Ablation Zone Diameter Research Articles

Application of Deep Learning for Real-Time Ablation Zone Measurement in Ultrasound Imaging.

The accurate delineation of ablation zones (AZs) is crucial for assessing radiofrequency ablation (RFA) therapy's efficacy. Manual measurement, the current standard, is subject to variability and potential inaccuracies. This study aims to assess the effectiveness of Artificial Intelligence (AI) in automating AZ measurements in ultrasound images and compare its accuracy with manual measurements in ultrasound images. An in vitro study was conducted using chicken breast and liver samples subjected to bipolar RFA. Ultrasound images were captured every 15 s, with the AI model Mask2Former trained for AZ segmentation. The measurements were compared across all methods, focusing on short-axis (SA) metrics. We performed 308 RFA procedures, generating 7275 ultrasound images across liver and chicken breast tissues. Manual and AI measurement comparisons for ablation zone diameters revealed no significant differences, with correlation coefficients exceeding 0.96 in both tissues (p < 0.001). Bland-Altman plots and a Deming regression analysis demonstrated a very close alignment between AI predictions and manual measurements, with the average difference between the two methods being -0.259 and -0.243 mm, for bovine liver and chicken breast tissue, respectively. The study validates the Mask2Former model as a promising tool for automating AZ measurement in RFA research, offering a significant step towards reducing manual measurement variability.

Important parameters should be paid attention in PTMC radiofrequency ablation

In order to provide clinical references for the RFA procedure and to study the pivotal factors affecting the recovery time of radiofrequency ablation (RFA) in patients with papillary thyroid microcarcinoma (PTMC), 176 patients with low-risk intrathyroidal PTMC were included in this research. We randomly divided the whole cohort into training and test groups at a ratio of 7:3. The two-sample t-test was used to detect differences between the two groups. Least absolute shrinkage and selection operator (LASSO) regression was used to select the best predictor variables for predicting the status of RFA zone. Multiple test methods were used to ensure the scientific nature and accuracy of the Cox proportional hazards model. We tested the performance for the parameters and revealed the best cut-off value of each variable by the ROC curve and log-rank tests. The results showed patients aged above 49 years old, with RFA energy above 2800 J, the average diameter of the original tumour above 0.6 cm, or the average diameter of ablation zone at 1 month after RFA above 1.1 cm are risk factors for RFA zone delayed healing.

Different power modes of microwave ablation for hepatocellular carcinoma: Evaluation of recurrence rate and factors related to recurrence

PurposeTo evaluate the safety and efficacy of different power modes(constant power and variable power) percutaneous microwave ablation (MWA) for treating hepatocellular carcinoma (HCC) and to predict the risk factors of recurrence after MWA. Materials and methodsIn this retrospective study, a total of 112 patients with solitary HCC were included from January 2015 to January 2021. All patients received MWA through a percutaneous approach that was guided by ultrasound, 45 patients received variable power MWA, and the remaining 67 were treated with constant power MWA. The complete ablation rates, local recurrence rates, complications, and short-term survival were analyzed. Possible risk factors for tumor recurrence were analyzed. ResultsThe complete ablation rates were 95.9% for the first ablation and 100% for the second ablation for ≤3 cm lesions. The complete ablation rates were 84.2%(95.9% versus 84.2%, p = 0.039) for the first ablation and 94.7% (100% versus 94.7%, p = 0.113) for the second ablation for 3–5 cm lesions. Local and distant recurrence rates were 18.7%(21/112) and 14.3%(16/112). The 1-, 2-year survival rates were 86.3 and 66.3%, respectively. Subgroup analysis showed that 1-, 2-year survival rates were 91.1% and 78.5% in ≤3 cm group, and were 74.4% and 40.9% in 3–5 cm group, respectively. Univariate analysis revealed that a positive correlation existed between the HBV DNA replication(p = 0.007), AFP level of pre-MWA(p = 0.001) and post-MWA(p<0.001), tumor diameter(p<0.001), irregular shape(p = 0.014), proximity to the risk location(p = 0.008), poor differentiation(p = 0.003), constant power(p = 0.028), length(p<0.001) and width of ablation zone(p = 0.001), and present complication(p<0.001), and early recurrence. Multivariate analysis identified HBV DNA replication(OR = 0.266, p = 0.036), AFP level of pre-MWA (OR = 4.001, p = 0.036), tumor diameter (OR = 2.153, p = 0.042), tumor location (OR = 0.910, p = 0.046), and width of ablation zone(OR = 2.530, p = 0.044) were independent prognosis factors causing postoperative HCC recurrence. ConclusionVariable power MWA of HCC appears to be a safe and effective treatment. HBV DNA, AFP level of pre-MWA, tumor diameter, tumor location, and width of ablation range appear to be independent predictors of tumor recurrence.

