Faculty Bibliography

PURPOSE/OBJECTIVE:To compare objective and subjective image quality in neck CT images acquired at different tube current-time products (275 mAs and 340 mAs) and reconstructed with filtered-back-projection (FBP) and adaptive statistical iterative reconstruction (ASIR). MATERIALS AND METHODS/METHODS:HIPAA-compliant study with IRB approval and waiver of informed consent. 66 consecutive patients were randomly assigned to undergo contrast-enhanced neck CT at a standard tube-current-time-product (340 mAs; n = 33) or reduced tube-current-time-product (275 mAs, n = 33). Data sets were reconstructed with FBP and 2 levels (30%, 40%) of ASIR-FBP blending at 340 mAs and 275 mAs. Two neuroradiologists assessed subjective image quality in a blinded and randomized manner. Volume CT dose index (CTDIvol), dose-length-product (DLP), effective dose, and objective image noise were recorded. Signal-to-noise ratio (SNR) was computed as mean attenuation in a region of interest in the sternocleidomastoid muscle divided by image noise. RESULTS:Compared with FBP, ASIR resulted in a reduction of image noise at both 340 mAs and 275 mAs. Reduction of tube current from 340 mAs to 275 mAs resulted in an increase in mean objective image noise (p=0.02) and a decrease in SNR (p = 0.03) when images were reconstructed with FBP. However, when the 275 mAs images were reconstructed using ASIR, the mean objective image noise and SNR were similar to those of the standard 340 mAs CT images reconstructed with FBP (p>0.05). Subjective image noise was ranked by both raters as either average or less-than-average irrespective of the tube current and iterative reconstruction technique. CONCLUSION/CONCLUSIONS:Adapting ASIR into neck CT protocols reduced effective dose by 17% without compromising image quality.

From a clinical-radiologic standpoint, there are a limited number of structures and disease entities in the temporal bone with which one must be familiar in order to proficiently interpret a computed tomographic or magnetic resonance imaging study of the temporal bone. It is helpful to examine the region in an organized and systematic fashion, going through the same checklist of key structures each time. This is the first of a two-part review that provides a practical approach to understanding temporal bone anatomy, localizing a pathologic process with a focus on inflammatory and neoplastic processes, identifying pertinent positives and negatives, and formulating a differential diagnosis.

BACKGROUND:Hydrogel scleral buckles were used for treating retinal detachment in the 1980s and early 1990 s. However, these devices have a propensity to degrade over time and cause several long-term complications, including hydration and overexpansion, fragmentation, extrusion, intrusion, and intraocular erosion, and the potential to mimic mass lesions. METHODS:The imaging features of hydrogel scleral buckles and their complications are reviewed in this article. RESULTS:Radiographic imaging plays an important role in managing patients with complications of hydrogel buckles. Hydrated buckles display attenuation intermediate between fluid and soft tissue on computed tomography, demonstrate approximately fluid signal on magnetic resonance imaging, and are anechoic on ultrasonography. Linear margins and peripheral dystrophic calcification are characteristic. CONCLUSION/CONCLUSIONS:The constellation of imaging features helps distinguish expanded hydrogel buckles from other orbital diseases. Imaging also serves to precisely localize hydrogel scleral buckle components requiring removal.

UNLABELLED/: BACKGROUND:Superior semicircular canal dehiscence (SSCD) may cause Tullio phenomenon (sound-induced vertigo) or Hennebert sign (valsalva-induced vertigo) due to the absence of bone overlying the SSC. We document a case series of elderly East Asian women with atypical SSCD symptoms, radiologically confirmed dehiscence and concurrent osteoporosis. METHODS:A retrospective record review was performed on patients with dizziness, vertigo, and/or imbalance from a neurology clinic in a community health center serving the East Asian population in Boston. SSCD was confirmed by multi-detector, high-resolution CT of the temporal bone (with Pöschl and Stenvers reformations) and osteoporosis was documented by bone mineral density (BMD) scans. RESULTS:Of the 496 patients seen in the neurology clinic of a community health center from 2008 to 2010, 76 (17.3%) had symptoms of dizziness, vertigo, and/or imbalance. Five (6.6%) had confirmed SSCD by multi-detector, high-resolution CT of the temporal bone with longitudinal areas of dehiscence along the long axis of SSC, ranging from 0.4 to 3.0 mm, as seen on the Pöschl view. Two of the 5 patients experienced motion-induced vertigo, two fell due to disequilibrium, and one had chronic dizziness. None had a history of head trauma, otologic surgery, or active intracerebral disease. On neurological examination, two patients had inducible vertigo on Dix-Hallpike maneuver and none experienced cerebellar deficit, Tullio phenomenon, or Hennebert sign. All had documented osteoporosis or osteopenia by BMD scans. Three of them had definite osteoporosis, with T-scores < -2.5 in the axial spine, while another had osteopenia with a T-score of -2.3 in the left femur. CONCLUSIONS:We describe an unusual presentation of SSCD without Tullio phenomenon or Hennebert sign in a population of elderly, East Asian women. There may be an association of SSCD and osteoporosis in this population. Further research is needed to determine the incidence and prevalence of this disorder, as well as the relationship of age, race, osteoporosis risk, and the development of SSCD.

Perineural tumor spread (PNS) is a mode of neoplastic spread whereby tumor cells use neural conduits to escape the borders of a primary tumor. MRI is generally favored over CT for evaluating PNS, and findings include obliteration of fat within skull base foramina, enlargement and enhancement of the involved nerves, and enlargement and destruction of the bony foramina. Careful examination of the entire course of the nerve allows detection of skip lesions. Recognition of the complete extent of PNS is crucial for correct treatment because it facilitates both surgical and radiotherapy targeting of entire extent of disease.

This article discusses the imaging manifestations of infectious and inflammatory conditions of the head and neck. Special attention is paid to the sites, routes of spread, and complications of neck infections. Because the clinical signs and symptoms and the complications of these conditions are often determined by the precise anatomic site involved, anatomic considerations are stressed. Familiarity with the fascial layers, spaces of the neck, and the contents of each space is helpful for this discussion. The fascial layers of the neck are important barriers to infection, and once infection is established, the fascial layers play a part in directing its spread.

Steatocystoma simplex is a rare entity characterized by the presence of a solitary cutaneous cyst derived from a sebaceous duct or gland. Multiple locations of this lesion have been reported previously. The purpose of this article is to report the unusual presentation of steatocystoma simplex as an infratemporal fossa mass. To the best of our knowledge, no case of steatocystoma simplex at this site has been previously reported. We also describe the radiologic and pathologic features of this entity, which might aid in diagnosis and management, and we discuss its etiology and treatment options.

Directed imaging is useful in assessing the thyroid gland. Nuclear scintigraphy reveals functional information about the thyroid gland, while cross-sectional imaging, including ultrasound, CT, and MR imaging provide important adjunctive anatomic information about the thyroid as well as about related structures in the neck, including the presence or absence of cervical and mediastinal lymphadenopathy, or extension of thyroid disease into adjacent soft tissues or the mediastinum. This article reviews the anatomy and physiology of the thyroid gland and addresses issues related to diseases affecting the thyroid gland, with an emphasis on neoplasms and the role of cross-sectional MR and CT imaging in the assessment of thyroid neoplasia.