Ashley H. Aiken

Quantitative apparent diffusion coefficients and T2 relaxation times in characterizing contrast enhancing brain tumors and regions of peritumoral edema

To investigate the potential value and relationship of in vivo quantification of apparent diffusion coefficients (ADCs) and T2 relaxation times for characterizing brain tumor cellularity and tumor‐related edema.

Image-Guided Robotic Stereotactic Body Radiotherapy for Benign Spinal Tumors: The University of California San Francisco Preliminary Experience

We evaluate our preliminary experience using the Cyberknife® Radiosurgery System in treating benign spinal tumors. A retrospective review of 16 consecutively treated patients, comprising 19 benign spinal tumors, was performed. Histologic types included neurofibroma [11], chordoma [4], hemangioma [2], and meningioma [2]. Three patients had Neurofibromatosis Type 1 (NF1). Only one tumor, recurrent chordoma, had been previously irradiated, and as such not considered in the local failure analysis. Local failure, for the remaining 18 tumors, was based clinically on symptom progression and/or tumor enlargement based on imaging. Indications for spine stereotactic body radiotherapy (SBRT) consisted of either adjuvant to subtotal resection (5/19), primary treatment alone (12/19), boost following external beam radiotherapy (1/19), and salvage following previous radiation (1/19). Median tumor follow-up is 25 months (2–37), and one patient (with NF1) died at 12 months from a stroke. The median total dose, number of fractions, and prescription isodose was 21 Gy (10–30 Gy), 3 fx (1–5 fx), 80% (42–87%). The median tumor volume was 7.6 cc (0.2–274.1 cc). The median V100 (volume V receiving 100% of the prescribed dose) and maximum tumor dose was 95% (77–100%) and 26.7 Gy (15.4–59.7 Gy), respectively. Three tumors progressed at 2, 4, and 36 months post-SR (n=18). Two tumors were neurofibromas (both in NF1 patients), and the third was an intramedullary hemangioblastoma. Based on imaging, two tumors had MRI documented progression, three had regressed, and 13 were unchanged (n=18). With short follow-up, local control following Cyberknife spine SBRT for benign spinal tumors appear acceptable.

Imaging Hodgkin and Non-Hodgkin Lymphoma in the Head and Neck

Hodgkin (HL) and non-Hodgkin lymphoma (NHL) involving the head and neck have many overlapping imaging features. Definitive diagnosis depends on histology, but imaging trends may help distinguish lymphoma from other common pathologic entities in the head and neck. CT is useful for staging and assessing bony involvement, whereas MR imaging is performed for soft tissue detail in extranodal disease, especially when there is transpatial disease or intracranial or intraspinal extension. Positron emission tomography has become an important part of staging and surveillance imaging and is particularly useful to distinguish posttreatment fibrosis and residual tumor.

Calcifying Pseudoneoplasms of the Neuraxis: CT, MR Imaging, and Histologic Features

BACKGROUND AND PURPOSE: Non-neoplastic, calcified, fibro-osseous lesions known as “calcifying pseudoneoplasms of the neuraxis” (CAPNON) are rare and can occur anywhere within the neuraxis. The radiologic and histopathologic characteristics of this unusual entity are not well understood. We present the largest series reviewing the MR imaging features of CAPNON. MATERIALS AND METHODS: The MR and CT imaging features in 4 patients with a pathologic diagnosis of “calcifying pseudoneoplasms of the neuraxis” were retrospectively reviewed. A neuropathologist also analyzed the histopathologic features for typical and atypical patterns. RESULTS: Imaging features were strikingly similar for all 4 patients. All lesions appeared T1 and T2 hypointense without vasogenic edema. All tumors had dense calcification, and 3 tumors showed minimal linear internal or rim enhancement on MR imaging. CONCLUSIONS: CAPNON may mimic more common vascular malformations or neoplasms and are often not considered in the differential diagnosis of calcified lesions. CAPNON should be included in the differential diagnosis of a calcified mass with marked T1 and T2 hypointensity and limited to no enhancement. Careful CT and MR imaging evaluation can suggest this entity, and this preoperative recognition may help subsequent management decisions.

