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Biomedical subjects

J L Ulmer

Publications and source records attributed to J L Ulmer.

At least 37 records · Page 2Linked to original sources
PubMed1995

Topical fumagillin in the treatment of microsporidial keratoconjunctivitis in AIDS.

OBJECTIVE: To report microsporidial keratoconjunctivitis in a patient infected with HIV who was treated with topical fumagillin. CASE SUMMARY: A 37-year-old white man who was experiencing redness, pain, irritation, decreased vision, and a foreign body sensation occurring in both eyes was referred to the ophthalmology clinic. The patient had a medical history significant for AIDS, Pneumocystis carinii pneumonia, and Cytomegalovirus retinitis. Conjunctival smears were taken and stained positive for the presence of Microsporidia. The patient was diagnosed with bilateral microsporidial keratoconjunctivitis and fumagillin therapy was initiated. After 5 days of therapy, the patient reported significant improvements characterized by a decrease in blurred vision with only slight blurring in the left eye, decrease in headache, and decreased foreign body sensation. The patient continued topical fumagillin therapy for more than 14 months, with only slight blurring in the left eye and no apparent ocular toxicity as a result of fumagillin therapy. DISCUSSION: Although rare in occurrence, increasing numbers of documented microsporidial infections are being reported in the medical literature, particularly in individuals who are seropositive for HIV. Clinicians need to be cognizant of microsporidial keratoconjunctivitis as another opportunistic infection in this patient population. CONCLUSIONS: Although a curative agent has yet to be discovered, fumagillin represents a safe, effective, low-cost, topical agent for the treatment of microsporidial keratoconjunctivitis.

AIDS-Related Opportunistic Infections↗
PubMed1995

Combined effects of magnetization transfer and gadolinium in cranial MR imaging and MR angiography.

Magnetization transfer (MT) imaging is an MR technique in which image contrast is altered by applying RF pulses that saturate a restricted pool of hydrogen protons associated with cell membranes, proteins, and other macromolecules. Protons in this restricted pool, unlike those in tissue-free water, are not visible on MR due to their short T2 relaxation times. However, these restricted protons modulate the observed signal from free water by dipolar and chemical exchange interactions. In MT imaging, specifically tailored RF pulses are applied to saturate selectively the restricted macromolecular pool. This saturation is "transferred" to the free protons, causing their signal amplitude to decrease [1]. Increased signal intensity due to T1 shortening caused by gadolinium administration does not depend upon macromolecular interactions and is not appreciably suppressed by MT pulses (Fig. 1). Consequently, MT pulses act synergistically with gadolinium to increase the visibility of enhancing lesions by preferentially suppressing nonenhancing background tissue [2]. The purpose of this paper is to demonstrate the principles underlying the synergistic effects of MT saturation and paramagnetic contrast agents and to illustrate these effects in clinical MR imaging and MR angiography.

Brain↗
PubMed1995

Lumbar spondylolysis: reactive marrow changes seen in adjacent pedicles on MR images.

OBJECTIVE: In a search for ancillary MR findings for the diagnosis of spondylolysis, we performed a retrospective study to characterize changes in MR signal intensity of marrow within lumbar pedicles at the level of a spondylolytic defect. These reactive marrow changes were classified according to the anatomic-pathologic scheme developed for degenerative disk disease by Modic et al. MATERIALS AND METHODS: Two neuroradiologists retrospectively reviewed MR images of 60 patients with lumbar spondylolysis confirmed by conventional radiography or CT. The MR signal of each pedicle at the level of a pars defect was compared on T1- and T2-weighted sagittal images to that at the next higher level. When both observers concurred that the signal of the involved pedicle differed significantly from that of its neighbor, this signal change was classified into one of three types (type I: hypointense on T1-weighted images, hyperintense on T2-weighted images; type II: hyperintense on T1-weighted images, isointense or hyperintense on T2-weighted images; type III: hypointense on both T1- and T2-weighted images). RESULTS: Changes in MR signal intensity of pedicles adjacent to spondylolytic defects were observed in 24 (40%) of the 60 patients. Type I changes were seen in three patients, all less than 24 years old. Type II changes were seen in 17 patients with a median age of 35 years. Type III changes were seen in four patients with a median age of 51 years. The distribution of changes in signal intensity in the pedicle as a function of age was significant (p = .001). CONCLUSION: Categories of changes in MR signal intensity, similar to those described adjacent to degenerating disks, can be seen in lumbar pedicles adjacent to a spondylolytic defect of the pars interarticularis and are distributed as a function of age. Awareness of this finding may aid in establishing the correct diagnosis of spondylolysis on MR imaging and prevent erroneous interpretation of abnormal signal intensity in the pedicles in these patients.

