Displaying publications 1 - 20 of 31 in total

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  1. 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: Catheter Ablation*
  2. 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: Catheter Ablation*
  3. Abdullah B, Singh S
    PMID: 33810309 DOI: 10.3390/ijerph18073441
    Surgical treatment of the inferior turbinates is required for hypertrophic inferior turbinates refractory to medical treatments. The main goal of surgical reduction of the inferior turbinate is to relieve the obstruction while preserving the function of the turbinate. There have been a variety of surgical techniques described and performed over the years. Irrespective of the techniques and technologies employed, the surgical techniques are classified into two types, the mucosal-sparing and non-mucosal-sparing, based on the preservation of the medial mucosa of the inferior turbinates. Although effective in relieving nasal block, the non-mucosal-sparing techniques have been associated with postoperative complications such as excessive bleeding, crusting, pain, and prolonged recovery period. These complications are avoided in the mucosal-sparing approach, rendering it the preferred option. Although widely performed, there is significant confusion and detachment between current practices and their basic objectives. This conflict may be explained by misperception over the myriad of available surgical techniques and misconception of the rationale in performing the turbinate reduction. A comprehensive review of each surgical intervention is crucial to better define each procedure and improve understanding of the principle and mechanism involved.
    Matched MeSH terms: Catheter Ablation*
  4. 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: Catheter Ablation*
  5. 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: Catheter Ablation*
  6. Mittal S
    Heart Rhythm, 2008 Jun;5(6 Suppl):S64-7.
    PMID: 18456205 DOI: 10.1016/j.hrthm.2008.03.023
    Catheter ablation has come to play an important therapeutic role in the management of some patients with ventricular arrhythmias. An important advance in catheter ablation of ventricular tachycardia (VT) has been the development of three-dimensional catheter-based mapping systems, which permit identification of the tachycardia circuit and facilitate a strategy for catheter ablation. As a result, patients who suffer from "focal" forms of VT have been identified. This can have implications with respect to underlying arrhythmia mechanism, patient prognosis, and therapeutic strategies. The article reviews some insights learned from catheter ablation of focal forms of VT.
    Matched MeSH terms: Catheter Ablation/methods*
  7. Phillips KP, Romanov A, Artemenko S, Folkeringa RJ, Szili-Torok T, Senatore G, et al.
    Europace, 2020 02 01;22(2):225-231.
    PMID: 31665276 DOI: 10.1093/europace/euz286
    AIMS: Clinical practice guidelines do not recommend discontinuation of long-term oral anticoagulation in patients with a high stroke risk after catheter ablation for atrial fibrillation (AF). Left atrial appendage closure (LAAC) with Watchman has emerged as an alternative to long-term anticoagulation for patients accepting of the procedural risks. We report on the long-term outcomes of combining catheter ablation procedures for AF and LAAC from multicentre registries.

    METHODS AND RESULTS: Data were pooled from two prospective, real-world Watchman LAAC registries running in parallel in Europe/Middle-East/Russia (EWOLUTION) and Asia/Australia (WASP) between 2013 and 2015. Of the 1140 patients, 142 subjects at 11 centres underwent a concomitant AF ablation and LAAC procedure. The mean CHA2DS2-VASc score was 3.4 ± 1.4 and HAS-BLED score 1.5 ± 0.9. Successful LAAC was achieved in 99.3% of patients. The 30-day device and/or procedure-related serious adverse event rate was 2.1%. After a mean follow-up time of 726 ± 91 days, 92% of patients remained off oral anticoagulation. The rates of the composite endpoint of ischaemic stroke/transient ischaemic attack/systemic thromboembolism were 1.09 per 100 patient-years (100-PY); and for non-procedural major bleeding were 1.09 per 100-PY. These represent relative reductions of 84% and 70% vs. expected rates per risk scores.

    CONCLUSION: The long-term outcomes from these international, multicentre registries show efficacy for all-cause stroke prevention and a significant reduction in late bleeding events in a population of high stroke risk post-ablation patients who have been withdrawn from oral anticoagulation.

