MR measurement of blood flow in the parotid gland without contrast medium: a functional study before and after gustatory stimulation

Population Based Average Parotid Gland Volume and Prevalence of Incidental Tumors in T1-MRI

Representative epidemiologic data on the average volume of the parotid gland in a large population-based MRI survey is non-existent. Within the Study of Health in Pomerania (SHIP), we examined the parotid gland in 1725 non-contrast MRI-scans in T1 weighted sequence of axial layers. Thus, a reliable standard operating procedure (Intraclass Correlation Coefficient > 0.8) could be established. In this study, we found an average, single sided parotid gland volume of 27.82 cm3 (95% confidence interval (CI) 27.15 to 28.50) in male and 21.60 cm3 (95% CI 21.16 to 22.05) in female subjects. We observed positive associations for age, body mass index (BMI), as well as male sex with parotid gland size in a multivariate model. The prevalence of incidental tumors within the parotid gland regardless of dignity was 3.94% in the Northeast German population, slightly higher than assumed. Further epidemiologic investigations regarding primary salivary gland diseases are necessary.

Detection of impaired renal allograft function in paediatric and young adult patients using arterial spin labelling MRI (ASL-MRI)

The study aimed to discriminate renal allografts with impaired function by measuring cortical renal blood flow (cRBF) using magnetic resonance imaging arterial spin labelling (ASL-MRI) in paediatric and young adult patients. We included 18 subjects and performed ASL-MRI on 1.5 T MRI to calculate cRBF on parameter maps. cRBF was correlated to calculated glomerular filtration rate (GFR) and compared between patient groups with good (GFR ≥ 60 mL/min/1.73 m²) and impaired allograft function (GFR < 60 mL/min/1.73 m²). Mean cRBF in patients with good allograft function was significantly higher than in patients with impaired allograft function (219.89 ± 57.24 mL/min/100 g vs. 146.22 ± 41.84 mL/min/100 g, p < 0.008), showing a highly significant correlation with GFR in all subjects (r = 0.75, p < 0.0001). Also, the diffusion-weighted imaging (DWI-MRI) apparent diffusion coefficient (ADC) and Doppler measurements of peak-systolic and end-diastolic velocities and the resistive index (PS, ED, RI) were performed and both methods showed no significant difference between groups. ADC implied no correlation with GFR (r = 0.198, p = 0.464), while PS indicated moderate correlation to GFR (r = 0.48, p < 0.05), and PS and ED moderate correlation to cRBF (r = 0.58, p < 0.05, r = 0.56, p < 0.05, respectively). Cortical perfusion as non-invasively measured by ASL-MRI differs between patients with good and impaired allograft function and correlates significantly with its function.

The effect of eating on the uptake of PSMA ligands in the salivary glands

Rationale

PSMA-directed therapy for metastatic prostate cancer is gaining adoption as a treatment option. However, accumulation of ¹⁷⁷Lu/²²⁵Ac-PSMA in the salivary glands remains a problem, with risk of dose-limiting xerostomia and potentially severe effect on the quality of life. Gustatory stimulation is an approach that has commonly been used in radioactive iodine therapy to reduce accumulation in the salivary glands. However, based on theoretical differences in biodistribution, it was hypothesized that this could potentially lead to adverse increased toxicity for PSMA-ligand therapy. The primary objective of this work was to determine if gustatory stimulation by eating an assortment of sweet/fatty/acidic foods during the biodistribution phase of [¹⁸F]DCFPyl could result in a clinically relevant (> 30%) change in the uptake of the tracer in the salivary glands.

Methods

10 patients who already received a whole-body [¹⁸F]DCFPyl PET/CT scan for evaluation of prostate cancer, underwent a repeat (intervention) PET/CT scan within a month of the first (control) scan. During the intervention scan, patients chose from an assortment of sweet/fatty/acidic foods, which they then chewed and swallowed for a period of time starting 1 min before tracer administration to 10 min thereafter. Data from both scans were analyzed by placing VOIs on the major salivary glands and segmenting them using relative thresholds.