Adult↗
PubMed1995

Lumbar spondylolysis without spondylolisthesis: recognition of isolated posterior element subluxation on sagittal MR.

PURPOSE: To document the occurrence of isolated dorsal subluxation of posterior elements in cases of lumbar spondylolysis without spondylolisthesis both quantitatively (using spinal canal measurements) and qualitatively (by visual inspection) on sagittal MR images. METHODS: Retrospective analysis identified 63 patients with lumbar spondylolysis (confirmed by CT or conventional radiography) who had undergone MR imaging. From these we identified 12 patients with pars interarticularis defects but no evidence of spondylolisthesis. Measurements of anteroposterior spinal canal diameters were performed in these 12 patients to ascertain whether the sagittal canal diameter at the level of the spondylolysis exceeded the normal range as determined from 100 control subjects. RESULTS: In 9 of 12 patients the spinal canal was abnormally widened at the level of the spondylolysis because of dorsal subluxation of posterior elements. In 5 of these patients, the subluxation was readily visible on midline sagittal MR images. In 4 patients, spinal canal measurements were necessary to document this phenomenon. CONCLUSION: In the majority of patients with spondylolysis but without spondylolisthesis, sagittal MR images can show isolated dorsal subluxation of posterior spinal elements.

Adolescent↗
PubMed1994

"Crisscross" MR imaging: improved resolution by averaging signals with swapped phase-encoding axes.

At conventional magnetic resonance imaging, the number of phase-encoding steps is often chosen to be less than the number of readout samples, resulting in reduced spatial resolution in the phase-encoding direction. Signal averaging improves the signal-to-noise ratio of the image but does not affect this asymmetry in resolution. By swapping the phase- and frequency-encoding directions between excitations and averaging the resultant data sets ("crisscross" imaging), equal spatial resolution can be obtained in both principal directions. Increased spatial resolution can be obtained with this method with no increase in imaging time, and the method can potentially be applied in echo-planar and three-dimensional Fourier transform imaging.

Brain↗
PubMed1994

Distinction between degenerative and isthmic spondylolisthesis on sagittal MR images: importance of increased anteroposterior diameter of the spinal canal ("wide canal sign").

