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Unlabelled: Precise assessment of lymph node metastases is critical to the treatment outcome and overall survival of patients with head and neck squamous cell carcinoma (HNSCC). The purpose of this study was to investigate the effect of time-of-flight (TOF) technique on the diagnostic performance of (18)F-FDG PET/CT for assessment of lymph node metastases in HNSCC patients. Methods: In 39 patients with an initial diagnosis of HNSCC, preoperative staging (18)F-FDG PET/CT was performed to assess lymph node metastases before surgery and histologic verification. Potential lymph node metastases were evaluated and documented separately for the right and left neck in accordance with the head and neck lymph node level classification. Two experienced readers measured lesion volume and uptake for every PET-positive lymph node. Sensitivity, specificity, image quality, and the PET characterization of the lesion (benign or malignant) were compared between different reconstruction methods (TOF PET and standard high-definition PET) and matrices for both readers. Results: TOF PET significantly increased the maximal standardized uptake value (SUVmax) but had no significant effect on lesion volume. However, a higher SUVmax did not result in a significant increase in small-lesion detection. Sensitivity and image quality were slightly improved with TOF PET but not significantly so. Matrix, on the other hand, had a significant effect on detected lesion numbers, sensitivity, and image quality. Conclusion: For preoperative assessment of lymph node metastases in HNSCC, (18)F-FDG PET/CT using TOF technique increases SUVmax in lesions and improves image quality but has no significant impact on small-lesion detectability. [ABSTRACT FROM AUTHOR]

Precise assessment of lymph node metastases is critical to the treatment outcome and overall survival of patients with head and neck squamous cell carcinoma (HNSCC). The purpose of this study was to investigate the effect of time-of-flight (TOF) technique on the diagnostic performance of 18F-FDG PET/CT for assessment of lymph node metastases in HNSCC patients. Methods: In 39 patients with an initial diagnosis of HNSCC, preoperative staging 18F-FDG PET/CT was performed to assess lymph node metastases before surgery and histologic verification. Potential lymph node metastases were evaluated and documented separately for the right and left neck in accordance with the head and neck lymph node level classification. Two experienced readers measured lesion volume and uptake for every PET-positive lymph node. Sensitivity, specificity, image quality, and the PET characterization of the lesion (benign or malignant) were compared between different reconstruction methods (TOF PET and standard high-definition PET) and matrices for both readers. Results: TOF PET significantly increased the maximal standardized uptake value (SUVmax) but had no significant effect on lesion volume. However, a higher SUVmax did not result in a significant increase in small-lesion detection. Sensitivity and image quality were slightly improved with TOF PET but not significantly so. Matrix, on the other hand, had a significant effect on detected lesion numbers, sensitivity, and image quality. Conclusion: For preoperative assessment of lymph node metastases in HNSCC, 18F-FDG PET/CT using TOF technique increases SUVmax in lesions and improves image quality but has no significant impact on small-lesion detectability. [ABSTRACT FROM AUTHOR]

Therapy outcome and overall survival in patients with head and neck squamous cell carcinoma (HNSCC) is influenced by precise localization of the primary tumor and detection of lymph node metastasis involvement at the time of initial diagnosis. Only accurate preoperative staging can improve primary tumor response and avoid early Iocoregional recurrence with lymph node metastases. The purpose of this study was the optimization of reconstruction parameters in high-definition PET/CT for the improved diagnostic assessment of lymph node metastases. Methods: In the experimental study, image contrast and signal-to-noise ratio were evaluated using a Jaszczak phantom. In the clinical study, 54 patients underwent head and neck imaging on a PET/CT scanner. Diagnostic findings were correlated with postoperative histopathology. For the 54 patients, 123 lymph nodes were evaluated on PET and histologically correlated with the neck dissection specimen. Forty-one lymph nodes were benign, and 82 findings were confirmed as being malignant. Both experimental and clinical studies were reconstructed into a 200 x 200 matrix using a 3-dimensional iterative reconstruction algorithm (ordered-subset expectation maximization [OSEM], 3 iterative steps, 24 subsets). Postfiltering with a 3-dimensional gaussian filter was applied. To study the effect of smoothing filter strength on the diagnostic accuracy of lymph node metastasis detection, 3 different cutoffs--1, 3, and 6 mm in full width at half maximum--were used to perform reconstructions. Results: Phantom studies showed that images reconstructed with 3-mm gaussian postfiltering gained a higher image quality and signal-to-noise ratio. Overall sensitivities for correctly diagnosed lymph nodes were best in 3-ram postfiltered images. Best results for true-positive lymph node findings were achieved with 3-mm postfiltering. With 1-mm postfiltering, accurate lesion detection was not improved, because increasing sensitivity (95% true-positive) correlated with decreasing specificity (12% false-positive). Conclusion: For lymph node assessment on a high-resolution PET/CT scanner, we consider the OSEM algorithm with 3 iterations and 24 subsets, combined with 3-dimensional 3-mm gaussian postfiltering, to be optimal. The continuous application of presently established PET protocols in patients with HNSCC will prove whether current acquisition and reconstruction methods are valuable and should be maintained. [ABSTRACT FROM AUTHOR]

