Acquired cystic disease of the kidneys. Computed tomography and ultrasonography appraisal in patients on peritoneal and hemodialysis.

Screening chronic hemodialysis patients (CHD) for acquired cystic disease of the kidneys (ACDK) and its complications (hemorrhage and neoplasm) has become accepted management. We evaluated patients on CHD as well as patients on chronic peritoneal dialysis (CPD) for ACDK. The kidneys of 80 chronic dialysis patients were examined by CT and real time sonography. Forty-four were hemodialysis and 36 were peritoneal dialysis patients. ACDK was found in more than 90% of both CHD and CPD patients who had been dialyzed longer than three years. Bilateral renal carcinoma was detected in one hemodialysis patient. Our results show that chronic peritoneal dialysis patients are also at risk for ACDK and its associated complications. A similar natural history for the development of ACDK in both forms of dialysis suggests that the same screening precautions should be instituted for chronic peritoneal dialysis patients.

Fat-suppression failure artifacts simulating pathology on frequency-selective fat-suppression MR images of the head and neck.

PURPOSE: To describe fat-suppression failure artifacts and to caution against their misinterpretation. METHOD: Magnetic-susceptibility artifacts were studied in a phantom model and the results were compared to MR images obtained in clinical cases. FINDINGS: Artifacts manifested themselves as regions of focal fat-suppression failure and appeared as bright signals without geometric distortions at magnetic-susceptibility interfaces along the static field (z) direction. The location and extent of these artifacts were independent of either frequency or phase-encoding direction and are different from those observed in gradient-echo images. CONCLUSIONS: In representative clinical MR exams, these artifacts were identified in the high nasopharynx and low orbit and should not be misinterpreted as pathology.

Magnetic resonance imaging of the larynx.

The development of appropriate surface coils has resulted in outstanding depiction of the laryngeal anatomy using MRI. The multiplanar capability of MR allows superior definition of anatomy and tumor extent compared with CT scanning. MR appears to be more effective in detecting cartilage invasion. MR is as effective as CT in defining adenopathy and extension into the carotid sheath. MRI is therefore the primary modality in imaging the larynx.

Magnetic resonance imaging of the tongue and oropharynx.

In general, MRI produces superior soft tissue detail in evaluating the tongue and oropharynx than does CT. MRI is therefore considered the study of choice in this area. Lack of artifact from dental amalgam and beam hardening artifact from the mandible on MRI also eliminates two major shortcomings of CT in the examination of this area. Finally, the ability of MRI to obtain direct coronal and sagittal scan planes is a distinct advantage in recognizing intrinsic tongue musculature and assessing tumor volume and spread for treatment planning.

Magnetic resonance imaging of metastatic cervical adenopathy.

Detecting cervical adenopathy is critical in the management of carcinomas in head and neck. CT scanning remains a very effective modality in defining adenopathy. T1-weighted MRI scans are comparable to CT in detecting lymph nodes. T2-weighted images are less useful as the lymph nodes tend to have long T2 relaxation times similar to the surrounding fat. MR has not proved to be useful in detecting carcinoma in non-enlarged cervical nodes. The morphologic criteria developed for metastatic nodes with CT are appropriate with MRI (size, shape, signal, extracapsular spread). Gadolinium is sometimes useful in defining central necrosis in metastatic squamous cell adenopathy.

Interventional magnetic resonance imaging in the head and neck.

Interventional MRI is clearly in its early stages of development. While the value of MR-guided aspiration cytology and MR evaluation of deep electrode implantation in the brain has already been confirmed with human clinical studies, the future of MR-guided interstitial laser therapy remains to be proven. Despite this, as we look ahead into the 1990s and the millennium, it is possible to imagine dedicated MR laser therapy units for combined radiological and surgical outpatient approaches in what may become the operating rooms of the 21st century.

Positron emission tomography: a new, precise imaging modality for detection of primary head and neck tumors and assessment of cervical adenopathy.

