Ultrafast computed tomography and three-dimensional image processing of CT sialography in patients with parotid masses poorly defined by magnetic resonance imaging

Comparison of Computed Tomography and Magnetic Resonance Imaging in the Diagnosis of Parotid Tumors

OBJECTIVE

The role of computed tomography (CT) and magnetic resonance imaging (MRI) in the diagnosis of parotid tumors was investigated.

METHODS

Forty patients with the clinical suspicion of a parotid mass underwent both CT and MRI of the parotid region. Two radiologists independently assessed the CT and MRI results with respect to tumor localization, tumor margin characteristics, and infiltration of surrounding tissue. Histopathologic specimens were obtained in all cases and correlated with the radiologic findings.

RESULTS

The sensitivity and specificity of CT and MRI were nearly the same for tumor location, tumor margin, and tumor infiltration.

CONCLUSION

The 2 imaging techniques provided the same information with respect to the presurgical planning and contribute to the diagnosis and therapy planning of parotid tumors.

A comparative study of the diagnostic capabilities of 2D plain radiograph and 3D cone beam CT sialography

OBJECTIVE

The aim of this study was to compare the diagnostic capabilities of two-dimensional sialography with a novel three-dimensional technique using cone beam CT (CBCT).

METHODS

47 subjects underwent parotid or submandibular gland sialography over a 2 year period using both plain imaging and CBCT. Both image sets were anonymized and independently reviewed by three certified oral and maxillofacial radiologists blinded to the clinical data. McNemar's χ(2) test was used to determine differences between the two modalities for feature visualization and interpretation.

RESULTS

CBCT outperformed plain imaging with respect to visualization of the gland parenchyma (p < 0.001) and identification of sialoliths (p = 0.02). Plain imaging outperformed CBCT for the identification of strictures (p = 0.04); however, the negative per cent agreement ("specificity") between the two imaging modalities was 100%. Although both imaging modalities performed equally in identifying normal and abnormal sialographic examinations, CBCT demonstrated a high negative per cent agreement for normal glands and a high positive per cent agreement ("sensitivity") for abnormal glands with inflammatory changes.

CONCLUSION

CBCT sialography allowed better visualization of gland parenchyma and identification of sialoliths. The high negative per cent agreement for strictures suggests that, if strictures are identified on CBCT images, then obstruction can be ruled in. Relative to plain images, the high negative per cent agreement for normal glands suggests that, if an abnormal finding is detected on CBCT images, then disease can be ruled in, and the high positive per cent agreement for glands with inflammatory changes suggests that inflammation can be ruled out if these changes are not seen on CBCT images.

Assessment of the role of cone beam computed sialography in diagnosing salivary gland lesions

Purpose

The purpose of this study was to assess cone-beam computed (CBCT) sialography imaging in the detection of different changes associated with lesions of salivary glands.

Materials and Methods

This study consisted of 8 cases with signs and symptoms from salivary gland lesions. Conventional sialography using digital panoramic and lateral oblique radiographs and CBCT sialography were performed for each subject. The radiographs were evaluated by 3 radiologists independently of each other. The results were compared between conventional sialography and CBCT sialography in the evaluation of various lesions associated with the salivary glands.

Results

There was an agreement between the radiologists in interpreting the lesions that affected salivary glands with both techniques. The detection of the presence of stones or filling defects, stenosis, ductal evagination, dilatation, and space occupying lesions was 83% for conventional sialography compared with CBCT sialography. CBCT sialography was superior to conventional sialography in revealing stones, stenosis, and strictures, especially in the second and third order branches.

Conclusion

It would be advisable to perform CBCT sialography in cases of obstructive salivary gland diseases for better demonstration of the ductal system of the gland.

Advances in imaging of obstructed salivary glands can improve diagnostic outcomes

INTRODUCTION

Obstruction of the major salivary glands is a relatively common condition defined as the blockage of the salivary outflow in the glandular ductal system. It can however mimic more aggressive pathology.

METHODS

The most common cause of salivary obstruction is sialolithiasis, followed by ductal strictures. Salivary obstruction is clinically characterized by a food-related painful swelling of the affected gland, known as 'mealtime syndrome'.

