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J A Sorenson

Publications and source records attributed to J A Sorenson.

At least 19 recordsLinked to original sources
PubMed1997

Spatially filtering functional magnetic resonance imaging data.

When constructing MR images from acquired spatial frequency data, it can be beneficial to apply a low-pass filter to remove high frequency noise from the resulting images. This amounts to attenuating high spatial frequency fluctuations that can affect detected MR signal. A study is presented of spatially filtering MR data and possible ramifications on detecting regionally specific activation signal. It is shown that absolute activation levels are strongly dependent on the parameters of the filter used in image construction and that significance of an activation signal can be enhanced through appropriate filter selection. A comparison is made between spatially filtering MR image data and applying a Gaussian convolution kernel to statistical parametric maps.

Magnetic Resonance Imaging↗
PubMed1997

Indocyanine green angiography of multifocal choroiditis.

PURPOSE: The purpose of the study is to determine indocyanine green (ICG) angiographic characteristics of patients with multifocal choroiditis (MC) and to identify features that may assist in the differentiation of MC from other ocular inflammatory diseases. METHODS: After complete ophthalmologic examination, fluorescein angiography and ICG angiography were performed in a series of 14 patients with MC. The ICG findings were then correlated with the clinical and fluorescein angiographic appearance of these patients to determine specific characteristics and distinguishing features of the entity. These findings then were compared with those of angiographic patterns observed in patients with ocular histoplasmosis syndrome to determine whether differentiating features could be identified. RESULTS: Fourteen (50%) of the 28 eyes were found to have large hypofluorescent spots in the posterior pole on ICG angiography, which, in most cases, did not correspond to clinically or fluorescein angiographically detectable lesions. Seventeen (61%) had smaller hypofluorescent lesions (approximately 50 pm in size) in the posterior pole on the ICG study. In seven eyes exhibiting enlarged blind spots on visual field testing, ICG angiography showed confluent hypofluorescence surrounding the optic nerve. The ICG angiogram was found useful in evaluating the natural course in two patients with MC as well as a response to oral prednisone therapy in four others. The ICG angiographic findings differed from those seen in patients with ocular histoplasmosis. CONCLUSIONS: Indocyanine green angiography can provide information that is not detectable by clinical or fluorescein angiographic examination in patients with MC. This information may prove useful in differentiating this condition from the ocular histoplasmosis syndrome, provide a better understanding of the natural course and progression of the disease, and provide a potential adjunct in the clinical evaluation of patients undergoing therapeutic regimens for active inflammatory lesions.

Adolescent↗
PubMed1997

Treatment of experimental methicillin-resistant Staphylococcus epidermidis endophthalmitis with intravitreal vancomycin and intravitreal dexamethasone.

The use of intravitreal steroids to treat bacterial endophthalmitis remains controversial. The efficacy of intravitreal vancomycin alone (group 1), intravitreal dexamethasone alone (group 2), and a combination of intravitreal vancomycin and dexamethasone (group 3) in the treatment of experimental methicillin-resistant Staphylococcus epidermidis endophthalmitis was evaluated in a rabbit model: 24 h after bacterial inoculation of all eyes, right eyes were treated and left eyes served as infected controls. Vitreal aspirations and grading of vitreal inflammatory reaction were done regularly until sacrifice. Group 2 eyes demonstrated more inflammation histologically than control eyes. Vitreal aspirations demonstrated no growth by 5 days from groups 1 and 3 eyes. Although the clinical appearance was not significantly different between groups 1 and 3, the histologic appearance of group 3 eyes showed less intense intraocular inflammation. Treatment with dexamethasone in the absence of appropriate antibiotics was more harmful than no treatment at all (P < .05). Therapy with both intravitreal vancomycin and dexamethasone results in less inflammation than intravitreal vancomycin alone in this model.

Animals↗
PubMed1996

Human amygdala activation detected with echo-planar functional magnetic resonance imaging.

