Biomedical subjects
Publications and source records attributed to D Front.
Perfusion blood pool mismatch using Tc-99m labeled red blood cells (RBCs) in a hemangioma of the tongue is described. The method is useful in the evaluation of size of the residual blood pool after irradiation of the tumor.
The diagnostic value of scintigraphy with technetium-99m labeled red blood cells (Tc-RBC) was assessed in 19 patients with clinical suggestion of superior sagittal sinus thrombosis (SSST). Comparison of Tc-RBC static images with dynamic flow studies in the brain showed a sensitivity of 100%, specificity of 86%, and accuracy of 94% for static studies and values of 87%, 20%, and 61%, respectively, for the flow studies. Tc-RBC scintigraphy enables direct visualization of the integrity of the superior sagittal sinus, whereas CT scanning shows various but nonspecific changes in the brain associated with SSST. Single-photon emission CT study using Tc-RBC, performed in six patients, appears to have potential in the diagnosis of SSST, allowing separation of vascular structures that are superimposed on the superior sagittal sinus in planar scintigraphy study.
An improved method of noninvasive assessment of pulmonary arterial pressure is presented. The already existing radionuclide method for assessment of pulmonary arterial pressure based on right ventricular ejection fraction, although having a relatively good positive predictive accuracy (75 percent), lacks in specificity and correlates only weakly with pulmonary arterial pressure, r = .66. In the present study a diastolic index of the ventricular performance (right atrial early diastolic emptying rate) was used to improve the predictive value of the right ventricular ejection fraction. Phase image analysis was used to differentiate the right atrium from the rest of the cardiac structures, and right atrial emptying rate was calculated after time activity curves were generated. A reasonably good correlation was found between right atrial emptying rate and pulmonary arterial pressure, r = .75. This diastolic index, however, was limited in its ability to detect patients with COPD and normal pulmonary arterial pressure (negative predictive value 62 percent). In order to improve the predictive value of right ventricular ejection fraction, having low specificity (33 percent) but high sensitivity (93 percent), a score index was constructed, combining right ventricular ejection fraction with right atrial emptying rate (having high specificity 100 percent, but modest sensitivity 78 percent). Score index proved to be an excellent indicator of pulmonary arterial hypertension (positive predictive value 93 percent, negative predictive value 100 percent.
The structural dimensions of capillary tight junctions and the uptake of 99mTc pertechnetate in human gliomas were studied. Quantitative analysis revealed a correlation between the uptake of radionuclides and the length of endothelial tight junctions. It is suggested that brain scintigraphy might be used for the selection of malignant brain tumors with altered tight junctions which might be accessible to chemotherapy with water-soluble agents.
Gaucher's disease involves the liver, the spleen, and the bone. Liver-spleen and bone scintigraphy were used during an 8-yr period to evaluate changes caused by this disease. Patients were investigated with a liver-spleen scan for abdominal pain, mechanical discomfort, enlarged liver or spleen on physical examination, abdominal mass, abnormal liver function tests, and symptoms of hypersplenism. Fourteen liver-spleen scans were performed in nine patients. Liver scintigraphy showed various degrees of enlargement and inhomogeneous uptake. In two patients focal defects were detected. In one, focal defects were due to liver involvement with Gaucher's disease, but in the other they were caused by metastatic pancreatic carcinoma. The study was also useful in detecting splenic infarction and in following enlargement of the spleen after partial splenectomy. The main indication for bone scintigraphy in six patients was bone pain. This was found to be caused by either aseptic necrosis of the head of the femur, bone infarction, pathological fractures, or osteomyelitis. Loosening after total hip replacement was ruled out in three patients and missed in one patient. Scintigraphy appears to be a simple, sensitive test for evaluation of the liver, spleen, and bony skeleton in patients with symptomatic Gaucher's disease.