RESULTS

When obstruction is clinically suspected, the role of imaging consists of confirming the obstruction, identifying its cause, evaluating the position and extent of the obstruction and evaluating for associated complications. However, if imaging shows up signs of a tumour or other pathology which can mimic an obstructed gland clinically instead, the radiologist can alert the clinician accordingly to change the course and plan of treatment. Several imaging techniques are available for investigating the obstructed salivary glands.

CONCLUSIONS

This review looks at the causes of obstruction and the use, diagnostic performance and practicality of the various imaging modalities. Importantly, an imaging approach algorithm for the evaluation of the obstructed salivary gland is also proposed.

A comparative study of the effective radiation doses from cone beam computed tomography and plain radiography for sialography

OBJECTIVES

As a first step in developing a protocol for multidimensional sialography using cone beam CT (CBCT), the objective of this study was to compare the effective radiation doses from sialography of the parotid and submandibular glands using plain radiography and CBCT.

METHODS

The effective doses were calculated from dose measurements made at 25 selected locations in the head and neck of a radiation analogue dosimeter (RANDO) phantom, using International Commission on Radiological Protection 2007 tissue weighting factors.

RESULTS

The effective dose (E) changed in relationship to changes in CBCT field of view (FOV), peak kilovoltage (kVp) and milliamperage (mA). Specifically, E decreased from a maximum of 932 microSv (30 cm FOV, 120 kVp, 15 mA) to 60 microSv (15 cm FOV, 80 kVp, 10 mA) for a parotid gland study and to 148 microSv (15 cm FOV, 80 kVp, 10 mA) for a submandibular study. The collective series of plain radiographs made during sialography of the parotid and submandibular glands yielded effective doses of 65 microSv and 156 microSv, respectively. The plain parotid gland series included one panoramic, two anterior-posterior skull and four lateral skull radiographs, whereas the submandibular gland series included one panoramic, one standard mandibular occlusal and four lateral skull radiographs.

CONCLUSION

The effective doses from CBCT examinations centred on the parotid and submandibular glands were similar to those calculated for plain radiograph sialography when a 15 cm FOV was chosen in combination with exposure conditions of 80 kVp and 10 mA.

The value of dynamic MRI studies in parotid tumors

RATIONALE AND OBJECTIVES

To evaluate the ability of dynamic contrast-enhanced magnetic resonance imaging (MRI) to differentiate several tumor entities of the parotid gland in a prospective clinical trial.

MATERIALS AND METHODS

A total of 112 patients with parotid tumors were examined with dynamic contrast-enhanced 1.5 T MRI. Precontrast axial T1-weighted imaging was used to select five slices for the dynamic study. Subsequently, a T1-weighted FLASH sequence was used for the dynamic contrast study (0.2 ml Gd/kg x body weight). Contrast agent application and the FLASH sequence were started simultaneously. Ten acquisitions of 10 seconds' scan time each were performed (total acquisition time 1:40 minutes). Signal intensity versus time (SIvT) curves was obtained for all tumors. After correlation of the categorized SIvT curves, these were compared with histopathology. Finally, all MRIs together with the tumor specific SIvT curves were re-read and correlated with histopathologic diagnosis. All reading sessions were done by three experienced radiologists.

RESULTS

Four characteristic intensity-time curves were observed: pleomorphic adenoma showed a gradual increase in signal intensity, followed by a plateau phase on a low intensity level. Cysts showed a vacillating course at a low signal intensity level. Adenolymphomas as well as carcinomas showed a rapid increase in signal intensity followed by a plateau phase. Statistic significance was found for the time-to-peak values for adenolymphomas and pleomorphic adenomas and for the maximum peak signal intensity values for carcinomas. Together with other morphologic MRI criteria (contrast enhancement, border characteristics) and clinical features, a differentiation between adenolymphoma and carcinoma was possible.

CONCLUSIONS

With additional dynamic contrast-enhanced MRI, a more reliable differentiation between common parotid tumors is possible before surgery.

Dynamic multislice computed tomography findings for parotid gland tumors

OBJECTIVE

Our aim was to research the enhancement features of parotid gland masses in detail and characterize if the masses were Warthin tumors, adenomas, or malignant tumors.