Results

A slight increase in PSMA uptake in the parotid glands was observed on the intervention scan when compared to the baseline scan (+ 7.1% SUL_mean and + 9.2% SUL_max, p < 0.05). No significant difference in PSMA uptake in the submandibular glands was seen.

Conclusions

Eating only slightly increases uptake of [¹⁸F]DCFPyl in the parotid glands. We nonetheless recommend refraining from gustatory stimulation during the administration and early biodistribution phase of radionuclide therapy with PSMA-ligands to reduce the risk of avoidable additional toxicity.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13550-021-00838-y.

Predicting Resolvin D1 Pharmacokinetics in Humans with Physiologically-Based Pharmacokinetic Modeling

Sjögren’s syndrome (SS) is an autoimmune disease with no effective treatment options. Resolvin D1 (RvD1) belongs to a class of lipid‐based specialized pro‐resolving mediators that showed efficacy in preclinical models of SS. We developed a physiologically‐based pharmacokinetic (PBPK) model of RvD1 in mice and optimized the model using plasma and salivary gland pharmacokinetic (PK) studies performed in NOD/ShiLtJ mice with SS‐like features. The predictive performance of the PBPK model was also evaluated with two external datasets from the literature reporting RvD1 PKs. The PBPK model adequately captured the observed concentrations of RvD1 administered at different doses and in different species. The PKs of RvD1 in virtual humans were predicted using the verified PBPK model at various doses (0.01–10 mg/kg). The first‐in‐human predictions of RvD1 will be useful for the clinical trial design and translation of RvD1 as an effective treatment strategy for SS.

Proton change of parotid glands after gustatory stimulation examined by magnetic resonance imaging

The aim of this study was to investigate proton changes of the parotid gland after gustatory stimulation by semi-quantitative parameters and an empirical mathematical model (EMM) using high-temporal-resolution, double-echo, echo-planar imaging (EPI). Approved by a local institutional review board, this study examined 20 parotid glands from 10 healthy volunteers (male:female = 6: 4; age ± standard deviation =35.1 ± 14.1 years) with written informed consent obtained. All participants underwent 1.5-T, double-echo EPI with gustatory stimulation. Semi-quantitative parameters, including maximal drop ratio (MDR), time to peak (TTP), drop slope (DS), recovery slope (RS) and recovery ratio (RR), were calculated. The effect of temporal resolution on parotid functional parameters was evaluated. An EMM comprising an output function ( Sot=Aoe-kot+B) and an input function ( Sint=Ain1-e-kint) was also applied to fit all dynamic curves. Kruskal-Wallis test, Wilcoxon test, linear regression analysis and goodness of fit were used for statistical analysis. p < 0.05 was considered to be statistically significant. The signal intensity dropped significantly after gustatory stimulation on the proton density (PD) image (p < 0.01). MDR was 8.26% in the PD image. MDR and RR were negatively associated with time interval, whereas DS and TTP were significantly positively associated with time interval (all p < 0.05). EMM parametric values derived from PD-time curves of parotid glands were 12.04 ± 6.81%, 6.43 ± 4.23 min^-1 , 88.73 ± 6.18%, 8.41 ± 4.86 min^-1 and 1.09 ± 1.35 for A_o , k_o , B, A_in and k_in , respectively. Semi-quantitative functional parameters and EMM parameters using high-temporal-resolution, double-echo EPI allow the quantification of parotid proton changes after gustatory stimulation.

Evaluating Instantaneous Perfusion Responses of Parotid Glands to Gustatory Stimulation Using High-Temporal-Resolution Echo-Planar Diffusion-Weighted Imaging

BACKGROUND AND PURPOSE

Parotid glands secrete and empty saliva into the oral cavity rapidly after gustatory stimulation. However, the role of the temporal resolution of DWI in investigating parotid gland function remains uncertain. Our aim was to design a high-temporal-resolution echo-planar DWI pulse sequence and to evaluate the instantaneous MR perfusion responses of the parotid glands to gustatory stimulation.

