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  1. Cheong JKK, Ooi EH, Ooi ET
    Int J Numer Method Biomed Eng, 2020 09;36(9):e3374.
    PMID: 32519516 DOI: 10.1002/cnm.3374
    Recent studies have demonstrated the effectiveness of switching bipolar radiofrequency ablation (bRFA) in treating liver cancer. Nevertheless, the clinical use of the treatment remains less common than conventional monopolar RFA - likely due to the lack of understanding of how the tissues respond thermally to the switching effect. The problem is exacerbated by the numerous possible switching combinations when bRFA is performed using bipolar needles, thus making theoretical deduction and experimental studies difficult. This article addresses this issue via computational modelling by examining if significant variation in the treatment outcome exists amongst six different electrode configurations defined by the X-, C-, U-, N-, Z- and O-models. Results indicated that the tissue thermal and thermal damage responses varied depending on the electrode configuration and the operating conditions (input voltage and ablation duration). For a spherical tumour, 30 mm in diameter, complete ablation could not be attained in all configurations with 70 V input voltage and 5 minutes ablation duration. Increasing the input voltage to 90 V enlarged the coagulation zone in the X-model only. With the other configurations, extending the ablation duration to 10 minutes was found to be the better at enlarging the coagulation zone.
    Matched MeSH terms: Liver/surgery
  2. Yip WP, Kho ASK, Ooi EH, Ooi ET
    Med Eng Phys, 2023 Feb;112:103950.
    PMID: 36842773 DOI: 10.1016/j.medengphy.2023.103950
    No-touch bipolar radiofrequency ablation (bRFA) is known to produce incomplete tumour ablation with a 'butterfly-shaped' coagulation zone when the interelectrode distance exceeds a certain threshold. Although non-confluent coagulation zone can be avoided by not implementing the no-touch mode, doing so exposes the patient to the risk of tumour track seeding. The present study investigates if prior infusion of saline into the tissue can overcome the issues of non-confluent or butterfly-shaped coagulation. A computational modelling approach based on the finite element method was carried out. A two-compartment model comprising the tumour that is surrounded by healthy liver tissue was developed. Three cases were considered; i) saline infusion into the tumour centre; ii) one-sided saline infusion outside the tumour; and iii) two-sided saline infusion outside the tumour. For each case, three different saline volumes were considered, i.e. 6, 14 and 22 ml. Saline concentration was set to 15% w/v. Numerical results showed that saline infusion into the tumour centre can overcome the butterfly-shaped coagulation only if the infusion volume is sufficient. On the other hand, one-sided infusion outside the tumour did not overcome this. Two-sided infusion outside the tumour produced confluent coagulation zone with the largest volume. Results obtained from the present study suggest that saline infusion, when carried out correctly, can be used to effectively eradicate liver cancer. This presents a practical solution to address non-confluent coagulation zone typical of that during two-probe bRFA treatment.
    Matched MeSH terms: Liver/surgery
  3. Kho ASK, Ooi EH, Foo JJ, Ooi ET
    Comput Methods Programs Biomed, 2021 Nov;211:106436.
    PMID: 34601185 DOI: 10.1016/j.cmpb.2021.106436
    BACKGROUND AND OBJECTIVE: Saline infusion is applied together with radiofrequency ablation (RFA) to enlarge the ablation zone. However, one of the issues with saline-infused RFA is backflow, which spreads saline along the insertion track. This raises the concern of not only thermally ablating the tissue within the backflow region, but also the loss of saline from the targeted tissue, which may affect the treatment efficacy.

    METHODS: In the present study, 2D axisymmetric models were developed to investigate how saline backflow influence saline-infused RFA and whether the aforementioned concerns are warranted. Saline-infused RFA was described using the dual porosity-Joule heating model. The hydrodynamics of backflow was described using Poiseuille law by assuming the flow to be similar to that in a thin annulus. Backflow lengths of 3, 4.5, 6 and 9 cm were considered.

    RESULTS: Results showed that there is no concern of thermally ablating the tissue in the backflow region. This is due to the Joule heating being inversely proportional to distance from the electrode to the fourth power. Results also indicated that larger backflow lengths led to larger growth of thermal damage along the backflow region and greater decrease in coagulation volume. Hence, backflow needs to be controlled to ensure an effective treatment of saline-infused RFA.