    Matched MeSH terms: Catheter Ablation*
  8. 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: Catheter Ablation/methods*
  9. Hairol AO, Affirul CA, Azlanudin A, Zamri Z, Razman J, Choi SY
    Clin Ter, 2017 Jan-Feb;168(1):e5-e7.
    PMID: 28240755 DOI: 10.7417/CT.2017.1974
    Radiofrequency ablation (RFA) has evolved to become the treatment of choice for non-resectable recurrent colorectal liver metastasis. It is however, not without complications. Portal vein thrombosis following RFA is rare but can be fatal to the outcome of the patient. Here, we present a case of a 66-year-old man who developed portal vein thrombosis following RFA. CT scan revealed a left portal vein thrombosis. This case report highlights the challenges and multimodal treatment of portal vein thrombosis following Radiofrequency ablation (RFA) in a cirrhotic patient.
    Matched MeSH terms: Catheter Ablation/adverse effects*
  10. Kumar SK, Oon OK, Horgan P, Leen E
    Malays J Med Sci, 2015 Nov;22(6):58-62.
    PMID: 28223887
    Radiofrequency ablation is one of the more established forms of local treatment in patients with unresectable tumours, including colorectal hepatic metastases. Complications associated with this method of intervention include thermal and mechanical injuries, including vascular insults resulting in haemorrhage or pseudoaneurysm formation. This is the first case demonstrating the detection of post-ablation acute pseudoaneurysm formation identified on the table using contrast-enhanced ultrasound (CEUS) and the subsequent successful management.
    Matched MeSH terms: Catheter Ablation
  11. Sridhar GS, Watson T, Han CK, Ahmad WA
    Arq. Bras. Cardiol., 2015 Aug;105(2):202-4.
    PMID: 26352181 DOI: 10.5935/abc.20150100
    Matched MeSH terms: Catheter Ablation/adverse effects; Catheter Ablation/methods
  12. Harjit S
    Med J Malaysia, 2005 Jul;60 Suppl B:108-11.
    PMID: 16108189
    Matched MeSH terms: Catheter Ablation
  13. Ch'ng LS, Tazuddin EEM, Young B, Ali AFM
    BJR Case Rep, 2016;2(2):20150306.
    PMID: 30363592 DOI: 10.1259/bjrcr.20150306
    Radiofrequency ablation (RFA) of a hepatic tumour is an established treatment option with an acceptable complication rate. Formation of a pseudoaneurysm after RFA of liver metastasis is an uncommon complication. We report the case of a 69-year-old female patient developing a hepatic pseudoaneurysm after RFA of liver metastasis. On a follow-up CT scan 6 weeks later, there was spontaneous resolution of the pseudoaneurysm. Hepatic pseudoaneurysms are usually treated owing to the risk of rupture. Invasive procedures or conservative management of an asymptomatic hepatic pseudoaneurysm is still the subject of debate. The spontaneous resolution of a hepatic pseudoaneurysm in our patient suggests that an asymptomatic pseudoaneurysm maybe observed for resolution instead of being treated at presentation.
    Matched MeSH terms: Catheter Ablation
  14. Abdullah BJ, Yeong CH, Goh KL, Yoong BK, Ho GF, Yim CC, et al.
    Eur Radiol, 2015 Jan;25(1):246-57.
    PMID: 25189152 DOI: 10.1007/s00330-014-3391-7
    OBJECTIVE: This study aimed to assess the technical success, radiation dose, safety and performance level of liver thermal ablation using a computed tomography (CT)-guided robotic positioning system.

    METHODS: Radiofrequency and microwave ablation of liver tumours were performed on 20 patients (40 lesions) with the assistance of a CT-guided robotic positioning system. The accuracy of probe placement, number of readjustments and total radiation dose to each patient were recorded. The performance level was evaluated on a five-point scale (5-1: excellent-poor). The radiation doses were compared against 30 patients with 48 lesions (control) treated without robotic assistance.

    RESULTS: Thermal ablation was successfully completed in 20 patients with 40 lesions and confirmed on multiphasic contrast-enhanced CT. No procedure related complications were noted in this study. The average number of needle readjustment was 0.8 ± 0.8. The total CT dose (DLP) for the entire robotic assisted thermal ablation was 1382 ± 536 mGy.cm, while the CT fluoroscopic dose (DLP) per lesion was 352 ± 228 mGy.cm. There was no statistically significant (p > 0.05) dose reduction found between the robotic-assisted versus the conventional method.

    CONCLUSION: This study revealed that robotic-assisted planning and needle placement appears to be safe, with high accuracy and a comparable radiation dose to patients.

    KEY POINTS: • Clinical experience on liver thermal ablation using CT-guided robotic system is reported. • The technical success, radiation dose, safety and performance level were assessed. • Thermal ablations were successfully performed, with an average performance score of 4.4/5.0. • Robotic-assisted ablation can potentially increase capabilities of less skilled interventional radiologists. • Cost-effectiveness needs to be proven in further studies.

