Development of non-invasive flexible directional microwave ablation for central lung cancer: a simulation study

Transbronchial microwave ablation (MWA) with flexible antennas has gradually become an attractive alternative to percutaneous MWA for lung cancer due to its characteristic of non-invasiveness. However, flexible antennas for the precision ablation of lung tumors that are adjacent to critical bronchial structures are still not available. In this study, a non-invasive flexible directional (FD) antenna for early stage central lung tumors surrounding the bronchia was proposed. A comprehensive numerical MWA model with the FD antenna was developed in a real human-sized left lung model. The structure of the antenna and the treatment protocol were optimized by a generic algorithm for the precision ablation of two cases of early stage central lung cancer (i.e. spherical-like and ellipsoidal tumors). The electromagnetic efficiency of the optimized antenna was also improved by implementing an optimizedπ-matching network for impedance matching. The results indicate that the electromagnetic energy of MWA can be restricted to a particular area for precision ablation of specific lung tumors using the FD antenna. This study contributes to the field of lung cancer management with MWA.

Optimal design of aperiodic tri-slot antennas for the conformal ablation of liver tumors using an experimentally validated MWA computer model

OBJECTIVE

This study aims to demonstrate that the conformal microwave ablation (MWA) of liver tumors could be attained by optimizing the structure of an aperiodic tri-slot coaxial antenna, its insertion depth, and input power.

METHODS

A computational MWA model with an aperiodic tri-slot coaxial antenna operating at the frequency of 2.45 GHz was built and validated by both an ex vivo and a pilot in vivo experiment with porcine healthy livers. The validated in vivo computational MWA model implemented with a liver tumor was then used as a testbed to investigate the conformal ablation of liver tumors. Five liver tumors in different sizes and shapes were investigated. A genetic algorithm optimization method (NSGA-II) was used to optimize the structure of antenna, insertion depth of antenna, and microwave antenna input power for the conformal ablation of liver tumors.

RESULTS

The validation results showed that a good agreement in both the spatiotemporal temperature distribution and ablation zone was found between the computer model and the ex vivo experiments at both 45 W, 5 min and 60 W, 3 min treatments and the in vivo experiment at 45 W, 5 min treatment. The optimized simulation results confirmed that five cases of liver tumors in different sizes and shapes can be conformally ablated by optimizing the aperiodic tri-slot coaxial antenna, antenna insertion depth, and microwave antenna input power.

CONCLUSION

This paper demonstrates that the aperiodic tri-slot coaxial antenna can be optimized with the insertion depth and input power for the conformal ablation of liver tumors, regardless the size and shape of liver tumors.

Preparation and Use of Decellularized Extracellular Matrix for Tissue Engineering

The multidisciplinary fields of tissue engineering and regenerative medicine have the potential to revolutionize the practise of medicine through the abilities to repair, regenerate, or replace tissues and organs with functional engineered constructs. To this end, tissue engineering combines scaffolding materials with cells and biologically active molecules into constructs with the appropriate structures and properties for tissue/organ regeneration, where scaffolding materials and biomolecules are the keys to mimic the native extracellular matrix (ECM). For this, one emerging way is to decellularize the native ECM into the materials suitable for, directly or in combination with other materials, creating functional constructs. Over the past decade, decellularized ECM (or dECM) has greatly facilitated the advance of tissue engineering and regenerative medicine, while being challenged in many ways. This article reviews the recent development of dECM for tissue engineering and regenerative medicine, with a focus on the preparation of dECM along with its influence on cell culture, the modification of dECM for use as a scaffolding material, and the novel techniques and emerging trends in processing dECM into functional constructs. We highlight the success of dECM and constructs in the in vitro, in vivo, and clinical applications and further identify the key issues and challenges involved, along with a discussion of future research directions.

Lethal Electric Field Thresholds for Cerebral Cells With Irreversible Electroporation and H-FIRE Protocols: An In Vitro Three-Dimensional Cell Model Study

The lethal electric field (LEF) thresholds for three typical cerebral cells, including a malignant glioblastoma (GBM) cell line and two cell lines from the healthy blood-brain barrier (BBB), treated by irreversible electroporation (IRE) or high-frequency irreversible electroporation (H-FIRE) protocols were investigated in an in vitro three-dimensional (3D) cell model. A conventional IRE protocol (90 pulses, 1 Hz, and 100-μs pulse duration) and three novel H-FIRE protocols (1-3-1, 0.5-1-0.5, and 1-1-1) were used to treat the cerebral cells in both 3D single-cell and two-cell models. The electrical conductivity of the 3D cell model under different electric field strengths were characterized with the method of electrochemical impedance spectroscopy (EIS). Based on EIS, a numerical electrothermal model of electroporation was built for the determination of the LEF threshold with different protocols and temperature monitoring. Cell viability was assessed by fluorescence staining 6 h after the treatment. The results showed no thermal lethal effect on cells when these protocols were used. The LEF threshold for GBM cells was significantly lower than that of the healthy BBB cells. These results suggest the possibility of selective ablation of human cerebral GBM by IRE and H-FIRE treatments with no injury or reversible injury to healthy cells, and the potential use of IRE or H-FIRE for transient disruption of the BBB to allow chemotherapy to reach the tumor.

Modeling and ex vivo experimental validation of liver tissue carbonization with laser ablation

OBJECTIVE

The purpose of this study was to model the process of liver tissue carbonization with laser ablation (LA).

METHODS

A dynamic heat source model was proposed and combined with the light distribution model as well as bioheat transfer model to predict the development of tissue carbonization with laser ablation (LA) using an ex vivo porcine liver tissue model. An ex vivo laser ablation experiment with porcine liver tissues using a custom-made 1064 nm bare fiber was then used to verify the simulation results at 3, 5, and 7 W laser administrations for 5 min. The spatiotemporal temperature distribution was monitored by measuring the temperature changes at three points close the fiber during LA. Both the experiment and simulation of the temperature, tissue carbonization zone, and ablation zone were then compared.

