Comparison of a Photon-Counting-Detector CT with an Energy-Integrating-Detector CT for Temporal Bone Imaging: A Cadaveric Study.

BACKGROUND AND PURPOSE: Evaluating abnormalities of the temporal bone requires high-spatial-resolution CT imaging. Our aim was to assess the performance of photon-counting-detector ultra-high-resolution acquisitions for temporal bone imaging and compare the results with those of energy-integrating-detector ultra-high-resolution acquisitions. MATERIALS AND METHODS: Phantom studies were conducted to quantify spatial resolution of the ultra-high-resolution mode on a prototype photon-counting-detector CT scanner and an energy-integrating-detector CT scanner that uses a comb filter. Ten cadaveric temporal bones were scanned on both systems with the radiation dose matched to that of the clinical examinations. Images were reconstructed using a sharp kernel, 0.6-mm (minimum) thickness for energy-integrating-detector CT, and 0.6- and 0.25-mm (minimum) thicknesses for photon-counting-detector CT. Image noise was measured and compared using adjusted 1-way ANOVA. Images were reviewed blindly by 3 neuroradiologists to assess the incudomallear joint, stapes footplate, modiolus, and overall image quality. The ranking results for each specimen and protocol were compared using the Friedman test. The Krippendorff α was used for interreader agreement. RESULTS: Photon-counting-detector CT showed an increase of in-plane resolution compared with energy-integrating-detector CT. At the same thickness (0.6 mm), images from photon-counting-detector CT had significantly lower (P < .001) image noise compared with energy-integrating-detector CT. Readers preferred the photon-counting-detector CT images to the energy-integrating-detector images for all 3 temporal bone structures. A moderate interreader agreement was observed with the Krippendorff α = 0.50. For overall image quality, photon-counting-detector CT image sets were ranked significantly higher than images from energy-integrating-detector CT (P < .001). CONCLUSIONS: This study demonstrated substantially better delineation of fine anatomy for the temporal bones scanned with the ultra-high-resolution mode of photon-counting-detector CT compared with the ultra-high-resolution mode of a commercial energy-integrating-detector CT scanner.

Temporal Bone CT: Improved Image Quality and Potential for Decreased Radiation Dose Using an Ultra-High-Resolution Scan Mode with an Iterative Reconstruction Algorithm.

BACKGROUND AND PURPOSE: Radiation dose in temporal bone CT imaging can be high due to the requirement of high spatial resolution. In this study, we assessed whether CT imaging of the temporal bone by using an ultra-high-resolution scan mode combined with iterative reconstruction provides higher spatial resolution and lower image noise than a z-axis ultra-high-resolution mode. MATERIALS AND METHODS: Patients with baseline temporal bone CT scans acquired by using a z-axis ultra-high-resolution protocol and a follow-up scan by using the ultra-high-resolution-iterative reconstruction technique were identified. Images of left and right temporal bones were reconstructed in the axial, coronal, and Poschl planes. Three neuroradiologists assessed the spatial resolution of the following structures: round and oval windows, incudomallear and incudostapedial joints, basal turn spiral lamina, and scutum. The paired z-axis ultra-high-resolution and ultra-high-resolution-iterative reconstruction images were displayed side by side in random order, with readers blinded to the imaging protocol. Image noise was compared in ROIs over the posterior fossa. RESULTS: We identified 8 patients, yielding 16 sets of temporal bone images (left and right). Three sets were excluded because the patient underwent surgery between the 2 examinations. Spatial resolution was comparable (Poschl) or slightly better (axial and coronal planes) with ultra-high-resolution-iterative reconstruction than with z-axis ultra-high-resolution. A paired t test indicated that noise was significantly lower with ultra-high-resolution-iterative reconstruction than with z-axis ultra-high-resolution (P < .001), with a mean noise reduction of 37% (range, 18%-49%). CONCLUSIONS: The ultra-high-resolution-iterative reconstruction scan mode has similar or slightly better resolution relative to the z-axis ultra-high-resolution mode for CT of the temporal bone but significantly (P < .01) lower image noise, which may enable the dose to be reduced by approximately 50%.

Wide, short bore magnetic resonance at 1.5 t: reducing the failure rate in claustrophobic patients.

