Dental CT: imaging technique,anatomy, and pathologic conditions of the jaws

In addition to conventional imaging methods, dental CT has become an established method for anatomic imaging of the jaws prior to dental implant placement. More recently, this high-resolution imaging technique has gained importance in diagnosing dental-associated diseases of the mandible and maxilla. Since most radiologists have had little experience in these areas, many of the CT findings remain undescribed. The objective of this review article is to present the technique of dental CT, to illustrate the typical appearance of jaw anatomy and dental-related diseases of the jaws with dental CT, and to show where it can serve as an addition to conventional imaging methods in dental radiology. Electronic Publication     

Root of the small-bowel mesentery: correlative anatomy and CT features of pathologic conditions.

The root of the small-bowel mesentery (SBM) is an important peritoneal fold that is contiguous to other peritoneal ligaments and mesocolons. Several pathologic conditions can occur in the SBM itself, and diseases that spread through the connections from adjacent organs frequently involve it. The root of the SBM is contiguous to the hepatoduodenal ligament around the superior mesenteric vein (SMV) and contiguous to the right side of the transverse mesocolon around the gastrocolic trunk. The inferior mesenteric vein, which is a landmark of the descending mesocolon, runs along the left side of the root of the SBM. Malignant neoplasms can spread to the SBM by means of direct extension, extension along the neural plexus, extension along neighboring ligaments, or extension along lymphatic vessels. Inflammatory conditions such as pancreatitis and perforation of a jejunal diverticulum can also spread to the SBM. Anomalies that can occur in the SBM include rotation anomalies and internal hernia. Vascular lesions of the SBM include thrombosis of the superior mesenteric artery (SMA), acute SMV thrombosis, SMA dissection, arterioportal fistula, and portal venous gas. Other pathologic conditions that can occur in the SBM are edema or congestion, mesenteric tear, mesenteric panniculitis, and tumors or tumorlike lesions.     

Radiation exposure at chest CT: a statement of the Fleischner Society

The introduction of helical single-detector row computed tomography (CT) and, more recently, multi-detector row CT has greatly increased the clinical indications for CT. Correspondingly, CT examinations now account for greater than one-half of the radiation dose due to medical procedures in the population of North America. The level of CT radiation dose, especially in the pediatric population, is of concern to radiologists, medical physicists, government regulators, and the media. This review addresses this problem with particular reference to radiation dose in chest CT. Specifically it outlines the topics of measurement units used to quantify radiation exposure, factors affecting CT scanner dose efficiency, scanner settings that determine the administered radiation dose, and radiation dose reduction in chest CT. A table of reference dose values is provided. Given the wide variation documented in chest CT radiation exposure, the authors suggest that reference standards be promoted to minimize excessive CT radiation exposure. In addition, further research into the complex relationship between radiation exposure, image quality, and diagnostic accuracy should be encouraged in order to establish the minimum radiation dose necessary to provide adequate diagnostic information for standard clinical questions.     

Small pulmonary nodules: detection at chest CT and outcome

PURPOSE: To determine the outcome of pulmonary nodules less than 1 cm in diameter detected at chest computed tomography (CT). MATERIALS AND METHODS: Reports of chest CT performed during 6 months were reviewed to find patients with pulmonary nodules smaller than 1 cm in long axis for which repeat CT was recommended. Records were studied to determine whether follow-up had been performed, the initial nodules had changed in size, or nodules had been resected. RESULTS: A total of 3,446 chest CT examinations were performed, with 334 patients meeting inclusion criteria. Three patients underwent nodule resection and had pathologic examination results positive for cancer; 185 underwent follow-up, of whom 13 had results excluded as indeterminate. In the remaining 172 patients, 88 had incomplete characterization because of follow-up of less than 2 years, which left 84 with nodule characterization at follow-up. When these 84 patients were combined with the three patients with nodule resection, the number yielded was 87 patients. Seventy-seven of 87 had benign nodules because of resolution or 2-year stability, and 10 of 87 had malignant nodules because of growth or positive histologic examination results. Nine of 10 with malignant nodules had a known primary neoplasm. CONCLUSION: CT commonly helped identify small nodules. Increase in size occurred infrequently and almost exclusively in patients with a known malignancy.     

Neuroradiology back to the future: spine imaging

Although radiography of the spine began shortly after Roentgen's discovery in 1895, there was little written in the medical literature about spine imaging until nearly 25 years later with the development of myelography, first by using air and then a variety of positive contrast agents. The history of spine imaging before CT and MR imaging is, in large part, a history of the development of contrast agents for intrathecal use. The advent of CT and, more important, MR imaging revolutionized spine imaging. The spinal cord and its surrounding structures could now be noninvasively visualized in great detail. In situations in which myelography is still necessary, advances in contrast agents have made the procedure less painful with fewer side effects. In this historical review, we will trace the evolution of spine imaging that has led to less invasive techniques for the evaluation of the spine and its contents and has resulted in more rapid, more specific diagnosis, therapy, and improved outcomes.     