OBJECTIVE: The purpose of this study was to determine whether a visually apparent increase in the anteroposterior diameter of the spinal canal ("wide canal sign") can be used reliably to differentiate degenerative from isthmic spondylolisthesis on midline sagittal MR images. We hypothesized that the wide canal sign would be present only in isthmic spondylolisthesis, where the vertebral ring is disrupted by defects in the pars interarticularis. MATERIALS AND METHODS: The midline sagittal MR images of 100 control subjects without spondylolysis or spondylolisthesis were analyzed to establish the normal range of sagittal canal diameters at the various lumbar levels. Midline sagittal MR images of the lumbar spine were reviewed in 53 patients in whom either isthmic (n = 35) or degenerative (n = 18) spondylolisthesis was confirmed with conventional radiography and/or CT. For each spinal level, the sagittal canal ratio, defined as the maximum anteroposterior diameter of the canal at that level divided by the diameter of the canal at L1, was calculated. From our analysis of the control subjects, a normal sagittal canal ratio was determined to be less than 1.25. A sagittal canal ratio of 1.25 or greater at the level of a spondylolisthesis was considered to represent an abnormally increased sagittal canal diameter (wide canal sign), indicating the presence of bilateral pars interarticularis defects. Using this sign alone, two neuroradiologists who had no knowledge of the true diagnosis classified the type of spondylolisthesis in a randomized subgroup of 34 age-matched adults (all more than 40 years old and with grade I isthmic or degenerative spondylolisthesis). RESULTS: In the 100 subjects without spondylolisthesis and in the 18 patients with degenerative spondylolisthesis, the sagittal canal ratio did not exceed 1.25 (mean values, 0.93-0.99) at any level of the lumbar spine. Conversely, the sagittal canal ratio at the level of isthmic spondylolisthesis exceeded 1.25 (mean value, 1.56) in 34 of 35 patients. In patients more than 40 years old, in whom degenerative spondylolisthesis is prevalent and misdiagnosis of isthmic spondylolisthesis is potentially more likely, both neuroradiologists were 100% accurate in correctly assigning the type of spondylolisthesis when using the wide canal sign alone. CONCLUSION: The wide canal sign on midline sagittal MR images (corresponding to an sagittal canal ratio > or = 1.25) is a reliable predictor of the presence of defects of the pars interarticularis at the level of a spondylolisthesis. This sign could be useful for distinguishing degenerative from isthmic spondylolisthesis when degenerative sclerosis in the pars interarticularis mimics spondylolysis, when direct axial imaging of the pars interarticularis has not been done, or when imaging is technically inadequate.

Adult↗
PubMed1993

Congenital cyst of the pancreas.

The case of a 4-month-old girl with a rare multilocular congenital pancreatic cyst is presented, along with radiological/pathological correlation and a review of the literature. Congenital cyst of the pancreas is a rare lesion most often seen in infant girls, although it may be demonstrated in utero. Conventional radiographic signs and clinical symptoms primarily reflect mass effects, whereas imaging modalities show the cystic nature of the mass. Although rare, this cyst should be considered in the differential diagnosis of fetal and pediatric cystic abdominal masses.

Female↗
PubMed1992

Fatal angioedema associated with lisinopril.

OBJECTIVE: To report a case of fatal angioedema associated with the use of lisinopril, a long-acting angiotensin-converting enzyme (ACE) inhibitor. DATA SOURCES: Case reports, review articles, short reports, and pertinent information from the patient's medical record. DATA EXTRACTION: Data was collected from contemporary medical journals and reviewed by both authors. DATA SYNTHESIS: Angioedema associated with ACE inhibitors (captopril and enalapril) is well documented in the literature. With increased prescribing of newer, longer-acting agents, this potentially lethal adverse reaction is of even greater concern. Because angioedema associated with ACE inhibitors is a class-related event, the number of reported cases would be expected to increase with increasing numbers of prescriptions written for these drugs. This report, describing a patient who developed angioedema following therapy with lisinopril, illustrates the severity of this adverse reaction. PATIENT: A 66-year-old man presented to the emergency room complaining of increased swelling of the back of his throat and difficulty breathing. Despite treatment with epinephrine, antihistamines, and corticosteroids, the patient's condition progressed from that of severe laryngeal edema to total laryngospasm and complete airway obstruction. Emergency measures to intubate the patient were complicated by severe swelling of his neck and oropharynx, forcing the physician to perform a grossly traumatic tracheotomy. The difficulty encountered during intubation deprived the patient of oxygen for a significant amount of time, precipitating cardiopulmonary arrest. The anoxic episode resulted in hypoxic, ischemic encephalopathy and, ultimately, death. CONCLUSIONS: Angioedema is a serious, potentially life-threatening adverse effect associated with the use of ACE inhibitors. Clinicians need to be aware of this effect when prescribing ACE inhibitors to treat hypertension and congestive heart failure, and when assessing patients presenting to the emergency room with complaints of tongue or pharyngeal swelling. Patients should be instructed to report immediately to an emergency room for medical attention if they experience any unexplained shortness of breath or swelling of the throat or tongue.