Positron emission tomography (PET) has been shown to be effective in detecting intracranial malignancies based on cerebral glucose metabolism. To evaluate the ability of PET to detect extracranial head and neck neoplasms and cervical metastases, 16 patients with primary squamous cell carcinomas were examined. All patients received preoperative computerized tomography (CT) and magnetic resonance imaging (MRI) scans and underwent PET evaluation using intravenous 18F-2-fluoro-2-deoxy-D-glucose (FDG). Histopathologic analysis compared tumor invasion and positive lymph nodes with findings on MRI, CT, and PET images. All primary tumors were delineated by PET, while MRI and CT failed to detect one superficial tumor involving the anterior tongue. Ten nodes were detected by CT and MRI versus 12 nodes demonstrated by PET. PET is highly effective in detecting head and neck carcinomas as well as metastatic cervical lymph nodes. In addition, PET may be useful in evaluating postsurgery and postradiotherapy patients for recurrent and new primary tumors.

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-microns 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.

Acute and chronic brain injury in United States National Team soccer players.

We designed a study to determine whether chronic encephalopathy occurs in elite, active soccer players resulting from repetitive heading of the soccer ball. Studies have suggested that the cumulative effects of heading a ball can cause a chronic brain syndrome similar to dementia pugilistica, which is seen in professional boxers. Twenty of 25 members of the U.S. Men's National Soccer Team training camp (average age, 24.9; average years of soccer, 17.7), who completed a questionnaire on head injury symptoms and had magnetic resonance imaging of the brain, were compared with 20 age-matched male elite track athletes. The soccer players were surveyed about playing position, teams, number of headers, acute head injuries, and years of playing experience. An exposure index to headers was developed to assess a dose-response effect of chronic heading. The soccer and track groups were questioned regarding alcohol use and history of acute head traumas. Questionnaire analysis and magnetic resonance imaging demonstrated no statistical differences between the two groups. Among the soccer players, symptoms and magnetic resonance imaging findings did not correlate with age, years of play, exposure index results, or number of headers. However, reported head injury symptoms, especially in soccer players, correlated with histories of prior acute head injuries (r = 0.63). These findings suggest that any evidence of encephalopathy in soccer players relates more to acute head injuries received playing soccer than from repetitive heading.

Imaging of the temporal bone.

Computed tomography remains the imaging modality of choice in investigating conductive hearing loss. The improvement of MR imaging surface-coil technology is allowing a number of inflammatory and neoplastic diseases in the temporal bone to be detected more effectively. These two modalities when used correctly will detect many of the soft tissue and bony abnormalities of the temporal bone.

Spontaneous dural carotid-cavernous fistula with central retinal vein occlusion and iris neovascularization.

Spontaneous dural carotid-cavernous fistulas are dural vascular malformations that usually run a benign course. We present a case of a spontaneously occurring dural carotid-cavernous fistula complicated by central retinal vein occlusion and iris neovascularization that led to progressive visual failure.

Nonneoplastic enhancing lesions mimicking intracanalicular acoustic neuroma on gadolinium-enhanced MR images.

The authors describe five patients with nonneoplastic lesions of the facial and/or vestibulocochlear nerves that demonstrated focal enhancement within the internal auditory canal on magnetic resonance (MR) images. MR and surgical findings for four patients with unilateral sensorineural hearing loss and one with Ramsay Hunt syndrome were reviewed. Three patients with hearing loss underwent surgical exploration and decompression of the internal auditory canal. The MR findings in all four patients with hearing loss were similar: Focal enhancement of the internal auditory canal was depicted on postcontrast T1-weighted images. Nonneoplastic lesions of the seventh and eighth cranial nerves may show focal enhancement on MR images, which mimics the appearance of a small intracanalicular neuroma. This potential for misdiagnosis may have important therapeutic implications.

MR imaging-guided interstitial Nd:YAG laser phototherapy: dosimetry study of acute tissue damage in an in vivo model.

