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Biomedical subjects

A C Mason

Publications and source records attributed to A C Mason.

At least 37 records · Page 2Linked to original sources
PubMed1999

Revascularization of the upper extremity in a preterm infant: a case report and review of the literature.

Upper extremity arterial injuries in preterm infants are usually of iatrogenic origin. Current microsurgical techniques permit extremity revascularization in these patients. The authors report the microsurgical repair of a 0.7-mm brachial artery in a 940-g preterm infant. The preterm infant warrants special consideration due to physiological immaturity. Rapid fluid shifts, a relative polycythemia, and the potential for low cardiac output states increase the risk for vascular thrombosis. Systemic heparinization is contraindicated in this population due to the risk of intraventricular hemorrhage. Optimization of various physiological variables should reduce the risk of thrombosis.

Anticoagulants↗
PubMed1999

Accuracy of CT for the detection of pleural adhesions: correlation with video-assisted thoracoscopic surgery.

STUDY OBJECTIVE: The presence of pleural adhesions may render video-assisted thoracoscopic surgery (VATS) difficult or impossible. The aim of this study was to assess the value of chest CT in the detection of pleural adhesions prior to VATS. DESIGN: Prospective study of the accuracy of chest CT in detecting pleural adhesions prior to VATS. SETTING: Tertiary-referra; teaching hospital and Veterans Administration hospital. PATIENTS: Between July 1994 and March 1995, 63 consecutive patients undergoing 64 VATS procedures were evaluated with chest CT prior to surgery. MEASUREMENTS AND RESULTS: Preoperative scans were interpreted by consensus of two pulmonary radiologists prior to surgery. Suspected pleural adhesions and other findings related to the pleura were recorded on a form given to the surgeon prior to VATS. The surgeon confirmed or excluded each suspected adhesion during VATS, and documented any other lesions not identified preoperatively. Patient-by-patient and lesion-by-lesion analyses were performed. Pleural adhesions were correctly identified by CT in 28 of 39 cases (sensitivity, 71%) and excluded in 18 of 25 cases (specificity, 72%). On a lesion-by-lesion basis, 73 adhesions were identified during VATS, of which only 28 were identified prospectively at CT. There were 45 missed adhesions and 20 adhesions that were suggested falsely (sensitivity, 38%; specificity, 46%). Eighteen pleural spaces were correctly identified as being free of pleural adhesions. CONCLUSIONS: CT is moderately sensitive and specific for preoperative identification of pleural adhesions in patients undergoing VATS but its accuracy is poorer for individual lesions.

Adult↗
PubMed1999

Bronchiectasis: accuracy of high-resolution CT in the differentiation of specific diseases.

OBJECTIVE: The aim of the study was to determine whether various causes of bronchiectasis can be differentiated by the pattern and distribution of abnormalities seen on high-resolution CT. MATERIALS AND METHODS: The retrospective study included 82 consecutive patients who had a specific diagnosis of bronchiectasis proven by appropriate clinical and laboratory criteria. All patients underwent high-resolution CT scanning (1- to 1.5-mm collimation). The CT scans were assessed for the presence, extent, type, and anatomic distribution of bronchiectasis by two independent observers who were not aware of the clinical data. The observers recorded their most likely diagnosis and the degree of confidence in that diagnosis. RESULTS: The two independent observers made a correct diagnosis in 61% of cases (100/164 interpretations). On average, a correct diagnosis was made in 19 (68%) of 28 cases of cystic fibrosis, 16 (67%) of 24 cases of previous tuberculosis, six (43%) of 14 cases of previous childhood infection, five (56%) of nine cases of allergic bronchopulmonary aspergillosis, and four (57%) of seven cases of other causes of bronchiectasis. We found moderate agreement between the observers for the correct diagnosis (kappa = .53) and good agreement for the presence or absence of bronchiectasis in each lobe (kappa = .71). CONCLUSION: The pattern and distribution of abnormalities revealed by high-resolution CT in patients with bronchiectasis are influenced by the underlying cause. Bilateral, predominantly upper lobe, bronchiectasis is seen most commonly in patients with cystic fibrosis and allergic bronchopulmonary aspergillosis, unilateral upper lobe predominance in patients with tuberculosis, and lower lobe predominance in patients after childhood viral infection.