MATERIALS AND METHODS

This prospective study enrolled 21 healthy volunteers (M/F = 2:1; mean age, 45.2 ± 12.9 years). All participants underwent echo-planar DWI (total scan time, 304 seconds; temporal resolution, 4 s/scan) on a 1.5T MR imaging scanner. T2WI (b = 0 s/mm²) and DWI (b = 200 s/mm²) were qualitatively assessed. Signal intensity of the parotid glands on T2WI, DWI, and ADC was quantitatively analyzed. One-way ANOVA with post hoc group comparisons with Bonferroni correction was used for statistical analysis. P < .05 was statistically significant.

RESULTS

Almost perfect interobserver agreement was achieved (κ ≥ 0.656). The parotid glands had magnetic susceptibility artifacts in 14.3% (3 of 21) of volunteers during swallowing on DWI but were free from perceptible artifacts at the baseline and at the end of scans on all images. Increased ADC and reduced signal intensity of the parotid glands on T2WI and DWI occurred immediately after oral administration of lemon juice. Maximal signal change of ADC (24.8% ± 10.8%) was significantly higher than that of T2WI (-10.1% ± 5.2%, P < .001). The recovery ratio of ADC (100.71% ± 42.34%) was also significantly higher than that of T2WI (22.36% ± 15.54%, P < .001).

CONCLUSIONS

Instantaneous parotid perfusion responses to gustatory stimulation can be quantified by ADC by using high-temporal-resolution echo-planar DWI.

Investigating the Effect of Ligand Amount and Injected Therapeutic Activity: A Simulation Study for 177Lu-Labeled PSMA-Targeting Peptides

In molecular radiotherapy with ¹⁷⁷Lu-labeled prostate specific membrane antigen (PSMA) peptides, kidney and/or salivary glands doses limit the activity which can be administered. The aim of this work was to investigate the effect of the ligand amount and injected activity on the tumor-to-normal tissue biologically effective dose (BED) ratio for ¹⁷⁷Lu-labeled PSMA peptides. For this retrospective study, a recently developed physiologically based pharmacokinetic model was adapted for PSMA targeting peptides. General physiological parameters were taken from the literature. Individual parameters were fitted to planar gamma camera measurements (¹⁷⁷Lu-PSMA I&T) of five patients with metastasizing prostate cancer. Based on the estimated parameters, the pharmacokinetics of tumor, salivary glands, kidneys, total body and red marrow was simulated and time-integrated activity coefficients were calculated for different peptide amounts. Based on these simulations, the absorbed doses and BEDs for normal tissue and tumor were calculated for all activities leading to a maximal tolerable kidney BED of 10 Gy_2.5/cycle, a maximal salivary gland absorbed dose of 7.5 Gy/cycle and a maximal red marrow BED of 0.25 Gy₁₅/cycle. The fits yielded coefficients of determination > 0.85, acceptable relative standard errors and low parameter correlations. All estimated parameters were in a physiologically reasonable range. The amounts (for 2⁵−2⁹ nmol) and pertaining activities leading to a maximal tumor dose, considering the defined maximal tolerable doses to organs of risk, were calculated to be 272±253 nmol (452±420 μg) and 7.3±5.1 GBq. Using the actually injected amount (235±155 μg) and the same maximal tolerable doses, the potential improvement for the tumor BED was 1–3 fold. The results suggest that currently given amounts for therapy are in the appropriate order of magnitude for many lesions. However, for lesions with high binding site density or lower perfusion, optimizing the peptide amount and activity might improve the tumor-to-kidney and tumor-to-salivary glands BED ratio considerably.

