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

Purpose: To assess the clinical accuracy of whole-body 2-[F-18]-fluoro-2-deoxy-D-glucose-positron emission tomography (FDG-PET) in the diagnosis of recurrent colorectal carcinoma in comparison to conventional computed tomography (CT).

Materials and methods: Forty patients with suspected recurrent colorectal carcinoma based on either progressive serial carcinoemrbyonic antigen (CEA) serum elevation or positive/equivocal CT findings underwent whole-body FDG-PET. PET results were compared with those of CT and correlated to the final histopathological and clinical findings.

Results: A final diagnosis was obtained at 93 sites in 35 patients by histology and in 5 patients by clinical follow up of at least 6 months. Of the 93 sites, 53 were determined to be malignant and 40 benign. FDG-PET evaluated on a 5-point scale (0–4) showed a positive and negative predictive value in the range of 96–98% and 83–93% respectively as the threshold for positivity was moved from 0 through 3. By comparison, CT, also evaluated on a 5-point scale showed a positive and negative predictive value in the range of 75–88% and 67–71% respectively. The area under the fitted receiver operating characteristic curve for PET: A_PET = 0.96 ± 0.02 was significantly greater (P < 0.001) than that observed for CT: A_CT = 0.77 ± 0.06. The distribution of maximum standardized uptake value (SUVmax) showed that all negative lesions have SUVmax below 5.0 whereas 75% of positive lesions were above 5.0 pointing to the fact that disease positivity is more likely in lesions with high SUV values.

Conclusion: The results of this study confirm that whole-body FDG-PET is more accurate than conventional CT in the staging of patients with suspected recurrent colorectal carcinoma.

Purpose: Yttrium-86 has been proposed for use as a quantitative positron emission tomography imaging agent to determine the in vivo distribution of therapeutic pharmaceuticals labeled with yttrium-90, a pure beta minus emitter. This study identifies, and proposes a solution for, an artifact, which interferes with quantitation.

Procedures: Yttrium-86 is a 14.7-hour halflife positron emitter (33% abundance) with multiple high energy gamma rays in cascade. Phantom measurements with a GE Advance PET scanner using standard attenuation and scatter corrections, demonstrated anomalous apparent activity in inactive higher density regions.

Results: Apparent activity up to 30% of the surrounding true activity was observed in a bone equivalent material. Even higher activities were observed if the scatter correction was omitted. This phenomenon was determined to result from the effect of attenuation correction on true coincidences between one gamma ray and a second gamma ray or annihilation photon.

Conclusion: A simple additional correction based on sinogram tail subtraction improves accuracy significantly.

Purpose: This investigation evaluated the effectiveness of positron emission tomography with 2-[F-18]fluoro-2-deoxy-D-glucose (PET-FDG) in assessing residual tumor or tumor recurrence in postradiation nasopharyngeal carcinoma (NPC) patients.

Procedures: Forty-six patients with histologically proven NPC who received radiotherapy were included. PET-FDG images were analyzed by a semiquantitative method, metabolic ratio (tumor to cerebellum ratio).

Results: The overall sensitivity and specificity of PET-FDG to detect residual tumors and recurrent lesions in the postradiation patients were 80% (12/15) and 87% (27/31), respectively. In patients with PET-FDG 6 months after radiation therapy, the sensitivity and specificity raised to 92% (11/12) and 100% (20/20), respectively.

Conclusions: PET-FDG is effective in the evaluation of NPC treated with radiation. The optimal timing in assessing residual tumor or tumor recurrence in postradiation patients should be 6 months or later.

Purpose: To study the role of positron emission tomography ¹⁸F-fluorodeoxyglucose (PET FDG) imaging in patients with a suspicion of breast cancer recurrence.

Procedures: Whole-body PET FDG was performed in 39 women. Thirty-four were included because of asymptomatic tumor marker increase. PET findings were confirmed by oriented imaging or by biopsy. Follow-up data were collected over a period of at least 12 months.

Results: PET FDG depicted 37/39 sites in 31/33 patients with recurrence. PET missed one locoregional recurrence and in one patient peritoneal carcinomatosis developed 6 months after a negative PET. False positive PET FDG corresponded to lung infection, degenerative bone disease, and reconstruction artifact. The conventional imaging work-up depicted sites of recurrence in 6/33 patients.

Conclusion: Whole-body PET FDG is highly sensitive for the detection of distant breast cancer recurrence. Prospective studies are mandatory to address its potential impact on patient management and survival.

Regional positron emission tomography (PET) imaging with F-18 Fluorodeoxyglucose (FDG) was performed in a patient with pathologically proven Merkel cell tumor around the right knee region. Prior to the PET imaging, whole-body Indium-111 octreotide scan was performed in this patient but was negative. F-18 FDG was offered as an attempt to image this somatostatin-receptor negative Merkel cell tumor. The PET images delineate a series of focal abnormal uptake along the right lower extremity without evidence of distant metastasis. Patient was treated locally. The positive accumulation of F-18 FDG in Merkel cells may offer a tool for defining the extent of this rare neuroendocrine tumor.