Echo-Planar functional magnetic resonance imaging (EP-fMRI) was used to study the activity of the amygdala while three normal female subjects viewed alternating blocks of affectively neutral and affectively negative still pictures. Bilateral activation in the amygdala that was significantly correlated with the changing valence of the visual stimuli was found in all three subjects. These findings are consistent with the large corpus of data from non-human studies suggesting that the amygdala is a key structure for extracting the affective significance from external stimuli. This is the first known report of phasic amygdala activation detected with EP-fMRI in normal human subjects responding to affective stimuli.

Adult↗
PubMed1996

Indocyanine green-guided laser photocoagulation of focal spots at the edge of plaques of choroidal neovascularization.

OBJECTIVE: To determine whether indocyanine green-guided laser photocoagulation of focal spots at the edge of plaques of neovascularization is beneficial for patients with untreatable occult choroidal neovascularization by fluorescein imaging. PATIENTS: A pilot series of 23 eyes were identified that had untreatable occult choroidal neovascularization secondary to age-related macular degeneration with focal spots at the edge of a plaque of neovascularization on the indocyanine green study. After informed consent was obtained, indocyanine green-guided laser photocoagulation was applied solely to the focal spot at the edge of the plaque. RESULTS: Anatomical success with resolution of the exudative findings was noted in 15 (79%) of 19 eyes at 6 months, 13 (68%) of 19 eyes at 12 months, and six (37.5%) of 16 eyes at 24 months. The median follow-up period was 18 months (range, 3 to 44 months). Visual acuity was stabilized or improved in nine (69%) of 13 successfully treated eyes at 1 year. Of the successfully treated cases at 1 year, nine (69%) of 13 had a final visual acuity of 20/100 or better. CONCLUSIONS: Our preliminary study of indocyanine green-guided laser photocoagulation of focal spots at the edge of plaques of neovascularization suggests that this technique may improve the visual prognosis of these patients with presently untreatable disease. A prospective, randomized, controlled clinical trial is warranted to evaluate this treatment approach.

Aged↗
PubMed1996

MR image segmentation using vector decomposition and probability techniques: a general model and its application to dual-echo images.

A general model is developed for segmenting magnetic resonance images using vector decomposition and probability techniques. Each voxel is assigned fractional volumes of q tissues from p differently weighted images (q < or = p + 1) in the presence of partial-volume mixing, random noise, and other tissues. Compared with the eigenimage method, fewer differently weighted images are needed for segmenting the q tissues, and the contrast-to-noise ratio in the calculated fractional volumes is improved. The model can produce composite tissue-type images similar to that of the probability methods, by comparing the fractional volumes assigned to different tissues on each voxel. A three-tissue (p = 2, q = 3) model is illustrated for segmenting three tissues from dual-echo images. It provides statistical analysis to the algebraic method. A three-compartment phantom is segmented for validation. Two clinical examples are presented.

Artifacts↗
PubMed1996

ROC methods for evaluation of fMRI techniques.

Receiver operating characteristic (ROC) methods provide a standardized and statistically meaningful means for comparing signal-detection accuracy. A brief overview of ROC methods is presented. Example applications include a comparison of four different postprocessing algorithms operating on simulated fMRI time-course data sets and on human null data sets to which a simulated fMR response had been added. ROC methods also were used to reanalyze one data set from a previously published work. Additional ROC methods that also may be useful for fMRI comparisons are described.

Algorithms↗
PubMed1996

Central serous chorioretinopathy in younger and older adults.

