The influence of clinical factors on human stimulated parotid flow rate in cancer and other patients

Apparent diffusion coefficient measurement of the parotid gland parenchyma

The measurements of apparent diffusion coefficient (ADC) with diffusion weighted magnetic resonance imaging (DW-MRI) is becoming a popular diagnostic and research tool for examination of parotid glands. However, there is little agreement between the reported ADC values of the parotid gland in published literature. In this review 43 studies on ADC measurement of the parotid glands were included. The analyses indicated several possible culprits of the observed ADC discrepancies. For example, DW-MRI examinations under gustatory stimulation gives higher ADC values compared to the unstimulated parotid gland (P=0.003). The diffusion weighting factors (b-values) can either increase (b-value <200 s/mm²) or decrease ADC values (b-values >1,000 s/mm²). The timing of follow-up DW-MRI after radiotherapy (RT) indicates correlation to the found ADC values (R² =0.39). Interestingly, the choice of regions of interest (ROI) appears not to affect the measurements of ADC (P=0.75). It can be concluded that there is a critical need for standardization of ADC measurement of the parotid glands to allow valid inter-study comparisons and eventually to reach consensus on the use of ADC as biomarker.

Spatially resolved sampling for untargeted metabolomics: A new tool for salivomics

Saliva is a complex bodily fluid composed of metabolites secreted by major and minor glands, as well as by-products of host oral cells, oral bacteria, gingival crevicular fluid, and exogenous compounds. Major salivary glands include the paired parotid, submandibular, and sublingual glands. The secreted fluids of the salivary glands vary in composition, flow rate, site of release, and clearance suggesting that different types of saliva fulfill different functions and therefore can provide unique biological information. Consequently, for the comprehension of the functionality of the salivary components, spatially resolved investigations are warranted. To understand and comprehensively map the highly heterogeneous environment of the oral cavity, advanced spatial sampling techniques for metabolomics analysis are needed. Here, we present a systematic evaluation of collection devices for spatially resolved sampling aimed at untargeted metabolomics and propose a comprehensive and reproducible collection and analysis protocol for the spatially resolved analysis of the human oral metabolome.

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Systematic evaluation of collection devices for untargeted metabolomics of saliva

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Spatially resolved sampling of saliva in the human oral cavity

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Enabling location-specific oral metabolomics

Influence of blade width and magnetic field strength on the ADC on PROPELLER DWI in head and neck

PURPOSE

The purpose of this study was to investigate the influence of blade width and magnetic field strength on apparent diffusion coefficient values of periodically rotated overlapping parallel lines with enhanced reconstruction (PROPELLER) diffusion-weighted imaging in the head and neck at 1.5 and 3.0 T magnetic resonance imaging.

METHODS

Fifteen healthy volunteers (eight men and seven women; mean age 36.4 ± 10.1 years) underwent PROPELLER diffusion-weighted imaging using four blade widths at 3.0 T and three blade widths at 1.5 T. For the multigroup comparison of apparent diffusion coefficient values, we performed analysis of variance and Tukey-Kramer tests. The apparent diffusion coefficient values in each organ were compared among the different blade widths and magnetic field strengths by a t test. Inter and intra-observer agreements regarding apparent diffusion coefficient value measurements were evaluated using the intraclass correlation coefficient.

RESULTS

No significant differences were observed in apparent diffusion coefficient values of the cerebellum in each blade width at both field strengths. The apparent diffusion coefficient values of the right parotid glands were significantly lower for blade width 32 than for blade width 16 at 3.0 T (1.16 × 10^-3 mm²/s vs. 1.01 × 10^-3 mm²/s; P < 0.05). The apparent diffusion coefficient values of bilateral parotid glands were significantly higher at 1.5 T than at 3.0 T. Intraclass correlation coefficients were almost perfect to substantial in the cerebellum, whereas they showed moderate agreement in the parotid glands.

CONCLUSION

The largest blade width 32 at 3.0 T and high magnetic field strength lowered the apparent diffusion coefficient values of parotid glands of PROPELLER diffusion-weighted imaging. The apparent diffusion coefficient values in the parotid glands of PROPELLER diffusion-weighted imaging may be affected for blade width and magnetic field strength.

Age-related relaxo-volumetric quantitative magnetic resonance imaging of the major salivary glands

OBJECTIVE

To study age-related characteristics of T1 and T2 relaxation times and volume of the major salivary glands.

METHODS

Thirty-five subjects (0.5-87 years old) with normal salivary glands were imaged with mixed turbo spin-echo pulse sequences at 1.5-T magnetic resonance units. Bilateral parotid, submandibular, and sublingual glands were segmented manually. Histograms for each salivary gland were generated and modeled with Gaussian functions for every parameter.