PURPOSE: Claustrophobic reactions in patients undergoing magnetic resonance imaging (MRI) have a significant impact on the workflow, patient acceptance and ultimately the costs involved in obtaining a diagnostic scan. The purpose of this study was to determine if the use of a wide, short bore MRI scanner could reduce the need for general anesthesia assistance in these cases. METHODS: Between September 2006 and March 2008, all patients for whom MRI examinations of the head and/or spine were canceled or prematurely terminated due to claustrophobia on a standard 60 cm bore, 1.5 T scanner were scheduled to be re-scanned on a 70 cm wide bore, 1.25 m long 1.5 T scanner. This re-scanning attempt was made 2 or more days prior to a scheduled anesthesia-assisted MRI appointment. If the patient successfully completed the wide bore MRI examination then the anesthesia-assisted MRI appointment was canceled. RESULTS: A total of 56 patients were included in this study. The examinations included individual body regions as well as combination examinations (head and cervical spine, entire spine etc.). A total of 72 body regions were examined in 56 patients. Of these regions, 65 (90%) were completed successfully, 50 patients (89%) successfully completed a diagnostic examination on the 70 cm scanner and 6 patients (11%), all of whom were scheduled for examinations which included the head, were unable to complete the examination on the wide bore scanner. CONCLUSIONS: A 1.5 T wide short bore scanner increases the examination success rate in patients with claustrophobia and substantially reduces the need for anesthesia-assisted MRI examinations even when claustrophobia is severe.

Correlation of outcome to neurosurgical lesions: confirmation of a new method using data after microelectrode-guided pallidotomy.

The purpose of this study was the development of a new method to correlate functional surgery with outcome measures. Lesions following microelectrode guided globus pallidus internus (GPi) pallidotomy for Parkinson's disease are presented to demonstrate this new method in regard to clinical outcome. A clinical series of 26 patients with extensive neurological and neuropsychological data were studied. Three-month postoperative MRI lesion borders at the AC-PC plane were scaled to a standard size, and the lesions were stored in a virtual array with a cell size of one voxel. The average outcome measure for each voxel is presented graphically. Unified Parkinson's disease rating scale (UPDRS) motor scores improved more with posterolateral and centrally located GPi lesions than with anteromedial lesions. A correlation of lesion location to outcome was also visible for subscales of the UPDRS. The distributions were similar for the left and right sides, as well as for ipsi- and contralateral measurements. In general, verbal fluency decreased after lesioning the dominant hemisphere, and posterolateral lesions caused less impairment. This method enables associative analyses between brain area and outcome down to the size of a few voxels. This may be particularly helpful for planning and validating neurosurgical targets for various disorders.

State of the art: 3T imaging of the membranous labyrinth.

This article reviews the anatomy of the membranous labyrinth and demonstrates the ability of high-resolution MR imaging at 3T to visualize the neurosensory epithelium by using the latest fast spin-echo techniques.

Quantitative and qualitative outcome measures after thalamic deep brain stimulation to treat disabling tremors.

OBJECTIVE: We studied outcome measures after unilateral and bilateral thalamic stimulation to treat disabling tremor resulting from essential tremor and Parkinson's disease. The surgical technique, qualitative and quantitative tremor assessments, stimulation parameters, locations of active electrodes, complications, and side effects are described and analyzed. METHODS: Forty-one patients with essential tremor or Parkinson's disease underwent implantation of 56 thalamic stimulators. Preoperative qualitative and quantitative tremor measurements were compared with those obtained after unilateral and bilateral surgery, with activated and deactivated stimulators. Stimulation parameters and stimulation-related side effects were recorded, and outcome measures were statistically analyzed. RESULTS: Qualitative measurements demonstrated significant improvement of contralateral upper-limb (P < 0.001), lower-limb (P < 0.01), and midline (P < 0.001) tremors after unilateral surgery. Ipsilateral arm tremor also improved (P < 0.01). No differences were observed with the Purdue pegboard task. Quantitative accelerometer measurements were correlated with qualitative assessments and confirmed improvements in contralateral resting (P < 0.001) and postural (P < 0.01) tremors and ipsilateral postural tremor (P < 0.05). Activities of daily living improved after unilateral surgery (P < 0.001) and additionally after bilateral surgery (P < 0.05). Adjustments of the pulse generator were required more frequently for tremor control than for amelioration of side effects. Bilateral thalamic stimulation caused more dysarthria and dysequilibrium than did unilateral stimulation. Stimulation-related side effects were reversible for all patients. Stimulation parameters did not change significantly with time. A significantly lower voltage and greater pulse width were used for patients with bilateral implants. CONCLUSION: Unilateral thalamic stimulation and bilateral thalamic stimulation are safe and effective procedures that produce qualitative and quantitative improvements in resting, postural, and kinetic tremor. Thalamic stimulation-related side effects are mild and reversible.