Incidence of cerebellar tonsillar ectopia in idiopathic intracranial hypertension: a mimic of the Chiari I malformation.

Some patients with intracranial hypertension may have nonrelated Chiari I malformations that are not responsive to surgical decompression. These authors set out to identify a subset of patients with IH who had tonsillar ectopia. They found that 21% of their patients with IH had cerebellar tonsillar ectopia that was often peglike and simulated true Chiari I malformations. An ancillary helpful finding was that in patients with IH and tonsillar ectopia the fourth ventricular obex was lower than in controls, implying that all posterior fossa structures are inferiorly displaced in this group of patients. BACKGROUND AND PURPOSE: IIH is a syndrome of elevated intracranial pressure without hydrocephalus, mass, or identifiable cause. Diagnosis is made by clinical presentation, intracranial pressure measurement, and supportive imaging findings. A subset of patients with IIH may have tonsillar ectopia, meeting the criteria for Chiari malformation type I but not responding to surgical decompression for Chiari I. The purpose of this study was to determine the incidence and morphology of cerebellar tonsillar ectopia in patients with IIH. MATERIALS AND METHODS: Forty-three patients with clinically confirmed IIH and 44 age-matched controls were included. Two neuroradiologists with CAQs reviewed sagittal T1-weighted MRI in a blinded fashion and measured cerebellar tonsil and obex positions relative to the foramen magnum and prepontine cistern width at the level of the midpons. RESULTS: Nine of 43 patients with IIH and 1/44 controls had cerebellar tonsillar ectopia of ≥5 mm. Five of 9 of patients with IIH with ectopia of ≥5 mm also had a “peglike” tonsil configuration. Patients with IIH had a significantly lower tonsillar position (2.1 ± 2.8 mm) than age-matched controls (0.7 ±1.9 mm, P < .05). The obex position was significantly lower in patients with IIH versus controls (−7.9 mm [above the FM] versus −9.4 mm [above the FM], P < .05). The prepontine width was not significantly different between the groups. CONCLUSIONS: Cerebellar tonsil position in patients with IIH was significantly lower than that in age-matched controls, often times peglike, mimicking Chiari I. A significantly lower obex position suggests an inferiorly displaced brain stem and cerebellum. When tonsillar ectopia of >5 mm is identified, imaging and clinical consideration of IIH are warranted to avoid misdiagnosis as Chiari I.

Interobserver Variability in the Assessment of CT Imaging Features of Traumatic Brain Injury

The goal of our study was to determine the interobserver variability between observers with different backgrounds and experience when interpreting computed tomography (CT) imaging features of traumatic brain injury (TBI). We retrospectively identified a consecutive series of 50 adult patients admitted at our institution with a suspicion of TBI, and displaying a Glasgow Coma Scale score < or =12. Noncontrast CT (NCT) studies were anonymized and sent to five reviewers with different backgrounds and levels of experience, who independently reviewed each NCT scan. Each reviewer assessed multiple CT imaging features of TBI and assigned every NCT scan a Marshall and a Rotterdam grading score. The interobserver agreement and coefficient of variation were calculated for individual CT imaging features of TBI as well as for the two scores. Our results indicated that the imaging review by both neuroradiologists and neurosurgeons were consistent with each other. The kappa coefficient of agreement for all CT characteristics showed no significant difference in interpretation between the neurosurgeons and neuroradiologists. The average Bland and Altman coefficients of variation for the Marshall and Rotterdam classification systems were 12.7% and 21.9%, respectively, which indicates acceptable agreement among all five reviewers. In conclusion, there is good interobserver reproducibility between neuroradiologists and neurosurgeons in the interpretation of CT imaging features of TBI and calculation of Marshall and Rotterdam scores.