RESULTS

Seventy parotid glands, 52 submandibular glands, and 50 sublingual glands were segmented and the histograms were analyzed. The parotid gland exhibited shorter-peak T1s and longer-peak T2s relative to the submandibular and sublingual glands. The peak T2s for all glands showed a minimum value between 2 and 4 years of age and increased monotonically thereafter. From birth to early adulthood, all glands increased in size logarithmically.

CONCLUSION

Age-related relaxo-volumetric changes of the major salivary glands show clear T2 and volumetric age-related patterns for all glands.

The unstimulated salivary flow rate in a jordanian healthy adult population

Background

Early diagnosis of xerostomia is very important for oral health. The purpose of this study was to determine the unstimulated whole salivary flow rates (UWSFR) in a Jordanian Arab population aged 15 years and older. The effect of age, gender, height, weight, body mass index (BMI), smoking, alcohol consumption, and dental conditions, on UWSFR was also investigated.

Methods

The study was conducted on 244 subjects, 110 males and 134 females, with an average age of 33 ± 15.5 years. They were healthy, unmedicated, and with no history of dry mouth. Unstimulated whole saliva was collected during five minutes, and UWSFRs (ml/min) were determined. Data were analyzed by univariate analysis and multivariate regression analysis.

Results

The mean UWSFR was 0.46 ± 0.25 ml/min (range: 0.10-1.6 ml/min). Eighteen patients (7.4%) had UWSFR between < 0.20 ml/min. In univariate analysis, UWSFR was significantly affected by age, BMI, number of missing and restored teeth, and DMFT score. Regression analysis revealed that only age and number of missing teeth were of significance in explaining the variability of the UWSFR.

Conclusions

We established basic standard values of UWSFR to be used in the evaluation of Jordanian patients with complaints of xerostomia and to be compared to data reported in other studies. UWSFR 0.1 ml/min could be considered the cut-off value that distinguishes normal from abnormal salivary function in this healthy unmedicated population.

Keywords

Whole saliva flow rate; Unstimulated; Jordan

Effects of benign parotid tumors on unstimulated saliva secretion from the parotid gland

OBJECTIVE

Salivary tumors can manifest as abnormalities of the gland itself and/or changes in salivary flow. However, effects of salivary tumors on saliva secretion have not been studied in much detail. The aim of the present study was to evaluate effects of benign parotid tumors on unstimulated saliva secretion from the affected gland.

METHODS

Unstimulated parotid saliva was collected bilaterally using the swab method in patients with unilateral pleomorphic adenoma (n=14) or Warthin's tumor (n=6). Pre-weighted cotton rolls were placed at the opening of each parotid duct for 15min.

RESULTS

The range of salivary flow was similar to that found in studies on unstimulated parotid saliva. Salivary flow did not differ between the involved and non-involved side. No difference was found between the involved and non-involved side when the patients with pleomorphic adenoma or Warthin's tumor were separately analyzed.

CONCLUSION

The present results suggest that the most common benign parotid tumors do not alter unstimulated salivary flow from the affected gland.

Evaluation of irradiated salivary gland function in patients with head and neck tumours treated with radiotherapy

Introduction:

Radiotherapy is an important treatment modality for head and neck tumours. One of its major drawbacks is post-treatment salivary gland hypofunction. This study was performed to objectively evaluate the salivary gland function in post-irradiated head and neck tumour patients.

Methods:

We performed a cross-sectional study of 30 patients with head and neck tumours who had received radiotherapy. Unstimulated and stimulated whole salivary flow rates were assessed in these 30 patients, and compared with those of 30 normal subjects. Unstimulated whole saliva was measured by the draining method, while the spitting method was used to collect stimulated whole saliva.

Results:

Both unstimulated and stimulated whole salivary flow rates were significantly reduced in the irradiated patients, compared with the normal subjects. This difference was statistically significant (p = 0.0001).

Conclusion:

Salivary function in post-irradiated head and neck tumour patients (assessed as salivary flow rates) was significantly reduced compared with normal controls, suggesting marked salivary gland hypofunction.

Randomized clinical trial comparing partial parotidectomy versus superficial or total parotidectomy

Background

In recent decades the treatment of benign parotid tumours has shifted from superficial or total parotidectomy to partial parotidectomy. This study examined whether current surgical techniques improved functional outcomes after surgery for benign parotid tumours.

Methods

One hundred and one patients were assigned randomly to conventional (49 patients) or function-preserving (52) surgery. The latter consisted of modified facelift incision, greater auricular nerve preservation, partial parotidectomy and coverage with parotid fascia.

Results

The mean duration of operation was 0·7 h shorter and the overall complication rate significantly lower in the functional surgery group. In this group, more patients were satisfied with their scars and facial contours, the auricular nerve sensory recovery rate was high, and transient facial paralysis and Frey's syndrome were infrequent (12 and 6 per cent respectively). Stimulated salivary flow on the operated side decreased to 71·9 per cent after function-preserving surgery compared with 20·7 per cent after conventional operation. There was no tumour recurrence in either group during a mean follow-up of 48 months.

