Joint reconstruction and segmentation in undersampled 3D knee MRI combining shape knowledge and deep learning.

Objective.Task-adapted image reconstruction methods using end-to-end trainable neural networks (NNs) have been proposed to optimize reconstruction for subsequent processing tasks, such as segmentation. However, their training typically requires considerable hardware resources and thus, only relatively simple building blocks, e.g. U-Nets, are typically used, which, albeit powerful, do not integrate model-specific knowledge.Approach.In this work, we extend an end-to-end trainable task-adapted image reconstruction method for a clinically realistic reconstruction and segmentation problem of bone and cartilage in 3D knee MRI by incorporating statistical shape models (SSMs). The SSMs model the prior information and help to regularize the segmentation maps as a final post-processing step. We compare the proposed method to a simultaneous multitask learning approach for image reconstruction and segmentation (MTL) and to a complex SSMs-informed segmentation pipeline (SIS).Main results.Our experiments show that the combination of joint end-to-end training and SSMs to further regularize the segmentation maps obtained by MTL highly improves the results, especially in terms of mean and maximal surface errors. In particular, we achieve the segmentation quality of SIS and, at the same time, a substantial model reduction that yields a five-fold decimation in model parameters and a computational speedup of an order of magnitude.Significance.Remarkably, even for undersampling factors of up toR= 8, the obtained segmentation maps are of comparable quality to those obtained by SIS from ground-truth images.

Ground-truth-free deep learning for artefacts reduction in 2D radial cardiac cine MRI using a synthetically generated dataset.

In this work, we consider the task of image reconstruction in 2D radial cardiac cine MRI using deep learning (DL)-based regularization. As the regularization is achieved by employing an image-prior predicted by a pre-trained convolutional neural network (CNN), the quality of the image-prior is of essential importance. The achievable performance of any DL-based method is limited by the amount and the quality of the available training data. For fast dynamic processes, obtaining good-quality MR data is challenging because of technical and physiological reasons. In this work, we try to overcome these problems by a transfer-learning approach which is motivated by a previously presented DL-method (XT,YT U-Net). There, instead of training the network on the whole 2D dynamic images, it is trained on 2D spatio-temporal profiles (xt,yt-slices) which show the temporal changes of the imaged object. Therefore, for the training and test data, it is more important that their spatio-temporal profiles share similar local features rather than being images of the same anatomy. This allows us to equip arbitrary data with simulated motion that resembles the cardiac motion and use it as training data. By doing so, it is possible to train a CNN which is applicable to cardiac cine MR data without using ground-truth cine MR images for training. We demonstrate that combining XT,YT U-Net with the proposed transfer-learning strategy delivers comparable performance to CNNs trained on cardiac cine MR images and in some cases even qualitatively surpasses these. Additionally, the transfer-learning strategy was investigated for a 2D and 3D U-Net. The images processed by the the CNNs were used as image-priors in the CNN-regularized iterative reconstruction. The XT,YT U-Net yielded visibly better results than the 2D U-Net and slightly better results than the 3D U-Net when used in combination with the presented transfer learning-strategy.

Neural networks-based regularization for large-scale medical image reconstruction.

In this paper we present a generalized Deep Learning-based approach for solving ill-posed large-scale inverse problems occuring in medical image reconstruction. Recently, Deep Learning methods using iterative neural networks (NNs) and cascaded NNs have been reported to achieve state-of-the-art results with respect to various quantitative quality measures as PSNR, NRMSE and SSIM across different imaging modalities. However, the fact that these approaches employ the application of the forward and adjoint operators repeatedly in the network architecture requires the network to process the whole images or volumes at once, which for some applications is computationally infeasible. In this work, we follow a different reconstruction strategy by strictly separating the application of the NN, the regularization of the solution and the consistency with the measured data. The regularization is given in the form of an image prior obtained by the output of a previously trained NN which is used in a Tikhonov regularization framework. By doing so, more complex and sophisticated network architectures can be used for the removal of the artefacts or noise than it is usually the case in iterative NNs. Due to the large scale of the considered problems and the resulting computational complexity of the employed networks, the priors are obtained by processing the images or volumes as patches or slices. We evaluated the method for the cases of 3D cone-beam low dose CT and undersampled 2D radial cine MRI and compared it to a total variation-minimization-based reconstruction algorithm as well as to a method with regularization based on learned overcomplete dictionaries. The proposed method outperformed all the reported methods with respect to all chosen quantitative measures and further accelerates the regularization step in the reconstruction by several orders of magnitude.

