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Biomedical subjects

C F Beckmann

Publications and source records attributed to C F Beckmann.

At least 19 recordsLinked to original sources
PubMed2006

Consistent resting-state networks across healthy subjects.

Functional MRI (fMRI) can be applied to study the functional connectivity of the human brain. It has been suggested that fluctuations in the blood oxygenation level-dependent (BOLD) signal during rest reflect the neuronal baseline activity of the brain, representing the state of the human brain in the absence of goal-directed neuronal action and external input, and that these slow fluctuations correspond to functionally relevant resting-state networks. Several studies on resting fMRI have been conducted, reporting an apparent similarity between the identified patterns. The spatial consistency of these resting patterns, however, has not yet been evaluated and quantified. In this study, we apply a data analysis approach called tensor probabilistic independent component analysis to resting-state fMRI data to find coherencies that are consistent across subjects and sessions. We characterize and quantify the consistency of these effects by using a bootstrapping approach, and we estimate the BOLD amplitude modulation as well as the voxel-wise cross-subject variation. The analysis found 10 patterns with potential functional relevance, consisting of regions known to be involved in motor function, visual processing, executive functioning, auditory processing, memory, and the so-called default-mode network, each with BOLD signal changes up to 3%. In general, areas with a high mean percentage BOLD signal are consistent and show the least variation around the mean. These findings show that the baseline activity of the brain is consistent across subjects exhibiting significant temporal dynamics, with percentage BOLD signal change comparable with the signal changes found in task-related experiments.

Brain↗
PubMed2005

fMRI resting state networks define distinct modes of long-distance interactions in the human brain.

Functional magnetic resonance imaging (fMRI) studies of the human brain have suggested that low-frequency fluctuations in resting fMRI data collected using blood oxygen level dependent (BOLD) contrast correspond to functionally relevant resting state networks (RSNs). Whether the fluctuations of resting fMRI signal in RSNs are a direct consequence of neocortical neuronal activity or are low-frequency artifacts due to other physiological processes (e.g., autonomically driven fluctuations in cerebral blood flow) is uncertain. In order to investigate further these fluctuations, we have characterized their spatial and temporal properties using probabilistic independent component analysis (PICA), a robust approach to RSN identification. Here, we provide evidence that: i. RSNs are not caused by signal artifacts due to low sampling rate (aliasing); ii. they are localized primarily to the cerebral cortex; iii. similar RSNs also can be identified in perfusion fMRI data; and iv. at least 5 distinct RSN patterns are reproducible across different subjects. The RSNs appear to reflect "default" interactions related to functional networks related to those recruited by specific types of cognitive processes. RSNs are a major source of non-modeled signal in BOLD fMRI data, so a full understanding of their dynamics will improve the interpretation of functional brain imaging studies more generally. Because RSNs reflect interactions in cognitively relevant functional networks, they offer a new approach to the characterization of state changes with pathology and the effects of drugs.

Adult↗
PubMed2005

Removal of FMRI environment artifacts from EEG data using optimal basis sets.

The combination of functional magnetic resonance imaging (FMRI) and electroencephalography (EEG) has received much recent attention, since it potentially offers a new tool for neuroscientists that makes simultaneous use of the strengths of the two modalities. However, EEG data collected in such experiments suffer from two kinds of artifact. First, gradient artifacts are caused by the switching of magnetic gradients during FMRI. Second, ballistocardiographic (BCG) artifacts related to cardiac activities further contaminate the EEG data. Here we present new methods to remove both kinds of artifact. The methods are based primarily on the idea that temporal variations in the artifacts can be captured by performing temporal principal component analysis (PCA), which leads to the identification of a set of basis functions which describe the temporal variations in the artifacts. These basis functions are then fitted to, and subtracted from, EEG data to produce artifact-free results. In addition, we also describe a robust algorithm for the accurate detection of heart beat peaks from poor quality electrocardiographic (ECG) data that are collected for the purpose of BCG artifact removal. The methods are tested and are shown to give superior results to existing methods. The methods also demonstrate the feasibility of simultaneous EEG/FMRI experiments using the relatively low EEG sampling frequency of 2048 Hz.