Our objective was to evaluate the impact of acquisition time on image quality, lesion detection rate, standardized uptake values, and lesion volume for 18F-FDG PET in cancer patients. Methods: Over 7 mo, 33 cancer patients were included in this study. In these patients, 63 lesions were independently evaluated by 2 nuclear medicine specialists (experienced and beginner). Two consecutive whole-body 18F-FDG PET/CT scans using a 3-min and 1.5-min acquisition time per bed position were obtained for each patient. Lesions were visually identified, and their locations were compared. The lesion volumes and standardized uptake values of the primary tumor, lymph nodes, and metastases were determined and compared. Image quality was scored using a 5-range Likert-type scale. For all parameters, inter-observer agreement was assessed. Results: All relevant lesions could be identified at both acquisition times. Image quality was slightly adversely affected by an acquisition time of 1.5 min but was excellent or good in 85% of the scans. In a patient with increased blood sugar levels, the image quality was rated moderate at 3 min and poor at 1.5 min. The quality of lesion visualization was excellent regardless of the acquisition time. Lesion volume and maximum standardized uptake value on PET images showed an excellent correlation between the 2 acquisition times (Pearson correlation coefficient, 0.99 and 0.97, respectively). Interobserver agreement was excellent (κ > 0.83). Conclusion: Although image quality is slightly poorer, reducing the acquisition time to 1.5 min per bed position seems to be clinically feasible without decreasing the lesion detection rate even for less experienced observers. [ABSTRACT FROM AUTHOR]

Unlabelled: Our objective was to evaluate the impact of acquisition time on image quality, lesion detection rate, standardized uptake values, and lesion volume for (18)F-FDG PET in cancer patients. Methods: Over 7 mo, 33 cancer patients were included in this study. In these patients, 63 lesions were independently evaluated by 2 nuclear medicine specialists (experienced and beginner). Two consecutive whole-body (18)F-FDG PET/CT scans using a 3-min and 1.5-min acquisition time per bed position were obtained for each patient. Lesions were visually identified, and their locations were compared. The lesion volumes and standardized uptake values of the primary tumor, lymph nodes, and metastases were determined and compared. Image quality was scored using a 5-range Likert-type scale. For all parameters, interobserver agreement was assessed. Results: All relevant lesions could be identified at both acquisition times. Image quality was slightly adversely affected by an acquisition time of 1.5 min but was excellent or good in 85% of the scans. In a patient with increased blood sugar levels, the image quality was rated moderate at 3 min and poor at 1.5 min. The quality of lesion visualization was excellent regardless of the acquisition time. Lesion volume and maximum standardized uptake value on PET images showed an excellent correlation between the 2 acquisition times (Pearson correlation coefficient, 0.99 and 0.97, respectively). Interobserver agreement was excellent (κ > 0.83). Conclusion: Although image quality is slightly poorer, reducing the acquisition time to 1.5 min per bed position seems to be clinically feasible without decreasing the lesion detection rate even for less experienced observers. [ABSTRACT FROM AUTHOR]