    CONCLUSIONS: There is no risk of ablating tissues around the needle insertion track due to backflow. Instead, the risk of underablation as a result of the loss of saline due to backflow was found to be of greater concern.

    Matched MeSH terms: Liver/surgery
  4. Ooi EH, Ooi ET
    Comput Biol Med, 2021 10;137:104832.
    PMID: 34508975 DOI: 10.1016/j.compbiomed.2021.104832
    Switching bipolar radiofrequency ablation (bRFA) is a thermal treatment modality used for liver cancer treatment that is capable of producing larger, more confluent and more regular thermal coagulation. When implemented in the no-touch mode, switching bRFA can prevent tumour track seeding; a medical phenomenon defined by the deposition of cancer cells along the insertion track. Nevertheless, the no-touch mode was found to yield significant unwanted thermal damage as a result of the electrodes' position outside the tumour. It is postulated that the unwanted thermal damage can be minimized if ablation can be directed such that it focuses only within the tumour domain. As it turns out, this can be achieved by partially insulating the active tip of the RF electrodes such that electric current flows in and out of the tissue only through the non-insulated section of the electrode. This concept is known as unidirectional ablation and has been shown to produce the desired effect in monopolar RFA. In this paper, computational models based on a well-established mathematical framework for modelling RFA was developed to investigate if unidirectional ablation can minimize unwanted thermal damage during time-based switching bRFA. From the numerical results, unidirectional ablation was shown to produce treatment efficacy of nearly 100%, while at the same time, minimizing the amount of unwanted thermal damage. Nevertheless, this effect was observed only when the switch interval of the time-based protocol was set to 50 s. An extended switch interval negated the benefits of unidirectional ablation.
    Matched MeSH terms: Liver/surgery
  5. Mak NL, Ng WH, Ooi EH, Lau EV, Pamidi N, Foo JJ, et al.
    Comput Methods Programs Biomed, 2024 Jan;243:107866.
    PMID: 37865059 DOI: 10.1016/j.cmpb.2023.107866
    BACKGROUND AND OBJECTIVES: Thermochemical ablation (TCA) is a cancer treatment that utilises the heat released from the neutralisation of acid and base to raise tissue temperature to levels sufficient to induce thermal coagulation. Computational studies have demonstrated that the coagulation volume produced by sequential injection is smaller than that with simultaneous injection. By injecting the reagents in an ensuing manner, the region of contact between acid and base is limited to a thin contact layer sandwiched between the distribution of acid and base. It is hypothesised that increasing the frequency of acid-base injections into the tissue by shortening the injection interval for each reagent can increase the effective area of contact between acid and base, thereby intensifying neutralisation and the exothermic heat released into the tissue.

    METHODS: To verify this hypothesis, a computational model was developed to simulate the thermochemical processes involved during TCA with sequential injection. Four major processes that take place during TCA were considered, i.e., the flow of acid and base, their neutralisation, the release of exothermic heat and the formation of thermal damage inside the tissue. Equimolar acid and base at 7.5 M was injected into the tissue intermittently. Six injection intervals, namely 3, 6, 15, 20, 30 and 60 s were investigated.

    RESULTS: Shortening of the injection interval led to the enlargement of coagulation volume. If one considers only the coagulation volume as the determining factor, then a 15 s injection interval was found to be optimum. Conversely, if one places priority on safety, then a 3 s injection interval would result in the lowest amount of reagent residue inside the tissue after treatment. With a 3 s injection interval, the coagulation volume was found to be larger than that of simultaneous injection with the same treatment parameters. Not only that, the volume also surpassed that of radiofrequency ablation (RFA); a conventional thermal ablation technique commonly used for liver cancer treatment.

    CONCLUSION: The numerical results verified the hypothesis that shortening the injection interval will lead to the formation of larger thermal coagulation zone during TCA with sequential injection. More importantly, a 3 s injection interval was found to be optimum for both efficacy (large coagulation volume) and safety (least amount of reagent residue).