Objective: Positron emission tomography (PET) using fluorine-18-fluoro-2-D-deoxyglucose (FDG) is increasingly being used to evaluate and manage oncology patients. Several reports have documented its utility in diagnosis, staging, response to treatment, and tumor viability assessment. There is, however, a paucity of literature on PET scanning in patients with osteosarcoma. We report results of serial F-18 FDG-PET scans in 16 untreated patients with osteosarcoma who underwent chemotherapy prior to surgical resection of the primary tumor site.

Procedure: Changes in tumor fluoro-2-D-deoxyglucose (FDG) uptake were correlated with percent tumor necrosis on histopathology. PET studies were analyzed by visual assessment of tumor uptake of FDG by 3 independent observers, calculating a tumor to normal background activity ratio (TBR) by drawing regions of interest (ROIs) around the tumor and background activity in the contralateral normal limb, and percent change in TBR values between baseline and presurgical study.

Results: All patients had positive baseline scans. Baseline TBRs ranged between 2.5–8.7 and visual assessment of intensity of FDG uptake was 2–3 on a scale of 0–3. At histopathologic examination, 8 patients were classified as good responses with more than 90% tumor necrosis and 8 patients as poor responses with less than 90% necrosis. Tumor necrosis was accurately predicted on PET scan in 15/16 patients by visual assessment, 14/15 patients by final TBR value on presurgery scans, and 7/15 patients using percent change of TBR on serial scans.

Conclusions: The results of this small series suggest that FDG-PET scanning is fairly accurate in evaluating the response of osteosarcoma to chemotherapy. Visual assessment and TBR are more accurate in predicting tumor necrosis than percent change in TBR on serial scans.

Objective: In patients with advanced cancer, total tumor burden affects the likelihood of tumor response and has important implications for prognosis. The aim of this study was to select the optimum 2-[F-18]fluoro-2-deoxy-D-glucose-positron emission tomography (FDG PET) tumor uptake parameter to accurately measure tumor burden in advanced metastatic renal cell cancer, in comparison with volumes measured with computed tomography (CT), as a reference test.

Materials and Methods: Six patients with metastatic renal cell carcinoma measurable on CT were studied. CT and FDG PET scans were carried out on all patients within 4 weeks prior to their entry into a phase I–II radioimmunotherapy trial. CT-based evaluation of disease extent (tumor volume) and 4 PET-based measurements (standardized uptake value[SUVmax], SUVav, volume, and total lesion glycolysis [TLG]) were performed independently by a radiologist (VN) and a nuclear medicine physician (TA). The degree of correlation between conventional (CT) extent of disease and parameters describing tumor concentration of FDG was then determined.

Results: Fifty-seven CT-measurable metastatic lesions in lung, abdomen, and scalp were evaluated in 6 patients. There was a high correlation between CT and FDG PET volume estimates for lesions greater than 5 cm³ in size. However, a PET-derived parameter that embodies both FDG uptake and lesion size, the TLG, correlated better with CT-derived tumor volume than did FDG PET volume alone.

Conclusion: Using CT volume as a gold standard, the optimal PET-based estimate of total tumor burden in patients with metastatic renal cancer is the sum over all lesions of the total lesion glycolysis.

The purpose of this study was to investigate metabolic changes associated with a right hypothalamic mass in a 26-year-old gelastic seizure patient. Positron emission tomography (PET) imaging of the brain was performed in the interictal state using 18F-fluorodeoxyglucose (18F-FDG) in this patient. Temporal lobe hypometabolism was noted ipsilateral to the hypothalamic lesion. The mass itself had little to no uptake of 18F-FDG. This is the first known PET imaging report of temporal lobe hypometabolism ipsilateral to a presumed hypothalamic hamartoma causing gelastic seizures. Further studies are needed in other patients to test whether interictal PET imaging may help plan the removal of epileptogenic hypothalamic lesions.

Purpose: To compare [¹⁸F]2-deoxy-2-fluoro-D-glucose-positron emission tomography (FDG-PET) and computed tomography (CT) scans in assessment of response to neoadjuvant chemotherapy in advanced head and neck cancer.

Materials and Methods: In a prospective clinical study, advanced head and neck cancer patients were enrolled in a neoadjuvant organ preservation protocol and received CT and FDG-PET scans prior to and after 2 or 3 rounds of chemotherapy. All patients had prechemotherapy and postchemotherapy tissue biopsies within the tumor region. Patients were then classified as pathologic complete response (PCR) or residual disease (RD) based on biopsies. Analysis of the tumor activity, using FDG-PET, was performed using standardized uptake ratios (SUR) in the region of the primary tumor. Analysis of the tumor size, using contrast enhanced CT, was performed using measurements of the primary tumor in 3 dimensions.

Results: Nineteen of the 28 patients with stage III and IV cancer of the head and neck enrolled between December 1994 and May 1996 completed the study. Three patients were PCR and had a mean SUR reduction of 82% by positron emission tomography (PET) and volume reduction of 80% by CT. Sixteen patients had RD after chemotherapy, their SUR and volume reductions were 32% and 41%, respectively. Reduction in SUR with PET was significant $\text{P = 0.01}$. The mean tumor volume reduction by CT approached statistical significance $\text{P = 0.09}$. There was a positive correlation between the percent reduction in tumor volume and SUR (P < 0.004).

Conclusion: FDG-PET and CT imaging are at least equivalent in correctly assessing tumor response to chemotherapy with a trend toward better performance by PET.