Aged↗
PubMed1991

Image-guided catheter drainage of the infected pleural space.

Thoracic empyema occurs at all ages and has reported mortality rates of 10% to 75%. Most authors agree that complete drainage of complicated effusions or organized empyemas and reexpansion of atelectatic lung are important in obtaining a satisfactory clinical outcome. For initial tube drainage, a 26-F to 36-F chest tube traditionally has been inserted at the bedside. The results of this method of empyema evacuation have varied widely, with an overall cure rate reported to be 47%. Image-guided placement of smaller 8-F to 14-F catheters has been offered as an alternative therapy with an overall reported cure rate of 81% in 104 patients.

Catheterization↗
PubMedDate not supplied

Effects of contrast dose, delayed imaging, and magnetization transfer saturation on gadolinium-enhanced MR imaging of brain lesions.

This paper discusses the types of paramagnetic agents available for clinical brain imaging and reviews investigations that have sought to optimize the use of these agents by varying the administered dose, delaying the imaging time after contrast administration, and altering image contrast by using magnetization transfer saturation pulses.

Blood-Brain Barrier↗
PubMedDate not supplied

Cortical activation response to acoustic echo planar scanner noise.

PURPOSE: Our goal was to determine the distribution of auditory and language cortex activation in response to acoustic echo planar scanner noise with functional MRI (fMRI). METHOD: Acoustic scanner noise and spoken text, reproduced on high output cassette tape, were separately delivered at equivalent intensities to six normal hearing adult volunteers through earphones during fMRI data acquisition. In nine other subjects, taped scanner noise was delivered in five successive iterations of the task to assess the consistency of cortical activation to the noise stimulus. Gyri of the auditory and language system were divided into 10 different subregions for analysis of cortical activation. The number of activated pixels and proportion of volunteers activating each cortical subregion were determined using a cross-correlation analysis. RESULTS: Cortical activation to taped acoustic scanner noise was present within the transverse temporal gyrus (primary auditory cortex) in all subjects, but activation was highly variable between subjects in auditory association and language relevant cortex. Auditory association cortex activation was seen in the planum polari, planum temporali, and middle temporal gyrus/superior temporal sulcus regions in one-half to two-thirds of the volunteers. There was no significant difference in the distribution of cortical activation within individual subjects across five successive iterations of the scanner noise task. Listening to spoken text consistently activated primary and association auditory cortex bilaterally as well as language relevant cortex in some cases. The mean number of activated pixels was significantly greater for text listening than acoustic scanner noise in auditory association and language relevant cortical subregions (p < 0.01), although the distribution of activity was similar between the two tasks. CONCLUSION: This preliminary investigation suggests that the complex sounds produced by the echo planar pulse sequence can activate relatively large regions of auditory and language cortex bilaterally, with the extent of activation outside the primary auditory cortex being variable between subjects. However, the distribution of activation within individual subjects was relatively constant across several iterations of the scanner noise stimulus.

Adult↗
PubMedDate not supplied

Acoustic echoplanar scanner noise and pure tone hearing thresholds: the effects of sequence repetition times and acoustic noise rates.

