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J P Karis

Publications and source records attributed to J P Karis.

10 recordsLinked to original sources
PubMed1999

Fast spin echo MR imaging.

For years, investigators have sought after faster MR scanning techniques. Gradient echo and echo planar imaging were potential candidates that met with limited success. Fast spin echo (FSE) imaging was an innovation that revolutionized the clinical utility of MR imaging and fulfilled the promise of fast diagnostic MR scanning. FSE allows for the acquisition of MR images that often equals and occasionally exceeds the quality of conventional spin echo imaging, all during less or similar scanning time.

Brain↗
PubMed1998

Bilateral temporal hypometabolism in epilepsy.

PURPOSE: Positron emission tomography (PET) has proven useful in epilepsy surgery for its ability to identify unilateral temporal hypometabolism (UTH), which is predictive of good surgical outcome. The significance of bilateral temporal hypometabolism (BTH) is not known. METHODS: We identified all patients who had marked bilateral reduction in temporal lobe metabolism relative to the cerebellar hemispheres and compared their clinical features and treatment outcomes with those of control patients with UTH. RESULTS: BTH was evident in 10% of PET scans for epilepsy at our institution. We compared these patients with age-matched controls with UTH. The BTH patients had a higher percentage of generalized seizures; were more likely to have bilateral, diffuse or extratemporal seizure onsets; and had bilateral or diffuse magnetic resonance imaging (MRI) findings. UTH patients were more likely to have unilateral mesial temporal atrophy on MRI. Even when electrical seizure onsets were well localized, surgical outcomes were markedly worse in these patients than in controls. Medical treatment was also less successful. Social and cognitive functioning was worse in the BTH group. The only death occurred in the group with BTH. CONCLUSIONS: Patients with BTH have features distinct from those with UTH and have a worse prognosis for seizure remission after surgery.

Adolescent↗
PubMed1998

Differentiating recurrent tumor from radiation necrosis: time for re-evaluation of positron emission tomography?

UNLABELLED: Our purpose was to evaluate the ability of FDG PET to differentiate recurrent tumor from posttherapy radiation necrosis. METHODS: MR images, PET scans, and medical records of 84 consecutive patients with a history of a treated intracranial neoplasm were evaluated retrospectively. In all patients, recurrent tumor or radiation necrosis was suggested by clinical or MR findings. Metabolic activity of the PET abnormality was compared qualitatively with normal contralateral gray and white matter. RESULTS: PET findings were confirmed histologically in 31 patients. With contralateral white matter as the standard of comparison, the PET scan sensitivity and specificity were found to be 86% and 22%, respectively. With contralateral gray matter as the reference standard, the sensitivity and specificity became 73% and 56%, respectively. Overall, nearly one third of the patients would have been treated inappropriately in either scheme had the PET scan been the sole determinant of therapy. CONCLUSION: Our data suggest that the ability of FDG PET to differentiate recurrent tumor from radiation necrosis is limited. Both false-positive and false-negative PET scan results contributed to unacceptably low sensitivity and specificity values.

Diagnosis, Differential↗
PubMed1996

An alternative to GRASE: toward spin-echo-like contrast with independent reconstruction of gradient-echo images.

Multiple gradient echoes are generated for each RF echo of a Carr-Purcell-Meiboom-Gill (CPMG) train. Independently, phase-encoded fast spin-echo images are obtained from the different gradient echoes. Presently, three images are formed from three gradient-echoes from each of four RF echoes. The two peripheral gradient echo images are encoded for a late effective TE, then summed after reconstruction: this image has decreased fat intensity and increased susceptibility contrast compared with fast spin echo. The central gradient echoes yielded another image of intermediate contrast useful for neuroimaging. Raw data from the variously timed gradient echoes are not combined as they are in GRASE.

Brain↗
PubMed1991

Sonographic diagnosis of premature cervical dilatation. Potential pitfall due to lower uterine segment contractions.

Antenatal sonography is an accepted method of evaluating the cervix and lower uterine segment. Dilatation of the endocervical canal can be missed due to compression by an overdistended urinary bladder, intermittent changes in configuration of the cervix, and suboptimal visualization. However, the potential for overdiagnosis of this entity has not been previously emphasized. We present 14 cases demonstrating how contractions in the lower uterine segment can result in an appearance that falsely simulates preterm dilatation of the endocervical canal. The overdiagnosis of this entity can be avoided by distinguishing the following features typical of "pseudodilatation" due to a contraction: (1) apparent cervical length greater than 5 cm; (2) demonstration of normal-appearing cervical tissue distal to the apparently dilated region; and (3) rounding of the myometrium surrounding the apparently dilated area. If any of these features is detected in a patient with sonographic characteristics suggesting dilatation of the cervix, the possibility of pseudodilatation should be considered, and the lower uterine segment should be rescanned later in the examination.

Cervix Uteri↗
PubMed1990

Counterclockwise exit of cardiac pacemaker leads: sign of pulse-generator flip.

Clockwise exit of pacing leads from transvenous cardiac pacemakers is generally essential for proper function. The authors report a case in which counterclockwise exit of the pacing leads signified a 180 degree flip of the pulse generator. Three types of pacing system malfunction can result from pacemaker flip.

Equipment Failure↗
PubMed1987

Rapid calculation of T1 using variable flip angle gradient refocused imaging.

We present a method for rapid measurement of T1 relaxation times using gradient refocused images at limited flip angles and short repetition times. This "variable nutation" techniques was investigated using a T1 phantom. There was a high correlation between measurements obtained with the variable nutation and partial saturation techniques. The ability of this method to create calculated T1 images is also demonstrated. We conclude that the variable nutation method may allow measurement of T1 relaxation times with a significant reduction in acquisition time compared to partial saturation techniques.

Humans↗
PubMedDate not supplied

MR "microscopy" of the rat thorax.

High resolution images can be obtained from anywhere in the body of small animals with magnetic resonance combined with cardiac gating and scan synchronous ventilation. We used these methods to examine the intrathoracic anatomy of the rat. Anesthetized rats were intubated and ventilated in synchrony with imaging acquisition. Images were obtained in a 1 m bore, 1.5 T system fitted with a 28 cm diameter high field gradient coil and a 5 cm radio-frequency coil. We used cardiac gated, three-dimensional spin warp acquisitions. Eight contiguous slices (2.5 mm thick) were obtained simultaneously. In addition to visualizing major vessels and cardiac chambers, cardiac valves and papillary muscles were clearly demonstrated. Major pulmonary vessels and peripheral parenchyma were also seen. These results demonstrate MR "microscopy" can be used to image all major cardiopulmonary structures in the rat with respect to selected times of the cardiac cycle. This capability for noninvasive "microscopy" opens new avenues for cardiopulmonary research using well characterized rodent models.

Animals↗
PubMedDate not supplied

Radiologic assessment of temporal lobe epilepsy.

Neuroimaging plays an important and increasing role in assessing patients with epilepsy. This article focuses on procedures used to evaluate patients who have failed medical treatment for epilepsy but may benefit from resective surgery. Radiologic assessment and use of the intracarotid amobarbital procedure are described.

Amobarbital↗