Clinical positron imaging : official journal of the Institute for Clinical P.E.T最新文献

Background and Purpose: [F-18]FDG has long been used for detection of the malignant tumors and assessment of the metabolic activity of the tumors. However, there are several drawbacks of FDG including hyperglycemic effect, nonspecific uptake on inflammation, sink phenomenon due to high accumulation of FDG in urinary tract, and physiologic uptake of FDG in the bowels and muscles, which may cause false positive as well as false negative results. [C-11]acetate, as a metabolic substrate of β-oxidation, precursors of amino acid, fatty acid and sterol, has been proved useful in detecting various malignancies. The aim of this study is to assess the feasibility of clinical application of [C-11]acetate in oncology.

Methods: High quality whole body images could be obtained by using large dosage (20 mCi) of [C-11]acetate and modern PET scanner. In the recent years, [C-11]acetate PET studies have been performed in 513 patients with various malignancies.

Results: The results showed that [C-11]acetate is more accurate in detecting meningioma (accuracy 97%), glioma (91%), nasopharyngeal cancer (93%), lymphoma (85%), non-small cell cancer (81%), colon cancer (78%), renal cell cancer (80%), ovarian cancer (76%), than in detecting small cell cancer of lung, thyroid cancer, and pancreas cancer. The advantages of [C-11]acetate are less time consuming (whole procedure completed within 45 min after injection), no hyperglycemic effect and no sink phenomenon. The disadvantages are increased uptake in salivary glands, pancreas, and sometimes the bowels, which may cause either false positive or false negative results, and on-site-cyclotron dependent.

Conclusion: In summary, [C-11]acetate is clinically useful in detecting various malignant tumors clinically and may play a complementary role to FDG.

Purpose: The aim of the study was to examine the utility of PET with ¹¹C-Methionine in diagnosis and evaluation of the treatment efficacy in childhood brain tumors.

Methods: 16 PET-studies were performed in 11 children, 4–17years old, 3 boys and 8 girls, with brain tumors or tumor suspicion. Reasons for PET-study were an unclear diagnosis of tumor (7 cases), treatment efficacy definition (5 cases) and identification of tumor recurrence (3 cases). Studies were performed after i.v. injection of ¹¹C-Methionine (6-9 MBq/kg). MRI or CT of brain was done before the PET-study in all patients. Diagnosis was confirmed by clinical follow-up or biopsy.

Results: In 2 of 7 patients with suspicion of brain tumor no areas with pathological uptake of ¹¹C-Methionine were found. In a patient with unclear tumor a benign process (ependimoma) was revealed that allowed avoiding a biopsy. A benign tumor detection in 2 patients with malignancy suspicion considerably affected treatment tactics. In 2 patients supposed benign growth was confirmed. In 2 of 3 patients with question of recurrence after surgery or radiotherapy and inconclusive MRI and CT picture malignant growth was found and in 1 patient was rejected. Repeated PET-studies in 2 patients with prolactinoma during therapy allowed prompt (within a few days) control of tumor response.

Conclusion: The assessment of tumor metabolic activity in paediatric oncological practice using PET with ¹¹C-Methionine is a reliable method in the correct indication of brain tumor origin and in prompt evaluation of treatment efficacy and control of recurrence.

Purpose: To assess the cost of implementing ¹⁸F-Fluorodeoxyglucose (¹⁸FDG) PET scan in the presurgical evaluation of patients with hepatic metastases from colorectal cancer (CRC) detected by Computed Tomography with arterial portography (CTAP).