A dosimetry study of acute tissue damage induced by interstitial application of the neodymium-yttrium-aluminum-garnet (Nd:YAG) laser was performed with magnetic resonance (MR) imaging. The MR appearance of the lesion was correlated with gross and histopathologic findings. Seventy-six lesions were induced in rabbit muscle with laser power outputs of 5-20 W and exposure times of 20-600 seconds. MR imaging was performed immediately after laser exposure. T2-weighted spin-echo images clearly showed the acute thermal injuries caused by laser energy deposition and correlated best with histopathologic findings. These images showed three distinct layers, corresponding to central ablation, coagulative necrosis, and interstitial edema, respectively, in the pathologic findings. Lesion diameters measured on MR images showed a linear correlation with those in gross sections. Lesion volume increased not only with increasing total energy delivered but with increasing power output for a fixed total energy delivered. MR imaging is an accurate modality for dosimetry studies of laser-induced acute lesions.

Neurovascular lesions and endovascular therapy: the role of MR.

Magnetic resonance imaging (MRI) studies were performed on 27 patients with vascular lesions of the central nervous system before and after embolization with either IBCA, polyvinyl alcohol foam particles, Avitene (microfibrillar collagen) or balloons. Thirteen pial brain arteriovenous malformations (AVMs), 3 brain AV fistulas, 2 giant aneurysms, 5 dural AVMs, 1 vertebro-vertebral fistula and 3 meningiomas were studied. The pre-embolization MR demonstrated the nidus and venous drainage of all pial AVMs. MR failed to detect 3 out of 5 dural AVMs using only spin echo sequences. A draining vein alone was seen in the remaining two cases. MR was superior to CT in detecting contiguous parenchymal changes such as atrophy, reversible ischemia, and mass effect in the pre-embolization studies. Following embolization, MR demonstrated partial or complete obliteration of the vascular nidus in all 13 pial AVMs. The embolized area was seen as an area of increased signal consistent with thrombus where previously there had been signal void. Ischemic or edematous changes in the brain parenchyma following embolization were seen on MR more easily than on CT scans. MR was accurate in the assessment of aneurysm patency, degree of thrombosis and balloon position in both giant aneurysms, and AV fistulae. These MR findings had an impact on patient management. MR will be an increasingly useful tool in the diagnosis and management of a number of neurovascular diseases requiring endovascular intervention.

Extracranial head and neck: PET imaging with 2-[F-18]fluoro-2-deoxy-D-glucose and MR imaging correlation.

The aim of this study was to define and quantitate the normal anatomy of the extracranial head and neck with 2-[fluorine-18]fluoro-2-deoxy-D-glucose (FDG) positron emission tomography (PET). This information was used to study 12 patients with primary squamous cell carcinomas. In all cases, the lymphoid tissue of the Waldeyer ring and the palatine and lingual tonsils could be differentiated from the airway, striated muscle, osseous structures, and salivary glands. Striated muscle had markedly less activity than lymphoid or salivary gland tissue. In the 12 patients with primary tumors, FDG PET depicted the tumor as an area of increased activity significantly higher than that of normal tissue. In one instance, FDG PET allowed detection of a tumor not seen at magnetic resonance (MR) imaging or computed tomography. Of the 34 lymph nodes positive for carcinoma, 24 were positive according to MR size criteria and 25 were detected with FDG PET. FDG PET allowed detection of three nonenlarged metastatic nodes that were negative at MR imaging.

Meckel cave lesions: percutaneous fine-needle-aspiration biopsy cytology.

The authors describe the novel combination of two traditional methods to facilitate diagnosis of Meckel cave lesions, which may otherwise require craniotomy to obtain adequate tissue samples. Fine-needle-aspiration biopsy cytology was performed on tissue obtained with a percutaneous approach via the foramen ovale with use of fluoroscopic guidance and intravenous analgesia during an outpatient procedure. This new application of fine-needle-aspiration biopsy cytology results in decreased patient morbidity and significant cost reduction.