Algorithms↗
PubMed2005

Tensorial extensions of independent component analysis for multisubject FMRI analysis.

We discuss model-free analysis of multisubject or multisession FMRI data by extending the single-session probabilistic independent component analysis model (PICA; Beckmann and Smith, 2004. IEEE Trans. on Medical Imaging, 23 (2) 137-152) to higher dimensions. This results in a three-way decomposition that represents the different signals and artefacts present in the data in terms of their temporal, spatial, and subject-dependent variations. The technique is derived from and compared with parallel factor analysis (PARAFAC; Harshman and Lundy, 1984. In Research methods for multimode data analysis, chapter 5, pages 122-215. Praeger, New York). Using simulated data as well as data from multisession and multisubject FMRI studies we demonstrate that the tensor PICA approach is able to efficiently and accurately extract signals of interest in the spatial, temporal, and subject/session domain. The final decompositions improve upon PARAFAC results in terms of greater accuracy, reduced interference between the different estimated sources (reduced cross-talk), robustness (against deviations of the data from modeling assumptions and against overfitting), and computational speed. On real FMRI 'activation' data, the tensor PICA approach is able to extract plausible activation maps, time courses, and session/subject modes as well as provide a rich description of additional processes of interest such as image artefacts or secondary activation patterns. The resulting data decomposition gives simple and useful representations of multisubject/multisession FMRI data that can aid the interpretation and optimization of group FMRI studies beyond what can be achieved using model-based analysis techniques.

Artifacts↗
PubMed2001

Exacerbation of pain by anxiety is associated with activity in a hippocampal network.

It is common clinical experience that anxiety about pain can exacerbate the pain sensation. Using event-related functional magnetic resonance imaging (FMRI), we compared activation responses to noxious thermal stimulation while perceived pain intensity was manipulated by changes in either physical intensity or induced anxiety. One visual signal, which reliably predicted noxious stimulation of moderate intensity, came to evoke low anxiety about the impending pain. Another visual signal was followed by the same, moderate-intensity stimulation on most of the trials, but occasionally by discriminably stronger noxious stimuli, and came to evoke higher anxiety. We found that the entorhinal cortex of the hippocampal formation responded differentially to identical noxious stimuli, dependent on whether the perceived pain intensity was enhanced by pain-relevant anxiety. During this emotional pain modulation, entorhinal responses predicted activity in closely connected, affective (perigenual cingulate), and intensity coding (mid-insula) areas. Our finding suggests that accurate preparatory information during medical and dental procedures alleviates pain by disengaging the hippocampus. It supports the proposal that during anxiety, the hippocampal formation amplifies aversive events to prime behavioral responses that are adaptive to the worst possible outcome.

Adult↗
PubMed1994

Surgery and percutaneous angioplasty in the management of renovascular hypertension.

Unfortunately, no randomized trials have compared PTRA for renovascular hypertension with surgical or medical treatment. PTRA appears to be a safe and relatively simple procedure with complication rates lower than those of operation. The outcome of renal angioplasty depends on the type of stenosis. In all published series, the cure rates for fibromuscular disease are significantly higher than for atherosclerotic disease, and PTRA appears to be the procedure of choice in the treatment of hypertension in patients with fibromuscular disease. The role of renal angioplasty in patients with renovascular hypertension due to atherosclerotic diseases is uncertain. Most large published series describing the success of angioplasty in patients with atherosclerotic lesions have been highly selective, primarily including patients with focal stenotic lesions. Despite this selectivity, the cure rate has been only 19%. In completely unselected patients, atherosclerotic lesions are associated with a very high rate of technical failure, possibly as high as 60%. From the data available, focal isolated stenotic lesions of the renal artery due to atherosclerotic disease can be treated with a reasonable rate of success. The success rate in patients with bilateral disease, osteal stenosis, or total occlusion of the renal arteries appears to be very limited. In these patients, angioplasty should be attempted only when a surgical contraindication exists.