Influence of amplitude-related perfusion parameters in the parotid glands by non-fat-saturated dynamic contrast-enhanced magnetic resonance imaging

PURPOSE

To verify whether quantification of parotid perfusion is affected by fat signals on non-fat-saturated (NFS) dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI) and whether the influence of fat is reduced with fat saturation (FS).

METHODS

This study consisted of three parts. First, a retrospective study analyzed DCE-MRI data previously acquired on different patients using NFS (n = 18) or FS (n = 18) scans. Second, a phantom study simulated the signal enhancements in the presence of gadolinium contrast agent at six concentrations and three fat contents. Finally, a prospective study recruited nine healthy volunteers to investigate the influence of fat suppression on perfusion quantification on the same subjects. Parotid perfusion parameters were derived from NFS and FS DCE-MRI data using both pharmacokinetic model analysis and semiquantitative parametric analysis. T tests and linear regression analysis were used for statistical analysis with correction for multiple comparisons.

RESULTS

NFS scans showed lower amplitude-related parameters, including parameter A, peak enhancement (PE), and slope than FS scans in the patients (all with P < 0.0167). The relative signal enhancement in the phantoms was proportional to the dose of contrast agent and was lower in NFS scans than in FS scans. The volunteer study showed lower parameter A (6.75 ± 2.38 a.u.), PE (42.12% ± 14.87%), and slope (1.43% ± 0.54% s(-1)) in NFS scans as compared to 17.63 ± 8.56 a.u., 104.22% ± 25.15%, and 9.68% ± 1.67% s(-1), respectively, in FS scans (all with P < 0.005). These amplitude-related parameters were negatively associated with the fat content in NFS scans only (all with P < 0.05).

CONCLUSIONS

On NFS DCE-MRI, quantification of parotid perfusion is adversely affected by the presence of fat signals for all amplitude-related parameters. The influence could be reduced on FS scans.

Arterial Spin Labeling Imaging for the Parotid Glands of Patients with Sjögren's Syndrome

Sjögren's syndrome (SS) is characterized by hypofunction of the salivary and lacrimal glands. The salivary function is largely dependent upon the blood supply in the glands. However, the diseased states of the gland perfusion are not well understood. The arterial spin labeling (ASL) technique allows noninvasive quantitative assessment of tissue perfusion without the need for contrast agent. Here, we prospectively compared the perfusion properties of the parotid glands between patients with SS and those with healthy glands using ASL MR imaging. We analyzed salivary blood flow (SBF) kinetics of 22 healthy parotid glands from 11 volunteers and 28 parotid glands from 14 SS patients using 3T pseudo-continuous ASL imaging. SBF was determined in resting state (base SBF) and at 3 sequential segments after gustatory stimulation. SBF kinetic profiles were characterized by base SBF level, increment ratio at the SBF peak, and the differences in segments where the peak appeared (SBF types). Base SBFs of the SS glands were significantly higher than those of healthy glands (59.2 ± 22.8 vs. 46.3 ± 9.0 mL/min/100 g, p = 0.01). SBF kinetic profiles of the SS glands also exhibited significantly later SBF peaks (p < 0.001) and higher SBF increment ratios (74 ± 49% vs. 47 ± 39%, p = 0.04) than the healthy glands. The best SBF criterion (= 51.2 mL/min/100 mg) differentiated between control subjects and SS patients with 71% sensitivity and 82% specificity. Taken together, these results showed that the SS parotid glands were mostly hyperemic and the SS gland responses to gustatory stimulation were stronger and more prolonged than those of the healthy glands. The ASL may be a promising technique for assessing the diseased salivary gland vascularization of SS patients.