METHODS

The prospective study included 25 parotid tumors in 21 patients. Neck computed tomography (CT) was performed using a multislice CT unit. A full-neck CT examination was done at 30 seconds after completion of contrast injection, and then tumor-level images were obtained at 90 seconds and at 5 and 25 minutes. Computed tomography number (lesion density in Hounsfield units) was determined at each phase, and differences within and among tumor groups were statistically analyzed. Diagnoses were confirmed by histopathology.

RESULTS

There were 11 Warthin tumors, 8 pleomorphic adenomas, 5 malignant tumors, and 1 basal cell adenoma. Ten Warthin tumors showed rapid contrast enhancement at 30 seconds and rapid reduction of enhancement from the first to the fourth phase. The basal cell adenoma showed also a peak enhancement at 30 seconds. Seven pleomorphic adenomas showed increased enhancement through the first 3 phases. Four malignant tumors showed peak enhancement at 90 seconds. Statistically significant differences within and among tumor groups were determined.

CONCLUSIONS

The data suggest that peak tumor enhancement at 30 and 90 seconds, respectively, might identify Warthin and malignant tumors. Increased enhancement through all phases might be an indicator for diagnosing pleomorphic adenomas.

Balanced Turbo Field-Echo Sequence for MRI of Parotid Gland Diseases

OBJECTIVE

A balanced turbo field-echo (FE) sequence is a balanced steady-state free precession sequence used for achieving rapid and high imaging. We tested whether this imaging technique is applicable to the diagnosis of parotid gland diseases.

CONCLUSION

The balanced turbo FE sequence is a novel alternative MRI technique for the diagnosis of various parotid gland diseases.

High-resolution magnetic resonance of the extracranial facial nerve and parotid duct: demonstration of the branches of the intraparotid facial nerve and its relation to parotid tumours by MRI with a surface coil

AIM

To investigate the usefulness of high-resolution MR imaging in the evaluation of the extracranial facial nerve, compared with surgical findings.

MATERIALS AND METHODS

Thirteen patients with benign parotid tumours were studied on a 1.5-T MR system with a 3 in circular surface coil. High-resolution T1-weighted spin-echo, T2-weighted fast spin-echo, and three-dimensional gradient-recalled acquisition in the steady state (GRASS) images were obtained in the axial planes. Oblique reformatted images were generated. Tumours, parotid ducts and facial nerves were identified on these images. The relationship of the tumours to the facial nerves was confirmed at surgery.

RESULTS

Facial nerves appeared as linear structures of low intensity on all pulse sequences. The main trunks and cervicofacial and temporofacial divisions of the facial nerves were identified in 100%, 84.1% and 53.8% of GRASS images, respectively. Parotid ducts appeared as structures of low intensity on T1-weighted (66.6%) and GRASS images (81.8%), and as structures of very high intensity on T2-weighted images (91.7%). The relationships of the tumours to the facial nerves were correctly diagnosed in 11 (91.7%) of 12 cases.

CONCLUSION

High-resolution MR imaging depicts the extracranial facial nerve and the parotid duct, and is useful for preoperative evaluation of parotid gland tumours.

Electrical impedance scanning used in addition to ultrasound for the verification of submandibular and parotid lesions: initial results

OBJECTIVES

Different dielectric properties of cancerous tissues are correlated with increased conductance potentially measurable using Electrical Impedance Scanning (EIS). Sonographically based differentiation of lesions in the salivary glands remains difficult. The clinical value of EIS used additionally to Ultrasound was investigated.

METHODS

Sonographically suspicious lesions of parotid (n = 25) and submandibular (n = 16) glands were examined using TransScan TS2000 (TransScan Medical, Israel; distributed by Siemens, Sweden). Bright focal spots representing areas of high conductance were read as positive; absence of a focal spot (ie, homogeneous gray) was read as negative. All lesions were histopathologically proved.

RESULTS

14/15 malignant (93.3%) and 13/26 benign lesions (50.0%) were correctly detected using EIS, NPV 93%, PPV 52%. All cases of squamous cell carcinoma were correctly identified. Lymph node relapse of T-cell lymphoma, lymph node relapse of malignant melanoma, malignant hemangioendothelioma and 2/3 adenocystic carcinoma (primary metastases) were correctly detected.