Methods: We performed a cost analysis of two diagnostic pathways based on a population of CRC patients with metastatic disease limited to the liver by (CTAP). The payers' perspective was utilized. The algorithms compared ¹⁸FDG-PET with Computed Tomography (CT) versus CT alone. Patients found to have extrahepatic disease by ¹⁸FDG-PET or CT were assigned to palliative care. Patients found to be negative for extrahepatic extension were assumed to be surgically resectable. The prevalence of extrahepatic disease, true and false positives and negatives for CT and ¹⁸FDG-PET were extracted from published reports (Medline, 1991 to 1999). Three possible outcomes for surgery were considered: uncomplicated, complicated, and death. Surgical complications considered were: urinary tract infection, wound sepsis, intra-abdominal abscess, septicemia, pneumonia, deep venous thrombosis, pulmonary embolism, anemia requiring transfusion, and myocardial infarction. Complication rates, costs for CT, CTAP, ¹⁸FDG-PET, surgery and post-surgical complications were obtained from HCFA published data (1997-2000). Palliative care costs were assumed to be identical in both branches.

Results: Average expected cost per patient with ¹⁸FDG-PET was $16,921, compared to $21,693 for a patient without PET scan. This represents net savings of $4,772 if PET is included in the diagnostic work up.

Conclusion: Integration of ¹⁸FDG-PET in the presurgical evaluation of patients with liver metastases from CRC by CTP would substantially reduce overall costs.

Background: In adults PET scanning of CNS tumors with the tracer FDG (¹⁸F-flourodeoxyglucose) can provide information about the degree of malignancy, tumor extent, and dissemination. FDG PET can also be able to assess tumor response to therapy and to differentiate recurrence from necrosis. Although CNS tumors are the most common solid tumor in childhood, so far only few PET-studies have been reported. Pre-operative assessment of malignancy would facilitate surgical planning and the use of pre-operative chemotherapy.

Materials and Methods: 21 children with CNS tumors were referred to clinical FDG PET prior to therapy (M/F = 12/9, median age: 9 (range 0-16)), (4 PNET/medulloblastomas; 1 gr. III ependymoma, 16 benign tumors)). Image processing included co-registration with MRI and image fusion. The FDG uptake in the tumors was ranked 0-5 by a hotspot/cortex-ratio by two observers independently. The FDG uptake in grey and white matter was used as reference for the grading system with FDG uptakes defined as 4 and 2 respectively.

Results: 15 of 16 patients with tumors WHO gr. I-II had FDG-uptake of 1-2, and all 5 patients with tumors WHO gr. III-IV had FDG-uptake of 3-4. A WHO gr. I papilloma, known to have a high metabolism caused by high mitochondrial activity, had FDG uptake of 5. Except for this tumor, the FDG uptake was positively correlated with tumor malignancy. MRI/PET co-registration and image fusion increased the specificity of tumor location, as well as of tumor extent, and of heterogeneity (e.g., areas of necrosis).

Conclusion: FDG PET with MRI/PET co-registration and image fusion could be an important adjunct in the diagnostic work up of pediatric CNS tumors, and could help define patients eligible for pre-operative chemotherapy.

Purpose: The aim of this preliminary study was to evaluate the role of FDG-CDET in detection of recurrence of ovarian cancer.

Methods and patients: After a fast of 6 hours, the patient (pt) was injected I. V. with 150–250 MBq of [F-18]-FDG and imaging (whole-body scan and at least a tomoscintigram) was started 45 min. later, using a PICKER Prism XP 2000 CDET gamma camera. Between July 1997 and December 1999, 40 patients were studied for ovarian carcinoma. To date, the results of 23 patients are evaluable with reference to histology after surgery or long-term follow-up. From these 23 patients, 18 pts were referred for suspected recurrence of ovarian carcinoma: occult recurrence (OR) defined by an increase in serum CA-125 levels with negative conventional imaging (13 pts) or equivocal aspect at conventional imaging (5 pts).