Evaluation of aortic cannula jet lesions in a porcine cardiopulmonary bypass (CPB) model.

In cardiosurgery patients atherosclerotic debris displaced from the cannulation site but also from the opposite aortic wall by the "sandblast-like" effect of the high-pressure jet emanating from the cannula is a potential source of intraoperative arterial embolization and consequently postoperative neurologic dysfunction. The present study examined the extent to which shear stress exerted on the intact aortic intima by an aortic cannula jet stream can cause endothelial lesions that promote thrombogenesis and consequently thrombembolism. A single-stream, straight-tip aortic cannula was used in a porcine cardiopulmonary bypass (CPB) model. Following a 120-minute CPB pump run, a 60-minute stabilization period was allowed before sacrificing the pigs (N.=40) for histological evaluation of the ascending aorta and the brain. Opposite the cannulation site endothelial lesions (diameter: 3.81±1.3 mm; depth: 0.017±0.003 mm) were present in 22.5% (9/40) of aortic specimens. Cerebral thrombembolic lesions were not found. The present study showed that single-stream, straight-tip aortic cannulas caused jet lesions of the formerly intact aortic endothelium opposite the cannulation site in 22.5% of cases in a porcine CPB model.

Lornoxicam characteristically modulates cerebral pain-processing in human volunteers: a functional magnetic resonance imaging study.

BACKGROUND: Lornoxicam like other non-steroidal anti-inflammatory drugs (NSAIDs) is widely used for postoperative pain therapy. Evaluation of the effect of lornoxicam on cerebral processing of surgical pain was thus the aim of the present functional magnetic resonance imaging (fMRI) study. METHODS: An fMRI-compatible pain model that mimics surgical pain was used to induce pain rated 4-5 on a visual analogue scale (VAS) at the anterior margin of the right tibia in volunteers (n=22) after i.v. administration of saline (n=11) or lornoxicam (0.1 mg kg(-1)) (n=11). RESULTS: Lornoxicam, which significantly reduced pain sensation [VAS: mean (sd) 4.6 (0.7) vs 1.2 (1.5)], completely suppressed pain-induced activation in the SII/operculum, anterior cingulate cortex, insula, parietal (inferior), prefrontal (inferior, medial), temporal (inferior, medial/superior) lobe, cerebellum, and contralateral (e.g. left-sided) postcentral gyrus (SI). Only the hippocampus and the contralateral superior parietal lobe (BA 7) were activated. CONCLUSIONS: As compared with saline, lornoxicam typically suppressed pain-induced brain activation in all regions except the hippocampus. Furthermore, de novo activation was found in the contralateral, superior parietal lobe (BA 7).

Does caffeine modulate verbal working memory processes? An fMRI study.

To assess the effect of caffeine on the functional MRI signal during a 2-back verbal working memory task, we examined blood oxygenation level-dependent regional brain activity in 15 healthy right-handed males. The subjects, all moderate caffeine consumers, underwent two scanning sessions on a 1.5-T MR-Scanner separated by a 24- to 48-h interval. Each participant received either placebo or 100 mg caffeine 20 min prior to the performance of the working memory task in blinded crossover fashion. The study was implemented as a blocked-design. Analysis was performed using SPM2. In both conditions, the characteristic working memory network of frontoparietal cortical activation including the precuneus and the anterior cingulate could be shown. In comparison to placebo, caffeine caused an increased response in the bilateral medial frontopolar cortex (BA 10), extending to the right anterior cingulate cortex (BA 32). These results suggest that caffeine modulates neuronal activity as evidenced by fMRI signal changes in a network of brain areas associated with executive and attentional functions during working memory processes.

Technical challenges in totally endoscopic robotic coronary artery bypass grafting.