CONCLUSIONS

Our initial results suggest EIS to be of interest when used adjunctively to ultrasound for the identification of malignant lesions of the salivary glands. However, low specificity induced in part by current technical restrictions (bone interference, skin alterations, contact artifacts, prominence of the lesions) limit this clinical application.

Preoperative computed tomography scans for parotid tumor evaluation

OBJECTIVE

We sought to determine whether an advantage is obtained in the routine use of computed tomography (CT) scans in preoperative assessments of parotid tumors.

METHODS

A prospective study of 32 consecutive cases of patients who underwent evaluation for parotidectomies was performed. Twenty-nine received preoperative CT scans. The scans were systematically reviewed to see if they correlated with the clinical findings. Specifically, we compared clinical and CT assessments of tumor size, location, density, and malignancy. Further comparisons were performed based on postoperative tissue pathology.

RESULTS

In our series of patients, routine preoperative CT scans resulted in the discovery of details not revealed on clinical examination: some masses were found to be extra-parotid rather than primary parotid tumors, some tumors deemed to be deep were superficial, tumor density was more clearly identified, and certain pathology correlates were clarified. Most importantly, there were instances of detection of additional tumors in the same lobe, and in one instance in the opposite lobe, that were not otherwise noticed.

CONCLUSIONS

To reduce errors of omission in the treatment of suspected parotid tumors, it would seem appropriate to consider the inclusion of CT scans for the routine preoperative evaluation of all parotid masses.

Sialolithiasis: MR sialography of the submandibular duct--an alternative to conventional sialography and US?

PURPOSE

To determine the value of magnetic resonance (MR) sialography for the diagnosis of sialolithiasis by comparing results prospectively with those of ultrasonography (US) and digital sialography.

MATERIALS AND METHODS

MR sialography was prospectively performed with T2-weighted three-dimensional (3D) constructive interference in steady-state (CISS) and rapid acquisition with relaxation-enhancement (RARE) sequences in 24 patients suspected of having sialolithiasis. Evoked salivation was used as contrast material. T1-weighted spin-echo and T2-weighted turbo spin-echo MR imaging also were performed. The results were then compared with those of US and digital sialography, with the latter as standard of reference.

RESULTS

The 3D CISS images were significantly (P: <.05) superior to RARE images for demonstrating the submandibular ductal system, followed by T2-weighted turbo spin-echo images (P: <.01) and T1-weighted spin-echo images (P: <.001). The sensitivity and specificity were 100% and 80%, respectively, for CISS MR sialography and 80% and 100%, respectively, for RARE MR imaging. The sensitivity and specificity of US were both 80%.

CONCLUSION

MR sialography with evoked salivation is noninvasive and allows delineation of the submandibular ductal system and detection of sialoliths with accuracy that is similar to that of digital sialography and superior to that of US.

The place of magnetic resonance and ultrasonographic examinations of the parotid gland in the diagnosis and follow-up of primary Sjögren's syndrome

OBJECTIVE

The aim was to determine the place of magnetic resonance imaging (MRI) and ultrasonographic (US) examination in the diagnosis and follow-up of Sjögren's syndrome (SS).

METHODS

Parotid MRI and US examinations were carried out on 44 primary SS patients and 52 controls of similar age.

RESULTS

The most important structural changes in SS were different degrees of parenchymal inhomogeneity, which could be detected by both methods, and were found more frequently in the SS patients than in the controls (MRI: 95.4 vs 17. 3%; US: 88.6 vs 7.7%; P<0.001). There was good agreement between the MRI and US findings both in the SS cases (93.2%) and in the controls (86.5%). In one SS patient who developed parotid lymphoma, the US examination showed a hypoechoic 'cobblestones'-like inhomogeneous internal pattern which was coupled with an almost homogeneous MRI pattern.

CONCLUSIONS

MRI appears unnecessary as a routine method in the diagnosis of SS; US examination is suitable both for the diagnosis and follow-up of SS. The above combination of the seemingly contradictory US and MRI findings is highly characteristic of lymphoma which has developed in the course of the disease.