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Fig. 27.2 Ultrasonographic images from different patients with Sjögren’s syndrome in different grades of disease. In grade 1, a barely seen heterogeneous parenchyma is noted due to ill-defined and small hypoechoic areas (arrows). Conversely, in grade 2–3, these areas are larger [small arrows representing lesions <2 mm, and the large arrow a larger hypoechoic area (>6 mm)] and echogenic bands (arrowheads) representing fibrotic changes are seen. Finally, in grade 4, multiple large and irregular but with well-defined hypoechoic cystic cavities are easily demonstrated. There is no increase in vascularity with color Doppler
27.4Tomography
Non-enhanced computed tomography (CT) scans can be employed when sialolithiasis is suspected (Fig. 27.3). CT examinations are helpful in distinguishing a single large stone from a cluster of stones [16]. Contrast-enhanced scans are indicated when complications such as abscess cannot be defined by ultrasound.
27.5Magnetic Resonance
Magnetic resonance imaging (MRI) has emerged as a reliable, noninvasive modality that can demonstrate glandular changes. The main advantages of the method include its multiplanar capability, the use of non-ionizing radiation, and the high-contrast
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G. Hernández-Molina et al. |
Fig. 27.3 Fifty-six-year-old female with Sjögren’s syndrome and an indurated palpable mass in the right parotid. The axial CT image demonstrates fatty infiltration of the left parotid with multiple tiny calcifications (sialolithiasis) (arrows) in the parenchyma. Conversely, notice the enlarged right parotid gland (*) with mildly heterogeneous density. When compared to MR Imaging (Fig. 27.4), CT has low tissue contrast resolution
tissue resolution. MRI sialography has now largely replaced conventional sialography for evaluations of the duct system [26, 27].
MRI findings that are characteristic of SS include inhomogeneous internal pattern on both T1 and T2 sequences. This pattern, described as a “salt and pepper” or “honeycomb” appearance, represents areas of increased fat and decreases in intact lobules. Such a pattern is characterized by multiple hypoand hyper-intense nodules of different sizes [26, 27] (Fig. 27.4). An MRI classification scheme for grading the structure of the parotid gland has been proposed (Table 27.4) [26]. Comparison studies between MRI and ultrasound have demonstrated good agreement (85%) in patients with primary SS, other patients with sicca symptoms without SS, and healthy controls [28, 29].
One investigation that validated MRI findings by comparison to histological analysis reported a sensitivity of 71% and a specificity of 100% for SS [30]. In another study that considered all MRI abnormalities (Grades 1–3) to be positive, the sensitivity of MRI was 100% and its specificity only 40%. The application of stricter criteria for a positive MRI study – grades 2 and 3 only – decreased the sensitivity to 88% but increased the specificity dramatically, to 100%. This discrepancy is explained by the fact that grade 1 MRI findings might be detected in normal subjects and patients with sicca symptoms who do not fulfill the criteria for SS [28].
Other MR modalities used in the evaluation of SS patients include MR sialography, functional MR sialography, and dynamic contrast-enhanced MRI. Dynamic, contrast-enhanced studies enable quantification of the microvascular characteristics of the gland [27].
In summary of the imaging section, there now exist many noninvasive imaging modalities for use in the assessment of salivary gland involvement in SS.
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Diagnostic Procedures (II): Parotid Scintigraphy, Parotid Ultrasound |
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Fig. 27.4 Same patient as shown in Fig. 27.3. Axial T1w (a), T2w (b), T2w gradient echo (c), and coronal T2w (d) images showing heterogeneous intensity of parotid parenchyma, best seen in the right side (* in a and b) with fatty infiltration of the left gland (arrows in a and b). There are multiple cystic lesions in both sides (arrowheads in c) and nonspecific lymph nodes in multiple levels of the head and neck (arrows in d)
Ultrasonography is a useful tool in the hands of an experienced operator. MRI can be used in lieu of ultrasound if there is not sufficient expertise with ultrasound. MRI is also useful when ultrasonographic studies have been negative, and when broader evaluation (e.g., for lymphadenopathy) is required in the setting of a tumor (Fig. 27.5). CT is mainly reserved for study of suspected sialolithiasis. It is likely that both ultrasound and MRI will find greater applications in the evaluation and care of patients with SS in the future.