RESULTS

Four stages were recognized in the development of liver tissue carbonization during LA. The growth of the carbonization zone along the fiber axial and radial directions were different in the four stages. The carbonization zone along the fiber axial direction (L2) grew in the four stages with a sharp increase in the initial period and a minor increase in Stage 4. However, the change in the carbonization zone along the fiber radial direction (D2) increased dramatically (Stage 1) to a long-time plateau (Stages 2 and 3) followed by a slow growth in Stage 4. An acceptable agreement between the computer simulation and ex vivo experiment in the temperature changes at the three points was found at all three testing laser administrations. A similar result was also obtained for the dimensions of coagulation zone and ablation zone between the computer simulation and ex vivo experiment (carbonization zone: 2.99± 0.10 vs. 2.78 mm², 67.39± 0.09 vs. 63.53 mm², and 90.53± 0.11 vs. 85.15 mm²; ablation zone: 68.95± 0.28 vs. 65.29 mm², 182.11± 0.24 vs. 213.81 mm², and 244.80± 0.06 vs. 251.79 mm² at 3, 5, and 7 W, respectively).

CONCLUSION

This study demonstrates that the proposed dynamic heat source model combined with the light distribution model as well as bioheat transfer model can predict the development of liver tissue carbonization with an acceptable accuracy. This study contributes to an improved understanding of the LA process in the treatment of liver tumors.

An in vivo study of a custom-made high-frequency irreversible electroporation generator on different tissues for clinically relevant ablation zones

PURPOSE

To examine the ablation zone, muscle contractions, and temperature increases in both rabbit liver and kidney models in vivo for a custom-made high-frequency irreversible electroporation (H-FIRE) generator.

MATERIALS AND METHODS

A total of 18 New Zealand white rabbits were used to investigate five H-FIRE protocols (n = 3 for each protocol) and an IRE protocol (n = 3) for the performance of the designed H-FIRE device in both liver and kidney tissues. The ablation zone was determined by using histological analysis 72 h after treatment. The extent of muscle contractions and temperature change during the application of pulse energy were measured by a commercial accelerometer attached to animals and fiber optic temperature probe inserted into organs with IRE electrodes, respectively.

RESULTS

All H-FIRE protocols were able to generate visible ablation zones without muscle contractions, for both liver and kidney tissues. The area of ablation zone generated in H-FIRE pulse protocols (e.g., 0.3-1 μs, 2000 V, and 90-195 bursts) appears similar to that of IRE protocol (100 μs, 1000 V, and 90 pulses) in both liver and kidney tissues. No significant temperature increase was noticed except for the protocol with the highest pulse energy (e.g., 1 μs, 2000 V, and 180 bursts).

CONCLUSION

Our work serves to complement the current H-FIRE pulse waveforms, which can be optimized to significantly improve the quality of ablation zone in terms of precision for liver and kidney tumors in clinical setting.

Electroporation-Based Therapy for Brain Tumors: A Review

Electroporation-based therapy (EBT), as a high-voltage-pulse technology has been prevalent with favorable clinical outcomes in the treatment of various solid tumors. This review paper aims to promote the clinical translation of EBT for brain tumors. First, we briefly introduced the mechanism of pore formation in a cell membrane activated by external electric fields using a single cell model. Then, we summarized and discussed the current in vitro and in vivo preclinical studies, in terms of (1) the safety and effectiveness of EBT for brain tumors in animal models, and (2) the blood-brain barrier (BBB) disruption induced by EBT. Two therapeutic effects could be achieved in EBT for brain tumors simultaneously, i.e., the tumor ablation induced by irreversible electroporation (IRE) and transient BBB disruption induced by reversible electroporation (RE). The BBB disruption could potentially improve the uptake of antitumor drugs thereby enhancing brain tumor treatment. The challenges that hinder the application of EBT in the treatment of human brain tumors are discussed in the review paper as well.

A review of antenna designs for percutaneous microwave ablation

Microwave (MW) antenna is a key element in microwave ablation (MWA) treatments as the means that energy is delivered in a focused manner to the tumor and its surrounding area. The energy delivered results in a rise in temperature to a lethal level, resulting in cell death in the ablation zone. The delivery of energy and hence the success of MWA is closely dependent on the structure of the antennas. Therefore, three design criteria, such as expected ablation zone pattern, efficiency of energy delivery, and minimization of the diameter of the antennas have been the focus along the evolution of the MW antenna. To further improve the performance of MWA in the treatment of various tumors through inventing novel antennas, this article reviews the state-of-the-art and summarizes the development of MW antenna designs regarding the three design criteria.

What Information Are Patients Receiving from the Internet about the Operative and Nonoperative Management of Acute Appendicitis?

INTRODUCTION

Recent studies suggest that nonoperative management of appendicitis (NOMA) may be a reasonable option for managing uncomplicated acute appendicitis. We examined the Internet to see if patients are likely to find the information they need to make an informed decision between the 2 options.

METHODS

A list of 29 search terms was established by a focus group and then entered into Google, resulting in 49 unique webpages, each reviewed by 3 reviewers. Consensus was obtained for bias (surgery, NOMA, or balanced), webpage type, JAMA score, reading grade, and DISCERN score, a measure of quality of written information for patients.

