Optimization of thoracic spiral CT: effects of iodinated contrast medium concentration

PURPOSE

To determine the effect of varying iodine concentration on arterial enhancement and perivenous artifact during thoracic spiral computed tomographic (CT) scanning.

MATERIALS AND METHODS

One hundred thirty-eight outpatients received 15.0 g (n = 76) or 22.5 g (n = 62) of iodine (300 mg/mL iodine) while undergoing thoracic spiral CT. Patients received either undiluted contrast medium, 1:1 normal saline dilution, or 3:1 normal saline dilution. Contrast medium was injected at a flow rate determined to deliver the entire iodine dose within 40 seconds. Attenuation was measured within arteries and veins. Three blinded thoracic radiologists independently graded perivenous artifact and arterial enhancement.

RESULTS

Perivenous artifacts were statistically significantly reduced with successive iodine dilution (P < .002). Arterial enhancement was statistically significantly better with 15.0 g of iodine diluted 1:1 when compared with the same iodine dose undiluted or diluted 3:1 (P < .01). Arterial enhancement achieved with 15.0 g of iodine diluted 1:1 was not statistically significantly lower than that achieved with 22.5 g of iodine diluted 1:1 (P > .31); however, venous artifact was greater with 22.5 g of iodine (P < .004).

CONCLUSION

Reduced iodine concentration appears to diminish perivenous artifact and to result in improved arterial enhancement during thoracic spiral CT.

Pneumothorax ex vacuo

Pneumothorax ex vacuo is a little-known complication of lobar collapse. In this condition, acute bronchial obstruction from mucous plugs, aspirated foreign bodies, or malpositioned endotracheal tubes causes acute lobar collapse and a marked increase in negative intrapleural pressure around the collapsed lobe. As a result, gas is drawn into the pleural space around the collapsed lobe while the seal between the visceral and parietal pleura of the adjacent lobe or lobes remains intact. The pneumothorax spontaneously resolves when the bronchial obstruction is relieved and the lobe reexpands. Recognition of pneumothorax ex vacuo is crucial in directing treatment to relieve the bronchial obstruction rather than inserting a chest tube into the pleural space.

Imaging in lung cancer

The diagnosis, staging, and follow-up of lung cancer is a clinical and therapeutic challenge. Recent radiographic advances are critical to the management of patients with lung cancer. This review focuses on state-of-the-art chest imaging modalities, including plain radiography, computed tomography; magnetic resonance imaging, as well as the newest technique, positron-emission tomography, and discusses the current literature.

Effects of lobar atelectasis on the distribution of pleural effusion and pneumothorax

Atelectasis is known to change the retractility of the involved part of the lung and the pleural pressure adjacent to it. Consequently, pleural effusions or pneumothoraxes will change their distribution and preferentially migrate toward the site of atelectasis. This alteration will often result in an atypical distribution of pleural liquid or gas. The radiological implications of this phenomenon are discussed herein.

Spiral CT of the chest: comparison of cine and film-based viewing

PURPOSE

To determine radiologists' ability to find lung nodules on spiral computed tomographic (CT) scans of the chest with both rapid sequential (cine) and conventional film-based viewing.

MATERIALS AND METHODS

Eight radiologists searched for lung nodules on spiral CT images (10-mm collimation, 10 mm/sec table speed) presented in two formats. Cine viewing was performed at a computer work-station; sections were viewed in 2-mm increments at frame rates up to 10 frames per second. Film-based viewing of images from a laser printer was performed with a lightbox; sections were viewed at 4-mm increments. Eight 3-5-mm-diameter simulated nodules were superimposed on each of five normal CT scans.

RESULTS

Radiologists found a higher fraction of nodules with the cine presentation than with film (mean, 0.69 +/- 0.02 [standard error] versus 0.58 +/- 0.03, respectively [P = .006]). Diameter thresholds for nodule detection (50% correctly localized) were 3.3 and 3.5 mm, respectively.

CONCLUSION

Cine viewing of spiral CT images of the chest improved radiologists' ability to detect nodules.

Subcarinal cavernous hemangioma: CT findings

Cavernous hemangiomas of the mediastinum, though unusual, have typically been described in the anterior or posterior mediastinum. We report such a tumor in the subcarinal region and describe the potential contribution of CT scanning in the work-up of these rare space-occupying lesions.

Glucagon effect on intracellular proteolysis and pericanalicular location of hepatocyte lysosomes in isolated perfused guinea pig livers

In guinea pigs, glucagon choleresis is accompanied by a significant, but transient, stimulation of biliary protein secretion, which can be accounted for mainly by biliary discharge of lysosomal enzymes. To clarify whether intracellular proteolysis--a process regulated by glucagon and taking place predominantly in the lysosomes--may interact with biliary protein secretion, we determined hepatic proteolytic activity and bile secretory function during substrate deprivation, amino acid supplementation, and glucagon administration in isolated perfused guinea pig livers. To further elucidate the nature of transient lysosomal enzyme release into bile during glucagon infusion, we analyzed pericanalicular distribution of lysosomes by quantitative electron microscopy. The results demonstrate that intracellular proteolysis is accompanied by biliary excretion of lysosomal enzymes. Glucagon-induced secretion of these enzymes as well as labeled proteins into bile occurs independent of protein breakdown and cannot be modulated by addition of amino acids as potent inhibitors of intracellular proteolysis. During glucagon administration, bile canalicular area and pericanalicular distribution of secondary lysosomes show a rapid increase, which persists during the entire infusion period and thus does not explain the transient biliary release of lysosomal enzymes. We therefore postulate that regulation of this process must be located beyond the lysosomal compartment, either involving transport processes or intracellular kinetics of lysosome formation or altered fusion kinetics at the bile canalicular membrane compartment. Metabolic and biliary effects of glucagon seem to occur independent of each other and to underly different regulatory mechanisms.

