Derk D. Purcell

Intracranial time-of-flight MR angiography at 7T with comparison to 3T.

To establish the feasibility of intracranial time‐of‐flight (TOF) MR angiography (MRA) at 7T using phased array coils and to compare its performance to 3T.

Establishment of Normative Cochlear and Vestibular Measurements to Aid in the Diagnosis of Inner Ear Malformations

OBJECTIVE: We sought to establish normative measurements of the inner ear using computed tomography (CT) of the temporal bone to aid in the diagnosis of inner ear malformations. STUDY DESIGN AND SETTING: Prospective measurements of the inner ear structures were made on axial and coronal temporal bone CT scans on 15 patients with normal hearing and 15 patients with sensorineural hearing loss. RESULTS: The vertical height of the cochlea on coronal scan and the size of the central bony island within the lateral semicircular canal on axial scan along with visual inspection identified 7 inner ear abnormalities in 6 patients: 5 cases of lateral semicircular canal dysplasia and 2 cases of cochlear hypoplasia. In contrast, visual inspection alone identified only 4 of the 7 abnormalities. CONCLUSIONS AND SIGNIFICANCE: Routine measurement of the cochlear height and bony island of the lateral semicircular canal, in conjunction with visual inspection of CT images, will increase recognition of common inner ear malformations.

Evaluation of intracranial stenoses and aneurysms with accelerated 4D flow

The aim of this study was to evaluate intracranial arterial stenoses and aneurysms with accelerated time-resolved three-dimensional (3D) phase-contrast MRI or 4D flow. The 4D flow technique was utilized to image four normal volunteers, two patients with intracranial stenoses and two patients with intracranial aneurysms. In order to reduce scan time, parallel imaging was combined with an acquisition strategy that eliminates the corners of k-space. In the two patients with intracranial stenoses, 4D flow velocity measurements showed that one patient had normal velocity profiles in agreement with a previous magnetic resonance angiogram (MRA), while the second showed increased velocities that indicated a less significant narrowing than suspected on a previous MRA, as confirmed by catheter angiography. This result may have prevented an invasive angiogram. In the two patients with 4-mm intracranial aneurysm, one had a stable helical flow pattern with a large jet, while the other had a temporally unstable flow pattern with a more focal jet possibly indicating that the second aneurysm may have a higher likelihood of rupture. Accelerated 4D flow provides time-resolved 3D velocity data in an 8- to 10-min scan. In the stenosis patients, the addition of 4D flow to a traditional MRA adds the velocity data provided from transcranial Doppler ultrasound (TCD) possibly allowing for more accurate grading of stenoses. In the aneurysm patients, visualization of flow patterns may help to provide prognostic information about future risk of rupture.

Complete intracranial arterial and venous blood flow evaluation with 4D flow MR imaging.

SUMMARY: Time-resolved, 3D velocity–encoded MR imaging (4D Flow) allows for the acquisition of dynamic, multidirectional data on blood flow and has recently been used for the evaluation of intracranial arterial flow. Using a 3T system with optimization of both temporal resolution and k-space subsampling with a combination of parallel imaging and cut-corner acquisition, we present the clinical assessment of a patient with an arteriovenous malformation by providing complete intracranial arterial and venous coverage in a reasonable scan time.

Two Temporal Bone Computed Tomography Measurements Increase Recognition of Malformations and Predict Sensorineural Hearing Loss

Objectives/Hypothesis: The objectives of this prospective study were to assess the reproducibility of the measurements of the cochlea and lateral semicircular canal (LSCC) and to determine if abnormal measurements predict sensorineural hearing loss (SNHL).

Identification of previously undetectable abnormalities of the bony labyrinth with computed tomography measurement

Background: In patients with congenital sensorineural hearing loss (SNHL), a computed tomography (CT) scan of the temporal bone identifies inner ear malformations in approximately 25%, whereas the inner ear is grossly normal to visual inspection in the remaining 75% of the patients. In the latter group, the hearing loss is often attributed to radiologically undetectable abnormalities of the membranous labyrinth. However, subtle bony malformations may be missed because visual inspection alone is insensitive for detection. Objective: To test the hypothesis that there are subtle bony abnormalities of the inner ear in patients with SNHL who are radiologically deemed to have normal otic bone, using standardized measurements of the inner ear. Study Design: Retrospective review. Methods: Measurements of the cochlea, vestibule, and semicircular canals (SCCs) were made on axial and coronal temporal bone CT scans on 15 patients with normal hearing and 15 patients with congenital SNHL and grossly normal temporal bone CT scans. Students t‐test was performed to compare the measurements of the two groups. Results: All studies from the SNHL group were deemed normal by visual inspection and standardized measurements (±2 SD from normal). Surprisingly, there were significant differences in the measurements of the cochlea and of the SCCs between patients with and without SHNL (P < .05). Conclusions: As a group, patients with SNHL and a “normal CT scan” have significant differences in the dimensions of the inner ear. This suggests that these patients have disturbed morphogenesis of both membranous and bony labyrinth. This novel observation has important implications for understanding the etiology of SNHL.

