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Biomedical subjects

John Huston

Publications and source records attributed to John Huston.

29 records · Page 2Linked to original sources
PubMed2004

Improved image quality of intracranial aneurysms: 3.0-T versus 1.5-T time-of-flight MR angiography.

BACKGROUND AND PURPOSE: We hypothesize that the nearly doubling of signal-to-noise ratio at 3.0 T compared with that at 1.5 T yields improved clinical MR angiograms and enables superior visualization of intracranial aneurysms. The goal of this study was to determine whether 3.0-T time-of-flight (TOF) MR angiography is superior to 1.5-T TOF MR angiography in the detection and characterization of intracranial aneurysms. METHODS: Fifty consecutive patients referred for MR angiography of a known or suspected intracranial aneurysm underwent 3-T TOF MR angiography. Seventeen of these 50 patients had also previously undergone 1.5-T TOF MR angiography and these images were used as a basis for comparison with images obtained at 3.0 T. Fourteen of 23 patients in whom aneurysms were identified also underwent prior conventional angiography, which was used as the reference standard. Readers blinded to patient history identified the presence and location of aneurysm(s) on angiograms and graded images for overall image quality by using a five-point scale. RESULTS: Twenty-eight aneurysms were identified in 23 of 50 patients. Seventeen aneurysms in 17 patients had been documented with 1.5-T MR angiography. The 3.0-T technique had a higher mean image quality score than that of the 1.5-T MR technique (P <.0001). Both 3.0-T and 1.5-T TOF MR angiography depicted all the aneurysms that had been documented by conventional angiography. CONCLUSION: 3D TOF MR angiography at 3 T offers superior depiction of intracranial aneurysms compared with that of 1.5-T TOF MR angiography.

Adult↗
PubMed2003

Reduction of RF power for magnetization transfer with optimized application of RF pulses in k-space.

More efficient use of RF power for RF-intensive applications such as magnetization transfer (MT) is necessary at high field strength (3.0 T or greater) to keep the specific absorption rate (SAR) within regulatory limits. It has been demonstrated that RF power deposition can be reduced with minimal impact on image quality by preferential application of MT pulses to the central phase-encoding views. This work extends that approach to both phase-encoding directions in a 3D acquisition (i.e., phase and slice) and further improves it by modulating the flip angle of the MT pulse according to the phase-encoded view's distance to the center of k-space. This technique is implemented for 3D time-of-flight (TOF) MR angiography (MRA) and the parameters for MT pulse are optimized based on phantom studies at 3.0 T. MT applied with this method at 3.0 T is shown to improve the blood vessel detectability in high-resolution intracranial 3D TOF MRA exams of 11 patients.

Adult↗
PubMed2003

Clinical profile of autosomal dominant polycystic liver disease.

Most reports on the natural history, manifestations, and treatment of polycystic liver disease are based on the disease as it manifests in patients with autosomal dominant polycystic kidney disease (ADPKD). The purpose of this study was to develop a clinical profile of isolated autosomal dominant polycystic liver disease (ADPLD) using nonaffected family members as controls. The study included 146 probands, known affected relatives, and first-degree relatives of affected individuals. Participants underwent a formalized medical history interview and physical examination, ultrasonographic examination of the liver and kidneys, magnetic resonance angiography of the brain, and echocardiography. Thirty-eight of the 49 individuals diagnosed with polycystic liver disease before participation in the study were or had been symptomatic. Of 97 previously undiagnosed at-risk individuals, 23 were affected, 39 were unaffected, and 35 were indeterminate. Compared with patients with a negative or indeterminate diagnosis, those with polycystic liver disease had slightly higher levels of serum alkaline phosphatase and total bilirubin and lower levels of total cholesterol and triglycerides. Female patients had a significantly higher mean cyst score than male patients. The cysts were found to arise from the dilatation of biliary microhamartomas and from peribiliary glands. Structural mitral leaflet abnormalities were detected more frequently in affected than in indeterminate or nonaffected individuals. A vascular phenotype was detected in 5.6% of the patients with isolated ADPLD diagnosed clinically and/or by linkage analysis but in none of the unaffected patients. In conclusion, isolated ADPLD is underdiagnosed and genetically distinct from polycystic liver disease associated with ADPKD but with similar pathogenesis, manifestations, and management.

