Evaluation of quality of life and function at 1 year after transanal endoscopic microsurgery.

AIM: Transanal endoscopic microsurgery (TEM) enables organ preservation after rectal tumour surgery. Its application is being expanded using adjuvant and neoadjuvant treatments. Our objective was to evaluate the changes over time in anorectal function, urinary symptoms and quality of life (QoL) in patients who had TEM surgery for a rectal tumour. METHOD: Between September 2009 and October 2012, a consecutive series of 102 patients underwent TEM at a single institution. Patients were asked to fill out standardized questionnaires at baseline and then at 6, 12, 26 and 52 weeks after surgery. The QoL among these patients was assessed using one generic (EQ-5D) and two disease-specific [European Organization for Research and Treatment of Cancer (EORTC) QLQ-C30 and QLQ-CR29] questionnaires. Anorectal and urinary symptoms were studied using the COlo-REctal Functional Outcome (COREFO) and the International Prostate Symptom Score (I-PSS) questionnaires, respectively. RESULTS: The response rate was 90% (92/102 patients). Postoperative complications occurred in 14% (13/92) of patients. The general QoL (as assessed using the EQ-5D) was lower 6 and 12 weeks after TEM compared with baseline QoL (P < 0.05) but returned towards baseline after 26 weeks. Anorectal function (determined using the COREFO) was worse 6 weeks postoperatively (P < 0.01) but had normalized by 12 weeks. Urinary function (determined using the I-PSS) was not affected at any time point after surgery. The total COREFO score and the American Society of Anesthesiologists (ASA) score were correlated with the deterioration in QoL. CONCLUSION: The study demonstrates that TEM has a temporary and reversible impact on QoL and anorectal function. Intensive interrogation of QoL and function using appropriate questionnaires will help to define the role of organ-preserving surgery for rectal cancer before and after chemoradiotherapy.

A contrast source method for nonlinear acoustic wave fields in media with spatially inhomogeneous attenuation.

Experimental data reveals that attenuation is an important phenomenon in medical ultrasound. Attenuation is particularly important for medical applications based on nonlinear acoustics, since higher harmonics experience higher attenuation than the fundamental. Here, a method is presented to accurately solve the wave equation for nonlinear acoustic media with spatially inhomogeneous attenuation. Losses are modeled by a spatially dependent compliance relaxation function, which is included in the Westervelt equation. Introduction of absorption in the form of a causal relaxation function automatically results in the appearance of dispersion. The appearance of inhomogeneities implies the presence of a spatially inhomogeneous contrast source in the presented full-wave method leading to inclusion of forward and backward scattering. The contrast source problem is solved iteratively using a Neumann scheme, similar to the iterative nonlinear contrast source (INCS) method. The presented method is directionally independent and capable of dealing with weakly to moderately nonlinear, large scale, three-dimensional wave fields occurring in diagnostic ultrasound. Convergence of the method has been investigated and results for homogeneous, lossy, linear media show full agreement with the exact results. Moreover, the performance of the method is demonstrated through simulations involving steered and unsteered beams in nonlinear media with spatially homogeneous and inhomogeneous attenuation.

An ultrasound cylindrical phased array for deep heating in the breast: theoretical design using heterogeneous models.

The objective of this theoretical study is to design an ultrasound (US) cylindrical phased array that can be used for hyperthermia (40-44 degrees C) treatment of tumours in the intact breast. Simultaneously, we characterize the influence of acoustic and thermal heterogeneities on the specific absorption rate (SAR) and temperature patterns to determine the necessity of using heterogeneous models for a US applicator design and treatment planning. Cylindrical configurations of monopole transducers are studied on their ability to generate interference patterns that can be steered electronically to the location of the target region. Hereto, design parameters such as frequency, number of transducers per ring, ring distance and number of rings are optimized to obtain a small primary focus, while suppressing secondary foci. The models account for local heterogeneities in both acoustic (wave velocity and absorption) and thermal (blood perfusion rate, heat capacity and conductivity) tissue properties. We used breast models with a central tumour (30x20x38 mm3) and an artificial thorax tumour (sphere with a radius of 25 mm) to test the design. Simulations predict that a US cylindrical phased array, consisting of six rings with 32 transducers per ring, a radius of 75 mm and 66 mm distance between the first and sixth transducer ring, operating at a frequency of 100 kHz, can be used to obtain 44 degrees C in the centre of tumours located anywhere in the intact breast. The dimensions of the volumes enclosed by the 41 degrees C iso-temperature are 19x19x21 mm3 and 21x21x32 mm3 for the central and the thorax tumours, respectively. It is demonstrated that acoustic and thermal heterogeneities do not disturb the SAR and temperature patterns.

Reconstructing 3D proton dose distribution using ionoacoustics.

In proton therapy high energy protons are used to irradiate a tumor. Ideally, the delivered proton dose distribution is measured during treatment to ensure patient safety and treatment effectiveness. Here we investigate if we can use the ionoacoustic wave field to monitor the actual proton dose distribution for the two most commonly used proton accelerators; the isochronous cyclotron and the synchrocyclotron. To this end we model the acoustic field generated by the protons when irradiating a heterogeneous cancerous breast with a 89 MeV proton beam. To differentiate between the systems, idealized temporal micro-structures of the beams have been implemented. Results show that by employing model-based inversion we are able to reconstruct the 3D dose distributions from the simulated noisy pressure fields. Good results are obtained for both systems; the absolute error in the position of the maximum amplitude of the dose distribution is 5.0 mm for the isochronous cyclotron and 5.2 mm for the synchrocyclotron. In conclusion, this numerical study suggests that the ionoacoustic wave field may be used to monitor the proton dose distribution during breast cancer treatment.