RESULTS

Thirty of the 49 websites (61%) favored surgery, while 13 (27%) favored NOMA, and 6 sites (12%) provided balanced information. Twelve of 49 sites (24%) did not list NOMA as an option. The majority of patient-directed (11/12 = 92%) and physician-directed (7/9 = 78%) webpages favored surgery, whereas academic webpages presented a more balanced distribution. Academic and physician-directed webpages ranked higher than commercial and news webpages (median ranks 3 and 4 vs. 7.5 and 8). Only 8/49 sites (16%) mentioned that the presence of a fecalith predicts the failure of NOMA. Reading grades were almost all well above the recommended grade 8 level.

CONCLUSION

Most of the webpages available on the Internet do not provide enough information, nor are they sufficiently understandable to allow most patients to make an informed decision about the current options for the management of acute appendicitis.

Protection of the transplant kidney during cold perfusion with doxycycline: proteomic analysis in a rat model

BACKGROUND

It has been previously shown that doxycycline (Doxy) protects the kidney from preservation injury by inhibition of matrix metalloproteinase. However, the precise molecular mechanism involved in this protection from injury is not known. We used a pharmaco-proteomics approach to identify potential molecular targets associated with kidney preservation injury.

METHODS

Rat kidneys were cold perfused with or without doxycycline (Doxy) for 22 h. Kidneys perfusates were analyzed for the presence of injury markers such as lactate dehydrogenase (LDH), and neutrophil-gelatinase associated lipocalin (NGAL). Proteins extracted from kidney tissue were analyzed by 2-dimensional gel electrophoresis. Proteins of interest were identified by mass spectrometry.

RESULTS

Triosephosphate isomerase, PGM, dihydropteridine reductase-2, pyridine nucleotide-disulfide oxidoreductase, phosphotriesterase-related protein, and aminoacylase-1A were not affected by cold perfusion. Perfusion with Doxy increased their levels. N(G),N(G)-dimethylarginine dimethylaminohydrolase and phosphoglycerate kinase 1 were decreased after cold perfusion. Perfusion with Doxy led to an increase in their levels.

CONCLUSIONS

This study revealed specific metabolic enzymes involved in preservation injury and in the mechanism whereby Doxy protects the kidney against injury during cold perfusion.

Chemical Enhancement of Irreversible Electroporation: A Review and Future Suggestions

Irreversible electroporation has raised great interest in the past decade as a means of destroying cancers in a way that does not involve heat. Irreversible electroporation is a novel ablation technology that uses short high-voltage electrical pulses to enhance the permeability of tumor cell membranes and generate irreversible nano-sized structural defects or pores, thus leading to cell death. Irreversible electroporation has many advantages over thermal therapies due to its nonthermal mechanism: (1) reduced risk of injury to surrounding organs and (2) no “heat-sink” effect due to nearby blood vessels. However, so far, it has been difficult for irreversible electroporation to completely ablate large tumors (eg, >3 cm in diameter). In order to overcome this problem, many preclinical and clinical studies have been performed to improve the efficacy of IRE in the treatment of large size of tumors through a chemical perspective. Due to the distribution of electric field, irreversible electroporation region, reversible electroporation region, and intact region can be found in the treatment of irreversible electroporation. Thus, 2 types of chemical enhancements of irreversible electroporation were discussed in the article, such as the reversible electroporation region enhanced and the irreversible electroporation region enhanced. Specifically, the state-of-the-art results regarding the following approaches that have the potential to be used in the enhancement of irreversible electroporation were systematically reviewed in the article, including (1) combination with cytotoxic drugs, (2) calcium electroporation, (3) modification of cell membrane, and (4) modification of the tumor cell microenvironment. In the end, we concluded with 4 issues that should be addressed in the future for improving irreversible electroporation further in a chemical way.

A Novel Method to Increase Tumor Ablation Zones With RFA by Injecting the Cationic Polymer Solution to Tissues: In Vivo and Computational Studies

OBJECTIVE

This study aims to examine, for the first time, the introduction of cationic polymer solutions to improve radiofrequency ablation (RFA) in terms of a potentially enlarged ablation zone.

METHODS

By using in vivo and computational RFA studies, two cationic polymers, Chitooligosaccharides (COS) and carboxymethyl chitosan (CMC), diluted in deionized water, were injected into tissues separately surrounding the RF bipolar electrode prior to power application. A total of 9 rabbits were used to 1) measure the increase in electrical conductivity of tissues injected with the cationic polymer solutions, and 2) explore the enhancement of the ablation performance in RFA trials. A computer model of RFA comprising a model of the solution diffusion with an RF thermal ablation model was also built, validated by the in vivo experiment, to quantitatively study the effect of cationic polymer solutions on ablation performances.

RESULTS

Compared to the control group, the electrical conductivity of rabbit liver tissues was increased by 42.20% (0.282 ± 0.006 vs. 0.401 ± 0.048 S/m, P = 0.001) and 43.97% (0.282 ± 0.006 vs. 0.406 ± 0.042 S/m, P = 0.001) by injecting the COS and CMC solution at the concentration of 100 mg/mL into the tissues, denoted COS_DW100 and CMC_DW100, respectively. Consequently, the in vivo experiments show that the ablation zone was enlarged by 95% (47.6 ± 6.3 vs. 92.6 ± 11.5 mm², P < 0.001) and 87% (47.6± 6.3 vs. 88.8 ± 9.6 mm², P < 0.001) by COS_DW100 and CMC_DW100, respectively. The computer simulation shows that the ablation zone was enlarged by 71% (51.9 vs. 88.7 mm²) and 63% (51.9 vs. 84.7 mm²) by COS_DW100 and CMC_DW100, respectively.

CONCLUSION

The injection of the cationic solution can greatly improve the performance of RFA treatment in terms of enlarging the ablation zone, which is due to the increase in the electrical conductivity of liver tissues surrounding the RF electrode.