Results: In 13 pts referred for suspicion of OR, FDG-CDET was true positive (TP) in 11 cases all confirmed by histology after surgery and was true negative (TN) in the remaining 2 cases as confirmed by spontaneous normalization of CA-125 levels and no events during a 20-month follow-up. In the 5 pts with equivocal aspect on CT, 4 were (TP) with recurrent foci at FDG-CDET in 1 case and 1 was (TN) corresponding to a leı̈omyoma on histology after surgery. In summary, the overall sensitivity and accuracy on a per patient basis were 18/18 for FDG-CDET while sensitivity and accuracy of conventional imaging was only 6/18.

Conclusion: These preliminary results in a clinical setting, which is not frequently evaluated on CDET gamma cameras, seem very promising.

Background: Cellular changes lead to coronary artery endothelial dysfunction (ED) and precede plaque formation. Clinical events, such as unstable angina and acute coronary syndromes, are common consequences of ED. Coronary artery ED, as characterized by Rb-82 PE, is a perfusion abnormality at rest, which improves following stress. In risk factor modification studies, particularly in cholesterol-lowering trials, coronary artery ED has been demonstrated to be reversible. Other studies have correlated low fat diet modification with improvement in coronary artery disease.

Purpose: This study evaluates changes in myocardial perfusion following meals with low versus high TG content, and its influence on post prandial serum TG.

Methods: With a randomized, double blind placebo controlled, cross over design, we investigated 19 patients (10 with ED and 9 with normal perfusion) with Rb-82 PET for myocardial blood flow at rest and with adenosine stress. PET images and serum triglycerides were obtained before and after an olestra (OA) meal (2.7g TG, 44g olestra) and a high-fat meal (46.7g TG). Meals were matched for carbohydrate, protein, and cholesterol content.

Results: Myocardial perfusion (uCi/cc) increased 11 – 12% following the OA meal compared to the high-fat meal in patients with ED. For all patients combined, serum TG increased significantly (p < 0.01) in the non-OA group with the median change from baseline to 170.0 mg/dl, compared to 21.5 mg/dl in the OA group during the 6 hours following the meal.

Conclusions: A single olestra meal significantly diminishes post prandial serum TG levels and improves myocardial perfusion in patients with endothelial disease.

Purpose: SCC represents nearly 90% of all oral malignancies, with an increasing incidence. Accurate Tumour-Node-Metastasis staging (TNM) is mandatory for planning surgical options and chemotherapy-radiotherapy management. Positron Emission Tomography (PET) using ¹⁸F-Fluorodeoxyglucose (FDG) provides functional information about tumoral tissues that may improve preoperative staging obtained by conventional morphologic procedures (CT-MRI). The purpose of this study is to evaluate the accuracy of FDG-PET in oral SCC staging and to compare those data from conventional and PET studies according to the pathologic results obtained from surgical specimen.

Methods: A prospective study of 30 patients was carried out, through a 26 months period. Inclusion criteria include positive biopsy for Oral SCC, no other malignancies during the past 5 year and surgery as preferred therapeutic option. All patients underwent CT, MRI, and FDG-PET studies consecutively. Results obtained from conventional and PET preoperative staging were compared with those from postoperative histopathological studies

Results: FDG-PET modified preoperative staging obtained by conventional morphologic studies in 21% cases, which was confirmed postoperatively by histological findings. Kappa test showed higher values for PET studies (0.89) than conventional studies (0.41), when compared with postoperative control

Conclusion: FDG-PET may be helpful to improve the accuracy of conventional studies in oral SCC preoperative TNM staging, although no definitive conclusions can be withdrawn due to the limited size of the sample. Modifications of preoperative staging showed by PET are a matter of controversy and must be kept in mind for further studies.

Calcium localization by Electron Beam CT (EBCT) in the coronary arteries is becoming an important non-invasive method for screening asymptomatic patients for early coronary atherosclerosis. However, the relationship between coronary artery calcium deposits and myocardial perfusion abnormalities has not been established. We have developed software to superimpose location of coronary calcium by EBCT onto PET myocardial perfusion images, so that we can determine the role of location and amount of calcium in the arteries to flow-limiting perfusion defects by PET.

