Joint sparse representation of brain activity patterns in multi-task fMRI data.

A single-task functional magnetic resonance imaging (fMRI) experiment may only partially highlight alterations to functional brain networks affected by a particular disorder. Multivariate analysis across multiple fMRI tasks may increase the sensitivity of fMRI-based diagnosis. Prior research using multi-task analysis in fMRI, such as those that use joint independent component analysis (jICA), has mainly assumed that brain activity patterns evoked by different tasks are independent. This may not be valid in practice. Here, we use sparsity, which is a natural characteristic of fMRI data in the spatial domain, and propose a joint sparse representation analysis (jSRA) method to identify common information across different functional subtraction (contrast) images in data from a multi-task fMRI experiment. Sparse representation methods do not require independence, or that the brain activity patterns be nonoverlapping. We use functional subtraction images within the joint sparse representation analysis to generate joint activation sources and their corresponding sparse modulation profiles. We evaluate the use of sparse representation analysis to capture individual differences with simulated fMRI data and with experimental fMRI data. The experimental fMRI data was acquired from 16 young (age: 19-26) and 16 older (age: 57-73) adults obtained from multiple speech comprehension tasks within subjects, where an independent measure (namely, age in years) can be used to differentiate between groups. Simulation results show that this method yields greater sensitivity, precision, and higher Jaccard indexes (which measures similarity and diversity of the true and estimated brain activation sources) than does the jICA method. Moreover, superiority of the jSRA method in capturing individual differences was successfully demonstrated using experimental fMRI data.

Classification of individuals based on sparse representation of brain cognitive patterns: a functional MRI study.

Many neurological disorders can change patterns of brain activity observed in functional imaging studies. These functional differences may be useful for classification of individuals into diagnostic categories. However, due to the high dimensionality of the input feature space and small set of subjects that are usually available, classification based on fMRI data is not trivial. Here, we evaluate the use of a Sparse Representation Analysis method within a Fisher Linear Discriminant (FLD) classification method, taking functional patterns characteristic of different cognitive tasks as the data input. As a test dataset, with a clear 'gold-standard' classification, we attempt to classify individuals as young, or older, based only on functional activation patterns in a speech listening task. Thirty two young (age: 19-26) and older (age: 57-73) adults (16 each) were scanned while listening to noise and to sentences degraded with noise, half of which contained meaningful context that could be used to enhance intelligibility. Different functional contrast images were used within K-SVD to generate basis activation sources and their corresponding sparse modulation profiles. Sparse modulation profiles were used in a FLD framework to classify individuals into the young and older categories. The results demonstrate the feasibility of the general approach, and confirm the potential applicability of the proposed method for real-world diagnostic problems.

Latissimus dorsi free flap for sacral wound closure: the world's longest vein grafts for free tissue transfer.

In 1983, Salibian et al. reported the use of a two-stage latissimus dorsi free tissue transfer to cover a sacral radiation ulcer using 28-centimeter thoracodorsal interposition vein grafts. In 1985, Nahai and Hagerty reported a similar case in which the procedure was performed in one stage with 25-centimeter vein grafts. We present a case in which a large sacral osteoradionecrosis ulcer is closed using this one-stage technique with 46-centimeter vein grafts, the longest ever reported for free tissue transfer.

First web space release with the dorsal hand rotation flap: closing the donor site.

Release of first web space contractures with the dorsal hand rotation flap depends on the mobilization of relatively large areas of skin. Fortunately, the dorsum of the hand has sufficient laxity to accommodate such substantial flaps. Closure of the resultant donor site may be challenging. Skin grafting over extensor paratenon requires prolonged immobilization and is often cosmetically unsatisfactory. The purpose of this report is to demonstrate various methods of closing these donor sites without skin grafting. We report a series of first web space contractures, all of which we released using the dorsal hand rotation flap. In closing the donor sites, we demonstrate the utility of advancing local tissues as well as bilobed rotational flaps. Our series shows that skin grafting is not necessary in the majority of patients. We expect that our results will encourage the use of the dorsal hand rotation flap because it yields both functionally and cosmetically acceptable results.

A rehabilitation nursing orientation program.

At Carondelet St. Mary's Hospital and Health Center in Tucson, AZ, a comprehensive orientation program for rehabilitation nursing in conjunction with a preceptor-guided orientation process was developed. This orientation program has provided a base of knowledge for entry-level staff and is an important source of review and reference for experienced rehabilitation nurses.

Changing role of splenectomy for hematologic disease.

