Automatic prediction of infarct growth in acute ischemic stroke from MR apparent diffusion coefficient maps

RATIONALE AND OBJECTIVES: We introduce a new approach to the prediction of final infarct growth in human acute ischemic stroke based on image analysis of the apparent diffusion coefficient (ADC) maps obtained from magnetic resonance imaging. Evidence from multiple previous studies indicate that ADC maps are likely to reveal brain regions belonging to the ischemic penumbra, that is, areas that may be at risk of infarction in the few hours following stroke onset. MATERIALS AND METHODS: In a context where "time is brain," and contrarily to the alternative-and still-debated-perfusion-diffusion weighted image (PWI/DWI) mismatch approach, the DWI magnetic resonance sequences are standardized, fast to acquire, and do not necessitate injection of a contrast agent. The image analysis approach presented here consists of the segmentation of the ischemic penumbra using a fast three-dimensional region-growing technique that mimics the growth of the infarct lesion during acute stroke. RESULTS: The method was evaluated with both numerical simulations and on two groups of 20 ischemic stroke patients (40 patients total). The first group of patient data was used to adjust the parameters of the model ruling the region-growing procedure. The second group of patient data was dedicated to evaluation purposes only, with no subsequent adjustment of the free parameters of the image-analysis procedure. Results indicate that the predicted final infarct volumes are significantly correlated with the true final lesion volumes as revealed by follow-up measurements from DWI sequences. CONCLUSION: The DWI-ADC mismatch method is an encouraging fast alternative to the PWI-DWI mismatch approach to evaluate the likeliness of infarct growth during the acute stage of ischemic stroke.     

Characterization of hepatocellular carcinoma and colorectal liver metastasis by means of perfusion MRI

PURPOSE: To characterize and compare hepatocellular carcinoma and liver metastases of colorectal metastatic cancer (CMC) by means of quantitative liver perfusion MRI. MATERIALS AND METHODS: Liver perfusion was assessed in 26 HCC and CMC patients (50 nodules) by means of contrast-enhanced MRI. Six perfusion parameters-hepatic perfusion index (HPI), mean transit time (MTT), distribution volume (DV), total blood flow (F(T)), arterial blood flow (F(A)), and portal blood flow (F(P))-were calculated in tumor nodules and the adjacent hepatic parenchyma. RESULTS: The values of F(T), F(A), F(P), and DV were significantly higher in the HCC than in the CMC group, whereas MTT was significantly higher in the CMC group. There was no significant difference in HPI. Arterial blood flow was higher than portal blood flow in the CMC group, while portal blood flow was slightly higher than arterial blood flow in the HCC group. CONCLUSION: The present work describes the use of dynamic MRI to quantitatively assess liver perfusion, which in the future may help studying liver cancers on the basis of their microvascular characteristics.     

Radiology resident interpretation of on-call CT pulmonary angiograms

RATIONALE AND OBJECTIVES: To evaluate the interpretation of computed tomographic pulmonary angiograms performed outside of regular reporting hours, comparing the initial interpretation by the radiology resident to the attending radiologist. MATERIALS AND METHODS: Records for 840 consecutive computed tomographic pulmonary angiograms (CTPA) performed outside of regular reporting hours at two tertiary referral centers from January 1, 2004-December 31, 2005 were reviewed. The preliminary interpretation by the on-call radiology resident was compared to the subsequent final report issued by a subspecialty trained chest radiologist. Studies were stratified as positive, negative, or equivocal for pulmonary embolus. Cases with discordant interpretations or negative CTPA were reviewed to determine impact on clinical outcome. Patients were followed up to 12 months after CTPA to document any subsequent thromboembolic event. RESULTS: Sixteen percent (131/840) of CTPAs were reported positive by the staff radiologist. There was agreement in 90% (752/840) of studies (P = .76, 95% confidence interval, 0.71-0.81) with 86% (114/133) agreement for studies interpreted as positive by residents, 95% (582/612) for studies interpreted as negative by residents, and 63% (60/95) for studies interpreted as equivocal by residents. Studies of optimal quality had higher interobserver agreement than studies of suboptimal quality (P < .0001). In-patient studies were more likely to be positive than emergency room patients (20% vs. 13%) (P = .004). No adverse clinical outcomes were attributed to discordant interpretations. CONCLUSIONS: Radiology residents provide a high level interpretation of on-call CTPA studies, achieving good concordance with the attending radiologists' assessment.     

Early mechanical failure in total knee arthroplasty

Early mechanical dysfunction of a total knee arthroplasty (TKA) is a challenging problem in terms of causality and solutions. The current strategy in our department is to perform a complete TKA revision rather than the less invasive partial procedures when a clear mechanical cause of failure has been found. In this investigation, we assessed 21 patients who underwent complete TKA revision in 2003-2004 in our institution within the first two years following the index TKA. Various clinical presentations included pain, stiffness, instability, and femoro-patellar signs. These corresponded to implant size, position, and fixation issues. The IKS knee score/function significantly increased from 47/47 to 85/78 at follow-up (six months minimum). Compared to the data in the literature, this systematic full revision seems to be a reasonable approach. This attitude takes advantage of the modularity of the implants for allowing perioperative adjustments of position, fixation, and constraint. Based on the results of our study, we propose a list of six mechanical pitfalls to be evaluated in the case of early dysfunction: frontal misalignment, sagittal overstuffing or malpositioning, axial malrotation, poor bone fixation, inappropriate constraint or ligamentous balance, and inappropriate level of the joint space.     