Conclusion

Compared with conventional procedures, function-preserving surgery for benign parotid tumours improved cosmetic, sensory and salivary functions, and reduced the duration of surgery and operative morbidity.

Long-term parotid gland function after radiotherapy

PURPOSE

Irradiation of the parotid glands causes salivary dysfunction, resulting in reduced salivary flow. Recovery can be seen with time; however, long-term prospective data are lacking. The objective of this study was to analyze the long-term parotid gland function after irradiation for head-and-neck cancer.

METHODS AND MATERIALS

A total of 52 patients with head-and-neck cancer and treated with radiotherapy (RT) were prospectively evaluated. Stimulated bilateral parotid salivary flow rates were measured before RT and 6 weeks, 6 months, 12 months, and at least 3.5 years after RT completion. A complication was defined as a stimulated parotid flow rate of <25% of the pre-RT flow rate. The normal tissue complication probability model proposed by Lyman was fit to the data. Multilevel techniques were used to model the patterns of flow rates with time.

RESULTS

The mean stimulated flow rate of the parotid glands before RT was 0.31 mL/min (standard deviation [SD], 0.21). This was reduced to 0.14 mL/min (SD, 0.15) at 6 weeks after RT and recovered to 0.20 mL/min (SD, 0.22) at 6 months and 0.19 mL/min (SD, 0.21) at 12 months after RT. The mean stimulated flow rate was 0.25 mL/min (SD, 0.28) 5 years after RT. The mean dose to the parotid gland resulting in a 50% complication probability increased from 34 Gy at 6 weeks to 40 Gy at 6 months, 42 Gy at 12 months, and 46 Gy at 5 years after RT. Multilevel modeling indicated that both dose and time were significantly associated with the flow ratio.

CONCLUSION

Salivary output can still recover many years after RT. At 5 years after RT, we found an increase in the salivary flow rate of approximately 32% compared with at 12 months after RT.

Gustatory Stimulation Changes the Apparent Diffusion Coefficient of Salivary Glands: Initial Experience

Echo-planar diffusion-weighted (DW) magnetic resonance (MR) imaging was used to evaluate changes in the parotid glands during gustatory stimulation. The study protocol was approved by the local ethics committee, and informed consent was obtained from all volunteers. Twelve healthy volunteers (five women, seven men) with a median age of 25 years (range, 22-30 years) were examined with a 1.5-T MR unit. A DW MR imaging sequence was performed once at rest and continuously repeated over a mean period of 26 minutes (range, 24-28 minutes) during salivary stimulation with a tablet of ascorbic acid given orally. During the first 5 minutes (range, 1 minute 30 seconds--7 minutes 30 seconds) of salivary stimulation, a decrease in apparent diffusion coefficient (ADC) was observed in both the parotid (P = .0001) and the submandibular (P = .0004) glands in all volunteers. During the following 15 minutes, a steady increase in ADC from the baseline value was noted for the parotid glands (P = .0022), and peak ADC was reached a median of 21 minutes (range, 14-21 minutes) after the start of gustatory stimulation. The ADC of the submandibular glands did not increase significantly after the start of gustatory stimulation compared with the ADC at baseline. In conclusion, DW MR imaging allows physicians to noninvasively demonstrate functional changes in the salivary glands.

Diffusion-weighted imaging of the parotid gland: Influence of the choice ofb-values on the apparent diffusion coefficient value

PURPOSE

To determine how the ADC value of parotid glands is influenced by the choice of b-values.

MATERIALS AND METHODS

In eight healthy volunteers, diffusion-weighted echo-planar imaging (DW-EPI) was performed on a 1.5 T system, with b-values (in seconds/mm2) of 0, 50, 100, 150, 200, 250, 300, 500, 750, and 1000. ADC values were calculated by two alternative methods (exponential vs. logarithmic fit) from five different sets of b-values: (A) all b-values; (B) b=0, 50, and 100; (C) b=0 and 750; (D) b=0, 500, and 1000; and (E) b=500, 750, and 1000.

RESULTS

The mean ADC values for the different settings were (in 10(-3) mm2/second, exponential fit): (A) 0.732+/-0.019, (B) 2.074+/-0.084, (C) 0.947+/-0.020, (D) 0.890+/-0.023, and (E) 0.581+/-0.021. ADC values were significantly (P <0.001) different for all pairwise comparisons of settings (A-E) of b-values, except for A vs. D (P=0.172) and C vs. D (P=0.380). The ADC(B) was significantly higher than ADC(C) or ADC(D), which was significantly higher than ADC(E). ADC values from exponential vs. logarithmic fit (P=0.542), as well as left vs. right parotid gland (P=0.962), were indistinguishable.

CONCLUSION

The ADC values calculated from low b-value settings were significantly higher than those calculated from high b-value settings. These results suggest that not only true diffusion but also perfusion and saliva flow may contribute to the ADC.