PURPOSE: The purpose of the study is to investigate the demographic characteristics and clinical findings of central serous chorioretinopathy (CSC). METHODS: This study examined a consecutive series of 130 patients with CSC seen over an 18-month period. RESULTS: The mean age of the patients when examined was 51 years, and the male-to-female ratio was 2.6:1.0. A total of 62 patients were older than 50 years of age when first examined. Although the patients shared some clinical and angiographic similarities, the older patients had a lower mean visual acuity and were more likely to have diffuse retinal pigment epitheliopathy, bilateral involvement, and secondary choroidal neovascularization than were the younger patients. With ophthalmoscopic and angiographic examination results, it was possible to differentiate CSC in older adults from choroidal neovascularization. CONCLUSION: This study expands the clinical concept of CSC. The male-to-female ratio was much lower, and the range of ages of the patients was much greater than in previous studies. Disease manifestations in older adults differed somewhat from those seen in younger adults. In older patients, CSC can be distinguished from other exudative maculopathies, particularly that of choroidal neovascularization secondary to age-related macular degeneration.

Adult↗
PubMed1996

Classification of choroidal neovascularization by digital indocyanine green videoangiography.

PURPOSE: The majority of patients with exudative maculopathy due to age-related macular degeneration present with poorly defined or occult choroidal neovascularization (CNV) that cannot be imaged adequately by fluorescein angiography. Digital indocyanine green (ICG) videoangiography is a new technique that allows enhanced imaging of these poorly defined or occult vessels. The authors studied 1000 consecutive cases of occult CNV using digital ICG angiography to describe the various types of neovascularization observed by this technique and to determine the frequency and natural history of the various lesions. MATERIALS AND METHODS: Digital ICG videoangiography was performed as described previously on 1000 consecutive eyes with occult CNV by fluorescein angiography. RESULTS: One thousand consecutive eyes with occult CNV by fluorescein angiography were imaged using digital ICG videoangiography. Three morphologic types of CNV were noted by ICG videoangiography, which included focal spots, plaques (well-defined or poorly defined), and combination lesions (in which both focal spots and plaques are noted). Combination lesions can be subdivided into marginal spots (focal spots at the edge of plaques of neovascularization), overlying spots (hot spots overlying plaques of neovascularization), or remote spots (a focal spot remote from a plaque of neovascularization). The relative frequency of these lesions was as follows: there were 283 cases (29%) of focal spots; 597 cases (61%) of plaques, consisting of 265 cases (27%) of well-defined plaques and 332 cases (34%) of poorly defined plaques; and 84 cases (8%) of combination lesions, consisting of 35 cases (3%) of marginal spots, 37 cases (4%) of overlying spots, and 12 cases (1%) of remote spots. In seven additional cases (1%), a mixture of the above lesions was noted. In 13 additional eyes (1%), no lesions were noted on the ICG angiogram. The studies of 16 eyes were unreadable or unobtainable. CONCLUSIONS: There are three types of CNV that can be observed by digital ICG videoangiography. Plaques are the most common type and have a poor natural history. Focal spots or hot spots are the next most frequently seen lesion and can potentially be treated by ICG-guided laser photocoagulation. Combination lesions, in which both focal spots and plaques are present, are rare. This study of 1000 consecutive cases of eyes with occult neovascularization that were imaged with digital ICG videoangiography serves to classify the various types of neovascularization observed by this technique. Digital ICG videoangiography is an important tool in better delineating eyes with occult CNV. Future studies are necessary to validate our findings.

Choroid↗
PubMed1996

Indocyanine green videoangiography of older patients with central serous chorioretinopathy.

PURPOSE: The authors studied the indocyanine green (ICG) videoangiography findings of central serous chorioretinopathy (CSC) in older adults. BACKGROUND: Central serous chorioretinopathy in older adults may be confused with the exudative forms of age-related macular degeneration (AMD) because the two entities may have similar ophthalmoscopic and fluorescein angiographic findings. Because of its enhanced ability to image the choroidal circulation, ICG videoangiography has been used to describe certain choroidal vascular abnormalities in young adults with CSC, as well as older patients with choroidal neovascularization (CNV). The ICG videoangiography findings in CSC in older adults is largely unknown. METHODS: The authors performed ICG videoangiography on 36 patients aged 50 years or older with CSC to characterize their findings. RESULTS: The ICG videoangiography findings of the patients were consistent, revealing choroidal vascular hyperpermeability manifested by areas of hyperfluorescence that were first seen in the midphase of the angiogram. In the later phases of the angiogram, there were dispersion of the hyperfluorescence and a distinctive silhouetting of the larger choroidal vessels. CONCLUSIONS: Older patients with CSC have a unique temporal and topographic pattern of hyperpermeability that can help establish the proper diagnosis.

