Mathematical evaluation of post-radiotherapy salivary gland function using salivary gland scintigraphy

Objective: Xerostomia is the most common treatment-related toxicity after radiotherapy (RT) for head and neck carcinoma, reducing the quality of life of patients due to a decrease in salivary gland function. Methods: Salivary gland scintigraphy was performed to quantitatively evaluate the salivary gland functions in patients undergoing RT. It was done chronologically for 62 salivary glands of 31 patients before RT and retested 12 months later. Results: The salivary gland functions of most patients deteriorated post-RT and recovered when the radiation dose to the salivary gland was not high. The mean dose to the salivary gland was found to be the most reliable factor in deteriorating salivary gland function, and the tolerance dose was determined to be 46 Gy. The recovery rate of salivary gland function after 1 year of RT was 72% in the RT alone group (n = 10), 56% in the conformal radiotherapy group (n = 15), and 44% in the bioradiotherapy group (n = 6). Conclusion: Scintigraphy revealed that the salivary glands recovered from post-RT hypofunction when decreased doses were administered. The determined tolerance dose of 46 Gy may guide the approach to minimizing associated xerostomia in RT. Advances in knowledge: In this study, the average tolerated dose to the salivary glands was 46 Gy.

Role and limitations of the geometric mean method regarding head rotation in salivary gland scintigraphy: a phantom study

To investigate the possible influence of head rotation on the results of salivary gland scintigraphy, a phantom study was designed to simulate clinical salivary gland scintigraphy. The quantitative accuracy of regional activity counts was compared for two data acquisition methods involving head rotation: (i) an anterior planar projection-only (ANT) method and (ii) a geometric mean (GM) method using both the anterior and posterior planar projections. The roles and limitations of the GM and ANT methods when used at different head rotation angles were examined. Parallel planar projections of a head phantom with four salivary gland simulators, containing 3.7 MBq 99mTc-sodium pertechnetate, at various rotational settings were acquired using a dual-head gamma camera. The difference between the standard activity counts (no phantom rotation) and the activity counts affected by the phantom rotation was calculated and defined as the rotational bias that decreased the accuracy of activity quantification. For small-angle rotation (≤10°), use of the GM method decreased the bias for all salivary gland simulators. In contrast, the bias of large-angle rotation (>10°) between four salivary gland simulators became conspicuous and complex in both methods. This bias may reflect different attenuation effects caused by displacement of the structures. Our data suggest that the GM method can be used when the head rotation angle is small (≤10°); however, when the head rotation angle is >10°, the non-negligible influence of head rotation should be considered during image acquisition.

The Validity of Salivary Gland Scintigraphy in Sjögren’s Syndrome Diagnosis: Comparison of Visual and Excretion Fraction Analysis

Introduction. The diagnostic value of salivary gland scintigraphy (SGS) in Sjögren’s syndrome (SS) is not completely known. Whether qualitative or quantitative methods of SGS interpretation are the most appropriate remains a matter of debate. We sought to determine whether the diagnostic discrimination of quantitative excretion fraction is higher compared to SGS qualitative visual analysis in a cohort of subjects with suspected SS. Materials and methods. Cross-sectional study that encompassed 204 subjects who underwent SGS for potential SS diagnosis. Based on clinical judgement, three groups were established: SS, non-SS autoimmune diseases (AID non-SS) and neither SS nor other AID (non-AID). In addition, American-European Consensus Group -AECG- and American College of Rheumatology -ACR- criteria were applied. Qualitative diagnosis through visual analysis -normal vs. abnormal and Schall’s classification grade- and semiquantitative and quantitative excretion fraction (EF%) scores were established following SGS assessment. The diagnostic discrimination of the different SGS scores for the various SS diagnostic modalities (clinical judgement and AECG and ACR criteria) was compared through their areas under the curve (AUC). Results. Most SGS parameters were significantly associated with SS-related clinical and laboratory features. Schall’s grade ≥ III was significantly more frequent in SS than in non-SS patients. In general, EF%-derived parameters did not show significant differences between groups. AUC of Schall’s classification reached statistical significance in its diagnostic discrimination for SS clinical judgement (AUC 0.704 [95%CI 0.597–0.811], p = 0.000) and AECG criteria (AUC 0.764 [95%CI 0.641–0.886], p = 0.000). Similarly the EF% submandibular mean (AUC 0.737 [95%CI 0.546–0.931] p = 0.032) was significantly associated with SS diagnosis through ACR criteria. However, AUC comparisons between qualitative and quantitative methods did not yield significant values. Conclusion. SS diagnostic discrimination of EF% is not superior to that obtained by qualitative visual analysis.

Potential Applications of 68Ga-PSMA-11 PET/CT in the Evaluation of Salivary Gland Uptake Function: Preliminary Observations and Comparison with 99mTcO4− Salivary Gland Scintigraphy

Purpose. To preliminarily evaluate the feasibility and potential of using 68Ga-PSMA-11 PET/CT in evaluating the function of salivary glands and lacrimal glands in comparison with 99mTc-pertechnetate (T99mcO4−) salivary gland scintigraphy (SGS). Methods. A retrospective study was performed in 15 patients with different degrees of xerostomia and suspected salivary gland dysfunction. Each patient underwent 68Ga-PSMA-11 PET/CT first and SGS the next day, and the findings of both scans were compared. Results. The results of 68Ga-PSMA-11 PET/CT and SGS were consistent in 12/15 patients (80%) and were inconsistent in the remaining patients (20%). For 5 (33.3%) of 15 patients, 68Ga-PSMA-11 PET/CT provided more information than did SGS. Additionally, 68Ga-PSMA-11 PET/CT corrected the misdiagnosis by SGS for 1 patient. Conclusions. 68Ga-PSMA-11 PET/CT is a potentially useful imaging tool for evaluating the function of salivary glands and lacrimal glands. 68Ga-PSMA-11 PET/CT can be a promising supplement to SGS, and its clinical value deserves further study.