To evaluate the damage of renal function in CIAKI rats at 3T: using ASL and BOLD MRI

Purpose. To investigate noninvasive arterial spin-labeling (ASL) and blood oxygen level-dependent imaging (BOLD) sequences for measuring renal hemodynamics and oxygenation in contrast induced acute kidney injury (CIAKI) rat. Materials and Methods. Thirteen SD rats were randomly grouped into CIAKI group and control group. Both ASL and BOLD sequences were performed at 24 h preinjection and at intervals of 0.5, 12, 24, 48, 72, and 96 h postinjection to assess renal blood flow (RBF) and relative spin-spin relaxation rate (R₂^*), respectively. Results. For the CIAKI group, the value of RBF in the cortex (CO) and outer medulla (OM) of the kidney was significantly decreased (P < 0.05) at 12–48 h and regressed to baseline level (P = NS) at 72–96 h. In OM, the value of R₂^* was increased at 0.5–48 h (P < 0.05) and not statistically significant (P = NS) at 72 and 96 h. Conclusions. RBF in OM and CO and oxygen level in OM were decreased postinjection of CM. ASL combining BOLD can further identify the primary cause of the decrease of renal oxygenation in CIAKI. This approach provides means for noninvasive monitoring renal function during the first 4 days of CIAKI in clinical routine work.

Functional evaluation of transplanted kidneys using arterial spin labeling MRI

PURPOSE

To investigate non-contrast-enhanced arterial spin labeling (ASL) MRI for functional assessment of transplanted kidneys at 1.5 Tesla (T) and 3T.

MATERIALS AND METHODS

This study was approved by the local ethics committee, and written informed consent was obtained from all participants. Ninety eight renal allograft recipients (mean age, 51.5 ± 14.6 years) were prospectively included in this study. ASL MRI was performed at 1.5T (n = 65) and 3T (n = 33) using a single-slice flow-sensitive alternating inversion recovery true-fast imaging with steady-state precession (FAIR True-FISP) sequence in the paracoronal plane. ASL perfusion was regional analyzed for the renal cortex on parameter maps. ASL was compared between patients with good or moderate allograft function (Group a; estimated glomerular filtration rate [eGFR] > 30 mL/min/1.73 m(2)) and patients with heavily impaired allograft function (Group b; eGFR ≤ 30 mL/min/1.73 m(2)) and correlated to renal function as determined by eGFR.

RESULTS

ASL perfusion and eGFR were comparable at 1.5T (246.9 ± 66.8 mL/100 g/min and 41.9 ± 22.7 mL/min/1.73 m(2)) and 3T (236.5 ± 102.3 mL/100 g/min and 35.9 ± 22.9 mL/min/1.73 m(2)). ASL perfusion was significantly higher in group a (282.7 ± 60.8 mL/100 g/min) as compared to group b (178.2 ± 63.3 mL/100 g/min) (P < 0.0001). ASL perfusion values exhibited a significant correlation with renal function as determined by eGFR (r = 0.59; P < 0.0001).

CONCLUSION

Cortical ASL perfusion values differ between patients with good or moderate allograft function and poor allograft function and correlate significantly with allograft function. Our results highlight the potential of ASL MRI for functional evaluation of renal allografts.

Correlation of biexponential diffusion parameters with arterial spin-labeling perfusion MRI: results in transplanted kidneys

PURPOSE

The purpose of the present study was to explore the correlation between diffusion parameters assessed by biexponential analysis and the tissue perfusion measured by arterial spin labeling (ASL) imaging in renal allografts.

MATERIAL AND METHODS

Seventeen recipients of renal allograft (11 men and 6 women; mean [SD] age, 53.6 [14.1] years) were included in this study. For diffusion-weighted imaging, a paracoronal echo-planar imaging sequence was acquired with 16 b values (range, b = 0-750 s/mm²) and 6 averages at 1.5 T. For the quantitative assessment of transplanted kidney perfusion, a flow-sensitive alternating inversion recovery true fast imaging with steady precession-ASL technique was applied. No respiratory gating was used. For quantitative analysis, region of interest measurements were performed on parameter maps. The Spearman correlation coefficients were calculated to determine the association between mean serum creatinine levels, estimated glomerular filtration rate, the apparent diffusion coefficient (ADC) of pure diffusion, the ADC of pseudodiffusion, the monoexponential ADC, the fraction of pseudodiffusion, and the tissue perfusion ASL values.

