of SjšgrenÕs syndrome] sialography has traditionally been used to evaluate the salivary component. Nuclear medicine (scintigraphy) has had a role in the diagnosis of SjšgrenÕs syndrome and is considered an important diagnostic tool. The presence of objective salivary gland involvement is deÞned by either unstimulated whole salivary ßow of less than or equal to 1.5 mL/15 min, diffuse sialectasis by parotid sialography, or salivary scintigraphy showing delayed uptake, reduced concentration, and/or delayed excretion of tracer [6]. Other imaging methods are available but not established as routine in diagnosing SjšgrenÕs syndrome. The available imaging methods are conventional radiographs (including sialography), computer tomography (CT), ultrasound (US), magnetic resonance imaging (MRI), and nuclear medicine (scintigraphy). These will be further described below.

7.1Conventional Radiographs

7.1.1 Sialography

Conventional X-rays are commonly used for examinations of joints, bones, and lungs. This does not give direct information concerning SjšgrenÕs syndrome but information concerning other effects of the disease. It is also a part of the diagnosis and follow-up of patients with rheumatic diseases. However, as a primary diagnostic examination for SjšgrenÕs syndrome, plain X-ray is not indicated. CT and MRI are also used for other organs in connection with SjšgrenÕs syndrome and rheumatic diseases but will not be dealt with here.

For SjšgrenÕs syndrome in particular, only sialography has a diagnostic yield, showing the ducts of the salivary glands [5]. The examination is performed by installing a contrast medium into the salivary ducts and then exposing radiographs of the area at different angles. It is a very good procedure for determining the architecture and conÞguration of the glandular ducts. In patients with SjšgrenÕs syndrome, the characteristic Þnding is a snowstorm-like or Christmas tree pattern. In cases where the glandular tissue

is severely damaged, complete absence of structures may be observed. Sialography is a wellestablished method, but has its limitations as it is time-consuming and may be painful and risky. In patients with severe salivary gland dysfunction, sialography is even contraindicated; due to reduced salivary ßow, the contrast medium injected may remain in the gland [7]. It is a cumbersome method to perform, may be uncomfortable to the patient, and similar diagnostic results may now be achieved with MR sialography [8].

Sialography is not suited for repetition and, therefore, not applicable for patient follow-up. Various stages of sialectasis can be detected in patients with SjšgrenÕs syndrome, and an abnormal result was determined in 72Ð86% of patients. Second only to lip biopsy and histopathological evaluation of the salivary glands, parotid sialography yielded the highest accuracy for the diagnosis of patients with SjšgrenÕs syndrome [9]. However, in a healthy population, 15Ð29% of otherwise healthy and asymptomatic individuals may also demonstrate sialectasis, and chronic sialadenitis of other causes may also show the same pattern, diminishing the value of the test, reviewed in [10].

7.2Computer Tomography

As conventional radiographs, CT is also based on ionizing radiation with an X-ray tube rotating around the patient. CT will thus expose patients to a signiÞcant radiation dose, and this may exclude younger patients.

At Þrst, this technique gave cross-sectional slices. Today CT provides a volume that can be analyzed in different planes as well as threedimensionally, all with a high spatial resolution. It is in many ways an excellent method but not for SjšgrenÕs syndrome. CT is the best method for detecting stones in the salivary ducts and is often used for preoperative staging of tumors in the salivary glands [11]. CT may also be used for sialography, providing a three-dimensional view of the ductal system. However, the tissue resolution is not sufÞcient for detecting tissue changes in the salivary glands, such as Þbrosis [12].

7.3Ultrasound

The salivary glands are situated superÞcially and thus well situated for the use of high frequency transducers (Fig. 7.1a, b). Ultrasound is based on sound waves, like SONAR. Piezoelectric crystals emit and receive sound, and the higher the frequency, the better the spatial resolution. The development of transducers has provided both high spatial and tissue resolution, giving excellent examinations of the salivary glands, and changes in tissue due to inßammation may be seen [13]. The salivary ducts can also be visualized, but the anatomical overview is difÞcult. One investigation compared US and scintigraphy and found US to be better [14] while another found US to be equivalent to MRI [15]. Ultrasound is easily available and ÒcomfortableÓ to the patient as well as providing good access to the parotid and submandibular glands. Accordingly, it is natural that during the development of ultrasound, several investigations on ultrasound and SjšgrenÕs syndrome have been made [16].

7.4Magnetic Resonance Imaging

The patient lies in a large magnet, the patientÕs nuclear spin will then align parallel or antiparallel to the magnetic Þeld. A radio frequency is sent to the patient. The frequency will be

chosen as to obtain resonance with given atoms. When the radio frequency is off, one measures given time constants in order to Þnd the amount of given atoms, mainly hydrogen atoms. The making of an image is based on this information. MRI gives better tissue resolution, but poorer spatial resolution, than CT and provides a similar anatomic overview. It too is used for preoperative staging of tumors, but due to better tissue resolution, it is better than CT in detecting and delineating pathologic changes in soft tissues (Fig. 7.2a, b) [11, 17].

A large number of articles concerning MRÐ sialography and SjšgrenÕs syndrome have been published [18, 19]. Dynamic MR sialography, by stimulating with citric acid, has been introduced as an improved method for SjšgrenÕs syndrome [20]. When performing MRI of the parotid glands, a small coil with a small Þeld of view is used. This gives a high tissue and spatial resolution, not only for the parotid glands, but for labial salivary glands as well [21]. It has been called MR microscopy of the salivary glands [22]. This method provides a resolution at least as good as ultrasound, a better overview over the entire glands and salivary ducts (MR sialography, Fig. 7.3), and may with contrast media provide information regarding function.

The recent development of MRI in the diagnosis of SjšgrenÕs syndrome is toward functional examinations, using perfusion techniques and diffusion-weighted techniques [2, 23, 24]. MR spectroscopy has been used for improving

Fig. 7.1 Ultrasound. a Longitudinal high-resolution image showing a normal parotid gland, illustrating how well the structure of the gland is seen. b We see a slightly

dilated duct in a submandibular gland of patient (marked with crosses)