A simple, easily reproducible, noninvasive, provocative test for the assessment of early diastolic impairment in long-standing hypertension is presented. Volume challenge of the heart was produced by elevating the subject's legs to 45 degrees for 5 minutes, thus increasing the venous return to the right heart. Using gated radionuclide ventriculography and Fourier analysis, the atrial structures were delineated and time-activity curves were generated. Early diastolic emptying slope of the left atrium was used to assess left ventricular compliance changes in hypertensives. The left atrial early diastolic emptying rate was markedly reduced in 38 hypertensive patients (45.5 +/- 15.4 counts/s) when compared with 14 healthy subjects (78 +/- 16 counts/s). The legs-up procedure induced subsequent decrease in left atrial emptying rate in patients with long-standing hypertension and left ventricular hypertrophy (-27.4 +/- 11%). In patients with recent onset hypertension there was a depressed early diastolic emptying rate (55.79 +/- 10 counts/s), but a "normal" response to the legs-up procedure (an increase in left atrial emptying rate: 12.84 +/- 7%). Global ejection fraction was normal in all subjects studied, decreasing after induction of augmented venous return in long-standing hypertension. Reduction in left atrial early diastolic emptying rate, caused by the legs-up manoeuvre appears to be an early and sensitive indicator of the left ventricular diastolic impairment in essential hypertension.
The relationship between bone pain and stress fractures diagnosed by bone scintigraphy was investigated in military recruits during active training. In three patients pain appeared in the site of abnormal uptake 7-14 days after the bone scan in a previously asymptomatic site. One hundred and twenty-four sites of stress fractures were found in 64 patients; 32 (26 per cent) were asymptomatic. In 38 patients (59 per cent) there were multiple stress fractures; 32 (33 per cent) had asymptomatic stress fractures. Fifty-three per cent of the regions with abnormal uptake in the femur were painless, compared with 17 per cent in the tibia. The necessity for imaging all bones susceptible to stress fractures, even when asymptomatic, is stressed. It is suggested that diagnosis of stress fracture should be made when typical abnormal uptake appears on scintigraphy. Bone pain in such cases may be delayed.
The uptake of [99mTc]MDP in metastatic lesions of the vertebrae was compared with the uptake in normal vertebrae. The ratio of these lesion-to-nonlesion uptakes at 4 and 24 hr was called the 24-hr/4-hr ratio (TF ratio). A similar ratio was measured for lesions in the spine due to degenerative bone disease. Lesions in vertebrae with degenerative bone disease and treated metastases had a significantly lower TF ratio than lesions in vertebrae with untreated bone metastases. These findings suggest that the TF ratio might be a reliable method for separating metastatic lesions from degenerative changes in the vertebral column, and could be especially useful in cancer patients whose bone scans demonstrate a single lesion in the spine.
Nine patients with cavernous hemangioma of the liver were examined by nuclear magnetic resonance imaging (MRI) with a 0.5 T superconductive magnet. Spin-echo technique was used with varying time to echo (TE) and repetition times (TR). Results were compared with 99mTc red blood cell (RBC) scintigraphy, computed tomography (CT), echography, and arteriography. Four illustrated cases are reported. It was possible to establish a pattern for MRI characteristics of cavernous hemangiomas; rounded or smooth lobulated shape, marked increase in T1 and T2 values as compared with normal liver values. It is concluded that, although more experience is necessary to compare the specificity with that of ultrasound and CT, MRI proved to be very sensitive for the diagnosis of liver hemangioma, especially in the case of small ones which may be missed by 99mTc-labeled RBC scintigraphy.
Uptake of 67Ga and [3H]DG after radiation and chemical therapy was measured in a tumor model. Uptake of both agents in treated viable tumors did not differ significantly from the uptake in viable control tumors. However, when tumors showed, after therapy, partial or complete fibrosis, there was a significant decrease in uptake. Viable tumors showed the whole range of weight response to therapy, and the mean weight of viable tumors did not differ significantly from the mean weight of partially viable tumors. The results indicate that, in the tumor model used in this study, 67Ga and [3H]DG could be used to monitor tumor response to therapy. Tumor weight was not a reliable indicator of the effect of therapy at early stages when the tumor is partially viable.