Aged↗
PubMed1995

3D localized 2D NMR spectroscopy on an MRI scanner.

Three-dimensionally localized versions of several two-dimensional NMR sequences have been implemented on a 1.5 T whole-body MRI/MRS scanner. In addition to the localization of voxels, the slice-selective RF pulses were also used for refocusing/transfer of various coherences in the 2D NMR sequences. Initial phantom and in vivo human studies are presented here. The sequences were localized versions of 2D J-resolved, 2D zero-quantum, 2D double-quantum, zero-quantum-filtered COSY and SECSY, and double-quantum-filtered COSY and SECSY. Two-dimensional plots for the J-resolved and multiple-quantum sequences are presented for a phantom containing an aqueous solution of 10 mM alanine. Sensitivity of different multiple-quantum-coherence orders to B0 inhomogeneity is discussed. Localized double-quantum-filtered COSY of a phantom containing physiological concentrations of several metabolites also is presented to demonstrate the feasibility of performing this technique within time limits reasonable for human comfort. The first-reported 2D J-resolved 1H in vivo MR spectrum localized in three dimensions in presented here, acquired predominantly from the cerebral white matter of a healthy volunteer and demonstrating the use of localized 2D NMR techniques in vivo.

Alanine↗
PubMed1995

Localized 2D J-resolved 1H MR spectroscopy: strong coupling effects in vitro and in vivo.

A two-dimensional (2D) J-resolved MR spectroscopy sequence (2D J-PRESS), fully localized in three dimensions, has been implemented on a whole-body MR scanner. A modified PRESS sequence with [90 degrees-180 degrees-t1/2-180 degrees-t1/2-acquisition] was used for voxel localization. An incremental delay (t1/2) was added to the intervals before and after the last slice-selective 180 degree RF pulse to monitor the J-evolution in a localized 2D MR spectrum. Spectra were recorded with phantoms containing common cerebral metabolites--alanine, N-acetyl aspartate, glutamine, glutamate, taurine, myo-inositol, glucose, aspartate, GABA, and choline at 50 mM. In conformity with previously reported results, additional cross-peaks due to strong coupling were monitored in many metabolites. A brain phantom was developed to mimic the gray matter of human brain with the metabolites at physiological concentrations (0.5-12 mM). In vivo 2D J-PRESS spectra (n = 18) of healthy human brain were in conformity with those recorded from the brain phantom.

Alanine↗
PubMed1995

Choroidal neovascularization in second eyes of patients with unilateral exudative age-related macular degeneration.

PURPOSE: To evaluate patients with unilateral occult choroidal neovascularization (CNV) secondary to age-related macular degeneration (AMD) for the nature of the neovascularization which develops in the fellow eyes. METHODS: Patients with newly diagnosed unilateral occult CNV were followed prospectively for the development of CNV in the fellow eye. Patients were classified based on the type of occult CNV in the first eye: (1) those with associated serous pigment epithelial detachment (serous PED) and (2) those without. Demographic and clinical data, including the type of CNV in the second eyes, were compared. RESULTS: Choroidal neovascularization developed in 115 patients in the second eye. Fifty-six patients had occult CNV with a serous PED (also termed vascularized PED) in the first eye, and 59 patients had occult CNV without serous PED. The two groups did not differ significantly in the demographic and the clinical features evaluated. Well-delineated (or classic) CNV developed in the fellow eye of one patient in each group. Of the remaining 55 patients with vascularized PED in the first eye, the same type of occult CNV developed in 48 (87%) patients in the second eye. Of 58 (84%) patients in the second group, the same type of occult CNV developed in the second eye of 49 patients. This symmetric distribution of type of CNV between eyes is highly significant (P < 0.001). CONCLUSIONS: Eyes with occult CNV secondary to AMD can be classified by the presence or absence of an associated serous PED. Patients with unilateral occult CNV have a significant risk of occult CNV developing in the second eye, and the type of occult disease in the first eye is highly predictive of the type of neovascularized disease in the second eye. These findings are important with respect to natural history, and possibly to the treatment response and visual prognosis of patients with neovascularized AMD.