    Matched MeSH terms: Liver/surgery
  6. Kho AS, Ooi EH, Foo JJ, Ooi ET
    Comput Biol Med, 2021 01;128:104112.
    PMID: 33212331 DOI: 10.1016/j.compbiomed.2020.104112
    Infusion of saline prior to radiofrequency ablation (RFA) is known to enlarge the thermal coagulation zone. The abundance of ions in saline elevate the electrical conductivity of the saline-saturated region. This promotes greater electric current flow inside the tissue, which increases the amount of RF energy deposition and subsequently enlarges the coagulation zone. In theory, infusion of higher concentration of saline should lead to larger coagulation zone due to the greater number of ions. Nevertheless, existing studies on the effects of concentration on saline-infused RFA have been conflicting, with the exact role of saline concentration yet to be fully elucidated. In this paper, computational models of saline-infused RFA were developed to investigate the role of saline concentration on the outcome of saline-infused RFA. The elevation in tissue electrical conductivity was modelled using the microscopic mixture model, while RFA was modelled using the coupled dual porosity-Joule heating model. Results obtained indicated that the presence of a concentration threshold to which no further elevation in tissue electrical conductivity and enlargement in thermal coagulation can occur. This threshold was determined to be at 15% NaCl. Analysis of the Joule heating distribution revealed the presence of a secondary Joule heating site located along the interface between wet and dry tissue. This secondary Joule heating was responsible for the enlargement in coagulation volume and its rapid growth phase during ablation.
    Matched MeSH terms: Liver/surgery
  7. Yap S, Ooi EH, Foo JJ, Ooi ET
    Comput Biol Med, 2021 04;131:104273.
    PMID: 33631495 DOI: 10.1016/j.compbiomed.2021.104273
    Radiofrequency ablation (RFA) is a thermal ablative treatment method that is commonly used to treat liver cancer. However, the thermal coagulation zone generated using the conventional RFA system can only successfully treat tumours up to 3 cm in diameter. Switching bipolar RFA has been proposed as a way to increase the thermal coagulation zone. Presently, the understanding of the underlying thermal processes that takes place during switching bipolar RFA remains limited. Hence, the objective of this study is to provide a comprehensive understanding on the thermal ablative effects of time-based switching bipolar RFA on liver tissue. Five switch intervals, namely 50, 100, 150, 200 and 300 s were investigated using a two-compartment 3D finite element model. The study was performed using two pairs of RF electrodes in a four-probe configuration, where the electrodes were alternated based on their respective switch interval. The physics employed in the present study were verified against experimental data from the literature. Results obtained show that using a shorter switch interval can improve the homogeneity of temperature distribution within the tissue and increase the rate of temperature rise by delaying the occurrence of roll-off. The coagulation volume obtained was the largest using switch interval of 50 s, followed by 100, 150, 200 and 300 s. The present study demonstrated that the transient thermal response of switching bipolar RFA can be improved by using shorter switch intervals.
    Matched MeSH terms: Liver/surgery
  8. Radhamanalan S, Thomas I
    Med J Malaysia, 1979 Sep;34(1):46-7.
    PMID: 542151
    Matched MeSH terms: Liver/surgery
  9. Kho ASK, Foo JJ, Ooi ET, Ooi EH
    Comput Methods Programs Biomed, 2020 Feb;184:105289.
    PMID: 31891903 DOI: 10.1016/j.cmpb.2019.105289
    BACKGROUND AND OBJECTIVE: The majority of the studies on radiofrequency ablation (RFA) have focused on enlarging the size of the coagulation zone. An aspect that is crucial but often overlooked is the shape of the coagulation zone. The shape is crucial because the majority of tumours are irregularly-shaped. In this paper, the ability to manipulate the shape of the coagulation zone following saline-infused RFA by altering the location of saline infusion is explored.

    METHODS: A 3D model of the liver tissue was developed. Saline infusion was described using the dual porosity model, while RFA was described using the electrostatic and bioheat transfer equations. Three infusion locations were investigated, namely at the proximal end, the middle and the distal end of the electrode. Investigations were carried out numerically using the finite element method.

    RESULTS: Results indicated that greater thermal coagulation was found in the region of tissue occupied by the saline bolus. Infusion at the middle of the electrode led to the largest coagulation volume followed by infusion at the proximal and distal ends. It was also found that the ability to delay roll-off, as commonly associated with saline-infused RFA, was true only for the case when infusion is carried out at the middle. When infused at the proximal and distal ends, the occurrence of roll-off was advanced. This may be due to the rapid and more intense heating experienced by the tissue when infusion is carried out at the electrode ends where Joule heating is dominant.

