Biomedical subjects
Publications and source records attributed to L M Zatz.
The suggestion that the Evans ratio, the ratio of the transverse diameter of the anterior horns of the lateral ventricles to the internal diameter of the skull, was a more significant quantity than the ventricular measurement alone was based on a calculation error. The value of this ratio and other such ratios involving linear skull measurements is unproven.
Two methods for quantitating cerebrospinal fluid (CSF) volume in each hemicranium and on the total section on cranial computed tomography are described and compared. Both analyses utilize information input by the user, but differ in their treatment of volume averaging. The second analysis (Automated Section Information-I) measured partially volumed CSF more sensitively. Potential inaccuracies due to technical artifacts are summarized.
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Some of the prior efforts at using postreconstruction dual kilovoltage CT scans to obtain an effective atomic number and electron density are reviewed. A prereconstruction method which avoids beam hardening is applied to a phantom and a beginning clinical trial is described.
Image quality in cranial computed tomography (CT) was evaluated with phantom and patient studies on both a first (single beam) and a second (multiple beam) generation scanner. When comparable radiation doses were used, there were only minor differences in resolution, low contrast detectability, and noise level. The pattern of noise relative to the size of the area in which it was measured was somewhat different. On patient studies, no differences were found when contrast-material-filled vessel visibility and gray--white matter distinction were analyzed. A lesion was obscured by streak artifacts in one scanner in one of 22 patients scanned on both machines. The major factor in image quality as seen in the two scanners seemed to be in the production of artifacts. This was apparent in artifacts from motion, high contrast discontinuities, beam hardening, and edge enhancement. Multiple factors must be considered in assessing CT image quality. In particular, further studies to quantitatively evaluate noise quality and artifact production are needed.
A conventional B scan ultrasound unit was modified by the addition of a specially built logarithmic amplifier and a high resolution nonstorage oscilloscope, as suggested by Taylor and Carpenter. One hundred five consecutive patients submitted for radionuclide imaging of the liver were examined with ultrasound using a standardized scanning system. The ultrasound technique produced scans that were technically poor or inadequate in 37 per cent of the patients studied. In the studies in which there has been confirmation, the ultrasound diagnosis was accurate in 73 per cent and the radionuclide diagnosis was correct in 83 per cent. The combined accuracy of the two studies was 93 per cent. In 11 patients, ultrasound more clearly defined the lesions that were demonstrated by both techniques or demonstrated the nature of suspicious or equivocal areas on the radionuclide images. In 48 patients, the radionuclide scan imaged the liver more completely or demonstrated lesions more clearly than did the ultrasound examination. This specific approach to ultrasound gray scale imaging appears to be a valuable supplemental tool to radionuclide imaging, but at its present stage of development cannot replace it as a routine screening technique for hepatic disease.
A variety of aphasic patients were studied to determine the relationship betweeen lesion size, as demonstrated by cranial computed tomography (CCT), and the type of aphasia, as classified by the Boston Diagnostic Aphasia Examination (BDAE). CCT demonstrated a variety of lesions. Those in nonfluent Broca's aphasics and fluent Wernicke's aphasics were separable into pre-Rolandic and post-Rolandic areas, respectively. Conduction, global, and anomic aphasics had different lesion sites. Correlation of lesion location by CCT with aphasia type supports Geschwind's concepts of aphasia.
By scanning the brain first at 100 and then at 140 kVp one can distinguish, in vivo, between blood and calcium or iodine solutions. The higher atomic number of calcium or iodine causes their CT values to decrease significantly while blood shows no significant change. This principle was applied to eight patients with hemorrhages, calcified lesions, or iodine-contrast augmented lesions. Hemorrhages showed no significant change with change in kVp, while the lesions containing calcium or iodine showed a highly significant change. This is a useful maneuver for determining the nature of a high-value lesion.
The CT values of a variety of materials were studied in an EMI and a Syntex head scanner. The presence of bone-simulating rings changed the CT values despite the use of constant length water paths and software corrections. Errors due to beam hardening in CT scanning are discussed. These errors could be of significance, particularly in quantitative studies. The changes in CT values with KV setting of the scanner are used to illustrate their energy dependence and the peculiarities of the scaling system introduced by EMI. The difficulty in specifying a standard scale or unit for CT scanners is discussed.
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A variety of materials and tissues as well as 3 patients were studied with the EMI scanner using the 100-, 120-, and 140-kVp settings. There was little shift in the EMI value for most tissues over this range, but significant shifts occurred with materials whose effective atomic number was moderately different from that of water. Use of the highest kVp setting may improve visualization of low-contrast images by decreasing the noise caused by statistical fluctuations. This shift in EMI values can be used to determine the approximate amount of material of high atomic number present, such as calcium or iodine.
Results are described of in vitro biological experimentation using a new through-transmission ultrasonic camera system developed at the Stanford Research Institute. The camera system produces real-time focused, orthographic images of a 15 times 15 cm field. The in vitro studies, which demonstrate the diagnostic potential of the new technique, include transmission images of selected excised organs such as liver, kidney, spleen, and uterus. In addition, preliminary studies evaluating ultrasonic image quality and the effect of out-of-focus structures are discussed.
A new transmission ultrasound camera system has provided focused images in real time through the abdomen of adult volunteers at average incident sound intensity levels of less than 1 mW/cm-2. The camera uses a unique acousto-mechanical lens/deflection system and a linear array of piezoelectric transducers to detect the ultrasound image. BONY STRUCTURES AND COSTAL CARTILAGES WERE CLEARLY SEEN. The colon was regularly seen and the kidney could be outlined in several subjects. The stomach and duodenal bulb were demonstrated and peristalsis was observed using a barium contrast material. The camera has the potential of extending the use of ultrasound in clinical medicine by providing an ultrasound soft tissue imaging system analogous to an x-ray fluoroscope. The need for further clinical evaluation and research to improve the images is emphasized.
Real-time transmission ultrasonic imaging of the abdomen in adult patients has been accomplished with a new camera system developed by Stanford Research Institute. Some inherent limitations of the transmission technique are apparent; these include obscuration of some structures by overlying bone or gas-filled organs. Other limitations produced by diffraction and refraction effects of the ultrasound beam in complex objects may be eliminated by additional research effort. With further improvements, this camera system may become a useful diagnostic instrument.
The thinnest pair of slices provided by the EMI scanner is 8 mm, producing an overlap of 6 mm. Resolution is reduced by averaging the density of structures throughout the thickness of the slice. The authors described special collimators which provide thinner slices with no overlap and thereby improve the quality of orbital scans.
A case of pericardial cyst development in the years after an episode of acute pericarditis is reported. The method of diagnosis allowed confirmation of the condition without thoracotomy. These aspects of the case are relevant to the genesis of pericardial cysts in general and establish ultrasound and subsequent contrast roentgenography are advocated as adequate means of diagnosis in this condition.