Angioplasty, Balloon↗
PubMed1993

Celiac plexus block: efficacy and safety of the anterior approach.

OBJECTIVE: A celiac plexus block performed via an anterior approach offers several potential advantages over a posterior approach, including shorter procedure time, less discomfort to the patient, and less risk of neurologic complications. We evaluated the use of an anterior approach to determine its efficacy and safety. MATERIALS AND METHODS: The procedure was performed in 17 consecutive patients referred for treatment of chronic abdominal pain thought clinically to be of celiac ganglion origin. A subjective evaluation of the degree of pain relief was obtained by retrospectively reviewing the notes of physicians and nurses. The degree of pain relief was graded from 1+ (no change) to 4+ (complete relief). An objective evaluation was also obtained by comparing average daily in-hospital analgesic usage before and after the procedure. RESULTS: Ethanol injection was performed successfully in 13 of 14 patients with pancreatic carcinoma and in two of three patients with other causes of pain. Eleven (79%) of the 14 patients with pancreatic carcinoma had some (2+ or greater) relief of pain, and eight of these patients had considerable or complete (3+ or 4+) relief of pain. Of the 10 patients with pancreatic carcinoma for whom complete data on the use of pain medication were available, the mean daily analgesic usage declined from 17% to 100% (mean, 58%) relative to preprocedure doses. Complications, all relatively mild, were encountered in only three of 17 patients, and no patient had neurologic symptoms or long-term sequelae. CONCLUSION: The anterior approach to a celiac plexus block is a safe and effective means of pain control in patients with pancreatic carcinoma. It offers several potential advantages to the posterior approach, and should be considered for all patients with pain caused by pancreatic carcinoma that is refractory to pain medication.

Abdominal Pain↗
PubMed1991

Percutaneous transluminal angioplasty of the peripheral arteries.

Balloon angioplasty is being used with increasing frequency in the management of patients with peripheral vascular disease. Balloon angioplasty is useful alone and as an adjunct to conventional surgery. Angioplasty is relatively inexpensive, is performed under local anesthesia, and is associated with few complications. Technical success depends on the morphologic characteristics of a lesion and on the skill and experience of the operator. Long-term patency is more likely with larger vessels and short-segment stenosis. Careful selection of patients is vital and depends on cooperation between the vascular consultant and radiologist. PCTA is most often used at the extremes of clinical severity. Most complications are minor and do not require surgical treatment. The main disadvantage is the high incidence of restenosis. Angioplasty can be repeated easily, however, and its use does not preclude later surgery.

Aged↗
PubMed1989

Dilation of benign ureteral strictures.

Balloon dilation of benign ureteral strictures was performed in 33 patients in a percutaneous antegrade (25 patients) or retrograde (eight patients) fashion followed by placement of a 7-10-F stent for 4-8 weeks. Dilation was possible in all patients. During the follow-up period of 1-40 months the overall success rate was 76%. The success rate in primary strictures at the ureteropelvic junction was 86%. Among 10 patients with postsurgical (pyeloplasty, ureteroenterostomy, and ureteroneocystostomy) anastomotic strictures, dilation was successful in 50%. Of six patients with postoperative strictures after calculus removal by ureterolithotomy or pyelolithotomy, four (67%) had good results. All patients with iatrogenic postureteroscopic strictures (five patients) or accidental ureteral ligation (two patients) had a normal pyelogram at follow-up. The success rate in acute strictures of less than 3 months duration was 88%; in strictures of more than 3 months duration the success rate was 67%. Cause, length, and duration of stricture are the prime determinants of success. Early intervention with balloon dilation is suggested.

Adolescent↗
PubMed1988

Percutaneous balloon dilatation in treatment of infected pyelocaliceal diverticulum.