    CONCLUSION: Altering the location of saline infusion can influence the shape of the coagulation zone following saline-infused RFA. The ability to 'shift' the coagulation zone to a desired location opens up great opportunities for the development of more precise saline-infused RFA treatment that targets specific regions within the tissue.

    Matched MeSH terms: Liver/surgery
  10. Ooi EH, J Y Chia N, Ooi ET, Foo JJ, Liao IY, R Nair S, et al.
    Int J Hyperthermia, 2018 12;34(8):1142-1156.
    PMID: 29490513 DOI: 10.1080/02656736.2018.1437282
    A recent study by Ooi and Ooi (EH Ooi, ET Ooi, Mass transport in biological tissues: Comparisons between single- and dual-porosity models in the context of saline-infused radiofrequency ablation, Applied Mathematical Modelling, 2017, 41, 271-284) has shown that single-porosity (SP) models for describing fluid transport in biological tissues significantly underestimate the fluid penetration depth when compared to dual-porosity (DP) models. This has raised some concerns on whether the SP model, when coupled with models of radiofrequency ablation (RFA) to simulate saline-infused RFA, could lead to an underestimation of the coagulation size. This paper compares the coagulation volumes obtained following saline-infused RFA predicted based on the SP and DP models for fluid transport. Results showed that the SP model predicted coagulation zones that are consistently 0.5 to 0.9 times smaller than that of DP model. This may be explained by the low permeability value of the tissue interstitial space, which causes the majority of the saline to flow through the vasculature. The absence of fluid flow tracking in the vasculature in the SP model meant that any flow of saline into the vasculature is treated as losses and do not contribute to the saline penetration depth of the tissue. Comparisons with experimental results from the literature revealed that the DP models predicted coagulation zone sizes that are closer to the experimental values than the SP models. This supports the hypothesis that the SP model is a poor choice for simulating the outcome of saline-infused RFA.
    Matched MeSH terms: Liver/surgery*
  11. Alirr OI, Rahni AAA, Golkar E
    Int J Comput Assist Radiol Surg, 2018 Aug;13(8):1169-1176.
    PMID: 29860549 DOI: 10.1007/s11548-018-1801-z
    PURPOSE: Segmentation of liver tumours is an important part of the 3D visualisation of the liver anatomy for surgical planning. The spatial relationship between tumours and other structures inside the liver forms the basis of preoperative surgical risk assessment. However, the automatic segmentation of liver tumours from abdominal CT scans is riddled with challenges. Tumours located at the border of the liver impose a big challenge as the surrounding tissues could have similar intensities.

    METHODS: In this work, we introduce a fully automated liver tumour segmentation approach in contrast-enhanced CT datasets. The method is a multi-stage technique which starts with contrast enhancement of the tumours using anisotropic filtering, followed by adaptive thresholding to extract the initial mask of the tumours from an identified liver region of interest. Localised level set-based active contours are used to extend the mask to the tumour boundaries.

    RESULTS: The proposed method is validated on the IRCAD database with pathologies that offer highly variable and complex liver tumours. The results are compared quantitatively to the ground truth, which is delineated by experts. We achieved an average dice similarity coefficient of 75% over all patients with liver tumours in the database with overall absolute relative volume difference of 11%. This is comparable to other recent works, which include semiautomated methods, although they were validated on different datasets.

    CONCLUSIONS: The proposed approach aims to segment tumours inside the liver envelope automatically with a level of accuracy adequate for its use as a tool for surgical planning using abdominal CT images. The approach will be validated on larger datasets in the future.

    Matched MeSH terms: Liver/surgery
  12. Givehchi S, Wong YH, Yeong CH, Abdullah BJJ
    Minim Invasive Ther Allied Technol, 2018 Apr;27(2):81-89.
    PMID: 28612670 DOI: 10.1080/13645706.2017.1330757
    PURPOSE: To investigate the effect of radiofrequency ablation (RFA) electrode trajectory on complete tumor ablation using computational simulation.