OBJECTIVE: Robotic technology is a prerequisite for performance of totally endoscopic coronary artery bypass grafting. During the implementation phase of totally endoscopic coronary artery bypass, surgeon-related technical difficulties might be encountered. It was the aim of this study to assess the incidence of these challenges, to find risk factors, and to describe clinical results associated with technical errors. METHODS: From October 2001 through October 2004, 40 patients received robotically assisted totally endoscopic left internal thoracic artery grafts to the left anterior descending coronary artery system with the da Vinci telemanipulation device. All patients underwent remote access cardiopulmonary bypass perfusion through groin access, and all anastomoses were performed on the arrested heart. RESULTS: Undesirable technical events of various grades occurred in 20 (50%) of 40 patients: bleeding from a port hole in 3 (8%), left internal thoracic artery damage in 3 (8%), epicardial lesion in 3 (8%), remote access perfusion problems in 9 (23%), bleeding from the anastomosis in 4 (10%), and anastomotic stenosis in 2 (5%). There was no hospital mortality. The following differences were noted between patients without technical difficulties (group 1) and those in whom problems occurred (group 2): total operative time of 314 minutes (260-540 minutes) versus 418 minutes (270-690 minutes; P = .007), ventilation time of 6 hours (0-26 hours) versus 14 hours (0-278 hours; P = .004), intensive care unit stay of 20 hours (11-70 hours) versus 44 hours (16-336 hours; P=.183), hospital stay of 7 days (4-13 days) versus 8 days (5-21 days; P = .038), and cumulative freedom from angina at 36 months of 93% versus 100% (P = .317). CONCLUSION: We conclude that technical difficulties during totally endoscopic coronary artery bypass grafting translate into markedly increased operative time, moderately prolonged postoperative ventilation time, and slightly increased hospital stay. Short-term survival and freedom from angina, however, do not seem to be compromised.

Incidence of lower thoracic ligamentum flavum midline gaps.

BACKGROUND: Lower thoracic epidural anaesthesia and analgesia (EDA) has gained increasing importance in perioperative pain therapy. The loss-of-resistance technique used to identify the epidural space is thought to rely on the penetration of the ligamentum flavum. Investigations at the cervical and lumbar regions have demonstrated that the ligamentum flavum frequently exhibits incomplete fusion at different vertebral levels. Therefore, the aim of this study was to directly investigate the incidence of lower thoracic ligamentum flavum midline gaps in embalmed cadavers. METHODS: Vertebral column specimens were obtained from 47 human cadavers. Ligamentum flavum midline gaps were recorded between the vertebral levels T6 and L1. RESULTS: The incidence of midline gaps/number of viable specimens at the following levels was: T6-7: 2/45 (4.4%), T7-8: 1/47 (2.1%), T8-9: 2/45 (4.4%), T9-10: 7/39 (17.9%), T10-11: 12/34 (35.2%), T11-12: 10/35 (28.5%), T12/L1: 6/38 (15.8%). CONCLUSIONS: In the present study we have determined the frequency of lower thoracic ligamentum flavum midline gaps. Gaps are less frequent than at cervical levels, but more frequent than at lumbar levels. Peak incidence was found in the region between T10 and T12. Using a strict midline approach, one cannot therefore rely on the ligamentum flavum to impede entering the epidural space in all patients.

[Evaluation of a cadaver workshop for education in regional anesthesia]. / Bewertung eines Anatomieworkshops für die Regionalanästhesieausbildung.

BACKGROUND: The aim of the present investigation was to survey former participants (n=869) of a cadaver workshop using a mail questionnaire to assess the demographic data and the impact of these courses on daily practice. METHODS: The deadline for acceptance of return mail was 60 days. Descriptive statistics were employed for analysis of results. RESULTS: The response rate was 36.7% and the course was judged to be recommendable by 98.2%. The average course attendant was board certified and had spent a mean time of 9+/-6 years in anesthesiology. The highest quality and degree of subsequent practicability in daily routine was attributed to peripheral nerve block training on cadavers. Of the course participants two-thirds performed regional anesthesia procedures more often following attendance. The majority of course attendants had to defray at least a part of the course fee themselves, and one-third was required to invest leisure time to attend. CONCLUSION: Attendance of a cadaver workshop increased knowledge of clinical anatomy and enhanced performance of regional anesthesia procedures. Courses of this format constitute a currently underestimated adjunct to contemporary regional anesthesia education.

Testing of a new pneumatic device to cause pain in humans.