SIGNIFICANCE

This study contributes to the improvement of RFA in the treatment of large tumors.

Direction of the Biopsy Needle in Ultrasound-Guided Renal Biopsy Impacts Specimen Adequacy and Risk of Bleeding

INTRODUCTION

Although medical factors such as hypertension and coagulopathy have been identified that are associated with hemorrhage after renal biopsy, little is known about the role of technical factors. The purpose of our study was to examine the effects of biopsy needle direction on renal biopsy specimen adequacy and bleeding complications.

METHODS

Two hundred and forty-two patients who had undergone ultrasound-guided renal biopsies were included. A printout of the ultrasound picture taken at the time of the biopsy was used to measure the biopsy angle ("angle of attack" [AOA]) and to determine if the biopsy needle was aimed at the upper or lower pole and if the medulla was targeted or avoided.

RESULTS

Of the 3 groups of biopsy angle, an AOA of between 50°-70° yielded the most glomeruli per core (P = .001) and the fewest inadequate specimens (4% vs 15% for > 70°, and 9% for < 50°, P = .038). Biopsy directed at a pole vs an interpolar region resulted in fewer inadequate specimens (8% vs 23%, P = .005), while biopsies that were medulla-avoiding resulted in fewer inadequate specimens (5% vs 16%, P = .004) and markedly reduced bleeding complications (12% vs 46%, P < .001) compared to biopsies where the medulla was entered.

DISCUSSION

An AOA of approximately 60°, aiming at the poles, and avoiding the medulla were each associated with fewer inadequate biopsies and bleeding complications. While biopsy of the medulla is necessary for some diagnoses, the increased bleeding risk emphasizes the need for communication between nephrologist, pathologist, and radiologist.

Tumor Ablation Enhancement by Combining Radiofrequency Ablation and Irreversible Electroporation: An In Vitro 3D Tumor Study

We hypothesized and demonstrated for the first time that significant tumor ablation enhancement can be achieved by combining radiofrequency ablation (RFA) and irreversible electroporation (IRE) using a 3D cervical cancer cell model. Three RFA (43, 50, and 60 °C for 2 min) and IRE protocols (350, 700, and 1050 V/cm) were used to study the combining effect in the 3D tumor cell model. The in vitro experiment showed that both RFA enhanced IRE and IRE enhanced RFA can lead to a significant increase in the size of the ablation zone compared to IRE and RFA alone. It was also noted that the sequence of applying ablation energy (RFA → RE or IRE → RFA) affected the efficacy of tumor ablation enhancement. The electrical conductivity of 3D tumor was found to be increased after preliminary RFA or IRE treatment. This increase in tumor conductivity may explain the enhancement of tumor ablation. Another explanation might be that there is repeat injury to the transitional zone of the first treatment by the second one. The promising results achieved in the study can provide us useful clues about the treatment of large tumors abutting large vessels or bile ducts.

Development of a statistical model for cervical cancer cell death with irreversible electroporation in vitro

PURPOSE

The aim of this study was to develop a statistical model for cell death by irreversible electroporation (IRE) and to show that the statistic model is more accurate than the electric field threshold model in the literature using cervical cancer cells in vitro.

METHODS

HeLa cell line was cultured and treated with different IRE protocols in order to obtain data for modeling the statistical relationship between the cell death and pulse-setting parameters. In total, 340 in vitro experiments were performed with a commercial IRE pulse system, including a pulse generator and an electric cuvette. Trypan blue staining technique was used to evaluate cell death after 4 hours of incubation following IRE treatment. Peleg-Fermi model was used in the study to build the statistical relationship using the cell viability data obtained from the in vitro experiments. A finite element model of IRE for the electric field distribution was also built. Comparison of ablation zones between the statistical model and electric threshold model (drawn from the finite element model) was used to show the accuracy of the proposed statistical model in the description of the ablation zone and its applicability in different pulse-setting parameters.

RESULTS

The statistical models describing the relationships between HeLa cell death and pulse length and the number of pulses, respectively, were built. The values of the curve fitting parameters were obtained using the Peleg-Fermi model for the treatment of cervical cancer with IRE. The difference in the ablation zone between the statistical model and the electric threshold model was also illustrated to show the accuracy of the proposed statistical model in the representation of ablation zone in IRE.

CONCLUSIONS

This study concluded that: (1) the proposed statistical model accurately described the ablation zone of IRE with cervical cancer cells, and was more accurate compared with the electric field model; (2) the proposed statistical model was able to estimate the value of electric field threshold for the computer simulation of IRE in the treatment of cervical cancer; and (3) the proposed statistical model was able to express the change in ablation zone with the change in pulse-setting parameters.

Proteomic Analysis of Perfusate from Machine Cold Perfusion of Transplant Kidneys: Insights Into Protection from Injury

Background

Machine cold perfusion is beneficial to the preservation of kidneys for transplantation. At the end of preservation, the perfusion solution contains many proteins. Using a proteomics approach, we searched for useful biomarkers and potential therapeutic targets in the perfusate. Our program is unique in that all transplant kidneys (even living donor kidneys, LKD) are placed on machine cold perfusion prior to transplantation.

Material/Methods

Perfusates from donation after neurological and circulatory determination of death (DNDD and DCDD respectively) and LKD were collected (n=41) and analyzed for LDH, neutrophil gelatinase-associated lipocalin (NGAL), and matrix metalloproteinase-2 (MMP-2) as markers of injury. Perfusate from each kidney was subjected to 2-dimensional gel electrophoresis, then analyzed using software to identify those spots which are significantly different between the 3 groups. Mass spectrometry was used to identify the proteins and their identity was confirmed with Western blot.