In the past decade the development of accurate imaging and the evolution of the medical management of hematologic diseases has led to changes in the indications for splenectomy for these disorders. To assess the impact of these developments, a multi-institutional, retrospective review was undertaken. One hundred fifty-six splenectomies were performed for hematologic disorders between July 1, 1979 and June 30, 1991. Patients were divided into 2 groups: those undergoing splenectomy from 1979-1985 (Period I), and those undergoing splenectomy from 1986-1991 (Period II). Diseases were classified into 3 groups: cytopenic/anemic conditions, symptomatic splenomegaly, and Hodgkin's disease. Data was compared between the two periods using chi-square analysis. More splenectomies were performed for hematologic disorders during Period II than Period I (P < .005). This increase is secondary to a rise in the number of splenectomies performed for cytopenia/anemia during Period II. In contrast, splenectomies for splenomegaly and Hodgkin's disease decreased during Period II (P < .005 and < .05). More Hodgkin's patients were upstaged on the basis of positive laparotomy findings in Period II, compared to Period I (40% versus 10%, P = .01). Surgeons are now performing more splenectomies for cytopenic/anemic diseases, and fewer for splenomegaly and Hodgkin's disease. These results are consistent with recent trends: (1) earlier splenectomy in patients with cytopenia/anemia; (2) earlier medical intervention in infiltrative splenic disorders; and (3) more reliance on radiologic staging in Hodgkin's disease and widespread use of combination chemotherapy, leaving surgical staging for those cases in which treatment would be changed by laparotomy findings.

Colorectal carcinoma in young patients.

Utilizing Tumor Registry records dating from 1935 to 1988, 50 patients diagnosed with colorectal adenocarcinoma at the age of 40 years or younger were retrospectively studied with respect to sex, race, family history, delay in diagnosis, primary tumor location, tumor differentiation, mucin production, stage at presentation, and the effect of these factors on 5-year survival. This younger group of patients was compared to a computer-generated, randomly selected group of 50 patients 40 years of age or older. There was no difference with respect to sex, racial distribution, family history, symptoms at presentation, or expediency of physician diagnosis between the two groups. Younger patients waited significantly longer to seek medical attention than did their older counterparts. However, those patients who delayed presentation had no higher incidence of advanced disease than those patients who presented earlier. Younger patients had a higher incidence of poorly differentiated, advanced, right-sided tumors. This is in contrast to a predominance of well-differentiated, less advanced, rectosigmoid lesions in the older patients. There was no age-related difference in the incidence of mucin-producing tumors. Overall 5-year survival was 75% in older patients, in contrast to only 51% in younger patients (P = 0.01). We conclude in this study that it is advanced stage at presentation that is the most significant prognostic indicator in patients of all ages. The high incidence of poorly differentiated, right-sided tumors is responsible for the majority of young patients presenting with advanced disease, resulting in their poorer prognosis.

Attenuation of permeability lung injury after phorbol myristate acetate by verapamil and OKY-046.

Phorbol myristate acetate (PMA), which produces an experimental model of acute lung injury similar to the adult respiratory distress syndrome, was studied in isolated dog lung lobes perfused at constant pressure in Zone 3 conditions. The effect of 25 to 50 micrograms PMA on pulmonary vascular permeability and resistance was observed in 4 groups of lungs: Group 1, perfused with a plasma/dextran solution; Group 2, perfused with blood; Group 3, blood-perfused and pretreated with verapamil (a calcium channel blocker); and Group 4, blood-perfused and pretreated with OKY-046 (a thromboxane synthetase inhibitor). Permeability changes were assessed by determining capillary filtration coefficient (Kf), isogravimetric capillary pressure (Pci), and in blood-perfused lungs, the protein reflection coefficient (sigma d). An increase in Kf, a decrease in Pci, and a decrease in sigma d, all indicative of an increase in vascular permeability, occurred 1 h after PMA in blood-perfused but not in plasma/dextran-perfused lungs. An increase in pulmonary vascular resistance occurred in both blood- and plasma/dextran-perfused lungs. Verapamil (2 X 10(-5) M) and OKY-046 (7 X 10(-4) M) pretreatment in blood-perfused lungs essentially blocked the PMA-induced change in permeability and significantly attenuated the increased vascular resistance. Total leukocyte and platelet counts fell in all blood-perfused lungs, whether pretreated or not. We conclude that cellular components of blood (platelets and/or leukocytes) are required to produce the permeability injury but not the pulmonary vasoconstriction and that the injury can be attenuated by either a calcium channel blocker or a specific thromboxane synthetase inhibitor. The left ventricular volume change caused by increasing right ventricular volume was measured at normal and elevated pericardial pressures.