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Objective: To estimate the prevalence of and symptoms associated with posterior semicircular canal dehiscence (PSCD) compared to superior semicircular canal dehiscence (SSCD) and nondehiscent semicircular canals (NDSC)., Study Design: Retrospective review., Setting: Academic tertiary referral center., Patients: Review of 412 temporal bone CT scans and associated patient records, excluding patients with prior mastoid or skull base surgery., Intervention(s): CT images (0.625 mm thick) were reviewed in the planes of the semicircular canals. Patient demographics and symptoms were tabulated and analyzed., Main Outcome Measure(s): Prevalence of PSCD and SSCD; degree of hearing loss; presence or absence of aural fullness, autophony, tinnitus, pulsatile tinnitus, disequilibrium, vertigo, and Tullio phenomenon., Results: Review of the 412 CT scans revealed 5 cases of PSCD (1.2%) and 20 cases of SSCD (4.9%). All patients with PSCD were male, aged 16 to 73 years. One patient with PSCD reported tinnitus, autophony, disequilibrium, vertigo, and Tullio phenomenon; 2 patients reported only tinnitus and aural fullness, and 1 patient had no symptoms. PSCD was commonly associated with SSCD. There were no significant differences in symptoms between PSCD patients and the other groups. There were, however, statistically significant differences between SSCD patients and NDSC patients in the rates of autophony, tinnitus, and disequilibrium., Conclusion: The prevalence of PSCD in patients undergoing temporal bone CT scans is considerably less than SSCD (1.2% versus 4.9%), and the 2 conditions commonly coexist. Given the small numbers in our study, we were not able to demonstrate any distinguishable clinical features for the PSCD patients.

In recent years, 5-aminolevulinic acid (ALA)-induced protoporphyrin IX (PpIX) fluorescence guidance has been used as a surgical adjunct to improve the extent of resection of gliomas. Exogenous administration of ALA before surgery leads to the accumulation of red fluorescent PpIX in tumor tissue that the surgeon can visualize and thereby discriminate between normal and tumor tissue. Selective accumulation of PpIX has been linked to numerous factors, of which blood-brain barrier breakdown has been suggested to be a key factor. To test the hypothesis that PpIX concentration positively correlates with gadolinium (Gd) concentrations, we performed ex vivo measurements of PpIX and of Gd using inductively coupled plasma mass spectrometry, the latter as a quantitative biomarker of blood-brain barrier breakdown; this was corroborated with immunohistochemistry of microvascular density in surgical biopsies of patients undergoing fluorescence-guided surgery for glioma. We found positive correlations between PpIX concentration and Gd concentration (r = 0.58, p < 0.0001) and between PpIX concentration and microvascular density (r = 0.55, p < 0.0001), suggesting a significant, yet limited, association between blood-brain barrier breakdown and ALA-induced PpIX fluorescence. To our knowledge, this is the first time that Gd measurements by inductively coupled plasma mass spectrometry have been used in human gliomas.

Glioblastoma is a highly malignant brain tumor that relentlessly defies therapy. Efforts over the past decade have begun to tease out the biochemical details that lead to its aggressive behavior and poor prognosis. There is hope that this new understanding will lead to improved treatment strategies for patients with glioblastoma, in the form of targeted, molecularly based therapies that are individualized to specific changes in individual tumors. However, these new therapies have the potential to fundamentally alter the biologic behavior of glioblastoma and, as a result, its imaging appearance. Knowledge about common genetic alterations and the resultant cellular and tissue changes (ie, induced angiogenesis and abnormal cell survival, proliferation, and invasion) in glioblastomas is important as a basis for understanding imaging findings before treatment. It is equally critical that radiologists understand which genetic pathway is targeted by each specific therapeutic agent or class of agents in order to accurately interpret changes in the imaging appearances of treated tumors., (© RSNA, 2011.)

The superb contrast resolution of MR imaging has significantly improved radiologists' ability to evaluate the anterior visual pathways and globe. Optimal imaging of the orbit requires the radiologist to have a working understanding of the clinical questions the ophthalmologist needs answered. In this article, basic orbit anatomy, MR imaging protocols for the orbit, and common clinical scenarios encountered when imaging the orbit are reviewed, with a focus on the optic nerve and globe.