    Matched MeSH terms: Catheter Ablation/methods*
  15. Manikam J, Mahadeva S, Goh KL, Abdullah BJ
    Hepatogastroenterology, 2009 Jan-Feb;56(89):227-30.
    PMID: 19453063
    Spontaneous rupture and hemorrhage is a devastating complication of hepatocellular carcinoma (HCC). Results from current therapeutic modalities remain varied. Recent development of percutaneous radiofrequency ablation (RFA) in the management of this condition has shown promise. We describe 2 cases of ruptured HCC in which nonoperative, percutaneous radio frequency ablation (RFA) was successful in achieving hemostasis. The advantageous of RFA over other interventional techniques in the management of ruptured HCC are discussed.
    Matched MeSH terms: Catheter Ablation/methods*
  16. Yeap EJ, Chong KW, Yeo W, Rikhraj IS
    J Orthop Surg (Hong Kong), 2009 Dec;17(3):325-30.
    PMID: 20065374
    To evaluate outcomes of radiofrequency coblation for chronic tendinosis of the foot and ankle tendons.
    Matched MeSH terms: Catheter Ablation*
  17. Alwi M, Kandavello G, Choo KK, Aziz BA, Samion H, Latiff HA
    Cardiol Young, 2005 Apr;15(2):141-7.
    PMID: 15845156
    Some patients with pulmonary atresia with an intact ventricular septum, mild to moderate right ventricular hypoplasia, and a patent infundibulum remain duct dependent on the flow of blood through the arterial duct despite adequate relief of the obstruction within the right ventricular outflow tract. The objective of our study was to review the risk factors for stenting of the patent arterial duct, or construction of a Blalock-Taussig shunt, in the patients with pulmonary atresia and an intact ventricular septum who remain duct-dependent following radiofrequency valvotomy and dilation of the imperforate pulmonary valve. We reviewed the data from 53 patients seen between November 1995 and December 2001. Of the 47 patients who survived, 6 required stenting of the patent arterial duct, while 4 needed construction of a modified Blalock-Taussig shunt to augment the flow of blood to the lungs at a mean of 7 plus or minus 5.7 days following the initial intervention. The remaining 37 patients required no additional procedures. We compared the findings in these two groups. The mean diameter of the tricuspid valve in the patients requiring early reintervention was 8.5 plus or minus 3.7 millimetres, giving a Z-score of -1.1 plus or minus 1.47, whilst those in the group without early reintervention had values of 10.7 plus or minus 2.2 millimetres, giving a Z-score of -0.58 plus or minus 1.18 (p equal to 0.003). No statistically significant differences were found in right ventricular morphology, McGoon ratio, or residual obstruction across the right ventricular outflow tract after decompression of the right ventricle. The diameter of the tricuspid valve, therefore, appears to be the only factor predicting the need for augmentation of flow of blood to the lungs. As just over one-fifth of our survivors required such augmentation, we hypothesize that stenting of the patent arterial duct may be performed as an integral part of primary transcatheter therapy in patients with pulmonary atresia and intact ventricular septum who have moderate right ventricular hypoplasia and a small tricuspid valve.
    Matched MeSH terms: Catheter Ablation*
  18. Acharya UR, Faust O, Ciaccio EJ, Koh JEW, Oh SL, Tan RS, et al.
    Comput Methods Programs Biomed, 2019 Jul;175:163-178.
    PMID: 31104705 DOI: 10.1016/j.cmpb.2019.04.018
    BACKGROUND AND OBJECTIVE: Complex fractionated atrial electrograms (CFAE) may contain information concerning the electrophysiological substrate of atrial fibrillation (AF); therefore they are of interest to guide catheter ablation treatment of AF. Electrogram signals are shaped by activation events, which are dynamical in nature. This makes it difficult to establish those signal properties that can provide insight into the ablation site location. Nonlinear measures may improve information. To test this hypothesis, we used nonlinear measures to analyze CFAE.

    METHODS: CFAE from several atrial sites, recorded for a duration of 16 s, were acquired from 10 patients with persistent and 9 patients with paroxysmal AF. These signals were appraised using non-overlapping windows of 1-, 2- and 4-s durations. The resulting data sets were analyzed with Recurrence Plots (RP) and Recurrence Quantification Analysis (RQA). The data was also quantified via entropy measures.

    RESULTS: RQA exhibited unique plots for persistent versus paroxysmal AF. Similar patterns were observed to be repeated throughout the RPs. Trends were consistent for signal segments of 1 and 2 s as well as 4 s in duration. This was suggestive that the underlying signal generation process is also repetitive, and that repetitiveness can be detected even in 1-s sequences. The results also showed that most entropy metrics exhibited higher measurement values (closer to equilibrium) for persistent AF data. It was also found that Determinism (DET), Trapping Time (TT), and Modified Multiscale Entropy (MMSE), extracted from signals that were acquired from locations at the posterior atrial free wall, are highly discriminative of persistent versus paroxysmal AF data.

    CONCLUSIONS: Short data sequences are sufficient to provide information to discern persistent versus paroxysmal AF data with a significant difference, and can be useful to detect repeating patterns of atrial activation.

    Matched MeSH terms: Catheter Ablation*
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