RESULTS

In the renal cortex, the fraction of pseudodiffusion was 17.4% ± 4.0%, the apparent diffusion coefficient of pure diffusion was 160.7 ± 15.0 × 10⁻⁵ mm²/s, the monoexponential ADC was 193.2 ± 16.7 × 10⁻⁵ mm²/s, and the ADC of pseudodiffusion was 1421.0 ± 237.7 × 10⁻⁵ mm²/s. Mean cortical perfusion of renal allografts, as assessed with ASL imaging, was 247.2 ± 75.0 mL/100 g/min. There was a significant correlation between ASL perfusion and the fraction of pseudodiffusion (r = 0.68; P < 0.005) but not with the other diffusion coefficients. Both ASL perfusion and the fraction of pseudodiffusion exhibited a significant correlation with serum creatinine levels (r = 0.51 and r= 0.53, respectively; P < 0.05) and estimated glomerular filtration rate (r = 0.63 and r = 0.54, respectively; P < 0.05).

CONCLUSIONS

This is the first study that shows a significant correlation between renal allograft perfusion, as assessed with ASL perfusion measurements, and the fraction of pseudodiffusion derived from biexponential diffusion-weighted imaging measurements.

Arterial spin labeling blood flow magnetic resonance imaging for evaluation of renal injury

A multitude of evidence suggests that iodinated contrast material causes nephrotoxicity; however, there have been no previous studies that use arterial spin labeling (ASL) blood flow functional magnetic resonance imaging (fMRI) to investigate the alterations in effective renal plasma flow between normointensive and hypertensive rats following injection of contrast media. We hypothesized that FAIR-SSFSE arterial spin labeling MRI may enable noninvasive and quantitative assessment of regional renal blood flow abnormalities and correlate with disease severity as assessed by histological methods. Renal blood flow (RBF) values of the cortex and medulla of rat kidneys were obtained from ASL images postprocessed at ADW4.3 workstation 0.3, 24, 48, and 72 h before and after injection of iodinated contrast media (6 ml/kg). The H&E method for morphometric measurements was used to confirm the MRI findings. The RBF values of the outer medulla were lower than those of the cortex and the inner medulla as reported previously. Iodinated contrast media treatment resulted in decreases in RBF in the outer medulla and cortex in spontaneously hypertensive rats (SHR), but only in the outer medulla in normotensive rats. The iodinated contrast agent significantly decreased the RBF value in the outer medulla and the cortex in SHR compared with normotensive rats after injection of the iodinated contrast media. Histological observations of kidney morphology were also consistent with ASL perfusion changes. These results demonstrate that the RBF value can reflect changes of renal perfusion in the cortex and medulla. ASL-MRI is a feasible and accurate method for evaluating nephrotoxic drugs-induced kidney damage.

Magnetic resonance perfusion imaging without contrast media

PURPOSE

Principles of magnetic resonance imaging techniques providing perfusion-related contrast weighting without administration of contrast media are reported and analysed systematically. Especially common approaches to arterial spin labelling (ASL) perfusion imaging allowing quantitative assessment of specific perfusion rates are described in detail. The potential of ASL for perfusion imaging was tested in several types of tissue.

METHODS

After a systematic comparison of technical aspects of continuous and pulsed ASL techniques the standard kinetic model and tissue properties of influence to quantitative measurements of perfusion are reported. For the applications demonstrated in this paper a flow-sensitive alternating inversion recovery (FAIR) ASL perfusion preparation approach followed by true fast imaging with steady precession (true FISP) data recording was developed and implemented on whole-body scanners operating at 0.2, 1.5 and 3 T for quantitative perfusion measurement in various types of tissue.