Abscess formation is a known complication of pyelocaliceal diverticulum. Although successful management of stones complicating pyelocaliceal diverticulum has been described utilizing percutaneous techniques, this is the first report to our knowledge of a percutaneous technique that simultaneously manages an acute abscess and provides for ablation of the diverticular cavity thus preventing future recurrences. The method involves placement of single or multiple stents spanning the diverticulum and the collecting system proper following percutaneous dilatation of the narrow isthmus that usually provides the communication with the main collecting system. The procedure offers an economical and tissue-sparing approach, which obviates the need for major abdominal or retroperitoneal operation.

Abscess↗
PubMed1988

Focal renal artery stenosis caused by fibromuscular dysplasia: treatment by percutaneous transluminal angioplasty.

We performed percutaneous transluminal angioplasty of the renal artery in five hypertensive patients with focal renal artery stenoses caused by fibromuscular dysplasia. In four patients, the hypertension decreased or resolved. In all patients, the stenoses displayed considerable resistance to dilatation, requiring maximum inflation of the angioplasty balloon with 10 atm of pressure (10.1 x 10(5) Pa). In two patients, the stenoses were extremely firm with a persistent waist noted in the maximally inflated balloon. One of these patients was left with a residual 40-50% stenosis after initial angioplasty, and a second attempt at dilatation after restenosis was also unsuccessful. This patient's blood pressure did not improve. When the results of our experience in these five patients were combined with 22 cases reported in the literature, we found that 23 (85%) of the 27 patients with focal renal artery stenoses caused by fibromuscular dysplasia had a decrease in blood pressure after percutaneous dilatation. Percutaneous transluminal angioplasty is an effective treatment for patients with renovascular hypertension caused by focal renal artery stenoses resulting from fibromuscular dysplasia.

Adolescent↗
PubMed1988

Complications of extracorporeal shock-wave lithotripsy and percutaneous nephrolithotomy.

The serious complications of ESWL associated with the Dornier HM-3 lithotripter are well known. It is incumbent on operators to recognize these problems and, when possible, to anticipate them and utilize a treatment plan that will minimize their occurrence. Appropriate use of percutaneous techniques, double-J stents, and ureteroscopy and aggressive use of antibiotics can minimize the serious complications associated with ESWL. It will be of interest to see whether newer generation lithotripters will produce an incidence of complications similar to that of the Dornier HM-3 or whether unique problems will call for new strategies. We have described the clinically important complications of ESWL and percutaneous nephrolithotomy. At this time, these modalities should be looked on as complementary procedures. Each has specific indications, and, when used appropriately, often in concert, both will provide safe, effective treatment for patients with renal calculus disease.

Anesthesia↗
PubMed1987

Secondary ureteropelvic junction stricture: percutaneous dilation.

Percutaneous incision and balloon catheter dilation of the ureteropelvic junction (UPJ) was performed in nine patients with secondary UPJ strictures. In all patients, the UPJ was successfully dilated, and no immediate complications were encountered. After a postoperative follow-up period of 4-27 months, six patients showed marked improvement on excretory urograms. Three patients had recurrent obstruction after 3-18 months. The 66% success rate of percutaneous balloon dilation with or without endopyelotomy compares favorably with the success rate of open surgical repair of secondary UPJ strictures in adults.

Adult↗
PubMed1986

Upper and midureteral calculi: percutaneous extraction with an occlusion balloon catheter.

In 44 patients with one or more calculi in the upper two-thirds of the ureter, single-stage percutaneous nephrolithotomy was performed through a middle or upper calyceal nephrostomy after cystoscopic placement of an occlusion balloon catheter distal to the calculus; in 42, the procedure was successful. The occlusion balloon catheter permitted retrograde opacification of all systems for enhanced renal puncture. In the last 30 patients an attempt was made either to push the calculus upward mechanically or to flush it upward into the renal pelvis with carbon dioxide or dilute contrast material. This was successful in 24 of these patients. Prior overnight occlusion of the ureter by means of ureteral dilatation further facilitates dislodgment of the calculus, which was successful in 12 of 13 patients.