BACKGROUND: Surgical pain typically combines superficial and deep pain. We wished to generate pain that resembled surgical pain, reliably and reproducibly, in volunteers. METHODS: We constructed a computer-controlled pneumatic device to apply pressure to the anterior tibia. The reproducibility of the pain was tested by rating the pressure that caused pain rated 4-5 on a visual analogue scale (VAS) on days 0, 7, and 24 in 10 volunteers. The effect of remifentanil (0.025, 0.05, 0.075, and 0.1 microg kg-1 min-1) on pain tolerance in another set of volunteers (n=11) was used as an indirect measure of the reliability of pain production. RESULTS: The pressure needed (0.7 (0.3) to 0.9 (0.4) atm (mean (SD)) to induce pain rated 4-5 (VAS) did not vary, showing long-term reproducibility of the method. When pressure was applied to cause increasing pain in volunteers (n=11) 0.05 microg kg-1 min-1 remifentanil increased pain tolerance by 50%. An approximate doubling of the dose (0.1 microg kg-1 min-1) increased pain tolerance significantly more. The linear logarithmic dose-effect relationship shows that the device causes pain reliably, and this can be reduced with opioid treatment. CONCLUSION: This pneumatic device can apply pain reliably and reproducibly.

[Evaluation of an established course of hospital management through structured telephone survey of former participants]. / Evaluierung eines etablierten Universitätslehrganges für Krankenhausmanagement durch telefonische Befragung ehemaliger Teilnehmer.

AIM OF THE STUDY: Participation in courses for health and hospital management is increasingly becoming a conditio sine qua non for candidates for executive positions in the health professions. The aim of this study was thus to evaluate the two-semester university course for health and hospital management offered by the University of Innsbruck since 1994. METHODS: A structured telephone survey was conducted to poll the participants (n = 184) of previous courses concerning time invested, cost-benefit ratio, quality of the course as well as implementation of course content. RESULTS: The university courses (n = 7) for health and hospital management of the University of Innsbruck evaluated in this study were rated in the upper half of the of the five-part scale (scores 2 to 3) for overall quality, cost-benefit ratio and implementation of course content. Only approx. 25 % of the course participants reported that the course had a positive influence on their career. The relatively high course fee was borne in part by the local hospital operator, a fact that had a certain influence on the selection of course participants. Participation in the course was largely made possible by exemptions from job duties (approx. 75 %) and to a lesser extent by vacation time (approx. 20 %) or time off for overtime (approx. 5 %). Of total absences from the course (3.18 +/- 3.41 d) 75 % was for job-related reasons, 6 % for illness and 19 % for other reasons. Overall, participants were absent more often, the larger the number of personnel in their department or clinic. CONCLUSION: All in all, the courses were considered important and recommendable, particularly with regard to communication, organization, time management and cost awareness. Streamlining (i. e. more content in less time), stronger practical orientation and a switch from mainly local to more international speakers would be important steps toward improving course quality. Thanks to its demonstrated quality, it can be said that the university course for health and hospital management held by the University of Innsbruck and evaluated in this study is certainly a worthwhile course offered in a still emerging market, namely one that will come under increasing pressure from the candidates for executive positions in the health professions to provide what is best for their careers and the health services industry in general.

Remifentanil and nitrous oxide reduce changes in cerebral blood flow velocity in the middle cerebral artery caused by pain.

BACKGROUND: Cerebral blood flow is affected by painful stimuli, and analgesic agents may alter the response of cerebral blood flow to pain. We set out to quantify the effects of remifentanil and nitrous oxide on blood flow changes caused by experimental pain. METHODS: We simulated surgical pain in 10 conscious volunteers using increasing mechanical pressure to the tibia. We measured changes in cerebral blood flow velocity in the middle cerebral artery (CBFV(MCA)) caused by the pain, using transcranial Doppler sonography. We gave increasing doses of remifentanil (0.025, 0.05 and 0.1 micro g kg(-1) min(-1)) or nitrous oxide [20%, 35% and 50% end-tidal concentration (FE'(N(2)O))] and compared these effects on blood flow changes. RESULTS: Nitrous oxide increased CBFV(MCA) only when given at 50% FE'(N(2)O). Remifentanil did not affect CBFV(MCA). Pain increased CBFV(MCA). Both agents attenuated this pain-induced change in CBFV(MCA) with the exception of nitrous oxide at 20% FE'(N(2)O). CONCLUSIONS: Inhalation of nitrous oxide or adminstration of remifentanil attenuated pain-induced changes in CBFV(MCA).

Use of neuronavigation and electrophysiology in surgery of subcortically located lesions in the sensorimotor strip.