Adolescent↗
PubMed1998

The role of computed tomography in the diagnosis and management of human immunodeficiency virus (HIV)-related pulmonary diseases.

This review summarizes the current role of CT in the diagnosis and management of respiratory disease in human immunodeficiency virus (HIV)-positive patients. Recommendations are made concerning optimum technique for diagnostic CT as well as practical considerations concerning the use of CT in biopsy and thoracic interventional procedures in acquired immune deficiency syndrome (AIDS)-related thoracic disease. Clinical scenarios discussed include the use of CT when the chest radiograph is normal in a patient with a high clinical suspicion of pulmonary disease, utility of CT in the differential diagnosis of parenchymal abnormalities and in the assessment of patients with airways disease, hemoptysis, progressive lung disease, and intrathoracic complications. Finally, the use of thoracic CT in the staging of AIDS-related neoplastic conditions involving the chest is discussed.

AIDS-Related Opportunistic Infections↗
PubMed1998

The role of radiologic imaging in diagnosing complications of video-assisted thoracoscopic surgery.

STUDY OBJECTIVE: To examine the role of radiologic imaging in evaluating complications of video-assisted thoracoscopic surgery. DESIGN: Retrospective review of radiographic and clinical data. SETTING: Tertiary referral hospital. PATIENTS: All patients who underwent thoracoscopy at the University of Maryland Hospital between July 1990 and June 1994. A total of 260 procedures were performed on 239 patients. MEASUREMENTS AND RESULTS: Imaging studies performed before, during, and after surgery in cases in which complications occurred were reviewed by two thoracic radiologists. A randomly selected group of 22 CT scans from uncomplicated cases were used as control subjects. Complications occurred in 24 (9.2%) of the 260 thoracoscopic procedures. Intraoperative complications developed in 14 (5.4%) patients. Ten of the 14 patients had an obliterated pleural space that prevented access of the trocars and videoscope. Preoperative imaging showed significant pleural thickening or calcifications in seven of these ten patients. Other intraoperative complications were malposition of the double-lumen endotracheal tube (n=2) and dislodgement of a localizing needle-wire (n=2). In 8 (3.1%) patients, radiographically evident postoperative complications developed; these complications included prolonged air leak, empyema, recurrent pneumothorax, pulmonary edema, and pneumonia. CONCLUSION: Pleural calcification or thickening that is found on preoperative studies may help predict difficulty in inserting the thoracoscopic instruments but also can be seen on preoperative CT scans in uncomplicated cases. Thoracic CT scans may fail to predict complete pleural symphysis.

Adult↗
PubMed1998

Hearing in mole crickets (Orthoptera: Gryllotalpidae) at sonic and ultrasonic frequencies.

We have studied auditory responses in two species of mole cricket (Scapteriscus borellii and S. abbreviatus) to determine (1) whether they show sensitivity to ultrasound, (2) whether their hearing (at both low and high frequencies) is based on the same neural circuitry as that of true crickets, and (3) whether ultrasound sensitivity in different mole cricket species varies with their ability to fly. S. borellii are sensitive to ultrasonic frequencies. There is evidence of a segregation of frequency bands in prothoracic auditory neurons. There are two pairs of omega neurons (ONs) with similar morphology to ON1 of true crickets. The two pairs of ONs differ in tuning. One pair has two sensitivity peaks: at the frequency of the calling song of this species (3 kHz), and in the ultrasonic range (25 kHz). The other pair lacks the high-frequency sensitivity and responds exclusively to frequencies in the range of the species song. These two types are not morphologically distinguishable. In S. abbreviatus, only one class of ON was found. S. abbreviatus ONs are narrowly tuned to the frequency of the species' calls. A T-neuron had the best ultrasonic frequency sensitivity in S. borellii. This cell showed a broad tuning to ultrasonic frequencies and was inhibited by low-frequency stimuli. A morphologically similar neuron was also recorded in S. abbreviatus, but lacked the high-frequency sensitivity peak of that in S. borellii. We also assessed the responses of flying S. borellii to ultrasound using field playbacks to free-flying animals. The attractiveness of broadcast calling song was diminished by the addition of an ultrasound signal, indicating that S. borellii avoid high-frequency sound. The results indicate that mole crickets process low-frequency auditory stimuli using mechanisms similar to those of true crickets. They show a negative behavioural response to high-frequency stimuli, as do true crickets, but the organization of ultrasound-sensitive auditory circuitry in mole crickets differs from that of true crickets.