    MATERIAL AND METHODS: The RFA of a spherical tumor of 2.0 cm diameter along with 0.5 cm clinical safety margin was simulated using Finite Element Analysis software. A total of 86 points inside one-eighth of the tumor volume along the axial, sagittal and coronal planes were selected as the target sites for electrode-tip placement. The angle of the electrode insertion in both craniocaudal and orbital planes ranged from -90° to +90° with 30° increment. The RFA electrode was simulated to pass through the target site at different angles in combination of both craniocaudal and orbital planes before being advanced to the edge of the tumor.

    RESULTS: Complete tumor ablation was observed whenever the electrode-tip penetrated through the epicenter of the tumor regardless of the angles of electrode insertion in both craniocaudal and orbital planes. Complete tumor ablation can also be achieved by placing the electrode-tip at several optimal sites and angles.

    CONCLUSIONS: Identification of the tumor epicenter on the central slice of the axial images is essential to enhance the success rate of complete tumor ablation during RFA procedures.

    Matched MeSH terms: Liver/surgery*
  13. Alirr OI, Abd Rahni AA
    Int J Comput Assist Radiol Surg, 2020 Feb;15(2):239-248.
    PMID: 31617057 DOI: 10.1007/s11548-019-02078-x
    PURPOSE: For the liver to remain viable, the resection during hepatectomy procedure should proceed along the major vessels; hence, the resection planes of the anatomic segments are defined, which mark the peripheries of the self-contained segments inside the liver. Liver anatomic segments identification represents an essential step in the preoperative planning for liver surgical resection treatment.

    METHOD: The method based on constructing atlases for the portal and the hepatic veins bifurcations, the atlas is used to localize the corresponding vein in each segmented vasculature using atlas matching. Point-based registration is used to deform the mesh of atlas to the vein branch. Three-dimensional distance map of the hepatic veins is constructed; the fast marching scheme is applied to extract the centerlines. The centerlines of the labeled major veins are extracted by defining the starting and the ending points of each labeled vein. Centerline is extracted by finding the shortest path between the two points. The extracted centerline is used to define the trajectories to plot the required planes between the anatomical segments.

    RESULTS: The proposed approach is validated on the IRCAD database. Using visual inspection, the method succeeded to extract the major veins centerlines. Based on that, the anatomic segments are defined according to Couinaud segmental anatomy.

    CONCLUSION: Automatic liver segmental anatomy identification assists the surgeons for liver analysis in a robust and reproducible way. The anatomic segments with other liver structures construct a 3D visualization tool that is used by the surgeons to study clearly the liver anatomy and the extension of the cancer inside the liver.