Virtual reality training for endoscopic surgery: voluntary or obligatory?

INTRODUCTION: Virtual reality (VR) simulators have been developed to train basic endoscopic surgical skills outside of the operating room. An important issue is how to create optimal conditions for integration of these types of simulators into the surgical training curriculum. The willingness of surgical residents to train these skills on a voluntary basis was surveyed. METHODS: Twenty-one surgical residents were given unrestricted access to a VR simulator for a period of four months. After this period, a competitive element was introduced to enhance individual training time spent on the simulator. The overall end-scores for individual residents were announced periodically to the full surgical department, and the winner was awarded a prize. RESULTS: In the first four months of study, only two of the 21 residents (10%) trained on the simulator, for a total time span of 163 minutes. After introducing the competitive element the number of trainees increased to seven residents (33%). The amount of training time spent on the simulator increased to 738 minutes. CONCLUSIONS: Free unlimited access to a VR simulator for training basic endoscopic skills, without any form of obligation or assessment, did not motivate surgical residents to use the simulator. Introducing a competitive element for enhancing training time had only a marginal effect. The acquisition of expensive devices to train basic psychomotor skills for endoscopic surgery is probably only effective when it is an integrated and mandatory part of the surgical curriculum.

Construct validity of the LapSim: can the LapSim virtual reality simulator distinguish between novices and experts?

BACKGROUND: Virtual reality simulators may be invaluable in training and assessing future endoscopic surgeons. The purpose of this study was to investigate if the results of a training session reflect the actual skill of the trainee who is being assessed and thereby establish construct validity for the LapSim virtual reality simulator (Surgical Science Ltd., Gothenburg, Sweden). METHODS: Forty-eight subjects were assigned to one of three groups: 16 novices (0 endoscopic procedures), 16 surgical residents in training (>10 but <100 endoscopic procedures), and 16 experienced endoscopic surgeons (>100 endoscopic procedures). Performance was measured by a relative scoring system that combines single parameters measured by the computer. RESULTS: The higher the level of endoscopic experience of a participant, the higher the score. Experienced surgeons and surgical residents in training showed statistically significant higher scores than novices for both overall score and efficiency, speed, and precision parameters. CONCLUSIONS: Our results show that performance of the various tasks on the simulator corresponds to the respective level of endoscopic experience in our research population. This study demonstrates construct validity for the LapSim virtual reality simulator. It thus measures relevant skills and can be integrated in an endoscopic training and assessment program.

Robot-assisted laparoscopic choledochojejunostomy.

BACKGROUND: Endoscopic stenting is the treatment of choice for palliative relief of biliary obstruction by a periampullary tumor. If treated surgically, a choledochojejunostomy and Roux-en-Y diversion is still performed by laparotomy in a large number of cases due to technical challenges of the biliodigestive anastomosis in the laparoscopic approach. Robotic systems may enhance dexterity and vision and might therefore support surgeons in delicate laparoscopic interventions. The purpose of this study is to assess the efficacy and safety of performing a laparoscopic choledochojejunostomy and Roux-en-Y reconstruction with the aid of a robotic system. METHODS: Ten laparoscopic procedures were performed in pigs with the da Vinci robotic system and compared to 10 procedures performed by laparotomy (controls). Operation room time, anastomoses time, blood loss, and complications were recorded. The effectiveness of the anastomoses was evaluated by postoperative observation for 14 days and by measuring passage, circumference, and number of stitches. RESULTS: Operating room time was significantly longer for the robot-assisted group than for controls (140 vs 82 min, p < 0.05). The anastomoses times were longer in the robot-assisted cases but not statistically significant (biliodigestive anastomosis, 29 vs 20 min; intestinal anastomosis, 30 vs 15 min), Blood loss was less than 10 cc in all robot-assisted cases and 30 cc (10-50 cc) in the controls. In both groups, there were no intraoperative complications. In the control group, one pig died of gastroparesis on postoperative day 6. In the robot-assisted group, one pig died on postoperative day 7 due to a volvulus of the jejunum. At autopsy, a bilioma was found in one pig in the robot-assisted group. In all pigs, the biliodigestive and intestinal anastomoses were macroscopically patent with an adequate passage. Circumference and number of stitches were similar. CONCLUSION: The safety and efficacy of robot-assisted laparoscopic choledochojejunostomy was proven in this study. The procedure can be performed within an acceptable time frame.

Rapid transient pressure field computations in the nearfield of circular transducers using frequency-domain time-space decomposition.

The fast nearfield method, when combined with time-space decomposition, is a rapid and accurate approach for calculating transient nearfield pressures generated by ultrasound transducers. However, the standard time-space decomposition approach is only applicable to certain analytical representations of the temporal transducer surface velocity that, when applied to the fast nearfield method, are expressed as a finite sum of products of separate temporal and spatial terms. To extend time-space decomposition such that accelerated transient field simulations are enabled in the nearfield for an arbitrary transducer surface velocity, a new transient simulation method, frequency-domain time-space decomposition (FDTSD), is derived. With this method, the temporal transducer surface velocity is transformed into the frequency domain, and then each complex-valued term is processed separately. Further improvements are achieved by spectral clipping, which reduces the number of terms and the computation time. Trade-offs between speed and accuracy are established for FDTSD calculations, and pressure fields obtained with the FDTSD method for a circular transducer are compared with those obtained with Field II and the impulse response method. The FDTSD approach, when combined with the fast nearfield method and spectral clipping, consistently achieves smaller errors in less time and requires less memory than Field II or the impulse response method.