Aged↗
PubMed1994

A pilot study of indocyanine green videoangiography-guided laser photocoagulation of occult choroidal neovascularization in age-related macular degeneration.

PURPOSE: To evaluate the use of digital indocyanine green videoangiography in patients with clinical and fluorescein angiographic evidence of "occult" choroidal neovascularization in age-related macular degeneration and to investigate indocyanine green videoangiography-guided laser photocoagulation as a therapeutic approach. METHODS: Three hundred forty-seven consecutive patients with exudative age-related macular degeneration and symptoms and clinical manifestations of occult choroidal neovascularization were studied with indocyanine green videoangiography. Patients were selected for laser treatment, using conventional guidelines, when indocyanine green videoangiography demonstrated a well-delineated area of hyperfluorescence, presumed to be a focal area of choroidal neovascularization. RESULTS: Seventy-nine (23%) of 347 eyes were found to have a localized and definable lesion that was potentially amenable to laser photocoagulation therapy; 44 (56%) of these 79 treated eyes had complete resolution of their exudative manifestations. Visual acuity improvement was noted in 10 (13%) of 79 eyes, and stabilization of vision achieved in 42 eyes (53%). CONCLUSION: Laser photocoagulation treatment guided by indocyanine green videoangiography was shown to produce promising anatomical and visual improvement in a small number of patients with occult choroidal neovascularization secondary to age-related macular degeneration. This pilot study warrants further research to investigate the efficacy and safety of this form of treatment.

Aged↗
PubMed1994

A pilot study of digital indocyanine green videoangiography for recurrent occult choroidal neovascularization in age-related macular degeneration.

PURPOSE: Digital indocyanine green videoangiography (ICG-V) was used to study recurrent choroidal neovascularization (CNV) in patients with the clinical and fluorescein angiographic findings indicative of ill-defined, or recurrent occult, CNV (RO-CNV). The use of ICG-V-guided laser caphotocoagulation as an alternative form of treatment was also investigated when a well-delineated area of CNV was imaged with this technique. METHODS: A consecutive series of 66 patients were studied who presented with exudative age-related macular degeneration and symptoms and clinical manifestations of recurrent CNV in which fluorescein angiography did not reveal classic, or well-defined, neovascularization. Patients were selected for laser treatment based on conventional guidelines if ICG-V imaged a well-delineated area of recurrent CNV. RESULTS: Indocyanine green videoangiography showed late staining that was consistent with recurrent CNV in 64 (97%) of these 66 patients with RO-CNV. Twenty-nine (44%) of the 66 were eligible for laser treatment, and 18 (62%) of these 29 patients experienced successful anatomic and visual results, which were defined as resolution of the exudative manifestations and improvement or stabilization (+/- 1 line on a Snellen chart) of vision. CONCLUSIONS: This pilot study suggests that ICG-V is of value in imaging patients with RO-CNV after laser photocoagulation for CNV secondary to age-related macular degeneration. Laser treatment of RO-CNV with ICG-V guidance may be successful both anatomically and functionally in a promising number of these otherwise untreatable cases. Further studies are necessary to validate these preliminary findings.

Aged↗