Adolescent↗
PubMed2003

Value of diffusion-weighted imaging in patients with a nonlocalizing examination and vasospasm from subarachnoid hemorrhage.

We evaluated the value of diffusion-weighted imaging (DWI) in patients with suspected vasospasm from subarachnoid hemorrhage (SAH). Magnetic resonance imaging (MRI), including DWI, was performed in 5 patients with vasospasm resulting from SAH. Restricted diffusion (ischemia) was present in 3 patients with symptomatic vasospasm. A diffusion abnormality was not demonstrated in 2 patients with asymptomatic vasospasm despite persistently elevated velocities by transcranial Doppler ultrasonography in 1. In this patient, serial MRI studies showed no ischemia. Our results suggest that DWI may provide a method to assess the presence and severity of ischemia in patients with SAH and vasospasm and assist in patient management.

Adult↗
PubMed2003

Intracranial aneurysms in patients with coarctation of the aorta: a prospective magnetic resonance angiographic study of 100 patients.

OBJECTIVE: To determine the frequency of intracranial aneurysms (IAs) detected in patients with coarctation of the aorta (CoA) with use of magnetic resonance angiography. PATIENTS AND METHODS: From January 1, 1980, to September 30, 2002, 277 adult patients with CoA were seen at the Mayo Clinic in Rochester, Minn, and were invited to participate in a study to detect IAs. Of these 277 patients (mean +/- SD age, 41.6 +/- 16.5; 70 men), 100 underwent cranial magnetic resonance angiography. RESULTS: Ten patients had an IA (95% confidence interval, 5%-18%), with a mean diameter of 3.5 mm (range, 2.0-8.0 mm). The frequency of IA was significantly higher than that predicted in the general population (10% vs 2%; P < .001). One patient had surgical intervention. No clinical or geographical differences were found between patients with CoA and IA and patients with CoA and no IA. CONCLUSIONS: The frequency of IA among patients with CoA is approximately 5-fold that of the general population. Although no risk factors were identified in this cohort, additional prospective evaluation is warranted. These data suggest that noninvasive cerebral imaging to screen for IA should be considered in patients with CoA.

Adult↗
PubMed2002

Semiautomated quantitation of carotid artery stenosis in gadolinium-bolus magnetic resonance angiography.

Magnetic resonance angiography (MRA) has become the standard method for evaluation of carotid occlusive disease. Fast imaging methods combined with bolus intravenous injection of gadolinium contrast have improved the quality of these images. Nevertheless, the gold standard for evaluation was based on projection arterial angiography. The properties of these images are rather different. Whereas most previous evaluations of MRA have used visual assessment of images, we evaluate an algorithm in which a computer algorithm plays the primary role in defining arterial lumen margins, hence, disease. The accuracy of this semiautomated algorithm is shown to compare favorably with gold-standard arteriography in a series of 50 patients.

Algorithms↗
PubMed2002

Hybrid phased array for improved internal auditory canal imaging at 3.0-T MR.

PURPOSE: To develop and evaluate a hybrid phased array for internal auditory canal (IAC) imaging at 3.0 T. MATERIALS AND METHODS: A hybrid phased array was designed and built as two circular surface receive-only coils combined with a volume transmit-receive birdcage head coil for simultaneous image acquisition. Phantom and volunteer images were obtained to assess the coil performance. RESULTS: The phantom data show that significant signal-to-noise ratio (SNR) improvement was achieved in the region corresponding to the inner ear, i.e., by a factor of 2.5 compared to the standard head coil data. Volunteer IAC image quality was deemed superior as compared to images acquired at 3.0 T using a standard head coil. CONCLUSION: This hybrid array combined with three-dimensional fast spin-echo (FSE) acquisition resulted in improved high spatial resolution IAC imaging.

Ear, Inner↗
PubMed2002

Measurement of cerebrospinal fluid flow at the cerebral aqueduct by use of phase-contrast magnetic resonance imaging: technique validation and utility in diagnosing idiopathic normal pressure hydrocephalus.

