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Our aim was to use MRI for the postsurgical assessment of a new form of integrated orbital implant composed of a porous calcium phosphate hydroxyapatite substrate. We studied ten patients 24-74 years of age who underwent enucleation and implantation of a hydroxyapatite ball; 5-13 months after surgery, each patient was examined by spinecho MRI, with fat suppression and gadolinium enhancement. Fibrovascular ingrowth was demonstrated in all ten patients as areas of enhancement at the periphery of the hydroxyapatite sphere that extended to the center to a variable degree. The radiologist should aware of the MRI appearances of the coralline hydroxyapatite orbital implant since it is now widely used following enucleation. MRI is a useful means to determine successful incorporation of the substrate into the orbital tissues. The normal pattern of contrast enhancement should not be mistaken for recurrent tumor or infection.

Magnetic resonance imaging of the temporomandibular joint is a topic of recent interest and has gained widespread use for the assessment of internal derangement and other temporomandibular joint-related symptoms. In this article the authors present six proven cases of pathologic abnormalities of the temporomandibular joint region that may clinically mimic internal derangement. These cases demonstrate the importance of the monitoring of studies by a radiologist and also the utility of computed tomography as an adjunctive modality. Magnetic resonance imaging and computed tomography are often complimentary in diagnosing etiologies that may mimic internal derangement. Because abnormalities other than internal derangement are often encountered during the use of magnetic resonance imaging, it is essential for the radiologist to assume an active role in monitoring such cases.

A multitude of histologic neoplasms occur within the boundaries of the parapharyngeal space. Contrast enhanced computed tomography and recently MRI have greatly enhanced the preoperative diagnosis of parapharyngeal space tumors. MRI is currently the modality of choice in evaluating masses originating in the parapharyngeal space or masses from adjacent spaces which grow into the parapharyngeal space. Gadolinium DTPA enhanced MRI of head and neck tumors is helpful for demonstrating neoplastic involvement of paranasal sinus, perineural tumor extension, or intracranial extension of neoplasms. Parapharyngeal space tumors are equally demonstrated by unenhanced MRI. The majority of tumors involving the parapharyngeal space are from the deep portion of the parotid gland or from minor salivary glands, and the majority of these tumors are benign mixed tumors. Based on the CT appearance and enhancement characteristics, it is difficult to accurately distinguish a minor salivary gland tumor from a neurogenic tumor. MR tissue signal characteristics alone cannot be reliably utilized in making this distinction. Internal carotid artery displacement remains the most reliable distinguishing feature. Minor salivary gland tumors will displace the internal carotid artery posterior and lateral, whereas neurogenic tumors will displace the internal carotid artery anterior and medial.