S. Atay

SPECT brain perfusion abnormalities in mild or moderate traumatic brain injury

The purpose of this atlas is to present a review of the literature showing the advantages of SPECT brain perfusion imaging (BPI) in mild or moderate traumatic brain injury (TBI) over other morphologic imaging modalities such as x-ray CT or MRI. The authors also present the technical recommendations for SPECT brain perfusion currently practiced at their center. For the radiopharmaceutical of choice, a comparison between early and delayed images using Tc-99m HMPAO and Tc-99m ECD showed that Tc-99m HMPAO is more stable in the brain with no washout over time. Therefore, the authors feel that Tc-99m HMPAO is preferable to Tc-99m ECD. Recommendations regarding standardizing intravenous injection, the acquisition, processing parameters, and interpretation of scans using a ten grade color scale, and use of the cerebellum as the reference organ are presented. SPECT images of 228 patients (age range, 11 to 88; mean, 40.8 years) with mild or moderate TBI and no significant medical history that interfered with the results of the SPECT BP were reviewed. The etiology of the trauma was in the following order of frequency: motor vehicle accidents (45%) followed by blow to the head (36%) and a fall (19%). Frequency of the symptoms was headache (60.9%), memory problems (27.6%), dizziness (26.7%), and sleep disorders (8.7%). Comparison between patients imaged early (<3 months) versus those imaged delayed (>3 months) from the time of the accident, showed that early imaging detected more lesions (4.2 abnormal lesions per study compared to 2.7 in those imaged more than 3 months after the accident). Of 41 patients who had mild traumatic injury without loss of consciousness and had normal CT, 28 studies were abnormal. Focal areas of hypoperfusion were seen in 77% (176 patients, 612 lesions) of the group of 228 patients. The sites of abnormalities were in the following order: basal ganglia and thalami, 55.2%, frontal lobes, 23.8%, temporal lobes, 13%, parietal, 3.7%, insular and occipital lobes together, 4.6%.

SPET brain perfusion imaging in mild traumatic brain injury without loss of consciousness and normal computed tomography.

We present SPET brain perfusion findings in 32 patients who suffered mild traumatic brain injury without loss of consciousness and normal computed tomography. None of the patients had previous traumatic brain injury, CVA, HIV, psychiatric disorders or a history of alcohol or drug abuse. Their ages ranged from 11 to 61 years (mean = 42). The study was performed in 20 patients (62%) within 3 months of the date of injury and in 12 (38%) patients more than 3 months post-injury. Nineteen patients (60%) were involved in a motor vehicle accident, 10 patients (31%) sustained a fall and three patients (9%) received a blow to the head. The most common complaints were headaches in 26 patients (81%), memory deficits in 15 (47%), dizziness in 13 (41%) and sleep disorders in eight (25%). The studies were acquired approximately 2 h after an intravenous injection of 740 MBq (20.0 mCi) of 99Tcm-HMPAO. All images were acquired on a triple-headed gamma camera. The data were displayed on a 10-grade colour scale, with 2-pixel thickness (7.4 mm), and were reviewed blind to the patients history of symptoms. The cerebellum was used as the reference site (100% maximum value). Any decrease in cerebral perfusion in the cortex or basal ganglia less than 70%, or less than 50% in the medial temporal lobe, compared to the cerebellar reference was considered abnormal. The results show that 13 (41%) had normal studies and 19 (59%) were abnormal (13 studies performed within 3 months of the date of injury and six studies performed more than 3 months post-injury). Analysis of the abnormal studies revealed that 17 showed 48 focal lesions and two showed diffuse supratentorial hypoperfusion (one from each of the early and delayed imaging groups). The 12 abnormal studies performed early had 37 focal lesions and averaged 3.1 lesions per patient, whereas there was a reduction to--an average of 2.2 lesions per patient in the five studies (total 11 lesions) performed more than 3 months post-injury. In the 17 abnormal studies with focal lesions, the following regions were involved in descending frequency: frontal lobes 58%, basal ganglia and thalami 47%, temporal lobes 26% and parietal lobes 16%. We conclude that: (1) SPET brain perfusion imaging is valuable and sensitive for the evaluation of cerebral perfusion changes following mild traumatic brain injury; (2) these changes can occur without loss of consciousness; (3) SPET brain perfusion imaging is more sensitive than computed tomography in detecting brain lesions; and (4) the changes may explain a neurological component of the patients symptoms in the absence of morphological abnormalities using other imaging modalities.

