Parotid gland: plain and gadolinium-enhanced MR imaging.

Abstract

The purpose of this study was to show the typical appearance of lesions of the parotid gland with plain MR imaging and MR imaging enhanced with gadopentetate dimeglumine. Seventeen patients with inflammatory changes and 43 with benign and malignant tumors were studied. The examinations were carried out with plain T1-weighted sequences with a repetition time (TR) of 500 msec and an echo time (TE) of 25 msec (TR/TE = 500/25), T2-weighted sequences (1,600/90), and gadolinium-enhanced T1-weighted sequences in axial, coronal, and sagittal orientations. For identifying normal anatomic structures such as the facial nerve and the main duct, the administration of gadopentetate dimeglumine was helpful. In inflammatory changes, gadolinium-enhanced images showed no diagnostic advantages. Gadopentetate dimeglumine proved helpful in delineating tumorous lesions and in differentiating benign and malignant lesions. However, an exact differentiation of the different histologic types was not possible. Post-operative fibrosis could be differentiated from recurrent tumors after administration of gadolinium. If a question regarding infiltration or definition of the boundaries of a lesion cannot be answered with non-enhanced MR imaging, gadopentetate dimeglumine administration is advised. However, for routine imaging of the parotid gland, its use is not recommended.

MRI findings of mucoepidermois carcinoma of the parotid gland: correlation with pathological features

“…A similar tendency of increased signal intensity on T 2 weighted images in lowergrade malignancies was reported for adenoid cystic carcinomas of the head and neck region [10]. In contrast with the previous literature that describes ill-defined margins on MR images as a predictor of high-grade malignancies [6][7][8][9], half of our low-grade MECs had illdefined margins on MR images, reflecting peritumoural inflammatory changes. This peritumoural reactive inflammation in low-grade MECs has also been described in the pathology literature [2,11]; however, our study is the first to present this radiologically.…”

“…This peritumoural reactive inflammation in low-grade MECs has also been described in the pathology literature [2,11]; however, our study is the first to present this radiologically. This may be because previous studies of MECs included only a small number of patients with low-grade MECs, ranging from one to four patients per study [6][7][8][9]. In contrast, our study is the first to radiologically evaluate more than ten cases of low-grade MECs.…”

“…Nevertheless, the MRI findings seem to have a tendency to be related to the histological grade. Among high-grade MECs, although non-specific, the tumours showed MRI findings suggesting high-grade malignancies [6][7][8][9]; low to intermediate signal intensities on T 2 weighted images reflect high-cellularity, the ill-defined margin reflects the invasive growth of tumour cells and the frequent nodal metastasis reflects a propensity of lymphatic involvement.…”

Spin lock and magnetization transfer imaging of head and neck tumors.

“…However, MR images were not specific in differentiation of adenocystic carcinomas from other types of tumors (Sigal et al 1992). It has been suggested that highly malignant parotid tumors are characterized by unsharp margins (Vogl et al 1990) and low signal intensity on both T1-and T2-weighted images Biller 1989, Takashima et al 1997). The authors suggested that in high-grade malignancies of parotid gland the cellularity and relative lack of free water and mobile protons produced a low T2-weighted signal.…”

Quantitative Diffusion-Weighted MR Imaging in the Differential Diagnosis of Parotid Gland Tumors: Is it a Useful Technique?

“…This va lu e was sig ni fi cantly hig her than the ot her tu mors. Ade noma to us tu mors may ha ve very high ADC va lu es beca u se of the flu id con ta i ning are as as al so pre vi o usly re por ted by Vogl et al 14 Mo re o ver, this va lu e is clo se to the thres hold va lu e (2.1 x 10 -3 mm 2 /sec) that was de ter mi ned by Sa ka mo to et al 15 for cystic le si ons. In the light of this in for ma ti on, we con si de red that ca na li cu lar ade no mas had high ADC va lu es du e to the ir ade no ma to us struc tu re.…”