    Matched MeSH terms: Liver/surgery*
  14. Hlaing KP, Othman F
    Singapore Med J, 2012 Sep;53(9):e186-8.
    PMID: 23023911
    Liver transplantation is the only solution for end-stage liver diseases. The common hepatic artery (CHA) arises from the coeliac trunk (CT), and the right (RHA) and left hepatic (LHA) arteries are its terminal branches. An abnormal arterial pattern would influence the surgical outcome. The anterior layer of the lesser omentum of a female cadaver was cleaned to identify the CHA, which was traced backwards for its origin and toward the porta hepatis for its terminal branches. In this case, the replaced RHA originated from the CT and ran posterior to the portal vein and the common bile duct. The replaced LHA arose from the left gastric artery. The CHA originated from the CT and branched out as the middle hepatic and gastroduodenal arteries. The replaced RHA and LHA with alteration in relation to the neighbouring structures is a complex and rare variant. Knowledge of this uncommon arterial anomaly is beneficial for hepatobiliary surgeons.
    Matched MeSH terms: Liver/surgery
  15. Hall SK, Ooi EH, Payne SJ
    Crit Rev Biomed Eng, 2014;42(5):383-417.
    PMID: 25745803
    Minimally invasive tumor ablations (MITAs) are an increasingly important tool in the treatment of solid tumors across multiple organs. The problems experienced in modeling different types of MITAs are very similar, but the development of mathematical models is mostly performed in isolation according to modality. Fundamental research into the modeling of specific types of MITAs is indeed required, but to choose the optimal treatment for an individual the primary clinical requirement is to have reliable predictions for a range of MITAs. In this review of the mathematical modeling of MITAs 4 modalities are considered: radiofrequency ablation, microwave ablation, cryoablation, and irreversible electroporation. The similarities in the mathematical modeling of these treatments are highlighted, and the analysis of the models within a general framework is discussed. This will aid in developing a deeper understanding of the sensitivity of MITA models to physiological parameters and the impact of uncertainty on predictions of the ablation zone. Through robust validation and analysis of the models it will be possible to choose the best model for a given application. This is important because many different models exist with no objective comparison of their performance. The collection of relevant in vivo experimental data is also critical to parameterize such models accurately. This approach will be necessary to translate the field into clinical practice.
    Matched MeSH terms: Liver/surgery
  16. Thambi Dorai CR, Visvanathan R, McAll GL
    Aust N Z J Surg, 1991 Jul;61(7):505-10.
    PMID: 1859310
    Type IVa choledochal cysts with cylindrical dilatation of the intrahepatic ducts constitute a relatively less recognized variety of choledochal cysts, and differ from cystic dilatation of intrahepatic ducts in their clinical manifestations and response to treatment. Five patients with type IVa choledochal cysts and cylindrical dilatation of major intrahepatic ducts who underwent cyst excision and Roux-en-Y hepaticojejunostomy are reported. The duration of symptoms was less than 1 year in all patients. Palpable abdominal mass and abdominal pain were present in 3 patients. The traid of jaundice, abdominal pain and mass was present in only 1 patient. The intrahepatic dilatation regressed after excision of the extrahepatic cyst just below the hilum of the liver. The surgical technique is described and the need for excision of the cyst is emphasized.
    Matched MeSH terms: Liver/surgery
  17. Balasegaram M, Joishy SK
    Am J Surg, 1981 Mar;141(3):360-5.
    PMID: 6259961
    Two hundred eight-eight hepatic resections performed over the past 15 years are discussed. The safety and success achieved are attributed to the original work in Malaysia on the anatomy of the liver and its anomalies, the use of surgical instruments specially designed for hepatic resection, various types of resections devised and studies on aids to liver regeneration after resection. The diversity of the principles and practice of surgery in the Western countries compared with those in Malaysia is illustrated.
    Matched MeSH terms: Liver/surgery*
  18. Shahrudin MD, Noori SM
    Hepatogastroenterology, 1997 Mar-Apr;44(14):519-21.
    PMID: 9164529
    To review our experience in managing post-hepatorrhaphy complications in liver trauma.
    Matched MeSH terms: Liver/surgery
  19. Balasegaram M
    Ann Surg, 1972 Apr;175(4):528-34.
    PMID: 4259839
    Matched MeSH terms: Liver/surgery
  20. Lee WS, Ong SY, Foo HW, Wong SY, Kong CX, Seah RB, et al.
    World J Gastroenterol, 2017 Nov 21;23(43):7776-7784.
    PMID: 29209118 DOI: 10.3748/wjg.v23.i43.7776
    AIM: To examine the medical status of children with biliary atresia (BA) surviving with native livers.

    METHODS: In this cross-sectional review, data collected included complications of chronic liver disease (CLD) (cholangitis in the preceding 12 mo, portal hypertension, variceal bleeding, fractures, hepatopulmonary syndrome, portopulmonary hypertension) and laboratory indices (white cell and platelet counts, total bilirubin, albumin, international normalized ratio, alanine aminotransferase, aspartate aminotransferase, γ-glutamyl transpeptidase). Ideal medical outcome was defined as absence of clinical evidence of CLD or abnormal laboratory indices.

    RESULTS: Fifty-two children [females = 32, 62%; median age 7.4 years, n = 35 (67%) older than 5 years] with BA (median age at surgery 60 d, range of 30 to 148 d) survived with native liver. Common complications of CLD noted were portal hypertension (40%, n = 21; 2 younger than 5 years), cholangitis (36%) and bleeding varices (25%, n = 13; 1 younger than 5 years). Fifteen (29%) had no clinical complications of CLD and three (6%) had normal laboratory indices. Ideal medical outcome was only seen in 1 patient (2%).

    CONCLUSION: Clinical or laboratory evidence of CLD are present in 98% of children with BA living with native livers after hepatoportoenterostomy. Portal hypertension and variceal bleeding may be seen in children younger than 5 years of age, underscoring the importance of medical surveillance for complications of BA starting at a young age.

    Matched MeSH terms: Liver/surgery
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