Results

The highest levels of MMP-2, LDH, and NGAL were seen for the DCDD kidneys, followed by the DNDD kidneys and then LDK. Peroxiredoxin-2, NGAL, and alpha-1-antitrypsin were identified as significantly different between the different types of donor kidneys, and their role and possible therapeutic strategies are discussed. Collagen fragments, albumin, and immunoglobulin were also identified as possible byproducts of the injury and may be useful is assessing the degree of injury.

Conclusions

Comparison of the perfusates from the different types of kidneys has allowed us to identify proteins that will be useful in future research into reducing injury in transplant kidneys.

Early experience with hypothermic machine perfusion of living donor kidneys - a retrospective study

Although hypothermic machine perfusion (HMP) has been shown to be beneficial to deceased donor kidneys, the effect of HMP on living donor kidneys (LDK) is unknown. LDK are subjected to minutes of normothermic ischemia at the time of recovery. Comparison of 16 LDK preserved by HMP with 16 LDK preserved by static cold storage (SCS). Outcomes of interest are resistive indices (RI), both while on HMP and postoperatively, and creatinine clearance (CrCl). Injury markers NGAL and LDH were seen in the perfusate of LDK in amounts similar to what is found for donation after neurological determination of death kidneys. Compared to SCS kidneys, CrCl was significantly higher in the HMP group from days 2 through 7 post-transplant [ie: day 7 (78.8 ± 5.4 vs. 54.0 ± 4.6 ml/min, P = 0.005)]. CrCl at 1 year was higher in the HMP group (81.2 ± 5.8 vs. 70.0 ± 5.3 ml/min, P = 0.03). Early post-transplant RI was significantly lower in the HMP group (0.61 ± 0.02 vs. 0.71 ± 0.02, P < 0.0001). Our data support the assertion that injury does occur during LDK procurement and suggest that some of this injury may be reversed with HMP, resulting in more favorable early RI and graft function compared to SCS kidneys.

Protection of the Transplant Kidney from Preservation Injury by Inhibition of Matrix Metalloproteinases

Background

Matrix metalloproteinases (MMPs), particularly MMP-2 and MMP-9, play an important role in ischemic injury to the heart, yet it is not known if these MMPs are involved in the injury that occurs to the transplant kidney. We therefore studied the pharmacologic protection of transplant kidneys during machine cold perfusion.

Methods

Human kidney perfusates were analyzed for the presence of injury markers such as cytochrome c oxidase, lactate dehydrogenase, and neutrophil-gelatinase associated lipocalin (NGAL), and MMP-2 and MMP-9 were measured. The effects of MMP inhibitors MMP-2 siRNA and doxycycline were studied in an animal model of donation after circulatory determination of death (DCDD).

Results

Markers of injury were present in all analyzed perfusates, with higher levels seen in perfusates from human kidneys donated after controlled DCDD compared to brain death and in perfusate from kidneys with delayed graft function. When rat kidneys were perfused at 4°C for 22 hours with the addition of MMP inhibitors, this resulted in markedly reduced levels of MMP-2, MMP-9 and analyzed injury markers.

Conclusions

Based on our study, MMPs are involved in preservation injury and the supplementation of preservation solution with MMP inhibitors is a potential novel strategy in protecting the transplant kidney from preservation injury.

Numerical analysis of the relationship between the area of target tissue necrosis and the size of target tissue in liver tumours with pulsed radiofrequency ablation

PURPOSE

Radiofrequency ablation (RFA) is currently restricted to the treatment of target tissues with a small size (<3 cm in diameter). To overcome this problem with RFA, some phenomena need to be understood first. The study presented in this paper investigated the relationship between the area of target tissue necrosis (TTN) and the size of target tissue in pulsed radiofrequency ablation (PRFA).

MATERIALS AND METHODS

Liver tumour, one of the common targets of RFA in clinical practice, was used as the target tissue in this study. Two types of pulsed RF power supply methods (half-square and half-sine) and three target tissues with different sizes (25 mm, 30 mm and 35 mm in diameter) were studied using finite element modelling. The finite element model (FEM) was validated by using an in vitro experiment with porcine liver tissue. The first roll-off occurrence or 720 s, whichever occurs first, was chosen as the ablation termination criterion in this study.

RESULTS

For each target tissue size, the largest TTN area was obtained using the maximum voltage applied (MVA) without roll-off occurrence. In this study, target tissues with a 25 mm diameter can be ablated cleanly but target tissues with 30-mm and 35-mm failed to be ablated.

CONCLUSIONS

The half-square PRFA could achieve a larger TTN area than the half-sine PRFA. The MVA decreases with an increase in the target tissue diameter in both the half-square PRFA and the half-sine PRFA. The findings of this study are in agreement with the clinical results that lesions (≥ 3 cm in diameter) have less favourable results from RFA.

Study of the relationship between the target tissue necrosis volume and the target tissue size in liver tumours using two-compartment finite element RFA modelling

PURPOSE

The aim of this study was to investigate the relationship between the target tissue necrosis volume and the target tissue size during the radiofrequency ablation (RFA) procedure.

MATERIALS AND METHODS

The target tissues with four different sizes (dxy = 20, 25, 30 and 35 mm) were modelled using a two-compartment radiofrequency ablation model. Different voltages were applied to seek the maximum target tissue necrosis volume for each target tissue size. The first roll-off occurrence or the standard ablation time (12 min) was taken as the sign for the termination of the RFA procedure.