Red blood cells labeled with 99mTc constitute a suitable intravascular agent for imaging of vascular abnormalities. Hemangiomas are characterized by low perfusion and a high blood pool. This "perfusion blood-pool mismatch," not encountered in other lesions, may help in the specific diagnosis of this tumor. This is particularly so in cavernous hemangiomas of the liver where three-phase 99mTc-labeled red blood cell scintigraphy should precede liver biopsy. Red cell scintigraphy also is useful for establishing the vascular nature of hemangiomas of the head and neck and the skin and for diagnosis of venous occlusion. Heat-damaged red blood cells provide a specific spleen imaging agent. This should be used when patients with suspected splenic pathology have equivocal colloid scintigraphy.
Through the first 2 hr, uptake of [Tc-99m]pertechnetate and of Co-57 bleomycin were assessed in 29 brain tumors and were correlated with the ultrastructure of the tumor's capillary endothelium. No difference in uptake was found between the two tracers. Permeability of brain tumors to these agents was found to be governed by the same ultrastructural features that determine permeability in experimental brain tumors: the type of junction between contiguous endothelial cells in the capillaries. Meningiomas, which showed very high uptake of the radiotracers, demonstrated open or punctate junctions with short fusion of apposed membranes. They also showed a large number of pinocytotic vesicles and fenestrae. Capillaries of tumors without uptake had a small number of short tight junctions (less than 0.25 mu) between adjacent endothelial cells and a relatively large number of long junctions (greater than 0.5 mu). In intracerebral tumors that showed relatively high uptake, the reverse was true: most of the junctions were short and only a few long junctions were found. That uptake of [Tc-99m]pertechnetate and of Co-57 bleomycin depends on tumor capillary ultrastructure (which determines the permeability) suggests the possibility of the use of radiopharmaceuticals as in vivo indicators of tumor permeability. Brain scintigraphy may help to asses brain-tumor availability to non-lipid-soluble chemotherapeutic drugs.
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One hundred ninety patients with breast cancer were prospectively evaluated for bone pain and had technetium Tc 99m-methylene diphosphonate bone scintigraphy for bone metastases. Of the 66 patients showing evidence for bone metastases, 21 (32%) did not have bone pain. There were 155 sites of skeletal metastases, but pain was found only in 50 sites. The age of the patient or involvement of weight-bearing bones did not seem to affect the association between bone metastases and pain. We discuss the need for periodic bone scintigraphy, even when the clinical state does not seem to warrant it.
Scintigraphy with 99mTc-labeled red blood cells was performed in five patients for demonstration of normal anatomy and in 18 patients for evaluation of suspected or apparent space-occupying abdominal lesions. In 14 cases of abdominal lesions, the study demonstrated the extent, vascularity, and relation of the lesion to neighboring organs. We found the method was primarily useful for evaluating cases of retroperitoneal tumor and vascular malformation.
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Patterns of pertechnetate uptake were correlated with ultrastructural properties of the endothelial wall in 14 human brain tumours. In tumours with reduced uptake of the radionuclide, intercellular tight junctions were observed whereas absence of intercellular tight junctions was characteristic of all tumours with an increased uptake of pertechnetate. In some tumours with increased uptake, fenestrated endothelial wall was seen while in others non-fenestrated wall was evident. We concluded that intercellular junctions and not fenestrations affect the permeability of brain tumours to pertechnetate.
Differences in the rate of uptake of 99Tcm-diphosphonate were found in 20 human bone tumours investigated. As some tumours have a slow rate of uptake it is suggested that the time used for routine scintigraphy at 3 hours is not always optimal and a further study should be performed in some cases. Various degrees of tumour vascularity and vessel permeability were found. The rate of diphosphonate uptake correlates with the vascularity, while it does not correlate with permeability which is generally increased as compared to normal bone.