Fluorine-18 Fluorodeoxyglucose Splenic Uptake From Extramedullary Hematopoiesis After Granulocyte Colony-stimulating Factor Stimulation

Two patients with sarcoma, one with recurrent osteosarcoma of the spine and the other with metastatic synovial cell sarcoma, were treated with high-dose chemotherapy that produced severe leukopenia. The patients received granulocyte colony-stimulating factor (G-CSF) to stimulate the bone marrow (480 mg given subcutaneously twice daily for 5 to 7 days); their responses were seen as a marked increase in peripheral leukocyte count with no change in the erythrocyte or platelet counts. The patients had fluorine-18 fluorodeoxyglucose (F-18 FDG) imaging 24 hours after the end of G-CSF treatment. Diffusely increased uptake of F-18 FDG was seen in the bone marrow in both patients. In addition, markedly increased uptake in the spleen was noted in both, indicating that the spleen was the site of extramedullary hematopoiesis. The patients had no evidence of splenic metastases. The first patient had a history of irradiation to the dorsal spine, which was less responsive to G-CSF administration than was the nonirradiated lumbar spine.

Acute cholecystitis in AIDS patients: Correlation of Tc-99m hepatobiliary scintigraphy with histopathologic laboratory findings and CD4 counts

BACKGROUND AIDS patients are susceptible to opportunistic gastrointestinal infections including ascending cholangitis and cholecystitis, especially if CD4 count is < 200. Incidence of acalculous cholecystitis has not been reported previously. PURPOSE We aim to evaluate the incidence of acalculous cholecystitis in AIDS patients and to identify causative organisms and mortality rate following cholecystectomy. MATERIALS AND METHODS We reviewed the files of 46 patients in order to meet the objectives of this study. RESULTS CD4 counts were < 200 in 31 patients and > 200 in 15 patients. HIDA imaging was performed in 31 patients; in 8, the CD4 count was > 200 and all had calculous cholecystitis. The gallbladder was visualized in 3 patients for a sensitivity of 63% and no organisms were found in the gallbladder specimens. In 23 patients, the CD4 count was < 200; the gallbladder was visualized in 5 patients for a HIDA sensitivity of 78%; 16 (52%) had acalculous cholecystitis; and 15 had calculous cholecystitis. In acalculous cholecystitis, Cryptosporidium was found in six cases, cytomegalovirus (CMV) in six cases, and fungus, yeast, tuberculosis, and mycobacterium avium intracellular each in one case. The thirty day mortality rate was 18%; 5 of 28 who underwent open cholecystectomy died within 30 days, 4 of them with a CD4 count < 200. There was no mortality in the 26 patients who underwent laparoscopic cholecystectomy. CONCLUSION AND RECOMMENDATIONS (1) Because of the high incidence of 52% of acalculous cholecystitis in AIDS patients with a CD4 count < 200, we recommend using intravenous cholecystokinin if the gallbladder is visualized on hepatobiliary scintigraphy in order to determine gallbladder ejection fraction and exclude acalculous cholecystitis. (2) Laparoscopic rather than open cholecystectomy should be the surgical procedure of choice in AIDS patients especially if the CD4 count is < 200.

Ga-67 imaging of perisplenic abscess after splenic embolization

Splenic artery embolization is emerging as a promising alternative to surgical splenectomy for hypersplenism. Presented is the case of a patient with non-Hodgkins lymphoma with splenomegaly, who was treated for thrombocytopenia and neutropenia with splenic artery embolization. A few days later, the patient developed a septic pattern. Abdominal CT with contrast enhancement showed an enlarged spleen with solid and cystic areas. Liver-spleen scintigraphy revealed minimal residual functioning splenic tissue, and Ga-67 scintigraphy revealed ring-shaped perisplenic uptake, suggesting a perisplenic abscess. The diagnosis was confirmed by needle aspiration of thick purulent fluid from the abscess which grew Moganella Morganii on culture.

Infected atrioventricular shunt: Importance of delayed (24-hour) Tc-99m HMPAO leukocyte imaging

The current recommendation for Tc-99m HMPAO-labeled leukocyte imaging is at 4-6 hours. This early imaging might not be long enough for localization of the labeled leukocytes at a site of infection and for further blood pool clearance. The scintigraphic findings of a patient with an infected ventriculoatrial shunt were negative at 4 hours, whereas at 24 hours there was intense uptake in the region of the right atrium. The case demonstrates that the 24-hour images were more sensitive to localize an infected catheter in the right atrium. If early images performed the same day as the administration of Tc-99m HMPAO-labeled leukocyte appear negative, delayed imaging the next day at 24 hours is recommended.

Postoperative Tc-99m DISIDA hepatic extravascular diffusion mimicking biliary leakage.

Postcholecystectomy hepatic extravascular leakage in the operative bed can mimic biliary leakage if a Tc-99m DISIDA study is performed in the first few days after surgery. In the case being reported here, the gallbladder was located partially intrahepatic and was not inflamed at the time of surgery. A Tc-99m DISIDA study was requested 5 days after surgery to evaluate biliary patency and to exclude biliary leakage. Increased uptake in the gallbladder fossa inside the liver at the operative site was detected in the early period of the study. It could be differentiated from biliary leakage by three important features: the early appearance of radioactivity in the first 30 minutes, the intensity of the abnormal focal increased activity decreased with time during the 60 minutes of the dynamic acquisition, and this activity did not increase or move with time. In true leakage, the abnormal activity should become more intense, should increase in size, and should progressively spread from its original site.