Letter: E.M.I. and radioisotope brain imaging.
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Physical and clinical data on a new emission transverse-section scanner are given. Comparative data from an earlier tomoscanner and a rotating gamma-camera system yield the following information for the three imagers. Resolution at the center of the field is 9 mm for this tomoscanner, 18 mm for the earlier tomoscanner, and 11 mm for the rotating camera; sensitivity (cps/muCi-ml) 36K, 15.4K, 1.9K; crystal area (cm2) 3096, 619, 490, respectively. The quantification of images is discussed. Clinical emission section scans of the brain, liver, chest and skull are presented and discussed. Forty brain scans were analyzed in conjunction with x-ray transmission tomography. No false positives were found. From a total of 15 lesions seen by the CT x-ray scanner, 14 were detected by the emission tomographic scanner, 12 by standard gamma-camera imaging. One false negative case (cyst) was seen by the transmission x-ray scanner but not by the emission scanner.
Four patients with lateral sinus thrombosis were studied by radionuclide (RN) dynamic studies and RN static brain scans. Findings included: (a) abrupt termination of RN activity in the midportion of a lateral sinus ("stump sign"); (b) nonvisualization on dynamic, increased visualization on static images ipsilateral to a prominent sinus groove on a plain skull radiograph; and (c) increased activity on static images with nonfilling on angiography. RN demonstration of the "stump sign" is pathognomonic of lateral sinus occlusion; the latter two patterns require radiographic demonstration of an ipsilateral sinus groove or angiography for significance.
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The Artronix 1,100 head scanner is a promising unit which allows reconstitution of the images in coronal and sagittal planes from the axial slice. The clinical usefulness of coronal and sagittal images thus obtained is illustrated and discussed.
Six selected cases demonstrate the appearance of subdural hematomas, tumor, stroke, and abscess on single-photon emission tomography. Conventional radionuclide images were obtained on every patient, and computed transmission tomographs were obtained on 4 of the patients. This early clinical experience suggests several promising areas for further investigation.
We have reviewed the medical records and radiographic examinations of 12 patients with herpes simplex encephalitis to assess the role of RN and CT in the early diagnosis of this disease. The initial RN study was positive in 83% (10/12) of cases while the initial CT study was positive in 75% (9/12) of cases. The earliest positive RN was seen on the second day after the onset of neurologic signs or symptoms while the earliest positive CT was seen on the third day. We describe various abnormal patterns encountered in HSE and discuss their diagnostic reliability. We make recommendations for the diagnosis of HSE based on our findings and on the information available in the literature
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Imaging of the brain by positron emission tomography can be optimized for sensitivity by dedicating the design of the tomograph to this application. We have designed a multislice positron emission tomograph (PETT V) for imaging the human brain and the whole body of small experimental animals. The detector system of PETT V consists of a circular array of 48 NaI(Tl) scintillation detectors, each fitted with two photomultiplier tubes, with one dimensional positioning capability. Suitable sampling is achieved by rotation of the circular array of detectors and by a wobbling motion of the detector circle. The proposed system is capable of providing seven slices simultaneously, with a spatial resolution in the plane of the slice from 7 to 15 mm and with slice thicknesses of 7 and 14 mm. The minimum scanning time is 1 sec. The estimated overall sensitivity of PETT V is 350,000 counts/sec/mCi in a 20 cm diameter phantom for a resolution of approximately 1.5 x 1.5 cm. The system is under construction.
A survey of the literature pertaining to several serial brain scanning procedures has been presented. These procedures include rapid brain imaging, sequential brain imaging, delayed from imaging, and follow-up brain imaging. Applications of these techniques to specific clinical problems have been stressed and the reported results reviewed. Thus, it has been indicated that rapid brain imaging is most useful in detecting lesions secondary to cerebrovascular disease but may also provide some helpful information pertaining to the differential diagnosis of other C.N.S. lesions demonstrated on subsequent static brain scans. Sequential brain imaging is a time-consuming adjunctive procedure which, however, can be extraordinarily helpful in a highly selected group of problem cases which present with relatively small lesions adjacent to normal anatomic structures which themselves have considerable radioactivity. Delayed brain imaging has the distinction of detecting the greatest number of intracranial lesions but is attended by tactical problems in maintaining an optimal patient flow through the department and also has the undesirable consequence of reduced information density and diminished image quality, unless greater radiation doses are injected. Follow-up brain imaging is useful in the differential diagnosis of cerebrovascular and neoplastic disease and in the assessment of effectiveness of radiation therapy.
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Unilateral innominate vein obstruction with patency of the superior vena cava was suspected when early jugular--sinuses--jugular reflux of tracer occurred during brain-flow imaging. Radiographic venography confirmed this pattern of venous obstruction.
Functional gamma imaging, in color, was established for regional cerebral blood flow (rCBF) using 133Xe. During 10 min after intracarotid injection of 133Xe in saline, 60 picture frames of the 133Xe clearance curve for the entire hemisphere were obtained. After nine-point smoothing, the rCBF for each of the 4,096 picture elements was calculated by two methods: the half-time method and the height-over-area method. Both the 133Xe clearance half-times and the calculated CBF values were displayed, using 13 steps of color, as functional CBF images of the brain. Images of peak count and total count were also displayed on the same frame of the color television. Forty-six studies, performed on 37 patients with various cerebral disorders, were divided into two types: diffuse and focal. In the diffuse type, a decrease in CBF was noted in cases of normal-pressure hydrocephalus; successful ventriculoperitoneal shunt operations were followed by recovery of CBF. Occlusion of the middle cerebral artery showed up as a wedge-shaped area of decreased CBF, even when the conventional brain scan looked normal. Increased perfusion to a tumor was frequently associated with decreased CBF in the rest of the lateral hemisphere; such a decrease could be improved by surgical removal of the tumor.
To investigate the potential application of radionuclide computed tomography (RCT) to nuclear medicine imaging using 99mTc, a tomographic system using a lightweight scintillation camera for brain imaging was constructed, and lesion contrast with RCT and conventional scintigraphy were compared. The detector revolves once around the patient's head at constant angular velocity, requiring approximately 20 min. Nine sections are reconstructed from the data, using either a Fourier transform or a filtered back-projection algorithm. In a phantom simulating the radionuclide distribution observed during brain imaging, quantitative lesion contrast was far superior in the RCT images. In a series of 25 patients with intracranial lesions, the average RCT lesion contrast was superior to that of standard scintigraphy by a factor of more than 2. An RCT image of an experimentally infarcted dog's heart, taken after the injection of 99mTc-MAA into the left atrium, also showed excellent correspondence to the gross anatomic defect. Although problems of photon absorption may occur in imaging larger body areas, RCT imaging in this feasibility study produced surprisingly good results that warrant further investigation of the technique.
The authors report a case of subdural hematoma in a patient who showed bilateral perfusion defects, highly characteristic of subdural hematoma, but did not show the expected complementary static abnormalities. This appears to be the first such case in the literature.