Simultaneous thalamic deep brain stimulation and implantable cardioverter-defibrillator.

Thalamic deep brain stimulation is becoming increasingly popular for the control of drug-refractory tremor. Implantable cardiac pacemakers and defibrillators are commonly used therapeutic modalities. Concerns exist about the potential interactions between these 2 devices in the same patient, but no experience has been reported previously. We describe a patient with essential tremor who had a deep brain stimulator implanted into the left ventral intermediate nucleus of thalamus, who subsequently needed an implantable cardioverter-defibrillator. Despite concerns about possible interactions between the 2 types of implanted electrical devices (i.e., a situation similar to drug-drug interactions), the deep brain stimulator and the implanted pacemaker-defibrillator functioned appropriately, and no interaction occurred in our patient.

Predictors of neuropsychological outcome in patients following microelectrode-guided pallidotomy for Parkinson's disease.

OBJECT: The authors studied neuropsychological performance following microelectrode-guided posteroventral pallidotomy in patients with Parkinson's disease (PD) and evaluated correlations with presurgical and surgical factors. METHODS: Neuropsychological changes 3 months (43 patients) and 12 months (27 patients) after microelectrode-guided pallidotomy for PD are reported in a series of 44 consecutive patients with the disease, who improved neurologically, as measured by the Unified Parkinson's Disease Rating Scale (UPDRS) in both the "off' (p<0.001) and best "on" (p<0.001) states. Findings of the vocabulary subtest of the Wechsler Adult Intelligence Scale-Revised (p<0.01), Letter Fluency (p<0.001), Verbal Fluency for semantic categories (p<0.001), and the Wisconsin Card Sorting Test (p<0.01) showed a significant decline in neuropsychological performance in patients 3 months after undergoing left-sided pallidotomy. Impairment in the language domain (semantic fluency) persisted at the 12-month follow-up examination (p<0.01). Visual memory improved after right-sided pallidotomies (p<0.01 after 3 months), with a nonsignificant trend toward persistent improvement 1 year postsurgery (p<0.02 after 12 months). Preoperative semantic fluency was influenced by patient age (p<0.001) and by the width of the third ventricle (p<0.05), as measured by magnetic resonance imaging. A regression model revealed that semantic fluency 3 months postoperatively was significantly affected by the baseline score (p<0.001), side of surgery (p<0.001), handedness (p<0.01), and patient age (p<0.05). However, postoperative lesion volume, lesion location, number of tracks, number of lesions, distance from anatomical landmarks, or UPDRS score did not significantly contribute to neuropsychological outcome. CONCLUSIONS: Neuropsychological changes in a cohort of patients with PD who underwent pallidotomy and experienced excellent clinical benefits and minimum postoperative complications, emphasize the importance of neuropsychological examinations and further investigation of predictive factors.

Signal intensity artifacts in clinical MR imaging.

Signal intensity artifacts are often encountered during magnetic resonance (MR) imaging. Occasionally, these artifacts are severe enough to degrade image quality and interfere with interpretation. Signal intensity artifacts inherent in local coil imaging include intensity gradients and local intensity shift artifact. The latter can be minimized but not eliminated with optimal coil design and tuning. Improper coil or patient positioning can produce subtle or, in some cases, severe signal intensity artifacts, and each is easily corrected. Signal intensity artifacts and image degradation can also occur in a perfectly functioning coil if protocols are not optimized. Failure of decoupling mechanisms can produce signal intensity artifacts that will not respond to protocol optimization and will worsen with gradient imaging. Improper coil tuning manifests as a shading artifact that can mimic other findings. Signal-degrading artifacts may be caused by a ferromagnetic foreign body in the imager. Signal intensity artifacts can also result from performing ultrafast imaging with coils that were not designed for this type of imaging or from MR imaging system malfunction. Familiarity with the various causes of signal intensity artifacts is necessary to maintain optimal image quality and should be required as part of any MR imaging quality assurance program.

Hemangioma of the mandibular branch of the trigeminal nerve in the Meckel cave presenting with facial pain and sixth nerve palsy.

In a 25-year-old woman with episodic periorbital-temporal pain who eventually developed a sixth nerve palsy, magnetic resonance imaging revealed a lesion predominantly in the Meckel cave that was found to be a capillary hemangioma arising from the mandibular division of the trigeminal nerve. Hemangiomas of the Meckel cave must be considered in cases of facial pain with a sixth nerve palsy. even if there are no clinical findings of trigeminal neuropathy.