Anterior layering of excreted 18F-FDG in the bladder on PET/CT: frequency and cause.

OBJECTIVE The objective of our study was to determine the frequency and cause of anterior layering of excreted 18F-FDG in the bladder on PET/CT. CONCLUSION Anterior layering of excreted FDG in the bladder is commonly seen on PET/CT scans obtained with i.v. iodinated contrast material and is due to displacement of FDG by excreted iodinated contrast material; this phenomenon may unmask FDG-avid bladder disease.

Amyloid PET Screening for Enrichment of Early-Stage Alzheimer Disease Clinical Trials: Experience in a Phase 1b Clinical Trial.

Amyloid positron emission tomography (PET) imaging is being investigated as a screening tool to identify amyloid-positive patients as an enrichment strategy for Alzheimer disease (AD) clinical trial enrollment. In a multicenter, phase 1b trial, patients meeting clinical criteria for prodromal or mild AD underwent florbetapir PET scanning at screening. PET, magnetic resonance imaging, and coregistered PET/magnetic resonance imaging scans were reviewed by 2 independent readers and binary visual readings tabulated. Semiquantitative values of cortical to whole cerebellar standard uptake value ratios were computed (threshold 1.10). Of 278 patients with an evaluable PET scan, 170 (61%) and 185 (67%) were amyloid-positive by visual reading and quantitative analysis, respectively; 39% were excluded from the study due to an amyloid-negative scan based on visual readings. More ApoE &egr;4 carriers than noncarriers were amyloid-positive (80% vs. 43%). Comparison of visual readings with quantitative results identified 21 discordant cases (92% agreement). Interreader and intrareader agreements from visual readings were 98% and 100%, respectively. Amyloid PET imaging is an effective and feasible screening tool for enrollment of amyloid-positive patients with early stages of AD into clinical trials.

High-resolution intracranial MRA at 7T using autocalibrating parallel imaging: initial experience in vascular disease patients

PURPOSE Greater spatial resolution in intracranial three-dimensional time-of-flight (TOF) magnetic resonance angiography (MRA) is possible at higher field strengths, due to the increased contrast-to-noise ratio (CNR) from the higher signal-to-noise ratio and the improved background suppression. However, at very high fields, spatial resolution is limited in practice by the acquisition time required for sequential phase encoding. In this study, we applied parallel imaging to 7T TOF MRA studies of normal volunteers and patients with vascular disease, in order to obtain very high resolution (0.12 mm(3)) images within a reasonable scan time. MATERIALS AND METHODS Custom parallel imaging acquisition and reconstruction methods were developed for 7T MRA, based on generalized autocalibrating partially parallel acquisition (GRAPPA). The techniques were compared and applied to studies of seven normal volunteers and three patients with cerebrovascular disease. RESULTS The technique produced high resolution studies free from discernible reconstruction artifacts in all subjects and provided excellent depiction of vascular pathology in patients. CONCLUSIONS 7T TOF MRA with parallel imaging is a valuable noninvasive angiographic technique that can attain very high spatial resolution.

Benign Anterior Temporal Epidural Hematoma: Indolent Lesion with a Characteristic CT Imaging Appearance after Blunt Head Trauma

PURPOSE To study the incidence, pathogenesis, imaging characteristics, and clinical importance of a unique subtype of epidural hematoma (EDH) associated with blunt head trauma. MATERIALS AND METHODS This study was reviewed and approved by the hospitals Institutional Review Board and was compliant with HIPAA. Informed consent was waived. The investigation was a retrospective study of 200 patients with acute supratentorial EDH, defined as a biconvex, high-attenuating, extraaxial hematoma. A subgroup of 21 patients in whom the EDH was located at the anterior aspect of the middle cranial fossa was defined. Computed tomographic images and inpatient medical records of these 21 patients were evaluated for imaging characteristics of the EDH, presence or absence of associated fracture, presence or absence of midline shift and/or mass effect, additional intracranial injury, and hospital clinical course. RESULTS Twenty-one (10.5%) of 200 traumatic EDHs localized to the anterior middle cranial fossa. All of these 21 anterior temporal EDHs were juxtaposed to the sphenoparietal sinus, and all but one were limited laterally by the sphenotemporal suture and medially by the orbital fissure; none extended above the lesser sphenoid wing. Maximum thickness was less than 1 cm in 13 (62%) of 21 and less than 2 cm in 20 (95%) of 21 patients. Isolated fractures of the greater sphenoid wing and ipsilateral zygomaticomaxillary fractures were present in 12 (57%) of 21 and nine (43%) of 21 patients, respectively. Concomitant intracranial injury was identified in 15 (71%) of 21 patients. Twenty (95%) of 21 lesions were present at the admission study, and all 21 were stable or smaller at follow-up imaging. No patient required neurosurgical intervention of their anterior temporal EDH. CONCLUSION Acute EDHs isolated to the anterior aspect of the middle cranial fossa constitute a subgroup of traumatic EDHs with a benign natural history. It is postulated that they arise from venous bleeding due to disruption of the sphenoparietal sinus.