OBJECTIVES: Subcortical lesions in the sensorimotor strip are often considered to be inoperable. The purpose of this study was to evaluate the usefulness of a combined approach for surgery in this region, aided by a robotic neuronavigation system under electrophysiological control. METHODS: In a prospective study on 10 patients, space occupying lesions in the sensorimotor central area were removed using the Surgiscope robotic navigation system and the Nicolet Viking IV electrophysiological system. RESULTS: Precise tumour localisation with the neuronavigation system and the information on the patient's cortical motor distribution obtained by bipolar cortical stimulation led to postoperative improvement in motor function in all but one patient. Seven of the patients had focal, defined pathology (four metastases; two cavernoma; one aspergilloma). CONCLUSION: Due to the implementation of two recent technologies, surgery of lesions in the subcortical sensorimotor region can be performed with greater confidence.

Subanesthetic concentration of sevoflurane increases regional cerebral blood flow more, but regional cerebral blood volume less, than subanesthetic concentration of isoflurane in human volunteers.

Both sevoflurane and isoflurane are used in moderate concentrations in neuroanesthesia practice. The limiting factors for using higher concentrations of inhalational anesthetics in patients undergoing neurosurgery are the agents' effects on cerebral blood flow (CBF) and cerebral blood volume (CBV). In particular, an increase in CBV, which is a key determinant of intracranial pressure, may add to the neurosurgical patient's perioperative risk. To compare the effects of a subanesthetic concentration (0.4 minimum alveolar concentration) of sevoflurane or isoflurane on regional CBF (rCBF), regional CBV (rCBV) and regional mean transit time (rMTT), contrast-enhanced magnetic resonance imaging perfusion measurements were made in spontaneously breathing human volunteers. Absolute changes in rCBF, regional CBV, and rMTT during administration of either drug in regions of interest outlined bilaterally in white and grey matter were nonparametrically (Mann-Whitney test) analyzed. Sevoflurane increased rCBF in practically all regions (absolute change, 4.44 +/- 2.87 to 61.54 +/- 2.39 mL/100g per minute) more than isoflurane did (absolute change, 12.91 +/- 2.52 to 52.67 +/- 3.32 mL/100g per minute), which decreased frontal, parietal, and white matter rCBF (absolute change, -1.12 +/- 0.59 to -14.69 +/- 3.03 mL/100g per minute). Regional CBV was higher in most regions during isoflurane administration (absolute change, 0.75 +/- 0.03 to 4.92 +/- 0.16 mL/100g) than during sevoflurane administration (absolute change, 0.05 +/- 0.14 to 3.57 +/- 0.14 mL/100g). Regional mean transit time was decreased by sevoflurane (absolute change, -0.18 +/- 0.05 to -0.60 +/- 0.04 s) but increased by isoflurane (absolute change, 0.19 +/- 0.03 to 0.69 +/- 0.04 s). In summary, regional CBV was significantly lower during sevoflurane than during isoflurane administration, although sevoflurane increased rCBF more than isoflurane, which even decreased rCBF in some regions. For sevoflurane and, even more pronouncedly, for isoflurane, the observed changes in cerebral hemodynamics cannot be explained by vasodilatation alone.

The impact of business cards on physician recognition after general anesthesia.

UNLABELLED: Despite their contribution to overall perioperative treatment of patients, anesthesiologists often remain in anonymity. We evaluated the impact of business cards on physician recognition after general anesthesia. Using a questionnaire, 441 patients were interviewed for recall of the anesthesiologist's name, the surgeon's name, and their overall satisfaction with anesthetic care 6 wk after undergoing surgery during general anesthesia. Of these patients, 155 had and 137 had not randomly received a business card during the preoperative visit, with another 149 patients serving as a control group. Business card recipients responded significantly more frequently than did nonrecipients or patients from the control group (65.8% vs 54.7% vs 53%), with recall of the anesthesiologist's name being significantly more frequent in the Business Card Recipient group (51.5% vs 14.3% vs 11.4%). Patient satisfaction with anesthetic care and recall of the surgeon's name were similar in all groups. The use of a simple tool such as a business card can indeed produce a measurable positive change in physician recognition on the part of the patient. IMPLICATIONS: Anesthesiologists often remain anonymous in everyday clinical practice. Handing a business card to the patient during the preoperative visit increased the postoperative recall of the anesthesiologist's name from 11% to 51%.