RESULTS

Four different maximum voltages without the roll-off occurrence were found for the four different sizes of target tissues (dxy = 20, 25, 30 and 35 mm), and they were 36.6, 35.4, 33.9 and 32.5 V, respectively. The target tissues with diameters of 20, 25 mm can be cleanly ablated at their own maximum voltages applied (MVA) but the same finding was not found for the 35-mm target tissue. For the target tissue with diameter of 30 mm, the 50 °C isothermal contour (IT50) result showed that the target tissue can be cleanly ablated, but the same result did not show in the Arrhenius damage model result. Furthermore, two optimal RFA protocols with a minimal thermal damage to the healthy tissues were found for the target tissues with diameters of 20 and 25 mm, respectively.

CONCLUSIONS

The study suggests that target tissues of different sizes should be treated with different RFA protocols. The maximum target tissue volume was achieved with the MVA without the roll-off occurrence for each target tissue size when a constant RF power supply was used.

Volatility of serum creatinine relative to tacrolimus levels predicts kidney transplant rejection

BACKGROUND

We hypothesized that greater volatility of creatinine (SCr) relative to tacrolimus levels [Tac] (VCT) is associated with an increased risk of rejection.

MATERIAL AND METHODS

Retrospective chart review was performed of all single-kidney-only transplants in our Renal Transplant Program from March 2004 to March 2010 (n=117) whose immunosuppressive regimen included tacrolimus (n=81). We collected all available SCr and [Tac] over the first 2 years post-transplant and calculated the VCT for each patient. SCr and [Tac] values were excluded from the first month and from the rise that occurred immediately preceding a rejection episode.

RESULTS

Univariate analysis revealed that VCT was associated with increased odds of biopsy-proven rejection. A logistic regression model including donor type and HLA matches revealed that VCT (OR=1.16 [1.07, 1.26], p=0.0004) was strongly associated with rejection. ROC curve analysis yielded an AUC=0.823 (p<0.0001).

CONCLUSIONS

Increased volatility of SCr relative to [Tac] is associated with an increased risk of rejection. Whereas increased variation in [Tac] levels has been shown to indicate reduced adherence, increased VCT may signal 'immunologic unrest' in the graft. Further studies are warranted to determine if intervention at the time when volatility increases can lower the risk of an acute rejection episode.

Evaluation of the current radiofrequency ablation systems using axiomatic design theory

This article evaluates current radiofrequency ablation systems using axiomatic design theory. Due to its minimally invasive procedure, short-time hospital stay, low cost, and tumour metastasis treatment, the radiofrequency ablation technique has been playing an important role in tumour treatment in recent decades. Although the radiofrequency ablation technique has many advantages, some issues still need to be addressed. Among these issues, the two most important are as follows: (1) the size of tumours to be removed (has to be larger than 3 cm in diameter) and (2) cleanness of the removal. Many device solutions have been proposed to address the two issues. However, there is a lack of knowledge regarding the systematic evaluation of these solutions. This article evaluates these systems in terms of their solution principles (or simply called conceptual design in general product design theory) using a design theory called axiomatic design theory. In addition, with the axiomatic design theory, a better conceptual design in terms of its feasibility to cope with incomplete target tissue necrosis from the large size of tumours has been found. The detailed analysis and simulation of the new conceptual design are conducted using finite element approach. The results in this article are proved by the information of animal experiments and clinical practices obtained from the literature. This study thus contributes to the current knowledge to further developments in radiofrequency ablation systems and procedure guidelines for physicians to perform the radiofrequency ablation operation more effectively.

The prognostic value of time needed on dialysis in patients with delayed graft function

INTRODUCTION

We hypothesize that in patients with delayed graft function (DGF), the need for a longer time needed on dialysis (TND) post-kidney transplant is associated with poorer long-term function and an increase in complications.

METHODS

This was a retrospective chart review involving collaboration between Western University (WU) Renal Transplant Program of London, Ontario and the Saskatchewan renal transplant program (SRTP). A total of 774 patients (567 WU and 207 SRTP) received kidney transplants between 2004 and 2011, of which 83 patients with deceased donor transplants (59 WU and 24 SRTP) developed DGF, defined as the need for dialysis in the first week posttransplant.

RESULTS

Patients with DGF were divided into three groups depending on TND [group 1: <7 days (n = 52), group 2: 7-14 days (n = 13) and group 3 (n = 18): >14 days]. The creatinine clearance (CrCl) at 30 days (42.5, 33.8, 20.0 cc/min; P < 0.001) and 1 year (56.7, 49.2, 37.3 cc/min, P = 0.031) were significantly different between the three groups. Multivariate regression analysis identified length of TND posttransplant (β = -0.5, P < 0.001) and donation after cardiac death (DCD) donor (β = 19.5, P < 0.001) as the most significant predictors of CrCl at 1 year in these patients with DGF. DCD kidneys with DGF had a higher CrCl at 1 year and fewer readmissions in the first year compared with non-DCD kidneys with DGF.

DISCUSSION

Our study suggests that increased TND is associated with worse CrCl at 1 year. The data also support the hypothesis of a different mechanism for DGF in DCD and non-DCD kidneys.

Peritoneal dialysis versus hemodialysis in patients with delayed graft function

Delayed graft function (DGF) in kidney transplantation affects adverse outcomes. It remains unclear whether the post-transplant dialysis modality alters perioperative or long-term graft outcomes. We performed a retrospective observational quality initiative at two Canadian renal transplant centers, in which DGF occurred in the recipient, necessitating one of peritoneal dialysis (PD) or hemodialysis (HD). There was no difference in baseline factors between patients with post-transplant PD (n = 14) or HD (n = 63). The use of PD was associated with an increased risk of wound infection/leakage (PD 5/14 vs. HD 6/63, p = 0.024), shorter length of hospitalization (13.7 vs. 18.7 d, p = 0.009) and time requiring dialysis post-operatively (6.5 vs 11.0 d, p = 0.043). There were no differences in readmission to hospital within 6 months (4/14 vs. 23/63, p = 0.759), graft loss (0/14 vs. 2/63, p = 1.000) or acute rejection episodes (1/14 vs. 4/63, p = 1.000) at one yr, and GFR did not differ between the PD or HD groups at 30 d (35.7 vs. 33.8 mL/min/m(2), p = 0.731), six months (46.9 vs. 45.5 mL/min/m(2), p = 0.835) or one yr (46.6 vs. 44.5 mL/min/m(2), p = 0.746). Further research is needed to determine which transplant patients are most appropriate to undergo PD catheter removal at the time of transplantation.

