Biomedical subjects
Publications and source records attributed to L A Mack.
Four cases of ectopia cordis are described. The fetal sonographic appearance is demonstrated, and the postnatal use of computed tomography in the estimation of thoracic volumes for surgical planning is discussed.
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Seven patients with gunshot wounds to the cervical, thoracic, or lumbar spine were evaluated with conventional radiography, complex motion tomography, and computed tomography (CT). Computed tomography was better than complex motion tomography or conventional radiography for the assessment of the presence of fracture(s), bony and metallic fragments, and associated soft tissue injuries. In each case CT provided additional information not available by the other techniques.
Eighteen patients who had fallen or jumped, and who had sustained fractures of the thoracolumbar spine, were examined with high-resolution computed tomography (CT). Two distinctive patterns of fracture were demonstrated: compression, or wedge, fractures of the vertebral body were present in seven patients, but they were not associated with permanent neurological deficit; and burst fractures with sagittal cleavage into two fragments occurred in five of 11 patients, and they were associated with permanent neurological deficit. CT provided precise and unique information that aided in clinical decision making for this group of patients.
Imaging of glenoid labrum pathology is useful to help plan surgical repair of the dislocating shoulder. Eleven patients with suspect labrum damage were imaged with computed tomography (CT) immediately after routine double-contrast shoulder arthrography. Lesions identified included attenuation, tears, and displacement of the labrum as well as stripping and stretching of the anterior shoulder joint capsule. Surgical confirmation of pathology was available in all but one case. CT of the glenoid labrum is easy to perform, low in radiation dose, and accurate.
Thirty-one postoperative pelvic computed tomographic (CT) scans in 29 patients studied between 1 day and 7 years after open reduction and internal fixation of acetabular fractures were reviewed. CT was most useful in the immediate postoperative period for detecting residual intraarticular fragments, localizing metallic fixation devices, and assessing the adequacy of reduction. CT scans obtained in the late postoperative period were useful primarily for determining the position and extent of ectopic bone before surgical removal.
A review of gallbladder scintigraphy in patients with potentially compromised hepatobiliary function revealed two groups in whom cholecystitis might be mistakenly diagnosed. In 200 consecutive hospitalized patients studied with technetium-99m-PIPIDA for acute cholecystitis or cholestasis, there were 41 alcoholics and 17 patients on total parenteral nutrition. In 60% of the alcoholics and 92% of those on parenteral nutrition, absent or delayed visualization of the gallbladder occurred without physical or clinical evidence of cholecystitis. A cholecystagogue, sincalide, did not prevent the false-positive features which presumably are due to altered bile flow kinetics related to alcoholism and parenteral nutrition. Four patients on parenteral nutrition undergoing cholecystectomy for suspected cholecystitis had normal gallbladders filled with jellylike viscous thick bile. A positive (nonvisualized or delayed visualized) gallbladder PIPIDA scintigram in these two populations should not be interpreted as indicating a need for cholecystectomy.
Thirty-one consecutive patients who sustained acetabular fracture or posterior femoral head dislocations were examined by computed tomography (CT). By analysis of closely spaced, thin CT images, it was possible to characterize the three-dimensional nature of these injuries. Traditional classification into anterior column, posterior column, and complex two-column fractures was facilitated. CT was especially useful in evaluation of the two-column fractures in which unique information concerning the configuration of the fracture, integrity of the acetabular dome and quadrilateral surface, and identification of the stable fragment was obtained. Surprisingly constant fracture patterns were identified. CT was also useful in determination of presence or absence of loose bodies in the joint and in evaluation of the femoral head and sacroiliac joint in all types of fracture.
Computed tomography (CT) and plain radiography of the pelvis were compared in 26 adult patients in whom acetabular fractures or posterior femoral head dislocations were demonstrated or suspected on initial radiographs. The detection of abnormalities of the sacrum, sacroiliac joint, iliac wing, acetabular roof, joint space, anterior pelvic column, posterior pelvic column, posterior acetabular lip, pubic rami, and quadrilateral surface of the ilium by the two methods was compared. The ability of the two techniques to establish the stable fragment was also examined. Three independent readings of each examination for each pelvic region were tabulated, and sensitivity and specificity values were calculated. There was no significant difference between plain radiography and computed tomography in detection of fractures of the iliac wing, anterior pelvic column, posterior pelvic column, and the pubic rami, with high sensitivity and specificity for both examinations. CT was more sensitive than plain radiography in detecting fractures involving the sacrum, quadrilateral surface, acetabular roof, and posterior acetabular lip. In addition, abnormalities of the hip joint space, principally loose bone fragments, were detected more often by CT. Sensitivity of both examinations for abnormalities of the sacroiliac joint was relatively poor, but examinations were highly specific. Determination of the stable fracture fragment(s) was readily accomplished by CT scanning in all 26 patients; in five patients incorrect determinations were made with conventional radiographs alone.