Changes in mass and performance in rabbit muscles after muscle damage with or without transplantation of primary satellite cells

Changes in morphology, metabolism, myosin heavy chain gene expression, and functional performances in damaged rabbit muscles with or without transplantation of primary satellite cells were investigated. For this purpose, we damaged bilaterally the fast muscle tibialis anterior (TA) with either 1.5 or 2.6 ml cardiotoxin 10(-5) M injections. Primary cultures of satellite cells were autotransplanted unilaterally 5 days after muscle degeneration. Two months postoperation, the masses of damaged TAs, with or without transplantation, were significantly larger than those of the controls. Furthermore, damaged transplanted muscles weighed significantly more than damaged muscles only. The increase in muscle mass was essentially due to increased fiber size. These results were independent of the quantity of cardiotoxin injected into the muscles. Maximal forces were similar in control and 2.6 ml damaged TAs with or without satellite cell transfer. In contrast, 1.5 ml damaged TAs showed a significant decrease in maximal forces that reached the level of controls after transplantation of satellite cells. Fatigue resistance was similar in control and 1.5 ml damaged TAs independently of satellite cell transfer. Fatigue index was significantly higher in 2.6 ml damaged muscles with or without cell transplantation. These changes could be explained in part by muscle metabolism, which shifted towards oxidative activities, and by gene expression of myosin heavy chain isoforms, which presented an increase in type IIa and a decrease in type I and IIb in all damaged muscles with or without cell transfer. Under our experimental conditions, these results show that muscle damage rather than satellite cell transplantation changes muscle metabolism, myosin heavy chain isoform gene expression, and, to a lesser extent, muscle contractile properties. In contrast, muscle weight and fiber size are increased both by muscle damage and by satellite cell transfer.     

Amniotic fluid beta-endorphin: a prognostic marker for gastroschisis?

Purpose: The aim of this work was to study amniotic fluid [beta ]-endorphin as a potential predictor for postnatal morbidity in gastroschisis. Methods: Beta-endorphin was assayed in 43 amniotic fluid samples from 13 pregnant women with fetal gastroschisis undergoing diagnostic amniocentesis or therapeutic amnioinfusion and compared with 33 controls. Within the gastroschisis group, the authors investigated the relationship between postnatal morbidity and the peak value of amniotic fluid [beta ]-endorphin (AFBE). Results: Ten AFBE values in 6 cases of gastroschisis were above the upper limit of the 95% confidence interval derived from controls. Postnatal morbidity was significantly higher when peak AFBE exceeded 10 [mu ]g/L (n = 4 pregnancies) compared with below 5 [mu ]g/L (n = 9 pregnancies), as shown by mean duration of mechanical ventilation (15.2 v 3 days; P = .01), of parenteral feeding (77 v. 18.7 days; P = .04), and of hospitalization (84 v 32.2 days; P = .04). There was no statistically significant association between postnatal morbidity markers and prenatal dilation of fetal bowel. Conclusions: The most severe cases of gastroschisis are associated with high levels of AFBE. The authors speculate that this fetal hormonal response could result from stress or pain caused by prenatal bowel damage.     

Surgical exclusion of a symptomatic circumflex coronary to right atrium fistula

Coronary artery fistulas are rare and half of them are symptomatic. Diagnosis is confirmed by echocardiography and coronarography and can be precisely located by multislice CT-scan. We report the case of a 56-year-old female patient with congestive heart failure caused by a coronaro-cardiac fistula established between the proximal circumflex coronary artery and the right atrium. Surgical exclusion of the fistula was achieved by ligation of both extremities and a running suture on the aneurysmal vessel. Follow-up at 6 months was satisfactory with an asymptomatic patient and absence of recurrence of the fistula on echocardiography.     

Methicillin-resistant Staphylococcus aureus infection in a cardiac surgical unit.

