribute significantly to individual differences in hemispheric specialization. Callosum size may, instead, be associated with degree of functional interhemispheric inhibition.

Effect of field strength on susceptibility artifacts in magnetic resonance imaging

In magnetic resonance imaging susceptibility artifacts occur at the interface of substances with large magnetic susceptibility differences, resulting in geometric distortions of the image at those boundaries. The susceptibility artifacts are often subtle on clinical images and if not carefully examined they may lead to misdiagnosis. Magnetic susceptibility artifacts are prevalent on the boundary of air-containing paranasal sinuses, as well as bone-soft tissue interfaces in the spinal canal. The appearance of these artifacts on images from three different magnetic field strength instruments, 0.3, 0.5, and 1.5 Tesla were studied. T1- and T2-weighted spin echo and gradient recalled echo pulse sequences were selected to image a water phantom containing substances of varying susceptibilities. The effects were also studied in MR images of the head in a normal human volunteer. At any given field strength the artifacts were more prominent in the gradient echo imaging than in the corresponding spin echo pulse sequence. As expected, the distortions were also greater at higher field strengths. The results in human subjects paralleled the findings in the phantom study.

Metastatic head and neck malignancy treated using MRI guided interstitial laser phototherapy: An initial case report

Interstitial laser phototherapy (ILP) guided by magnetic resonance imaging (MRI) may become an attractive adjunctive modality for the treatment of deep and surgically inaccessible tumors of the head and neck when accurate methods of laser dosimetry and “real‐time” monitoring techniques with the MRI are introduced. We recently demonstrated in ex vivo and in vivo models, a linear relationship between levels of laser energies, thermal profiles, MR signal intensity changes, and histopathological tissue damage. Results of treatment in a patient with an unresectable large right jugulodigastric metastatic squamous carcinoma using new approach of MRI guided ILP are now reported. The patient complained of significant right‐sided neck pain and headaches secondary to a rapidly growing metastatic lymphadenopathy which recurred after previous surgery, radiation, and chemotherapy. Two treatment sessions were used at an interval of 2 weeks. Each treatment was performed in the MRI suite under heavy sedation. Using a 600‐μm bare fiber of the Nd:YAG laser implanted interstitially under MR guidance, the metastatic node was treated at three sites. T1‐ and T2‐weighted images were performed prior to, immediately after, 24 and 48 hours, and 4, 5, 7, 9, 16, and 25 days post‐treatment. Successful relief of pain and growth arrest of this node was observed after the second treatment and at the 3‐month follow‐up. These results demonstrate that this technique of ILP guided by MRI may be feasible in humans, and will become clinically practical when appropriate methods of dosimetry and instrumentation are developed.

The use of positron emission tomography for early detection of recurrent head and neck squamous cell carcinoma in postradiotherapy patients

Positron emission tomography (PET) has recently proved to be highly sensitive in detecting known extracranial head and neck squamous cell carcinomas when compared to computed tomography and magnetic resonance imaging (MRI). The ability of PET to detect early subclinical recurrent squamous cell malignancies in patients who received primary radiotherapy was evaluated. A new PET‐MRI coregistration technique was used to determine precise anatomic tumor location, enabling directed biopsies to confirm the presence of malignancy, and to plan additional therapeutic strategies. Ten patients underwent PET evaluation with intravenous [18F]‐fluorodeoxyglucose and received postradiotherapy MRI scans. In all cases, PET accurately detected the presence of recurrent disease despite negative or equivocal MRI scans and indeterminate clinical examinations. PET appears to be highly effective in detecting early recurrent head and neck squamous cell malignancies in postirradiated patients.

Diagnosis of endolymphatic hydrops in vivo with magnetic resonance imaging.

Hypothesis High-resolution magnetic resonance imaging (MRI) at 1.5 T preferentially enhances the perilymph over endolymph after administration of contrast with gadodiamide, which allows for differentiation of the membranous labyrinth. Furthermore, this imaging allows for the detection of endolymphatic hydrops. Background Endolymphatic hydrops is believed to be associated with a number of ear diseases, including Ménières disease. Although the pathologic changes of overaccumulation of endolymph in the inner ear are obvious on postmortem histologic examination of the temporal bone, they have yet to be observed in a living organism. Previous attempts to visualize this condition with high-resolution contrast-enhanced computed tomographic imaging and MRI have been unsuccessful. Methods Healthy pigmented guinea pigs underwent a unilateral surgical ablation of the endolymphatic sac to create endolymphatic hydrops in the ear. High-resolution temporal bone imaging was performed by use of a 1.5-T MRI system. Two-dimensional images were acquired by a spin-echo technique with and without contrast enhancement by gadodiamide. Results T1-weighted gadodiamide contrast-enhanced MRI of the midmodiolar level of the cochlea demonstrated that the perilymph appeared to be preferentially enhanced relative to the endolymph, resulting in a clear distinction between the scalae of the inner ear. The contrast-enhanced T1-weighted MRI of the midmodiolar level of the hydropic cochlea demonstrated a significantly enlarged scala media in comparison with the normal cochlea in the same animal. Conclusion The demonstration of endolymphatic hydrops has been possible for the first time in vivo by the use of a standard 1.5-T MRI system. This research has important clinical implications: Specifically, this technique may allow for the noninvasive diagnosis of Ménières disease.