Acoustic Stimulation↗
PubMed1996

Nutrition Societies Presidents' Forum: future challenges and opportunities for nutrition societies in the 21st century.

The Chair introduced "Pasteur's Quadrant" as a potentially useful paradigm for modern science. Developed by Princeton's Donald E Stokes, the quadrant is two-by-two matrix that classifies knowledge as fundamental and/or applied. The Chair also noted the effect of competitive pressures, and the necessity for cooperation among nutrition societies. The Presidents of The American Society for Nutritional Sciences (ASNS), The American Society for Clinical Nutrition (ASCN), The American Society for Parenteral and Enteral Nutrition (ASPEN), and the Chair of the Institute of Food Technologist's (IFT) Nutrition Division presented their views on how societies can prepare to meet their members' upcoming needs. The Director of the Center for Food and Nutrition Policy discussed the future role of nutrition societies and how they might interact with various interest groups. The Forum, which included an opportunity for audience participation, took place soon after the February 1996 release of "Meeting the Challenge: A Research Agenda for America's Health, Safety, and Food." Published by the Executive Office of the President's Office of Science and Technology Policy, the report highlights the importance of nutrition to our nation's health.

Humans↗
PubMed1996

From the archives of the AFIP. Malignant pleural mesothelioma: radiologic-pathologic correlation.

Malignant pleural mesothelioma (MPM) is a rare malignant neoplasm that typically affects individuals occupationally exposed to asbestos through a variety of industries. The patients experience an insidious onset of symptoms, including dyspnea, chest pain, cough, malaise, and weight loss. The pathologic diagnosis of MPM is difficult, and special stains or immunohistochemical or ultrastructural analysis may be required to differentiate MPM from metastatic adenocarcinoma. The tumor affects both the parietal and visceral pleural surfaces and progresses to encase the lung and invade the lung, mediastinum, and chest wall. Radiologically, MPM manifests as unilateral pleural effusion, pleural nodules, or pleural masses. Imaging studies are useful for diagnosis and staging in patients who are potential surgical candidates. Although a variety of multimodality therapies are available and radical surgical procedures have been developed, the prognosis remains dismal.

Aged↗
PubMed1996

Primary carcinoma of the lung overlooked at CT: analysis of findings in 14 patients.

PURPOSE: To describe the appearances of overlooked lung cancer at computed tomographic (CT) examination and to analyze the reasons for failure to diagnose these lesions. MATERIALS AND METHODS: Fourteen patients with 15 overlooked lung cancers were identified by radiologists at three institutions. Location, shape, and cell type of each cancer were reviewed, and other relevant findings of CT examinations were assessed. RESULTS: The missed tumors manifested as endobronchial lesion (n = 10), solitary parenchymal nodule (n = 2), area of focal peripheral air-space disease (n = 2), or pleural-based thickening (n = 1). Eleven (73%) of the 15 lesions were located in a lower lobe. In six (43%) of 14 patients, major distracting findings were present elsewhere in the thorax. CONCLUSION: Endobronchial location and lower lobe predominance were the most common characteristics of overlooked lung cancer at CT. The presence of unrelated major abnormalities at CT may also have contributed to failure to diagnose the tumor.

