Improved beta-amyloid PET reproducibility using two-phase acquisition and grey matter delineation.

PURPOSE: We investigated whether the reproducibility of standard visual reporting (STD method) in flutemetamol (FMM) PET can be improved using a newly introduced method that uses grey matter edges derived from the perfusion phase (GM-EDGE method). METHODS: Two-phase FMM PET was performed in 121 patients with mild cognitive impairment. Five nuclear medicine physicians blindly and independently evaluated all late-phase scans, initially employing the STD method and later the GM-EDGE method. A five-point scale was used to express the degree of amyloid positivity, and a binary classification (positive/negative) was used in combination with subjective confidence (five-point scale). Multirater Fleiss' kappa, intraclass correlation coefficient (ICC) and inter-rater reliability (Cohen's kappa) were determined for the STD and GM-EDGE methods. RESULTS: The weighted Cohen's kappa values for the five-point measure of amyloid positivity ranged from 0.63 to 0.73 (median 0.70) for the STD method and from 0.76 to 0.89 (median 0.80) for the GM-EDGE method (ICC 0.84, 95% CI 0.79-0.88, for the STD method; 0.91, 95% CI 0.89-0.94, for the GM-EDGE method). The nonweighted Cohen's kappa value for the binary classification ranged from 0.73 to 0.93 (median 0.82) for the STD method and 0.90 to 0.97 (median 0.93) for the GM-EDGE method (Fleiss' kappa 0.82, 95% CI 0.77-0.88, for the STD method; 0.93, 95% CI 0.87-0.99, for the GM-EDGE method). The GM-EDGE method resulted in significantly greater subjective confidence in the readings of four physicians (p < 0.010). The binary classification was concordant among all five physicians in 80.8% of the scans using the STD method and in 91.6% of the scans using the GM-EDGE method (p = 0.016). CONCLUSION: The newly introduced GM-EDGE method was associated with significantly higher inter-rater agreement among physicians and higher subjective confidence in the reading. The method is easy to implement in clinical practice, especially when the perfusion phase is utilized clinically.

Monte Carlo simulation of PET images for injection dose optimization.

When a patient is examined by positron emission tomography (PET), radiotracer dose amount (activity) has to be determined. However, the rules for activity correction according to patients' weight used nowadays do not correspond with practical experience. Very high image quality is achieved for slim patients, whereas noisy images are produced for obese patients. There is opportunity to modify the correction rule with the aim to equalize image quality within the broad spectrum of patients and to diminish radiation risk to slim patients, with special importance for children. We have built a model of a particular PET scanner and approximated human trunk, which is our region of interest, by a cylindrical model with segments of liver, outer adipose tissue, and the rest. We have performed Monte Carlo simulations of PET imaging using the GATE simulation package. Under reasonably simplifying assumptions and for special parameters, we have developed curves that recommend amount of injected activity based on body parameters to give PET images of constant quality, the quality being expressed in terms of noise equivalent counts. The dependence qualitatively differs from the rules used in clinical practice nowadays, and the results indicate potential for improvement.

Role of [18F]-fluoro-2-deoxy-D-glucose positron emission tomography in early and late therapy assessment of patients with advanced Hodgkin lymphoma treated with bleomycin, etoposide, adriamycin, cyclophosphamide, vincristine, procarbazine and prednisone.

The prognostic value of positron emission tomography (PET) in early therapy response assessment, after completion of chemotherapy and 3 months after the end of treatment in advanced Hodgkin lymphoma (HL) remains to be defined. We report the results of 69 patients with first presentation of advanced HL. [18F]-fluoro-2-deoxy-d-glucose (FDG)-PET scan was performed after four cycles (PET-4), on completion of chemotherapy after 6/8 cycles (PET-6/8) and 3 months after the completion of chemotherapy (PET 3-months). Median follow-up was 55 months. The negative predictive value (NPV) for PET-4, PET-6/8 and PET 3-months was 98%, 95% and 97%, respectively. The 4-year progression-free survival (PFS) for PET-4 negative (n = 51) and PET-4 positive (n = 18) patients was 96% and 78%, respectively (p = 0.016). The 4-year PFS for PET-6/8 negative (n = 59) and PET-6/8 positive (n = 9) patients was 95% and 78%, respectively (p = 0.046). Patients with a large mediastinal mass constituted nearly all of the PET-4 positive (16/18) and PET-6/8 positive (8/9) patients. After radiotherapy of PET-6/8 positive patients, PET 3-months was negative in 64 (97%) and positive in two (3%) patients. PET 3-months after the end of chemotherapy was of limited value when the interim PET-4 was negative. Interim PET after four cycles of bleomycin, etoposide, adriamycin, cyclophosphamide, vincristine, procarbazine and prednisone (BEACOPP) is a strong prognostic marker for PFS in advanced HL.

Prognostic and diagnostic accuracy of [18F]FDG-PET/CT in 190 patients with carcinoma of unknown primary.

PURPOSE: The aim of the study was to determine the accuracy of [(18)F]fluorodeoxyglucose (FDG) PET/CT in the search for the primary and the presence of a malignancy. The prognostic value of FDG-PET/CT information was tested. METHODS: A total of 190 patients were retrospectively analysed: 82 with histologically proven metastases (HPM) and 108 with clinical suspicion of the presence of a malignancy (CSM). The sensitivity and specificity were determined. Overall survival was calculated to evaluate the prognostic value of the FDG-PET/CT findings. RESULTS: In the search for the primary, the sensitivity and specificity were 62.0% and 81.9%, respectively. In the search for the presence of a malignancy, the sensitivity and specificity were 93.6% and 85.7%, respectively. Between the HPM and CSM groups, no significant difference in sensitivity and specificity was found either in the search for the primary or in the search for the presence of a malignancy. No significant difference in the sensitivity and specificity was found between 78 patients who were investigated by contrast-enhanced FDG-PET/CT and the remaining patients. A significantly shorter overall survival was found among patients with positive FDG-PET/CT findings compared with patients with negative findings (p = 0.00001); no significant difference in survival was found between the HPM and the CSM group (p = 0.770). CONCLUSION: FDG-PET/CT imaging is very helpful in the search for the presence of a malignancy in patients with carcinoma of unknown primary syndrome. FDG-PET/CT is less accurate in identifying exactly the site of a primary. Discovery of a hypermetabolic lesion was associated with the worst survival rate.