ABSTRACT
The purpose of this study was to develop techniques for registering image sets associated with staged or multifraction radiosurgical treatments of large targets with the Leksell gamma knife to transform shot coordinates between treatment sessions and produce cumulative dose distributions and to investigate the theoretical biological effects of such protracted treatments by means of such concepts as the linear-quadratic model and biologically effective dose. An image registration technique based on normalized mutual information was adapted to produce one fused-image study from an imaging series acquired during distinct treatment sessions. A spreadsheet computer program was developed to determine coordinate transformations between the associated stereotactic coordinate systems based on digitized coordinates of fiducial markers appearing on the fused images. Coordinates of shots used during one treatment session could then be transformed to the stereotactic space of another session, and cumulative dose distributions could be computed. The procedure was applied to the two-stage treatment of a giant arteriovenous malformation (AVM). Overall uncertainty in each transformed shot position is approximately 0.7 mm. An effective single-fraction dose (D(eff)) was defined and computed for the two-stage AVM treatment. The simple summed dose distribution was compared with the D(eff) distribution. Because dose values differ significantly in overlap regions between the individual distributions, the clinical usefulness of the simple cumulative distribution is dubious. It may be useful for a future update of the GammaPlan treatment planning software to generate effective single-session dose distributions for such cases.
Subject(s)
Image Processing, Computer-Assisted , Intracranial Arteriovenous Malformations/surgery , Magnetic Resonance Imaging , Radiosurgery , Humans , Intracranial Arteriovenous Malformations/diagnosis , Reoperation , Reproducibility of Results , SoftwareABSTRACT
We report a young woman with clinical hypopituitarism and systemic sarcoidosis involving the lung, gastrointestinal tract, and peripheral lymph nodes. Laboratory evaluation confirmed that cortisol, thyroid indices, insulin-like growth factor 1, follicle-stimulating hormone, luteinizing hormone, and estradiol levels were low, with a normal prolactin. Magnetic resonance imaging revealed a large cystic pituitary lesion compressing the optic chiasm and exhibiting rim but not hypothalamic enhancement. The differential diagnosis included cystic macroadenoma, Rathke's cleft cyst, craniopharyngioma, and simple cyst. A transsphenoidal procedure provided decompression and diagnosis: pathology was consistent with sarcoidosis. Postoperatively, the patient's neurosarcoid disease markedly worsened, requiring hypothalamic irradiation. To our knowledge, this is the first report of intracranial sarcoidosis presenting solely as a cystic pituitary mass. An awareness of this possibility is important to prevent inappropriate neurosurgical intervention and subsequent potential exacerbation of neurosarcoidosis.
Subject(s)
Brain Diseases/diagnosis , Cysts/diagnosis , Hypopituitarism/diagnosis , Pituitary Diseases/diagnosis , Sarcoidosis/diagnosis , Adult , Diagnosis, Differential , Female , Humans , Hypothalamic Diseases/diagnosis , Hypothalamic Diseases/drug therapy , Hypothalamic Diseases/radiotherapy , Magnetic Resonance Imaging , Pituitary Diseases/pathology , Pituitary Diseases/surgery , Prednisone/therapeutic use , Sarcoidosis/pathology , Sarcoidosis/surgeryABSTRACT
OBJECTIVE: Recent advances in neurosurgical treatment of traumatic and birth-related brachial plexus injuries require differentiation of preganglionic nerve rootlet avulsion from postganglionic lesions. The purpose of this study was to evaluate the efficacy of thin-section high-resolution CT myelography for revealing cervicothoracic nerve rootlet avulsion in patients with brachial plexus injuries before surgery. MATERIALS AND METHODS: We evaluated eight patients with posttraumatic or birth-related brachial plexus injury on cervical plain film myelography and high-resolution CT myelography before surgical exploration and repair. CT myelograms were retrospectively evaluated for nerve rootlet avulsion, traumatic pseudomeningocele, and deformity of the subarachnoid space. Results were correlated with surgical exploration and intraoperative somatosensory evoked potentials. RESULTS: Seventy-two (95%) of 76 imaged cervicothoracic levels were adequately shown on CT myelography. Nerve rootlet avulsion, or preganglionic disruption, was shown at 21 levels. Associated pseudomeningocele, or deformity of the subarachnoid space, was seen at 12 (57%) of the 21 avulsion levels. Surgical exploration and intraoperative somatosensory evoked potentials showed complete preganglionic nerve rootlet avulsion at 22 levels. One of the complete avulsions revealed by surgery was not included on the patient's CT myelogram. Of the 21 imaged levels, 20 were correctly revealed on CT myelography (95% sensitivity, 98% specificity). At surgery, partial nerve rootlet avulsion was found at three other levels. None of the partial avulsions was correctly identified on the CT myelograms. CONCLUSIONS: High-resolution CT myelography with thin contiguous axial section is sensitive for revealing complete nerve rootlet avulsion in patients with brachial plexus birth palsies and brachial plexus injuries after trauma. Preoperative CT myelography in these patients allows a more complete injury evaluation for accurate prognosis and surgical planning.