PURPOSE: Our goal was to determine the effects of acoustic echoplanar scanner noise on pure tone hearing thresholds in normal volunteers and to determine the influence of echoplanar sequence repetition time on threshold effects. METHOD: With use of a calibrated audiometer, pure tones ranging from 125 to 8,000 Hz were delivered monaurally to 10 normal-hearing volunteers in a quiet MR scanner suite and in the presence of acoustic scanner noise produced by three separate single shot blipped echoplanar pulse sequences varying only in repetition time (TR = 1,000, 2,000, or 3,000 ms), with all other parameters including the number of slices held constant. The magnitude of noise-induced threshold changes and the slopes of the threshold curves produced by each of the three echoplanar pulse sequences were then analyzed using multiple comparisons and a least significant difference method. The shapes of the threshold curves produced in each background state were best fit using a quadratic effect for frequency in a mixed effects linear model and compared using F test statistics. RESULTS: All of the volunteers demonstrated entirely normal hearing thresholds throughout the full range of tonal frequencies tested (< 25 dB) when no acoustic scanner noise was present in the scanner suite. Pure tone hearing thresholds significantly increased (p < 0.01) in the presence of acoustic scanner noise, with the magnitude of change inversely proportional to the repetition time and therefore the rate of periodic noise production by the echoplanar sequence used. The shape of the threshold curve in the presence of noise produced by the 1,000 ms TR sequence was not equivalent across the frequency spectrum tested but had a quadratic distribution with peak effects at 750-2,000 Hz. As the repetition time was increased and the periodic noise rate decreased, the magnitude of the noise-induced threshold changes significantly lessened (p < 0.01) and the quadratic distributions of the threshold curves changed significantly (p < 0.01), tending toward a more planar configuration. CONCLUSION: Background acoustic echoplanar scanner noise can significantly increase pure tone thresholds in the optimal frequency hearing range (125-8,000 Hz). However, the threshold effects are not equivalent across the frequency spectrum, and the magnitude of threshold changes is dependent on the rate at which periodic acoustic scanner noises are produced for a given sequence repetition time.

Acoustic Stimulation↗
PubMedDate not supplied

Blind source separation of multiple signal sources of fMRI data sets using independent component analysis.

PURPOSE: The objective of this study was to separate multiple signal components present in functional MRI (fMRI) data sets. Blind source separation techniques were applied to the analysis of fMRI data to determine multiple physiologically relevant independent signal sources. METHOD: Computer simulations were performed to test the reliability and robustness of the independent component analysis (ICA). Four subjects (3 males and 1 female between 14 and 29 years old) were scanned under various stimulus conditions: (1) rest while breathing room air, (2) bilateral finger tapping while breathing room air, and (3) hypercapnia during bilateral finger tapping. RESULTS: Simulations performed on synthetic data sets demonstrated that not only could the algorithm reliably detect the shapes of each of the source signals, but it also preserved their relative amplitudes. The algorithm also performed robustly in the presence of noise. With use of fMRI time series data sets from bilateral finger tapping during hypercapnia, distinct physiologically relevant independent sources were reliably estimated. One independent component corresponded to the hypercapnic cerebrovascular response, and another independent component corresponded to cortical activation from bilateral finger tapping. In three of the four subjects, the underlying fluctuations in signal related to baseline respiratory rate were identified in the third independent component. Principal component analysis (PCA) could not separate these two independent physiological components. CONCLUSION: With use of ICA, signals originating from independent sources could be separated from a linear mixture of observed data. Limitations of PCA were also demonstrated.

Adolescent↗
PubMedDate not supplied

Depiction of intracranial vessels with MRA: utility of magnetization transfer saturation and gadolinium.

PURPOSE: The purpose of this work was to quantitate the individual and combined effects of magnetization transfer (MT) saturation and gadolinium (Gd) on the visualization of intracranial vessels with MR angiography (MRA). METHOD: Thirty-five subjects underwent two three-dimensional time-of-flight MRA sequences without and with MT and/or Gd. There were 14 MR angiograms without Gd or MT, 18 with MT only, 17 with Gd only, and 21 with both Gd and MT. On a projection image, a region of interest was drawn to delineate the arteries in the middle cerebral artery territory. The total area of blood vessels in the region of interest was calculated for each MR angiogram. Mean vessel areas for the four types of MRA were compared with analysis of variance. RESULTS: MRA with either MT or Gd alone showed significantly more vessel area than MRA without either (p < 0.05). MRA with MT alone and MRA with Gd alone were not different from each other (p = 0.29). The improvement in vessel area measured by using MT and Gd together was significantly more than expected from the cumulative improvement of adding each alone (p < 0.05). CONCLUSION: Combining MT and Gd synergistically improved the visualization of intracranial vessels on MRA.