A group of 75 patients with acute right upper quadrant pain was evaluated with both sonography and cholescintigraphy. Accuracy in screening for gallbladder disease was significantly greater with sonography (96%) than with cholescintigraphy (74%). For selecting patients with acute cholecystitis from this population that included acute and chronic cholecystitis as well as nonbiliary pathology, PIPIDA was less accurate (77%) than might be expected based on previous reports primarily due to false positive nonvisualization caused by chronic cholecystitis. Of patients with nonbiliary pathology, sonography was able to detect the cause of the right upper quadrant pain in 21%. Patients with acute right upper quadrant pain should first be screened with sonography. If cholescintigraphy is subsequently used for suspected acute cholecystitis, positive results should be interpreted with caution before surgery is planned.
LOCATE, a new computer software program, was used to outline tumor margins on scanned projection radiographs (ScoutView). This information was transferred to simulator radiographs and the results compared with tumor margins determined by all other methods. Twenty-two patients with various types of tumors in different parts of the body were studied with computed tomography and then therapy planned without the benefit of images from this program. When program information was made available, it stimulated a change in the radiation therapy plan in 18 cases (82%). Phantom studies demonstrated that magnification inherent in the program images was not significantly different from that in simulator radiographs. Program-generated tumor margins on ScoutView images were shown to accurately reflect tumor margins outlined on cross-sectional computed tomographic images as long as no patient motion occurred on the table during the study. LOCATE provides a useful means of tumor localization for therapy planning in many cases.
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Fifty patients with radiographic pleural or pleural-based opacities were examined with high resolution real-time sonographic sector scanning. In 90% of cases selected for thoracentesis, fluid sufficient for diagnosis was obtained. Complex, septated pleural loculations contained an exudative effusion in 74% of the patients, while anechoic areas yielded exudative and transudative effusions with almost equal frequency. The use of real-time scanning is stressed because of greater flexibility and shorter examination time compared to compound scanning, and its utility for portable scanning on critically ill patients.
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The real-time high resolution mechanical sonographic sector scanner is a convenient and useful instrument for the detection of intracranial hemorrhage in premature infants. Experience with 27 infants with intracranial hemorrhage detected by sonography and confirmed by computed tomography (CT) or by autopsy is analyzed. The severity of the hemorrhage shown by those methods was graded by an accepted classification for standardized reporting. The extent of intraparenchymal and intraventricular hemorrhage was accurately assessed by sonography in all cases except for small amounts of blood in normal sized ventricles in five of 12 instances. Sonography also failed to detect subarachnoid hemorrhage in each of 13 cases. There were no known false-positive sonograms. From this experience the authors believe sonographic sector scanning should be the initial examination in all infants at high risk for intracranial hemorrhage. When the ventricles are of normal size, CT scanning is recommended to search for small intraventricular hemorrhage that may not be detected by sonography. For subarachnoid bleeding, CT is preferable to sonography.
A commercially available wide field of view real-time mechanical sector scanner can be used to image the neonatal cranium. Because of the small transducer head size, the open anterior fontanelle can function as an acoustic window. By thus avoiding bone, higher frequency transducers may be used to improve image resolution. Infants may be scanned quickly without sedation in their isolettes in the neonatal intensive care unit. Sterility of the infant environment is maintained by placing the transducer in a surgical glove. Using this technique, detailed normal anatomy can be seen such as vascular structures, caudate nucleus, thalamus, third ventricle, cavum septum pellucidum, and the thalamocaudate notch. Angled coronal and sagittal sonographic anatomy is correlated with neonatal cadaver brain sections sliced in similar planes centered on the anterior fontanelle.
Eleven patients with focal nodular hyperplasia of the liver underwent a combination of radiologic procedures, including sonography, computed tomography (CT), hepatic scintigraphy, and angiography. This paper describes the radiologic findings in this group of patients and reviews the current literature. In the present series, sonography was the most sensitive (100%) method for detection of focal nodular hyperplasia, while CT was able to detect only seven (78%) of nine cases. Arteriographic findings were felt to be characteristic in nine (82%) of 11 cases. Hepatic scintigraphy demonstrated normal colloid uptake in six (55%) of 11 lesions. In this series, an accurate radiologic diagnosis of focal nodular hyperplasia was made in 73% of cases. Hepatic scintigraphy is the pivotal examination. Normal colloid uptake by a focal hepatic mass is virtually diagnostic. However, in the patients in whom the colloid scan shows decreased or absent uptake, angiography may show findings diagnostic of focal nodular hyperplasia in up to 75% of cases, thus avoiding the need need for liver biopsy or surgery.
Computed tomography (CT) is used commonly to "rule-out" disease. In 123 consecutive patients with psychiatric diseases in three institutions, 105 CT scans (85.4%) interpreted as normal or normal except for atrophy did not influence management, only reassured clinicians and patients. Incidental and false positive findings were more numerous than true positive findings. All six true positive findings occurred in patients with focal findings on neurologic examination; four led to management changes. The lower 954% confidence limit of the cost of case finding by CT only was estimated to be $2931 for all patients; $603 for patients with focal findings; and at least $7083 for patients without focal findings. Computed tomography is a sensitive diagnostic method that may detect more false and incidental positive findings when used somewhat unselectively to "rule-out" disease. In these patients, a examination suggesting structural intracranial abnormalities would have been less expensive and more effective.