Purpose: To investigate the clinical and histologic response of Novabone-C/M as an osteoproductive alloplastic implant for volume augmentation in the orbit in the treatment of enophthalmos and to compare its outcome alone versus its use in combination with autogenous bone or Medpor granules., Methods: Novabone-C/M, a bioactive silicone glass material, was implanted in the subperiosteal space of the left orbit of 12 New Zealand White rabbits. The animals were divided into 3 groups, each with 4 animals, based on the material implanted in the orbit: group 1, Novabone alone; group 2, Novabone plus Medpor granules; and group 3, Novabone plus autogenous bone fragments. All rabbits were studied clinically, radiographically, and histologically at 1-, 3-, and 6-month intervals. Animals underwent preoperative and postoperative computed tomography (CT) with 3-dimensional reconstruction, proptosis measurements, and volumetric analysis. Orbit specimens were studied histologically with mineralized bone stain (MIBS) to look for bone formation, reactivity, infection, implant resorption, and migration., Results: There were no signs of significant inflammation or infection. Subcutaneous migration of the implant was seen radiographically but not clinically in groups 1 and 3. Induced proptosis averaged 2.5 mm (at 1 month) and showed regression in all groups over a 6-month period but was not statistically significant. Implant volume was markedly reduced in all groups, averaging 69% in group 1, 37% in group 2, and 59% in group 3 at 6 months. New bone formation and bone remodeling was present in all 3 groups at 3 months and only in group 2 at 6 months. The rate and amount of implant remodeling and bone formation was greatest in the Novabone/Medpor group (group 2)., Conclusions: Bioglass particulate is biocompatible, easy to use in the orbit, and stimulates bone growth. Bioglass is associated with volume loss and migration over 6 months and may not provide adequate volume augmentation in the orbit when used alone for the treatment of enophthalmos. The duration and amount of bone formation may be enhanced when Novabone is used in conjunction with Medpor.

Objective: The objective of our study was to describe the CT and MR imaging appearances of the surgical bed in the brains of patients receiving biodegradable polymers impregnated with N, N'1, 3-Bis-(2-chloroethyl)-N-nitrosourea (BCNU) for recurrent glioma and to determine whether patients receiving placebos could be differentiated from those receiving BCNU based on the pattern and growth kinetics of tumor recurrence., Materials and Methods: The CT and MR images of 20 patients who underwent surgery for resection of recurrent high-grade gliomas and placement of intratumoral wafers (11 received BCNU polymer wafers, nine received control wafers) were analyzed for wafer appearance, volume of gas in the tumor bed, and volume of enhancement on serial scans., Results: Wafers appeared as linear hyperdense structures on CT and as linear low-signal-intensity structures on MR imaging and caused no significant enhancement. In the BCNU polymer group, gas volume was 4.0 +/- 3.4 cm(3) (mean +/- SD), whereas gas volume was 1.6 +/- 3.0 cm(3) for the placebo group (Mann-Whitney test, p = 0.03). A trend toward linear rather than exponential recurrent tumor growth was identified for the BCNU polymer group but not for the placebo group., Conclusion: BCNU polymer wafers have a specific appearance on CT and MR imaging with which radiologists should be familiar: gas in the surgical bed is an expected transient finding, and tumor regrowth in patients receiving BCNU polymer wafers appeared to occur at a slower rate than in those receiving the placebo.

Purpose: To describe the computed tomographic (CT) findings at different collimation widths associated with superior semicircular canal (SSC) dehiscence syndrome and to determine the frequency of these findings in a control population., Materials and Methods: Temporal bone CT scans with 1.0-mm and/or 0.5-mm collimation were obtained in 50 patients with sound- and/or pressure-induced vestibular symptoms. The control population consisted of 50 patients undergoing CT at 1.0-mm collimation and 57 patients undergoing CT at 0.5-mm collimation for other reasons., Results: SSC dehiscence was documented on CT scans in all 36 patients with the clinical syndrome, with bilateral findings in six patients. Six other patients without specific clinical signs appeared to have dehiscence on 1.0-mm-collimated scans. Intact bone overlaying the SSC was subsequently identified with 0.5-mm-collimated CT in each case. On the 1.0-mm-collimated scans in 50 control patients, an area judged as possible or definite dehiscence was identified in 18 of 100 ears. The bone overlaying the SSC was intact in each of the 114 control ears evaluated with 0.5-mm-collimated CT. CT findings from the patients with vestibular symptoms combined with those in the control population indicated that the positive predictive value of an apparent dehiscence in the diagnosis of SSC dehiscence syndrome improved from 50% with 1.0-mm-collimated CT with transverse and coronal images to 93% with 0.5-mm-collimated CT with reformation in the plane of the SSC., Conclusion: The positive predictive value of CT in identification of SSC dehiscence syndrome improves with 0.5-mm-collimated helical CT and reformation in the SSC plane.

MR imaging is an important tool for the evaluation of the optic nerve and globe. A working knowledge of the clinical questions an ophthalmologist faces helps radiologists optimize MR imaging protocols and focus their attention on the important clinical issues.