Adult↗
PubMedDate not supplied

Magnetization transfer imaging of skeletal muscle in autosomal recessive limb girdle muscular dystrophy.

PURPOSE: The purpose of this work was to characterize magnetization transfer (MT) contrast of skeletal muscles in limb girdle muscular dystrophy (LGMD). METHOD: The calf muscles of five LGMD patients and 10 normal volunteers were imaged with an off-resonance MT suppression pulse applied to T1-weighted images. MT suppression ratios were calculated for anterior tibialis, posterior tibialis, soleus, and gastrocnemius muscles in the LGMD and control groups. The relationship between MT of individual muscles and the duration of LGMD symptoms was determined. RESULTS: Strong MT contrast was observed in normal calf muscles, with mean (+/-SD) suppression ratios ranging from 37.9% (+/-3.0) to 41.1% (+/-2.1). In diseased muscle, MT signal suppression ranged from 11 to 38%, demonstrating an inverse relationship between symptom duration and suppression ratios. MT contrast in the LGMD patients, as a reflection of muscle tissue integrity, was preserved in posterior or anterior tibialis, soleus, and gastrocnemius muscles, respectively. Suppression ratios were dramatically reduced in muscles with gross fatty infiltration but also were reduced in muscle tissues without visual evidence of fatty infiltration. CONCLUSION: MT imaging provides a quantitative measure of pathologic changes occurring within the skeletal muscles of patients with LGMD relative to normal and may be useful in evaluating disease extent, progression, and response to new therapies as they become available.

Adolescent↗
PubMedDate not supplied

Use of jackknife resampling techniques to estimate the confidence intervals of fMRI parameters.

PURPOSE: The objective of this study was to determine the reliability and the confidence intervals of task-activated functional MRI (fMRI) parameters using a computer-intensive resampling technique. The jackknife, a commonly used method for resampling mathematical data, was used to calculate the confidence interval of fMRI parameters for a simple bilateral finger-tapping paradigm. METHOD: Four healthy test subjects (three men, one woman) were used to test the correlation coefficient and variability in the data. Each subject performed 4.5 cycles, each cycle having 20 s of bilateral finger tapping alternating with rest periods of equal time, producing 90 images. One additional scan of 10 cycles (200 images) was used to test the stability of the method itself. One thousand jackknifed resampled data sets of 85 elements each (from 90 original points) were generated, and the correlation coefficient was determined using an idealized "on/off" box-car reference waveform. RESULTS: Activation maps were generated that had the same confidence intervals at each pixel. These maps were more localized with less extraneous activated pixels than the maps generated with a fixed correlation coefficient threshold. There was no significant difference in the distribution of correlation coefficients between the 85, 90, and 95 element, jackknifed data sets; similar robustness was seen, as well. CONCLUSION: The jackknife resampling technique for data analysis produced reliable distributions and statistical parameters. The jackknife estimates were shown to be stable, even from a small initial sample size. This method may be used in lieu of test-retest analysis.

Adolescent↗
PubMedDate not supplied

Physiologic mechanisms underlying the delayed delta sign.

The negative or empty delta sign is considered to be nearly pathognomonic of superior sagittal sinus thrombosis on contrast-enhanced CT scans. We describe a visually similar sign, seen in five (10%) of 50 patients who had delayed cranial CT scans performed at intervals greater than 30 min after injection of contrast material. This new sign (which we call the delayed delta sign) closely mimics the classic negative delta sign and may thus represent a potential visual pitfall leading to an erroneous diagnosis of sagittal sinus thrombosis if only postcontrast images are viewed. The physiologic mechanisms underlying the appearance of the delayed delta sign are discussed.

Adolescent↗