Catheterization↗
PubMed1985

Use of retrograde occlusion balloon catheters in percutaneous removal of renal calculi.

The best results in percutaneous renal calculus removal are in patients with solitary pelvic stones and dilated collecting systems. Calyceal and/or infundibular calculi and ureteral calculi constitute more complex problems and are less successfully removed. Placement failure of the nephrostomy tube, and inability to gain access to calyceal calculi, and to engage impacted stones are the usual causes for unsuccessful procedures. To try to improve overall success we inserted occlusion balloon catheters prior to nephrostomy insertion in 60 of 71 patients. In a select group of 23 patients with a small renal pelvis and large calculi or infundibular calculi or patients with ureteral calculi, overnight application of 20 cm of hydrostatic pressure through the ureteric catheter led to marked dilatation in all instances. In all other patients the occlusion balloon catheter was placed immediately prior to the definitive nephrostolithotomy procedure. These ureteral catheters allow for better opacification and for dilatation of a small collecting system thereby facilitating the placement of the nephrostomy tube. They permit manipulation of calyceal and especially ureteral calculi. Placement of ureteral occlusion catheters is a safe adjunct to nephrostolithotomies and, in our experience, resulted in increased overall success.

Catheterization↗
PubMed1985

Management of cancer of the bile duct.

Tumors of the bile duct are uncommon. Most patients will present with a syndrome of obstructive jaundice, but in a few patients the tumor can mimic benign disease of the biliary tract. Cholangiography continues to be the basis of diagnosis and gives important information for a decision on therapy. Histologic diagnosis is helpful when available, although frequently difficult to obtain and not always possible. The overall prognosis for these patients remains poor. Currently, a multidisciplinary approach is required to select for each patient the best therapy with the lowest morbidity and mortality. It should include a surgeon, gastrointestinal endoscopist, interventional radiologist, and radiotherapist. The prognosis for a patient appears to be related to the tumor's location, resectability, and, in our experience, differentiation. Therapy should be tailored to each patient based on location of the tumor, extent of the disease, condition of the patient, expertise available in each institution, and morbidity and mortality associated with each procedure. At the Lahey Clinic, the resectability rate for bile duct tumor is currently 25 per cent. Resection is more frequently possible for tumor of the distal bile duct and can result in a five-year survival rate of up to 30 per cent. For patients with unresectable distal tumor at the time of operation, a proximal hepaticojejunostomy is the palliative procedure of choice. If nonresectability of a distal tumor is determined before operation, the decision to proceed with an endoscopic placement of a stent versus surgical hepaticojejunostomy or placement of a T tube needs to be an individual one. Although five-year survival for tumor of the proximal bile duct is anecdotal, those patients who undergo resection have the longest survival and may have better palliation than those who undergo strictly palliative, nonresective procedures. To warrant exploration for resection of tumor of the proximal bile duct, careful patient selection is required, and the morbidity and mortality of operation must be minimized. An increasing role of percutaneous transhepatic techniques of decompression of the biliary tract is expected as they improve and gain wider acceptance. They are the procedures of choice in very high-risk surgical patients or in patients determined before operation to have unresectable disease. Improvement in the survival of patients with cancer of the bile duct probably depends on development of better adjuvant therapy, such as new techniques of radiation therapy and new modalities of chemotherapy, in association with surgery or with a percutaneous or endoscopic intubation technique.

Bile Duct Neoplasms↗
PubMed1984

Renal infarction: computerized tomographic appearance with angiographic correlation.

The clinical diagnosis of renal infarction can be difficult to make and the computerized tomographic appearance can be misleading at times. The different computerized tomographic images can be explained angiographically by the arrangement of the vascular planes of the kidney and by the particular branches that are occluded. We report 2 cases with different angiographic and computerized tomographic appearance to document this correlation.

Aged↗