A 44-year-old white male with an isolated central nervous system relapse of acute lymphoblastic leukemia was treated with intrathecal cytarabine. He developed Staphylococcus epidermidis meningitis, which was treated successfully with intrathecal vancomycin. Four weeks after the initiation of intrathecal cytarabine, the patient developed progressive ascending paralysis to the upper cervical level. Initial magnetic resonance imaging of the brain and spine were normal, and cerebrospinal fluid evaluation showed no evidence of ongoing infection and clearance of lymphoblasts. Three weeks later, magnetic resonance imaging demonstrated marked edema and peripheral enhancement of the spinal cord, consistent with cytarabine toxicity.

Purpose: To describe the computed tomographic (CT) measurements and features that enable accurate diagnosis of congenital nasal piriform aperture stenosis (CNPAS)., Materials and Methods: The clinical and imaging features of six patients (age range, 0-11 months) with CNPAS were retrospectively evaluated and compared with those of 61 control subjects younger than 24 months., Results: The average widths of the piriform aperture in patients aged 0-3, 4-6, and 10-12 months were 4.8, 7.0, and 6.0 mm, respectively, compared with 13.4 (P < .001), 14.9, and 15.6 mm, respectively, in the age-matched control subjects. The average areas of the piriform aperture in patients in the three age groups measured 0.24, 0.46, and 0.36 cm2, respectively, compared with 0.67 (P < .001), 0.86, and 1.11 cm2, respectively, in the age-matched control subjects. The width of the nasal cavity in patients with CNPAS was in the less than 5th percentile compard with that in the control subjects. Abnormal dentition and a midline bone ridge projecting from the inferior palate were present in all six patients., Conclusion: CT measurement of the piriform aperture width is a simple and accurate method for diagnosing CNPAS; a width less than 11 mm in a term infant is considered to be diagnostic. An abnormal dentition and a bone ridge along the underside of the palate are confirmatory imaging findings.

The anatomy of the skull base is complex. In the infant and child, the complexity is magnified by the numerous sutures, synchondroses, and normal variants that are present. In this article, the normal anatomy of the skull and skull base is presented using radiographs, computed tomography, and magnetic resonance imaging. Specific attention to the postnatal development of each portion is given.

In the past 20 years, CT and MR imaging have emerged as the primary modalities for the evaluation of orbital disease. One can safely say that plain films have no role in the detailed evaluation of disorders of this morphological area. Given the bony enclosure, small size, soft tissue and fat content of this region, as well as globe movement, obtaining high-quality images of the orbit can be technically challenging. Our aim in this article, is to provide specific parameters for properly evaluating the orbit with CT and MRI.

The visibility of support lines and tubes was compared in computed radiography (CR) and screen-film adult chest radiographs. Parameters investigated were radiation dose, image minification, and the use of unsharp mask enhancement. Five radiologists rated the visibility of support lines and tubes on a five-point scale ranging from 1 (entire course of line visible) to 5 (line not visible or only small portion seen). These CR results were compared with the visibility of support lines and tubes as assessed by the same readers for conventional screen-film radiographs (600 speed). Support line and tube visibility improved with image enhancement, image minification, and increasing radiation dose. At the same radiation exposure, support line and tube visibility of the screen-film combination was superior to that of standard CR images. Application of an unsharp mask enhancement algorithm to CR images, however, significantly improved support line and tube visibility in comparison to that obtained with the screen-film combination. It was concluded that unsharp mask processing is a valuable tool for improving the visibility of support lines and tubes in CR chest radiographs.

Rationale and Objectives: Use of small focal spots with low x-ray tube currents may result in very long exposure times and thus result in motion blur in magnification mammography. The authors investigated the reduction in exposure time with increasing x-ray tube kVp and the corresponding decrease in perceived visibility of low-contrast objects in phantom images., Methods: Exposure times required to radiograph an RMI 156 phantom in a magnification geometry were measured as a function of x-ray tube kVp when operated under automatic exposure control. Magnification images of the RMI 156 phantom were obtained at x-ray tube voltages ranging from 28 to 34 kVp. Five radiology residents ranked the visibility of two borderline fibers and six borderline microcalcification specks using a 5-point scale ranging from excellent to barely visible., Results: Between 28 and 34 kVp, the density of the RMI phantom images was nearly constant with a mean value of 1.32 +/- 0.04. Increasing the x-ray tube voltage from 28 kVp to 34 kVp reduced the exposure time from 1.27 seconds to 0.66 seconds. Image quality at 30 and 32 kVp was not significantly worse than that achieved at 28 kVp. Increasing the x-ray tube voltage to 34 kVp, however, resulted in a statistically significant (P < 0.001) deterioration in the relative visibility of fibers and microcalcification specks., Conclusions: Magnification mammography performed at 32 kVp will decrease exposure times significantly and result in a microcalcification and fiber visibility that is similar to that achieved at 28 kVp.

