Imaging of orbital lymphoproliferative disorders

Lymphomas and leukemias account for a large portion of orbital tumors. Orbital lymphoma accounts for 55% of malignant orbital tumors in adults. Idiopathic orbital inflammatory pseudotumors are pathologic entities that often challenge ophthalmologists and radiologists. This article describes the MR and CT features of orbital lymphoma, leukemia, and some other lymphoproliferative disorders.     

The role of magnetic resonance imaging in the diagnosis and management of ameloblastoma

Magnetic resonance (MR) images of ameloblastoma are compared with computed tomographic (CT) images with the use of three parameters: artifact degradation, edge definition, and conspicuity. As a basis for comparison, MR imaging characterization of normal tissues is reviewed. The three cases studied demonstrate the importance of weighing heavily on MR for evaluation of tumor-normal tissue interface. MR generally proved to be superior to CT in the evaluation of recurrent disease because of its ability to differentiate tissues on the basis of their proton composition. CT images reflect the electron densities of tissues. Hence, interpreting inflammatory and postsurgical changes and differentiating them from neoplasm may be difficult. At the present time, familiarity with CT dictates that the MR evaluation complement and not substitute the CT evaluation.     

Photodynamic therapy in the treatment of squamous cell carcinoma of the head and neck

Photodynamic therapy is an experimental modality for tumor treatment based on the combined action of the tumor-localizing agent, ie, hematoporphyrin derivative, and red light. From 1985 through 1989, 26 patients were treated using hematoporphyrin-derived drugs and 630-nm light delivered by a tunable dye laser. All patients had biopsy-proved squamous cell carcinoma of the head and neck, and they had either failed the traditional treatment modalities or refused conventional therapies. Histological complete responses were achieved in 20 (77%) of 26 patients and partial responses in 5 (19%) of 26 patients for periods up to 48 months. Only minimal toxic reaction was noted in the group. As a guide to treatment planning for a patient group with large tumors, we used an optical dosimetry model based on tissue optics. The rate of complete responses to this treatment was 8 (73%) of 11. Our data indicate that photodynamic therapy is capable of inducing significant clinical and histological responses in the majority of those treated, and in some patients a prolonged response is produced. In certain select head and neck malignancies, photodynamic therapy has an important role as a treatment modality.     

Diagnostic potential of CT in neurotological disorders

The reliability of a neurotological evaluation in differentiating labyrinthine (end organ) lesions from retrolabyrinthine lesions has been well established. The purpose of this communication is to determine the diagnostic potential of computed tomography (CT) in patients suspected of having retrolabyrinthine lesions on the basis of their neurotological evaluations. Our study indicates that the validity of central vestibular and audiometric signs can be best substantiated with CT. The anatomy of neurovascular bundles within the internal auditory canal and cerebellopontine cistern can be readily visualized and identified by CT pneumocisternomeatography. By obtaining appropriate thin CT sections not only can very small lesions be identified but their anatomic locations can also be accurately established. CT pneumocisternomeatography is the method of choice to diagnose an intracanalicular acoustic neuroma. An unusually large vascular loop of the internal auditory canal may be responsible for sensorineural hearing loss and tinnitus in some patients.     

Computed tomography in the diagnosis of primary tumors of the petrous bone

This paper constitutes an evaluation of 23 patients with signs and symptoms of 4 types of tumors: 6 congenital epidermoids, 3 cases of meningiomas presenting within the temporal bone, 2 cases of jugular fossa schwannomns, 3 cases of glomus tympanicum, and 9 selected cases of glomus jugulare tumors. Since these tumors occur insidiously and are located in an inaccessible region of the skull, they are usually not diagnosed until they reach considerable size and cause multiple cranial nerve deficits or intracranial complications. Assessment of these tumors and subsequent surgical management depend primarily on the preoperative radiographic findings. CT and dynamic CT study have proven to be extremely valuable and accurate in the diagnosis of these lesions. Epidermoids have a characteristic CT appearance. Dynamic CT is often helpful in differentiating glomus tumors from meningiomas and schwannomas. Involvement of the middle ear, labyrinth, intracranial, and extracranial components of these tumors can be best evaluated by CT. This paper places special emphasis on congenital cholcsteatoma (epidermoid) and draws relevant conclusions about the diagnostic work-up.     

Dynamic computed tomography of the head and neck: differential diagnostic value

A retrospective review of the dynamic CT studies performed in our institution on head and neck lesions, excluding the brain, was carried out. Five basic types of density vs. time curves were obtained. Dynamic CT scanning is valuable in the differential diagnosis, management, and followup of such cases; its usefulness as an imaging modality in diagnosis and followup of hemangiomas is stressed.     

Dynamic computed tomography. Its use in the assessment of vascular malformations and angiofibroma

Reliable diagnostic methods for head and neck vascular lesions are needed. The technique of dynamic computed tomography (CT) is used to delineate two aberrant subclavian arteries, one carotid artery aneurysm, and one angiofibroma. Five or six 4.8-s CT scans were obtained sequentially, separated by a 1.2-s interscan interval. Computer-generated iodinated contrast concentration (CT number) v time curves showed rapid influx of contrast, high peak density, and rapid uninterrupted contrast runoff. Simultaneous bone and soft-tissue visualization at the time of peak contrast enhancement provides excellent delineation of the malformations and angiofibroma. The technique is noninvasive, and it eliminates the potential complications of arteriography and biopsy. We conclude that dynamic CT is an excellent method for diagnosis of head and neck vascular lesions.     

Medical imaging in pediatric ophthalmology

The use of CT and MR imaging has improved the understanding of many congenital and acquired conditions in pediatric ophthalmology, resulting in more appropriate therapeutic intervention and giving insight into the pathogenesis of these conditions.