Modeling and in vitro experimental validation for kinetics of the colonoscope in colonoscopy

Colonoscopy is the most sensitive and specific means for detection of colon cancers and polyps. To make colonoscopy more effective several problems must be overcome including: pain associated with the procedure, the risk of perforation, and incomplete intubation colonoscopy. Technically, these problems are the result of loop formation during colonoscopy. Although, several solutions such as modifying the stiffness of the colonoscope, using an overtube and developing image-guided instruments have been introduced to resolve the looping problem, the results of these systems are not completely satisfactory. A new paradigm to overcome loop formation is proposed that is doctor-assistive colonoscopy. In this approach, the endoscopists performance is enhanced by providing using a kinetic model that provides information such as the shape of the scope, direction of the colon and forces exerted within certain sections. It is expected that with the help of this model, the endoscopist would be able to adjust the manipulation to avoid loop formation. In the present studies, the kinetic model is developed and validated using an ex vivo colonoscopy test-bed with a comprehensive kinematic and kinetic data collection. The model utilizes an established colon model based on animal tissue with position tracking sensors, contact force sensors for the intraluminal portion of the scope and a Colonoscopy Force Monitor for the external insertion tube.

Analysis of and mathematical model insight into loop formation in colonoscopy

The colonoscope is an important tool in the diagnosis and management of diseases of the colon; yet its design has not changed appreciably since it was first introduced to clinical practice 40 years ago. One of the ongoing challenges with this device is that the natural shape of the colon predisposes to loop formation by the scope during the examination. The result of this looping is that further insertion of the scope results in a larger loop size without any advancement of the tip of the scope. Looping thus causes pain in the patient, risks perforation of the colon, and results in incomplete examinations. In this article, loop formation is analyzed in terms of frictional force state and Kirchhoff's slender rod model in order to better understand the generic principle of loop formation. Next, a mathematical model of deformation of the colon with respect to external manipulation involving a number of variables involved in loop formation is constructed. Finally, a model of the motion of the scope relative to the colon when looping occurs is presented. The model has clinical significance for prediction of advancement of the tip of the scope when looping occurs. The mathematical model was then validated and verified using data available from the literature. Our models are an important starting point in the development of a novel device to overcome loop formation and result in increased patient comfort and an improved completion rate for colonoscopy procedures.

Patients aged 80 years and older accrue similar benefits from total parenteral nutrition compared to middle-aged patients

Age is becoming less of a consideration to aggressive medical and surgical interventions. The aim of this study was to evaluate whether patients older than 80 years showed similar gains from total parenteral nutrition (TPN) in terms of nutritional and inflammatory markers compared to patients 35 to 50 years old. A database of patients aged ≥80 years old (group 1) and patients between 35 and 50 (group 2), on TPN for greater than 1 week, was compiled from the Nutrition Support Service (NSS) database. Patients had C-reactive protein (CRP), prealbumin, and albumin drawn twice weekly. Patients were matched 1:1 based on gender, diabetes, smoking, Subjective Global Assessment score, and diagnosis. Both groups showed comparable improvements in nutritional and inflammatory markers. There were no statistically significant differences in weekly changes to prealbumin, albumin, CRP, and CRP:prealbumin (C:P) ratio between group 1 and group 2 patients. Both groups had similar complication rates (line-related thrombosis, catheter-related bloodstream infections, intra-abdominal sepsis), days on TPN, length of hospitalization, and mortality rate. Patients older than 80 years benefit from aggressive nutritional support by administration of TPN. Age should not be used as an exclusion criterion for patients requiring TPN.

Overview of upcoming advances in colonoscopy

Although colonoscopy is a very commonly carried out procedure, it is not without its problems, including a risk of perforation and significant patient discomfort, especially associated with looping formation. Furthermore, looping formation may prevent a complete colonoscopy from being carried out in certain patients. The conventional colonoscope has not changed very much since its original introduction. We review promising technologies that are being promoted as a way to address the problems with current colonoscopy. There are some methods to prevent looping formation, including overtube, variable stiffness, computer-guided scopes, Aer-O-Scope, magnetic endoscopic imaging and the capsule endoscope. In recent years, with the progress of microelectromechanical and microelectronic technologies, many biomedical and robotic researchers are developing autonomous endoscopes with miniaturization of size and integration functionality that represent state of the art of the micro-robotic endoscope. The initial results by using aforementioned methods seem promising; however, there are some conflicting reports of clinical trials with the overtube colonoscope, the computer-guided scope and the variable stiffness colonoscope. There are also some limitations in the use of the Aer-o-scope and the capsule endoscope. The autonomous endoscope is based on a self-propelling property that is able to avoid looping completely. This novel technology could potentially become the next generation endoscope; however, there are still critical techniques to be approached in order to develop the effective and efficient novel endoscope.

The C-reactive protein-to-prealbumin ratio predicts fistula closure

BACKGROUND

The purpose of this study was to evaluate the predictability of fistula closure using the ratio of C-reactive protein to prealbumin (C:P ratio).