Determination of gene structure by intron trapping using polymerase chain reaction: application to the human plasma prekallikrein gene

We have devised a method to determine gene structure that utilizes the known gene structure of homologous proteins and the polymerase chain reaction (PCR). Because homologous proteins have evolved from a common ancestral gene, it is possible to design primers corresponding to the adjacent exon sequences in the protein of interest. These primers could then be used in a PCR using normal genomic DNA as template. The resultant PCR product is then subcloned and the nuceotide sequence of the insert is determined. This information provides the exon-intron junction sequences and the partial sequences of the intron. We have applied this method to trap introns A, H, and J of human plasma prekallikrein gene and determined their exon-intron junction sequences. The primers were designed based on the known cDNA sequence of human plasma prekallikrein and gene structures of rat plasma prekallikrein and human coagulation factor XI (which is 50% identical in the primary sequence). The intron-exon junctions are at identical sites to those of the rat plasma prekallikrein gene. The intron sequences thus obtained will be useful in designing primers for exon trapping and sequence analysis of plasma prekallikrein gene from patients with defective plasma prekallikrein. This technique will also allow the determination of the entire gene structure.

Imaging of tracheobronchial injuries

Tracheobronchial injuries are rare and can be life threatening. They can result from external injuries due to blunt or penetrating trauma or from internal injuries subsequent to inhalation of fumes, gases, and aspiration of liquids or foreign bodies. The most dangerous aspect of tracheal trauma is the fact that it is easily overlooked initially. Imaging studies play a pivotal role in timely diagnosis.

Aneurysms of the pulmonary artery. Radiographic manifestations

We analyzed the radiographic manifestations of aneurysms of the pulmonary artery in a retrospective study of 16 patients. The location, shape, size, and number of these lesions were assessed. Pulmonary artery aneurysms can be fusiform or saccular, central or peripheral, solitary or multiple. Many disease processes can lead to aneurysm formation. Correct diagnosis of these vascular lesions is important for patient management.

Epithelial markers in malignant melanoma. A study of primary lesions and their metastases

In order to determine epithelial markers in malignant melanoma in routinely processed paraffin sections and to compare the staining of primary (cutaneous) malignant melanomas and their metastases, we stained formalin-fixed paraffin sections of 13 primary and 18 metastatic malignant melanomas using the streptavidin-biotin peroxidase method by antibodies to S-100, vimentin, HMB-45, polyclonal carcinoembryonic antigen (CEA), monoclonal CEA, cytokeratins (CAM 5.2 and broad-spectrum CKKES), and epithelial membrane antigen (EMA). All primary and most metastatic malignant melanomas showed positive staining with anti-S-100, HMB-45, and anti-vimentin. Reactivity with polyclonal CEA was observed in 15 (48%) of the 31 lesions; 14 of them were metastatic. No lesion was reactive with monoclonal CEA. Significant cytokeratin (CK) staining was evident in only three (9.7%) lesions (all metastatic), which also stained specifically with anti-CK 18. EMA was observed only focally in two (6.5%) lesions. There was no correlation between epithelial markers staining of the primary tumours and their metastases. All lesions with CK or EMA staining showed concomitant extensive staining for S-100, HMB-45, and vimentin. We conclude that (a) polyclonal CEA staining in malignant melanoma is not rare and is probably due to CEA-related molecules; (b) significant CK reactivity is rare and related to simple CK, such as CK 18; (c) epithelial marker reactivity is more common in metastases of malignant melanomas and is not correlated to the reactivity in their primary tumors. Considering our results and reports of positive S-100, vimentin, and HMB-45 in epithelial tumors, a wide panel of antibodies is recommended for the study of undifferentiated tumors.

Patterns of consultation among adolescent minors obtaining an abortion

Interviews with 184 adolescents revealed that all had consulted at least one individual before obtaining an abortion, although one-quarter, primarily the older adolescents, did not consult an adult prior to pregnancy counseling. At both the time of the abortion and one year later, the adolescents perceived their mother and their male partner as the two most important and helpful people in reaching a decision.

The voices of reform. The final stretch. Interview by Renee Blankenau

Following a complex research and development process last year that led to the drafting of a comprehensive health care reform proposal, President Bill Clinton presented the U.S. Congress and the nation with an outline for reform in September, and followed up with a detailed plan and with a reform bill in October. Now it's Congress' turn to respond. Hospitals & Health Networks' senior editor Renee Blankenau interviewed 11 members of Congress whose views represent a broad spectrum of congressional opinion. What version of federal reform will emerge this year? These legislators have the inside track.

Primary intrathoracic malignant mesenchymal tumors: pictorial essay

Primary mesenchymal intrathoracic tumors are unusual. They can originate from the lung, the pleura, or the mediastinal structures. These sarcomas have protean, nonspecific imaging features. This pictorial essay illustrates a large number of these tumors, describes the plain film findings, and emphasizes the contribution of the new imaging modalities. The cross-sectional display and the high contrast resolution computed tomography (CT) and the ability to image vascular structures and chest wall with magnetic resonance (MR) allow excellent delineation of tumor extent and assessment of chest wall or vascular invasion. Early recognition of recurrence or metastases can be facilitated. In rare instances, the intrinsic characteristics of the tumor allow a specific diagnosis.