Distinguishing primary angiitis of the central nervous system from cerebral autosomal dominant arteriopathy with subcortical infarcts and leukoencephalopathy: the importance of family history.

Cerebral autosomal dominant arteriopathy with subcortical infarcts and leukoencephalopathy (CADASIL) is a genetically linked neurologic disease characterized by recurrent strokes and progressive or stepwise dementia, with or without migraine-like headaches, seizures, and pseudobulbar palsy. We describe a patient referred with a diagnosis of treatment-refractory primary angiitis of the central nervous system. Meningocortical and skin biopsies confirmed that the patient had CADASIL. Clinical and radiographic differences in these disorders may be subtle, but awareness of them is crucial if the patient is to avoid unnecessary exposure to potentially deleterious immunosuppressive therapy.

Neuroradiologic applications of central nervous system SPECT.

Single photon emission computed tomography (SPECT) of the central nervous system (CNS) has many potentially useful interventional neuroradiologic applications. CNS SPECT allows easy and safe evaluation of the collateral circulation during internal carotid balloon test occlusion. The cerebrovascular distribution of intracarotid amobarbital sodium, which is used in the Wada test, can be accurately determined with simultaneous injection of a radiopharmaceutical. Easy and safe evaluation of the extent and distribution of vasospasm associated with subarachnoid hemorrhage or cerebral angiography is also possible with CNS SPECT. Images obtained after administration of acetazolamide can be compared with baseline images to evaluate cerebrovascular reserve before carotid endarterectomy. Seizure foci can be identified if peripheral intravenous injection is performed during an ictus. Thallium-201 imaging can be used to direct stereotactic brain biopsy to check for tumor recurrence. Radiologists need to familiarize themselves and their clinical colleagues with the many uses of this imaging technique.

Life-threatening anaphylactoid reaction after intravenous gadoteridol administration in a patient who had previously received gadopentetate dimeglumine.

We report a case of a life-threatening anaphylactoid reaction to gadoteridol. The reaction resulted in hospitalization but did respond to medical treatment. Resuscitation equipment and properly trained personnel should be available if these agents are being administered.

Diffuse pulmonary alveolar hemorrhage after bone marrow transplantation: radiographic findings in 39 patients.

Diffuse alveolar hemorrhage is a life-threatening complication after bone marrow transplantation. We investigated the radiographic abnormalities that occurred in 39 transplantation patients with a diagnosis of diffuse alveolar hemorrhage and correlated the findings with the patients' clinical course. The initial radiographic abnormalities after diffuse alveolar hemorrhage developed an average of 11 days after bone marrow transplantation, and the radiographic abnormalities preceded the clinical diagnosis by an average of 3 days. Twenty-seven patients initially had bilateral radiographic abnormalities; 10 initially had unilateral abnormalities (seven in the right lung, three in the left lung). Two patients had normal chest radiographs throughout their clinical course. All 37 patients with radiographic abnormalities had abnormalities involving the central portion of the lung, primarily the middle and lower lung zones. The initial radiographic pattern was interstitial in 27 and alveolar in 10. In 24 patients, radiographic abnormalities were initially judged to be mild; three were severe from the onset. Radiographic abnormalities rapidly worsened in most patients over 6 days. In 30 patients, diffuse bilateral radiographic abnormalities involving all lung zones developed. Eleven patients persisted in having only interstitial radiographic abnormalities; 26 had a confluent alveolar pattern. At the height of radiographic abnormalities, 27 cases were judged to be severe, and only one case was judged to be mild. The mortality rate in patients with diffuse alveolar hemorrhage was 77%. The radiographic abnormalities of diffuse alveolar hemorrhage are nonspecific and usually precede the clinical diagnosis. The clinical course after hemorrhage is short, often resulting in death.

Indium-111 labeled leukocyte imaging following hepatic artery embolization.

The use of In-111 labeled leukocytes for abscess localization is becoming well established. The first report of In-111 imaging following hepatic embolization is presented. A 45-year-old man with adenocarcinoma of the colon and metastatic liver disease was treated for intractable pain using particulate embolization of the hepatic artery. In-111 leukocyte imaging was performed to rule out abscess formation. The distribution of the labeled leukocytes demonstrated hepatic uptake commensurate with Tc-99m sulfur colloid (SC) images. Areas of embolization did not accumulate tracer. Pathologic examination at autopsy correlated with the distribution of the labeled leukocytes. Thus, therapeutic embolization did not alter the normal distribution of this tracer in functional hepatic tissue.