Diagnostic Errors↗
PubMed1995

MR imaging of slipped stacked breast implants: a potential pitfall in the diagnosis of intracapsular rupture.

The integrity of silicone-gel breast implants can be evaluated by MR imaging. The findings of intra- and extracapsular rupture have been described. Increasingly sophisticated breast reconstruction techniques such as stacking of prostheses have lead to a wider range of implant appearances. We report a case where intracapsular rupture was simulated by slippage of two retropectoral stacked implants in relation to each other. The MR and CT findings are described.

Breast↗
PubMed1995

Calcification of aortic valve detected incidentally on CT scans: prevalence and clinical significance.

OBJECTIVE: Aortic valve calcification that is visualized on chest radiographs is considered a marker for clinically significant aortic stenosis, but the clinical importance of this finding on CT is unknown. Accordingly, we studied the prevalence and clinical relevance of aortic valve calcification found incidentally on CT scans of the chest. MATERIALS AND METHODS: After comparing computer records of chest CTs and echocardiograms, we identified 109 patients who underwent both studies during a 2-year period. Two thoracic radiologists reviewed the CT scans to identify and quantify aortic valve calcification. The quantity of aortic valve calcification was graded on a scale of 1 to 3, with grade 3 indicating the most severe calcification. The prevalence of calcification was correlated with patient age and sex. The findings on CT were correlated with hemodynamic data from echocardiography. At echocardiography, a peak aortic valve gradient of greater than 25 mm Hg was defined as abnormal. RESULTS: Aortic valve calcification was noted on CT scans in 33 (30%) of the 109 patients. Aortic valve calcification shown by CT was significantly more common in patients more than 65 years old (p < .01). Five (15%) of 33 patients with aortic valve calcification shown by CT had abnormal aortic valve gradients at echocardiography. In contrast, none of 76 patients without aortic valve calcification shown by CT had abnormal aortic valve gradients (p < .01). All five patients with abnormal aortic valve gradients had moderate quantities of aortic valve calcification seen on CT scans. Two of the five were younger than 55 years old. CONCLUSION: Aortic valve calcification is a common finding on CT scans and is usually clinically insignificant. Nevertheless, some patients with aortic valve calcification on CT have aortic stenosis, particularly those younger than 55 years old and those with moderately dense aortic valve calcification shown by CT. These patients may benefit from hemodynamic assessment of the aortic valve by echocardiography.

Adult↗
PubMed1995

Informed consent for percutaneous lung biopsy: comparison of two consent protocols based on patient recall after the procedure.

OBJECTIVE: Informed consent is now required for the majority of radiologic procedures, but few studies have evaluated the efficacy of informed consent protocols. We compared our standard consent protocol of obtaining consent prior to percutaneous lung biopsy with a modified protocol by using patients' recall of procedure risks after the biopsy as an indicator of patients' comprehension. SUBJECTS AND METHODS: The study sample consisted of 50 patients who underwent percutaneous lung biopsy between December 1992 and June 1994. Twenty-seven patients received our standard informed consent procedure in which four important procedure risks were described briefly using our standard method. Twenty-three patients underwent a consent procedure that had the following modification. After the four procedure risks were described, the patient was tested verbally until all risks could be recited to the physician. This change required 5 additional min at most. In both protocols, efficacy of the procedure was evaluated by testing patient recall 4 hr after consent was obtained. We also assessed any effect that might have been introduced by differences between the groups, age, sex, time between consent and recall, and complications during the procedure. RESULTS: Patients' recall was significantly better in the modified consent group than in the standard group (p = .005). This result could not be attributed to differences in age, sex, or time between consent and recall. There was a trend for improved recall in patients with complications. This trend did not appear to influence our principal finding. CONCLUSION: The standard consent procedure for lung biopsy appears inadequate when patients' recall of procedure risks later is used as a measure of the patients' comprehension. Based on this study, the informed consent process may be improved substantially by teaching patients to recite the procedure risks to the physician as part of the informed consent protocol.

Adult↗