Crazy-paving appearance at thin-section CT: spectrum of disease and pathologic findings

PURPOSE: To determine the spectrum of disease associated with a fine reticular pattern superimposed on areas of ground-glass opacity (i.e., "crazy-paving" appearance) at thin-section computed tomography (CT) and to determine the underlying pathologic features. MATERIALS AND METHODS: In the in vivo study, the cases of 46 patients (21 male, 25 female; age range, 13-82 years) were retrospectively reviewed, with special attention paid to the size and extent of the reticular network. In the in vitro study, the thin-section CT findings in 20 inflated and fixed lungs were precisely correlated with the gross appearance, contact radiograph findings, stereomicroscopic views, and histologic findings. RESULTS: In the in vivo study, 15 different diseases were identified, including alveolar proteinosis, adult respiratory distress syndrome, acute interstitial pneumonia, diffuse alveolar damage superimposed on usual interstitial pneumonia, and drug-induced pneumonitis. In the in vitro study, the fine networks at pathologic analysis were due to an alveolar filling process (n = 10), an interstitial fibrotic process (n = 7), or a combination of interstitial and intraalveolar processes (n = 3). Twelve (60%) cases did not have thickening of the interlobular septa within the areas of the crazy-paving appearance. CONCLUSION: The crazy-paving appearance is a nonspecific finding seen in a variety of interstitial and airspace lung diseases.     

CT of the spine

Summary The level of CT section in the lumbosacral region may be correlated with routine AP views of the spine using a reference plane constructed according to the distance between the iliac crests. CT scans of the spine in 100 patients have been analyzed. The majority of these cases consisted of primary or secondary bone or soft-tissue tumors. CT examination was valuable to supplement plain films and/or myelograms in evaluation of the extent of pathology. It was also useful in the work-up of patients with malignant tumors whose other studies were equivocal.     

CT of the spine: are plain spine radiographs necessary?

This study was designed to determine whether plain radiographs added any information of clinical significance to the information provided by CT (computed tomography) and its standard digital radiographs in 100 patients presenting for CT of the lumbar spine and 46 patients presenting for cervical spine CT. In only three (3%) of the lumbar studies and two (4.3%) of the cervical studies did the plain radiographs add diagnostic information. The added diagnostic information did not affect patient management in all cases with indications other than trauma. Good quality oblique cervical spine digital radiographs were obtained in 10 cases simply by moving the tube and detectors to the 45 degrees and 135 degrees azimuths. The evidence from this study suggests that when a CT examination of lumbar or cervical spines is planned on a high resolution CT scanner for indications other than trauma, a conventional plain radiographic examination can be omitted in the first instance.     

MR imaging of the scrotum: pathologic conditions

The utility of high-resolution magnetic resonance (MR) imaging in studying a variety of intratesticular and extratesticular pathologic conditions was assessed. The high magnetic signal intensity of the testis provided an excellent background for visualization of intratesticular abnormalities. Except for old blood, all intratesticular processes were less intense than testis, especially on T2-weighted images. The visualization of the tunica albuginea is a distinct advantage, allowing its assessment in cases of trauma or testicular tumors. Epididymal and spermatic cord abnormalities were easily recognized. All pathologic conditions were best seen on T2-weighted images acquired in the coronal plane. Balanced images allowed for tissue characterization.     

CT and MR imaging of the normal and pathologic conditions of the facial nerve.

Computed tomography (CT) and magnetic resonance imaging (MRI) are well established imaging modalities to examine the facial nerve as well as the course of the facial nerve itself. High spatial resolution is guaranteed not only in the x- and y-axis, but also in the z-axis using multislice spiral CT. With this technique, reformatted multiplanar images in oblique planes, avoiding additional examinations in the coronal plane, facilitate the delineation of the facial nerve canal. This is beneficial in patients with temporal bone trauma, malformation or osseous changes. MR has a superior soft-tissue contrast to CT that enables imaging of the facial nerve itself. Therefore the normal facial nerve as well as pathologic changes of the facial nerve is readily visualized from the brain stem to the parotid gland. This review article presents anatomy, pathology and imaging strategies in the diagnostics of the facial nerve.     

Common and uncommon manifestations of Wegener granulomatosis at chest CT: radiologic-pathologic correlation

Wegener granulomatosis is an uncommon necrotizing vasculitis that classically manifests as a clinical triad consisting of upper and lower airway involvement and glomerulonephritis. Other less frequently involved organ systems include the central and peripheral nervous system and large joints. The diagnosis is based on a combination of clinical and laboratory findings. Because thoracic involvement often predominates, chest radiographic findings are often the first to suggest the diagnosis. However, chest computed tomography (CT) has superior sensitivity and specificity for evaluation of the airways, lung parenchyma, and mediastinum, particularly with the use of multiplanar reformatted and three-dimensional images. Common pulmonary radiologic findings include waxing and waning nodules, masses, ground-glass opacities, and consolidation. Airway involvement is usually characterized by circumferential tracheobronchial thickening, which can be smooth or nodular. Pleural effusions are the most common manifestation of pleural disease and can result from primary involvement or be secondary to renal failure. Mediastinal lymphadenopathy is a nonspecific finding and is usually reactive. Uncommon thoracic radiologic manifestations include involvement of the heart and great vessels. CT is the imaging modality of choice for diagnosis, surveillance, and follow-up in patients with Wegener granulomatosis.     

Neural foraminal ligaments of the lumbar spine: appearance at CT and MR imaging.

Axial and parasagittal computed tomographic (CT) scans and magnetic resonance (MR) images and exactly corresponding sections obtained with the freezing microtome in 18 human cadavers were examined to characterize the radiologic appearance of the lumbar neural forminal ligaments, which have been thought to contribute to nerve root compression. In the CT component of this study, 114 neural foramina at 57 spinal levels were studied; in the MR component, 27 neural foramina were studied. The ligaments originated from the posterolateral margin of the intervertebral disk and attached to the inferior pedicle, superior articular process, transverse process, or ligamentum flavum. On CT scans, they appeared as linear structures with higher attenuation coefficients than those of the adjacent fat and areolar tissue; on MR images, as linear structures with lower signal intensities than those of the adjacent fat and areolar tissue in the neural foramina. It is concluded that the ligaments in the neural foramen can be effectively depicted with CT or MR imaging.