OBJECTIVE: We analyzed the reliability of a protocol for measuring quantitative cerebrospinal fluid (CSF) flow at the cerebral aqueduct and established the range of CSF flows in normal elderly patients, patients with Alzheimer's and other forms of dementia, and patients with idiopathic normal pressure hydrocephalus (NPH). METHODS: A constant flow phantom was used to establish the accuracy of the CSF flow measurement. The clinical variability of the measurement was estimated by calculating the standard deviations and coefficients of variation of intra- and interobserver and intertrial data sets derived from three normal volunteers. A total of 236 patients were studied, including 47 normal elderly patients, 115 patients with cognitive impairment (9 with mild cognitive impairment, 46 with Alzheimer's disease, and 60 with other cognitive impairment), 31 patients in whom NPH was suspected but ultimately excluded, and 43 patients with a final clinical diagnosis of NPH. RESULTS: The intraobserver, interobserver, and intertrial measurement variations of 6.4, 5.4, and 8.8%, respectively, were substantially smaller than the wide variation observed among subjects. There was no statistically significant difference in flow between normal elderly patients and patients with cognitive impairment (P = 0.91). When these populations were pooled, the average flow was 8.47 ml/min (standard deviation, 4.23; range, 0.9-18.5 ml/min). The average flow rate in patients with a final clinical diagnosis of NPH was 27.4 ml/min (standard deviation, 15.3; range, 3.13-62.2 ml/min). This was significantly higher than the flow rate in each of the other three groups (all, P < 0.001). CONCLUSION: CSF flow measurements of less than 18 ml/min with a sinusoidal flow pattern are normal. CSF flow of greater than 18 ml/min suggests idiopathic NPH.

Adult↗
PubMed2002

Intracranial saccular aneurysm enlargement determined using serial magnetic resonance angiography.

OBJECT: The goal of this study was to determine the frequency of enlargement of unruptured intracranial aneurysms by using serial magnetic resonance (MR) angiography and to investigate whether aneurysm characteristics and demographic factors predict changes in aneurysm size. METHODS: A retrospective review of MR angiograms obtained in 57 patients with 62 unruptured, untreated saccular aneurysms was performed. Fifty-five of the 57 patients had no history of subarachnoid hemorrhage. The means of three measurements of the maximum diameters of these lesions on MR source images defined the aneurysm size. The median follow-up period was 47 months (mean 50 months, range 17-90 months). No aneurysm ruptured during the follow-up period. Four patients (7%) harbored aneurysms that had increased in size. No aneurysms smaller than 9 mm in diameter grew larger, whereas four (44%) of the nine aneurysms with initial diameters of 9 mm or larger increased in size. Factors that predicted aneurysm growth included the size of the lesion (p < 0.001) and the presence of multiple lobes (p = 0.021). The location of the aneurysm did not predict an increased risk of enlargement. CONCLUSIONS: Patients with medium-sized or large aneurysms and patients harboring aneurysms with multiple lobes may be at increased risk for aneurysm growth and should be followed up with MR imaging if the aneurysm is left untreated.

Aged↗
PubMed2002

Cervical artery dissections: evidence for redissection in previously dissected arteries: report of three cases.

OBJECTIVE AND IMPORTANCE: Among patients with spontaneous internal carotid artery (ICA) or vertebral artery dissections, there is a small but significant risk of development of dissection in an uninvolved ICA or vertebral artery at some time in the future. Recurrence of dissection in a previously dissected and healed ICA or vertebral artery is very rare. We retrospectively reviewed more than 400 cases of cervical artery dissections in our cerebrovascular records for 1970 through 2000. CLINICAL PRESENTATION: Three patients with recurrence of dissection in previously dissected and presumably healed ICAs were identified. All three patients were women. Their ages at the time of the initial dissection were 42, 38, and 31 years. Initial ICA dissections were bilateral in all cases, occurring simultaneously in one case and 1 year apart in the other two cases. All dissections were spontaneous. Redissection of a previously dissected and healed ICA in these three patents occurred 11, 6, and 12 years later, respectively. Two patients had fibromuscular dysplasia. CONCLUSION: Our experience with these three cases, from among more than 400 cases of cervical artery dissections treated at our institution, and the very limited number of reported cases in the literature indicate the rarity of recurrence of dissection in previously dissected and healed cervical arteries. An underlying arteriopathy may be suspected in many of these cases. Management requires medical and sometimes surgical approaches.

Adult↗