BACKGROUND: Increased antibiotic resistance of common bacteria is attributed in part to the widespread use of various antibiotic agents. Prophylactic and therapeutic antibiotic treatments are routinely used in cardiac surgical units, and it is no surprise that methicillin-resistant Staphylococcus aureus infection is becoming a major cause of surgical infections in cardiac patients. METHODS: We reviewed our experience with patients who underwent cardiac surgery and experienced infection caused by methicillin-resistant Staphylococcus aureus. Between 1992 and 2000 at the Montreal Heart Institute, 39 patients had methicillin-resistant Staphylococcus aureus surgical infections, and 13,199 patients underwent cardiac surgery. The yearly incidence of methicillin-resistant Staphylococcus aureus infection, the relative risk of acute mediastinitis and of superficial wound infections or other types of methicillin-resistant Staphylococcus aureus infection episodes, and the effect of preventive measures were analyzed. RESULTS: The annual incidence of methicillin-resistant Staphylococcus aureus acute mediastinitis decreased from 0.37% (5/1321) of cardiac patients in 1992 and 0.44% (6/1355) in 1993 to 0% between 1994 and 1997, 0.13% (2/1528) in 1999, and 0% (0/1700) in 2000. The total incidence of methicillin-resistant Staphylococcus aureus infection, including mediastinitis, superficial and deep sternal and leg wound infection, and all systemic infection episodes ranged from 0.68% of patients in 1992 and 0.96% of patients in 1993 to 0.46% of patients in 1999 and 0.53% of patients in 2000. The relative risk of severe mediastinal methicillin-resistant Staphylococcus aureus infection to all other methicillin-resistant Staphylococcus aureus infection episodes decreased from 1.65 in 1992 to 0.41 in 1999 and 0 in 2000. Beginning in 1993, all patients given a diagnosis methicillin-resistant Staphylococcus aureus infection and all nasal carriers of methicillin-resistant Staphylococcus aureus were strictly isolated on the surgical unit, and vancomycin was used as the prophylactic antibiotic agent for cardiac surgery in these patients. Moreover, since 1998, all patients admitted in the hospital were screened, and nasal carriers were isolated and treated with topical antibiotic ointment. CONCLUSION: Mediastinal and other infections caused by methicillin-resistant Staphylococcus aureus have a significant morbidity in cardiac surgical patients. After an outbreak of methicillin-resistant Staphylococcus aureus mediastinal infections, several preventive measures to control methicillin-resistant Staphylococcus aureus contamination of surgical patients were implemented (nasal screening, preventive isolation, application of mupirocin, prophylaxis with vancomycin and alcohol gels) and were effective in decreasing the incidence of methicillin-resistant Staphylococcus aureus infection and mediastinitis after cardiac surgery.     

Off-pump coronary artery bypass grafting: a case-matched comparison of hemodynamic outcome.

OBJECTIVE: The objective of this study was to assess improved myocardial protection by performing coronary artery bypass grafting (CABG) on the beating heart. A case-matched study was conducted among patients who underwent CABG either on-pump (group 1), or off-pump (group 2). METHODS: Forty-five pairs of patients, having a similar clinical profile, were selected on the basis of five variables: age, gender, body surface area, ejection fraction, extent of coronary disease. Operative risk predicted by the The Society of Thoracic Surgeons national database was 1.80+/-0.35% in group 1, and 1.89+/-0.37% in group 2 (NS). Cold blood cardioplegia and 28 degrees C cardiopulmonary bypass were used in group 1. In group 2, beating heart coronary grafting was achieved with the Octopus 1 and 2 stabilizers. The average number of distal anastomoses was 2.8+/-0.1 in group 1 and 2.3+/-0.1 in group 2 (P=0.015). RESULTS: There was no significant difference among the groups regarding the trend in cardiac index, left and right ventricular stroke work indexes, and systemic and pulmonary vascular resistance indexes. However, heart rate trend was slower in group 2 (P=0.05). Pharmacological support was required in 65% of the patients in group 1, and in 33% in group 2 (P<0.001). The total amount of Dobutamine and/or Dopamine administered during the first 48 h was 3914+/-1306 gamma/kg in group 1 and 1645+/-697 gamma/kg in group 2 (P=0.049). Release of creatine kinase MB mass isoenzyme (CK-MB mass) was markedly reduced in group 2 (P<10(-4)). CONCLUSIONS: Hemodynamic outcome following off-pump CABG is similar to on-pump CABG but the need for inotropic support is significantly reduced and CPK-MB mass release is markedly lower.     

Challenges in accessing multidisciplinary pain treatment facilities in Canada

PURPOSE: The objective of this survey was to examine the services offered by multidisciplinary pain treatment facilities (MPTFs) across Canada and to compare access to care at these MPTFs. METHODS: A MPTF was defined as a clinic that advertised specialized multidisciplinary services for the diagnosis and management of patients with chronic pain, having a minimum of three different health care disciplines (including at least one medical speciality) available and integrated within the facility. The search method included approaching all hospital and rehabilitation centre administrators in Canada, the Insurance Bureau of Canada, the Workplace Safety and Insurance Board or similar body in each province. Designated investigators were responsible for confirming and supplementing MPTFs from the preliminary list for each province. Administrative leads at each eligible MPTF were asked to complete a detailed questionnaire regarding their MPTF infrastructure, clinical, research, teaching and administrative activities. RESULTS: Completed survey forms were received from 102 MPTFs (response rate 85%) with 80% concentrated in major cities, and none in Prince Edward Island and the Territories. The MPTFs offer a wide variety of treatments including non-pharmacological modalities such as interventional, physical and psychological therapy. The median wait time for a first appointment in public MPTFs is six months, which is approximately 12 times longer than non-public MPTFs. Eighteen pain fellowship programs exist in Canadian MPTFs and 64% engage in some form of research activities CONCLUSION: Canadian MPTFs are unable to meet clinical demands of patients suffering from chronic pain, both in terms of regional accessibility and reasonable wait time for patients' first appointment.