MR Imaging of Optic Neuropathy with Extended Echo-Train Acquisition Fluid-Attenuated Inversion Recovery

BACKGROUND AND PURPOSE: XETA, also known as Cube, is a relatively new 3D FSE sequence that can be used to perform whole-brain FLAIR T2-weighted imaging at isotropic high spatial resolution. This high-resolution volumetric imaging, coupled with both fat and fluid suppression, permits ideal evaluation of optic nerve anatomy and signal intensity; therefore, we hypothesized that XETA FLAIR would be useful for the detection of T2 signal-intensity abnormality in the optic nerve. Our purpose was to evaluate the sensitivity of XETA FLAIR for this abnormality and to compare it with the coronal FSE T2 FS. MATERIALS AND METHODS: After obtaining approval of the institutional review board, 2 CAQ neuroradiologists retrospectively reviewed all patients with a clinical diagnosis of optic neuropathy who had undergone XETA FLAIR and standard orbital imaging from September 2006 to February 2009. Fifteen patients met these criteria and underwent the following sequences: XETA FLAIR, coronal FSE T2 FS, and T1-weighted postgadolinium sequences with FS. RESULTS: Signal-intensity abnormality was identified on the correct side of the patients vision loss in all 15 patients on XETA but in only 11/15 patients on the coronal FSE T2-weighted imaging. Reviewer 1 perceived the signal-intensity abnormality better on the XETA versus T2-weighted imaging in 10/15 patients, and reviewer 2, in 9/15 patients. Neither reviewer visualized any of the imaging better by using the conventional coronal FSE T2 FS sequence. CONCLUSIONS: XETA FLAIR was more sensitive than coronal FSE T2 FS for identifying abnormal signal intensity within the optic nerves in patients with optic neuropathy.

MR Imaging of the Temporomandibular Joint

MR imaging allows detailed evaluation of temporomandibular (TMJ) anatomy because of its inherent tissue contrast and high resolution. Joint biomechanics can be assessed through imaging patients in the closed and open jaw positions. Despite the accuracy of MR imaging in detecting disc position, results must be interpreted together with clinical findings, because an anteriorly displaced disc can be seen in up to one-third of asymptomatic patients, and a normal disc position can be seen in up to one-quarter of symptomatic patients. Interpretation of MR imaging requires knowledge of the normal anatomy and an understanding of normal and abnormal biomechanics.

Longitudinal Magnetic Resonance Imaging Features of Glioblastoma Multiforme Treated With Radiotherapy With or Without Brachytherapy

PURPOSE To compare temporal patterns of recurrent contrast enhancement in patients with glioblastoma multiforme (GBM) treated with brachytherapy plus external beam radiotherapy (EBRT) vs. EBRT alone. METHODS AND MATERIALS We evaluated serial MRI scans for 15 patients who received brachytherapy followed by EBRT (6000 cGy) and 20 patients who received standard EBRT alone (5940-6000 cGy). Brachytherapy consisted of permanent, low-activity (125)I seeds placed around the resection cavity at the time of initial gross total resection. Contrast enhancement (linear, nodular, feathery, or solid), serial progression, and location of contrast enhancement were described. RESULTS In the EBRT group, 14 patients demonstrated focal nodular contrast enhancement along the resection cavity within 4 months. The 6 remaining EBRT patients developed either transient linear enhancement or no abnormal enhancement. In the brachytherapy plus EBRT group, 7 patients initially developed linear rim enhancement within 4 months that progressed to feathery contrast enhancement over the course of 1 to 2 years. Histopathology confirmed radiation necrosis in all 7 patients. The remaining 8 brachytherapy patients eventually developed focal nodular contrast enhancement along the resection cavity and tumor recurrence. CONCLUSIONS Our data suggest that longitudinal MRI features differ between GBM patients treated with EBRT vs. brachytherapy plus EBRT. In both groups, nodular enhancement adjacent to or remote from the resection cavity strongly suggested tumor recurrence. Feathery enhancement, which progressed from linear rim enhancement immediately adjacent to the cavity, seen only in brachytherapy patients, strongly indicated radiation necrosis.

Laryngeal tumor volume as a predictor for thyroid cartilage penetration

Review of laryngectomy specimens demonstrated that preoperative CT scanning is suboptimal in predicting both thyroid cartilage penetration and extralaryngeal spread. We investigated the association between the CT‐based gross tumor volume (GTV) with pathologic evidence of thyroid cartilage penetration among patients undergoing laryngectomy for squamous cell carcinoma (SCC) of the larynx.