Purpose: To describe the normal CT appearance of the developing anterior skull base in children 24 months of age and younger., Methods: A retrospective review of the CT examinations of a healthy population of 61 subjects newborn through 24 months of age was performed. Two investigators independently reviewed the examinations, making measurements and observations regarding the length of the skull base, ossification pattern, and development of the crista galli, perpendicular plate of the ethmoid bone, and fovea ethmoidalis., Results: At birth, the anterior skull base is largely cartilaginous. Ossification begins in the roof of the ethmoidal labyrinth laterally and spreads toward the midline. By 6 months of age, 50% of the anterior skull base has completely ossified. This percentage steadily increases over the first 2 years of life, and by 24 months, 84% of the anterior skull base is completely ossified, with a cartilaginous gap anteriorly in the region of the foramen cecum, the residual unossified portion. Ossification of the crista galli and perpendicular plate of the ethmoid bone begins around 2 months of age, shows a steady increase in ossification to 14 months of age, then increases little to 24 months of age. The fovea ethmoidalis begins development by 6 months of age, with the anterior portion the most developed in 82% of the population., Conclusion: The timing and pattern of ossification we observed differ somewhat from that reported in prior radiologic and anatomic studies, with the earliest bony bridging of the ethmoidal complex to the crista galli seen as early as 2 months of age. Development of the anterior skull base follows a predictable and orderly pattern that is important for understanding how to avoid errors in interpreting CT examinations through this region.

Purpose: To investigate the relationship between radiation exposure and perceived mottle at bedside pediatric chest examinations performed with screen-film and computed radiographic techniques., Materials and Methods: In a pediatric intensive care unit, chest radiographs were obtained with both computed radiography (60 radiographs) and a 600-speed screen-film system (14 radiographs). The relative radiation exposure was estimated by using the sensitivity value obtained in the processing of each computed radiograph. Five radiologists assessed the mottle present in the computed radiographs and screen-film images., Results: For computed radiographs, the perceived level of mottle was inversely related to radiation exposure. For the same radiation exposure, the perceived mottle on computed radiographs was significantly higher than that on screen-film images (P < .001 for small cassettes; P < .01 for large cassettes)., Conclusion: Pediatric computed radiography of the chest requires approximately twice the exposure of a 600-speed screen-film system to attain the same level of mottle.

Rationale and Objectives: We compared subjective and objective measures of imaging performance using variations of Rose- and Burger-type low-contrast phantoms with trained (radiology residents) and untrained (graduate students) observers., Methods: With one phantom variant, observers indicated the total number of objects seen when test objects were presented in a regular pattern (subjective). With the second phantom variant, observers stated whether a low-contrast disk was present in each locale, thereby permitting the true-positive fraction and false-positive fraction to be determined (objective)., Results: The untrained-observer group had a significantly lower imaging performance than the trained observer group in subjective tests. These differences were not found on objective tests. For the trained-observer group, similar contrast levels were required in subjective and objective tests to yield a 50% rate of detection., Conclusion: Trained observers are superior subjects compared with untrained observers for assessing imaging performance using subjective low-contrast phantoms. In experiments using phantoms that allowed objective testing, both groups of observers yield similar results.

Cystic pheochromocytoma is a rare tumor of the adrenal gland that can pose a diagnostic challenge. We report a case of a 14-year-old boy who had an adrenal lesion that appeared cystic by both sonography and CT, but that demonstrated hemorrhage into the lesion at MR imaging, and proved to be a cystic pheochromocytoma. We emphasize the importance of considering the diagnosis of pheochromocytoma when faced with a cystic lesion of the adrenal gland.

Color Doppler imaging of the orbit shows promise in evaluation of several types of orbital abnormalities. The most promising use is for evaluation of vascular disorders. Screening for orbital varices and cavernous-carotid fistulas is easily accomplished. Color Doppler imaging can also be useful in diagnosis of ocular ischemia, central retinal vessel occlusion, and anterior ischemic optic neuropathy. In cases of inflammatory disease, it may be helpful in searching for complications of infection and in monitoring the size of fluid collections. In cases of tumors, color Doppler imaging can be used to monitor lesion size and in surgical planning. More work needs to be done to determine the role of color Doppler imaging in evaluation of trauma and congenital abnormalities. An understanding of the basic anatomy of the orbit, examination techniques, and common disease processes in the orbit will allow the radiologist to offer this potentially valuable modality to referring clinicians.

Wegener's granulomatosis causes a variety of ophthalmologic disorders, some of which occasionally constitute the initial presentation of the disease. We describe a patient who presented with bilateral, isolated, consecutive, posterior optic neuropathy with light perception and no light perception vision. The patient had no other symptoms or signs of orbital disease. Investigations revealed cavitary lung lesions, positive antineutrophilic cytoplasmic antibody (ANCA) titers, subtle focal enhancement of the intracanalicular optic nerves on magnetic resonance imaging, and a confirmatory bronchial biopsy. This exceedingly rare ocular presentation of Wegener's granulomatosis may pose a diagnostic quandary.