EBCT and PET transaxial images are each first converted to three-dimensional arrays of 1 mm voxels. The resulting two image volumes sets are displayed so that a vertical line can be drawn from the clavicle to the spine for proper rotation of the body. The rotated images are then displayed superimposed and are shifted in the vertical, horizontal, and the long axis directions to co-register the EBCT and PET images. The EBCT images are windowed for calcium Houndsfield numbers and calcium location is added to the PET images as a maximum intensity value in the image. The modified PET image volume is then translated back to the PET data format and reprocessed using cardiac analysis software such that the calcium location is superimposed on the PET myocardial perfusion images.

Preliminary results of the PET-EBCT superimposition program correlate with location of coronary calcium by EBCT and PET perfusion defects following stress. This technique may be useful for identifying flow-limiting calcium deposits in the coronary arteries.

Purpose: PET can be useful in determining the progression of malignant disease over time as well as the response to therapy. To achieve this, the physician must be able to unambiguously identify and characterize individual tumors among several different scans.

Methods: We have developed a spherical coordinate system for identifying individual tumor sites on PET scans, using the carina on the transmission scan as a point of origin. Using this system, each tumor is given a set of spherical coordinates that identifies its position: a rho (ρ, displacement from carina), a theta (θ, angle between the A-P axis and the tumor), and a phi (φ, angle between the cranial-caudal axis and the tumor).

Results: We tested this method on a patient with metastatic thyroid cancer, who underwent ¹⁸FDG and ¹²⁴I-Iodide PET scans in the same week. The patient had a total of 90 tumors, 82 of them identified in the ¹⁸FDG scan and 35 in the ¹²⁴I-Iodide scan, with 27 tumors identified in both. For ρ, θ, and φ among the 27 matching pairs of tumors, the mean differences were 6.80 + 5 mm, 6.22 + 4.54°, and 5.51 + 5.81°, respectively. After thorough analysis, we have determined that corresponding tumors with ρ < 15 mm, θ and φ < 15° difference usually indicate a match. The disparity in coordinate values between corresponding tumors can be explained by the distinctive uptake patterns of the radiopharmaceuticals.

Conclusion: Within a mean difference of 6.8 mm and 6°, this spherical coordinate system facilitates the identification and characterization of individual tumors among multiple scans, thus aiding in both the assessment of diagnostic capabilities of different tracers, and the tracking of tumors following therapy.

Purpose: F-18 FDG (FDG) is reportedly useful for detecting infection. Because the procedure is simple, with results being readily available, this prospective study was undertaken to evaluate the utility of FDG imaging for diagnosing infected joint replacements.

Methods: 26 pts, 18 females and 4 males between 37 and 87 years old, with 31 joint replacements were studied. 21 pts had single joint replacement (10 hip, 11 knee); 5 pts had bilateral replacements (1 hip, 4 knee). Imaging was performed on a Hybrid PET system, with measured attenuation correction, one hour after administration of 150 MBq FDG. Increased peri-prosthetic uptake compared to adjacent, presumably normal, activity was interpreted as positive for infection.

Results: 11 of 31 prostheses were infected. Sensitivity, specificity, and accuracy of FDG were 100%, 55%, and 71% respectively. The PPV was 55% and the NPV was 100%. Excluding the 5 asymptomatic prostheses in pts with bilateral joint replacements, the sensitivity, specificity, and accuracy were 100%, 47%, and 69% respectively. The PPV was 58% and the NPV was 100%. 4 pts with infected prostheses underwent a total of 6 follow-up studies after treatment. In 1 pt with persistent infection, all 3 follow-up studies were true positive. In the other 3 pts in whom infection had been eradicated, follow-up FDG studies were false positive.

Conclusion: FDG imaging is sensitive but not specific; consequently, its role in pts with suspected prosthetic infection is limited to that of a screening test. These data also suggest that this technique is not useful for monitoring response to treatment.