METHODS

A database of 89 patients with gastrointestinal fistulas (1994-2009) was created based on the records of our Nutrition Support Services Team. All patients had weekly blood work including C-reactive protein level, prealbumin level, and albumin level. Forty-three fistulas were managed without surgery for 6 weeks or more; of these, 29 closed.

RESULTS

The median C:P ratio for those fistulas that remained open after 6 weeks of conservative management differed significantly from those that closed (.10 vs .35; P < .001). For patients with a C:P ratio of .25 or less, fistula closure occurred in 87.0% (95% confidence interval, 74.0-94.3), whereas for patients with a ratio of greater than 1.0, no fistulas closed.

CONCLUSION

Our results suggest that the C:P ratio is a predictor of fistula closure.

Intrapancreatic accessory spleen: A case report and review of the literature

We present the case of a 26 year old male who was found to have a mass in the tail of the pancreas on an ultrasound scan. The lesion was suspicious for a non-functioning pancreatic neuroendocrine tumour (PNET) and so he underwent distal pancreatectomy. Pathology revealed this to be an intrapancreatic accessory spleen (IPAS). This is a rare entity, and the literature on this subject is reviewed. A lesion in the pancreas that enhances in a manner similar to the spleen, whether the contrast is used in the setting of a Contrast Enhanced Ultrasound, a contrast enhanced CT scan, or a gadolinium enhanced MRI scan, is suggestive of IPAS. Nonetheless, the majority of these rare lesions are likely to be surgically excised rather than observed due to the similar appearance to PNET.

How useful are bowel sounds in assessing the abdomen?

BACKGROUND

The purpose of our study is to determine the accuracy of bowel sounds in the diagnosis of ileus and bowel obstruction.

METHODS

Healthy volunteers (n = 10) and patients with radiologically or laparotomy confirmed small bowel obstruction (n = 9) and ileus (n = 7) were enrolled. Two 30-second recordings from each subject were obtained using an electronic stethoscope. Study physicians (n = 20) were then presented with 43 recordings in blinded fashion and were asked whether each was from a normal subject or from a subject with bowel obstruction or ileus.

RESULTS

Physicians arrived at the correct diagnosis a median of 30 times out of 43 (69.8%). Intra-observer variation (κ = 0.72, agreement 81.3%) and intra-subject variation (κ = 0.63, agreement 78.7%) were very good. Bowel sounds from subjects with ileus and normal bowel sounds were correctly identified most of the time (84.5 and 78.1%, respectively). Bowel sounds from patients with obstruction were correctly identified only 42.1% of the time, but if a physician believed he or she was hearing a bowel obstruction, this had a strong positive predictive value (PPV, 72.7%).

CONCLUSION

Our results suggest that the auscultation of bowel sounds is useful, especially in detecting ileus. The diagnosis of obstruction had a high PPV.

Recent experience with laparoscopic appendectomy in a Canadian teaching centre

OBJECTIVE

Laparoscopic appendectomy (LA) remains controversial in our city, in part because of results obtained early in the learning curve. In 1995, our centre reported that LA took 30 minutes longer and yet resulted in similar length of hospital stay, compared with open appendectomy (OA). The purpose of the current study is to reexamine LA now that more experience has been gained with the procedure and to document the learning curve at a typical Canadian teaching centre.

METHODS

We undertook a retrospective chart review of patients undergoing nonelective appendectomy between January 2001 and June 2004; this yielded 201 charts that satisfied the inclusion criteria. The 201 cases were divided into 3 groups, each consisting of 67 consecutive cases, to allow for comparison between early, middle and late experience. The main outcomes of interest were operative time, length of stay and the changes over time that occurred in these 2 measures. An intent-to-treat analysis was performed.

RESULTS

The mean operative time differed by only minutes: 54.9 (standard error of mean [SEM] 1.9) minutes for LA and 48.8 (SEM 1.4) minutes for OA (p = 0.004). Length of stay was 1.3 (SEM 0.1) days and 2.9 (SEM 0.2) days for LA and OA groups, respectively (p 0.0001). Analysis of the 3 time periods (early, middle and late) revealed significant improvements in operative time and length of stay for LA in the middle, compared with the early, time periods.

CONCLUSION

These data suggest that, with experience, LA operative time approaches that of OA and length of stay decreases. A shortened hospital stay and similar operative time, along with educational advantages, support the use of the LA in teaching centres.

Options for induction immunosuppression in liver transplant recipients

Immunosuppression administered in the early postoperative period following liver transplantation plays a crucial role in the survival of the graft and the patient. The introduction of cyclosporin was an important landmark in transplantation, and to this day, calcineurin inhibitors form the basis of most induction immunosuppression regimens. New drugs are being developed which are more specifically targeted to prevention of rejection, and multiple drug combinations have been proposed as a means of reducing the adverse effects of individual drugs. Azathioprine and the newer antimetabolite mycophenolate mofetil have been added to calcineurin inhibitor-based regimens with varying amounts of success. Antibody induction has evolved as a potent form of immunosuppression as well as a means of avoiding certain adverse effects, particularly nephrotoxicity. The numerous adverse effects encountered with polyclonal preparations have been reduced with the development of more specific monoclonal antibodies such as muromonab CD3 (OKT3) or interleukin (IL)-2 receptor (IL-2R) antagonists. The anti-IL-2R antibody preparations basiliximab and daclizumab have shown excellent early results due to their potent yet highly targeted immunosuppressive effect and minimal adverse effects. Further study is needed to determine the most appropriate dosage, timing and patient population for these new drugs in the setting of liver transplantation. Although a number of different induction regimens have been described, no single protocol is suitable for all liver transplant recipients. Rather, certain regimens have advantages that could favour their use in a specific subgroup of patients. A number of clinical trials are underway to identify new, more specific drugs and combinations which could be useful in induction immunosuppression.