CT features of congenital nasal piriform aperture stenosis: initial experience.

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 skull base and calvaria. Adult and pediatric.

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.

Support line and tube visibility in chest examinations using computed radiography.

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.

Optimal technique factors for magnification mammography.

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.

The developing anterior skull base: CT appearance from birth to 2 years of age.

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.

Orbital imaging techniques.

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.

Mottle on computed radiographs of the chest in pediatric patients.

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.

Comparison of trained and untrained observers using subjective and objective measures of imaging performance.

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.

MR demonstration of a cystic pheochromocytoma.

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 US of the orbit.

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.

Bilateral isolated retrobulbar optic neuropathy in limited Wegener's granulomatosis.

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.