RESULTS

ASL imaging provides a non-invasive tool for assessment of tissue perfusion rates in vivo. Images recorded from kidney, lung, brain, salivary gland and thyroid gland provide a spatial resolution of a few millimetres and sufficient signal to noise ratio in perfusion maps after 2-5 min of examination time.

CONCLUSIONS

Newly developed ASL techniques provide especially high image quality and quantitative perfusion maps in tissues with relatively high perfusion rates (as also present in many tumours). Averaging of acquisitions and image subtraction procedures are mandatory, leading to the necessity of synchronization of data recording to breathing in abdominal and thoracic organs.

Quantification of renal allograft perfusion using arterial spin labeling MRI: initial results

OBJECTIVE

To quantify renal allograft perfusion in recipients with stable allograft function and acute decrease in allograft function using nonenhanced flow-sensitive alternating inversion recovery (FAIR)-TrueFISP arterial spin labeling (ASL) MR imaging.

METHODS

Following approval of the local ethics committee, 20 renal allograft recipients were included in this study. ASL perfusion measurement and an anatomical T2-weighted single-shot fast spin-echo (HASTE) sequence were performed on a 1.5-T scanner (Magnetom Avanto, Siemens, Erlangen, Germany). T2-weighted MR urography was performed in patients with suspected ureteral obstruction. Patients were assigned to three groups: group a, 6 patients with stable allograft function over the previous 4 months; group b, 7 patients with good allograft function who underwent transplantation during the previous 3 weeks; group c, 7 allograft recipients with an acute deterioration of renal function.

RESULTS

Mean cortical perfusion values were 304.8 +/- 34.4, 296.5 +/- 44.1, and 181.9 +/- 53.4 mg/100 ml/min for groups a, b and c, respectively. Reduction in cortical perfusion in group c was statistically significant.

CONCLUSION

Our results indicate that ASL is a promising technique for nonenhanced quantification of cortical perfusion of renal allografts. Further studies are required to determine the clinical value of ASL for monitoring renal allograft recipients.

Autoimmune thyroid disease: arterial spin-labeling perfusion MR imaging

PURPOSE

To assess thyroid perfusion in patients with autoimmune thyroid diseases compared with that in healthy control subjects by using an arterial spin-labeling (ASL) magnetic resonance (MR) technique and to assess whether thyroid perfusion is associated with endocrine laboratory abnormalities.

MATERIALS AND METHODS

This study was approved by the local institutional review board. All participants gave written informed consent. Perfusion imaging of the thyroid gland was performed in 10 patients with Graves disease (GD) and 10 patients with Hashimoto thyroiditis (HT). Ten healthy individuals served as control subjects. Perfusion imaging was performed with a 1.5-T MR unit by using a flow-sensitive alternating inversion recovery-true fast imaging with steady-state precession technique. Perfusion maps of the entire thyroid gland were calculated on the basis of extended Bloch equations. Analysis of variance with a post hoc test (Tukey honestly significant difference) was performed to assess differences in perfusion between groups. Associations between perfusion and laboratory parameters were analyzed with univariate regression analysis.

RESULTS

Mean thyroid perfusion was 1596 mL/min/100 g +/- 436 (standard deviation) in patients with GD, 825 mL/min/100 g +/- 264 in patients with HT, and 491 mL/min/100 g +/- 89 in healthy control subjects. Perfusion was significantly higher in patients with GD (P < .0001) and those with HT (P < .05) than in control subjects. A significant difference in thyroid perfusion was detected between the two autoimmune entities (P < .0001). In patients with GD, significant associations were found between perfusion and serum concentrations of free thyroid hormones and anti-thyroid-stimulating hormone receptor antibodies (P < .05 for all).

CONCLUSION

Quantitative ASL perfusion imaging of the thyroid gland revealed significant perfusion differences in the autoimmune thyroid diseases GD and HT. Absolute quantification of thyroid perfusion may be useful in the clinical assessment of autoimmune thyroid disorders and when monitoring therapeutic treatment in GD.