Chondroid tumors of the larynx: Computed tomography findings

PURPOSE Chondromas and chondrosarcomas of the larynx are rare cartilaginous tumors making up less than 1% of all laryngeal tumors. Patients typically present with symptoms of hoarseness, dysphagia, or dyspnea. The most common location in the larynx for these tumors is the cricoid cartilage. Radiographically, these lesions are typically hypodense, well-circumscribed masses containing mottled calcifications with smooth walls centered within the cartilage. MATERIALS AND METHODS We present 6 cases of chondroid tumors of the larynx. RESULTS One patient had a chondroma, 4 patients had low-grade chondrosarcomas, and 1 patient had an intermediate-grade chondrosarcoma. Two partial laryngeal resections and 4 total laryngectomies were performed. CONCLUSIONS In most cases of chondroma or chondrosarcoma of the larynx, conservative surgery should be attempted, but total laryngectomy may be required for large or recurrent lesions.

Early postoperative appearance of radiofrequency lesions on magnetic resonance imaging.

Eleven patients who underwent stereotactic radiofrequency lesions in the central nervous system had magnetic resonance imaging follow-up within 72 hours of surgery to determine the early appearance of their lesions. Eight patients with severe tremor, one with chronic pain, and two with dystonia were analyzed. There were six female patients and five male patients, age 7 to 75 years (mean +/- standard deviation = 42 +/- 21). Magnetic resonance imaging was performed postoperatively at 32 +/- 25 hours (range, 3-72). Postoperative T1-weighted spin echo images demonstrated foci of iso- to hyperintensity surrounded by an edge of hypointensity, and corresponding T2-weighted images showed a lesion with three concentric zones consisting of inner hypointense, middle hyperintense, and outer hypointense zones. Gadolinium increased T1-weighted image lesion visibility, and a ring of enhancement around the zone of hypointensity was observed. Lesions could be seen as early as 3 hours after surgery. The lesions were best shown on gadolinium-enhanced T1-weighted images and on T2-weighted images. The edema surrounding the lesion increased over time, up to the 72 hours studied. These data provide important information on the development of lesion appearance, which may be applied in the development of real-time magnetic resonance imaging monitoring of radiofrequency lesion formation. This technique associated with electrophysiological response and the real-time visualization of the anatomic correlation of the probe may allow for a very precise and selected lesion in the central nervous system for the treatment of functional disorders and brain tumors.

A QUANTITATIVE PHYSIOLOGIC MODEL OF BLOOD OXYGENATION FOR FUNCTIONAL MAGNETIC RESONANCE IMAGING

RATIONALE AND OBJECTIVES. Variations in venous deoxyhemoglobin levels in response to neuronal activation represent a complex interplay between focal changes in cerebral blood flow (CBF), cerebral blood volume (CBV), and regional metabolism. The authors present a mathematic model that characterizes the response of venous oxygenation to changes in these variables. METHODS.Using a mass balance approach, the equations for a simple input-output model are derived and solved using Matlab. Changes in blood oxygenation are related to available results from functional magnetic resonance imaging experiments. RESULTS.Increases in CBF produce declines in oxygen extraction fraction and venous deoxyhemoglobin according to Ficks law, and are quantitatively in agreement with available magnetic resonance and positron-emission tomography data. A flow-volume envelope defines the changes in CBF relative to CBV. CONCLUSIONS.It is possible to obtain a quantitative understanding of changes in blood oxygenation and to relate these changes to the observed dynamics of magnetic resonance signal change in the setting of functional stimulation.

Interstitial laser phototherapy assisted by magnetic resonance imaging: A new technique for monitoring laser-tissue interaction

The rapid technological advances of magnetic resonance imaging, laser fiberoptics, and compatible probes may allow treatment of deep and sometimes surgically unreach‐able tumors of the head and neck with minimal morbidity through interstitial laser phototherapy. In this study, a new application of magnetic resonance imaging was developed to monitor and quantify laser‐induced tissue damages. Pig skin was exposed to increased levels of argon laser (514.5 ran) at energy densitites between 62.5 and 375 J/cm2 as determined by an accurate and reproducible method of dosimetry. Thermal profiles were recorded using an infrared sensor and Tl‐ and T2‐weighted magnetic resonance images were taken; afterward, biopsies were performed to quantitate the level of tissue damage. Our results demonstrate that above a certain threshold of laser energy, the magnetic resonance imaging findings are temperature dependent. Appropriate development of a scale matching laser energies, temperature profiles, Tl‐ and T2‐weighted magnetic resonance images, and histological quantitation of tissue destruction will allow us to optimize the three‐dimensional control and monitoring of laser‐tissue interactions.