Safety and Feasibility of a Novel Externally Cooled Bronchoscopic Radiofrequency Ablation Catheter for Ablation of Peripheral Lung Tumours: A First-In-Human Dose Escalation Study

Background: Radiofrequency ablation (RFA) is an established modality for percutaneous ablation of non-small cell lung cancer (NSCLC) in medically inoperable patients but is underutilized clinically due to side effects. We have developed a novel, completely endobronchial RFA catheter with an externally cooled electrode. Objectives: The objective of this study was to establish the safety and feasibility of bronchoscopic RFA using a novel, externally cooled catheter for ablation of peripheral NSCLC. Methods: Patients with stage I biopsy-confirmed NSCLC underwent bronchoscopic RFA of tumour 7 days prior to lobectomy. The RFA catheter was delivered bronchoscopically to peripheral NSCLC lesions, guided by radial endobronchial ultrasound, with positioning confirmed using intra-procedural cone beam CT. Pre-operative CT chest and histologic examination of resected specimens were used to establish distribution/uniformity of ablation and efficacy of tumour ablation. Results: RFA in the first patient was complicated by dispersal of heated saline due to cough, resulting in ICU admission. The patient recovered fully and underwent uncomplicated lobectomy. Subsequently, the protocol was altered to mandate neuromuscular blockade with a pre-determined dose escalation, with algorithm-restricted energy (kJ) and irrigated saline volume (mL) constraints. A further 10 patients consented and seven underwent successful bronchoscopic RFA of peripheral NSCLC. No significant adverse events were noted. Ablation zone included tumour in all cases (proportion of tumour ablated ranged 8–72%), with uniform necrosis of tissue within ablation zones observed at higher energy levels. Ablation zone diameter correlated with RFA energy delivered (R² = 0.553), with maximum long axis diameter of ablation zone 3.1 cm (22.9 kJ). Conclusion: Bronchoscopic RFA using an externally cooled catheter is feasible, appears safe, and achieves uniform ablation within the treatment zone. Uncontrolled escape of heated saline poses a major safety risk but can be prevented procedurally through neuromuscular blockade and by limiting irrigation.

TRANSPARENCHYMAL MICROWAVE ABLATION ASSESSMENT IN A SURVIVAL PORCINE LUNG MODEL

TOPIC: Procedures TYPE: Original Investigations PURPOSE: Percutaneous microwave ablation (MWA) is an established approach for CT-guided treatment of pulmonary tumors. A percutaneous approach for pulmonary MWA limits potential targets to peripheral lesions, and pneumothorax, hemorrhage, and fistula are some of the common complications. We have developed a system for bronchoscopic transparenchymal MWA of pulmonary tumors. Integration of the MWA system with virtual bronchoscopy and transparenchymal nodule access offers potential to enable minimally invasive diagnosis, staging, and treatment of peripheral lung nodules in a single session. In a survival porcine model, we assessed the feasibility of safely delivering MWA by introducing the applicator into lung targets via transparenchymal tunnel through the airway wall. METHODS: A total of 8 MWAs (90 W, 5 min) were performed in 4 pigs with a custom water-cooled, microwave catheter operating at 2.45 GHz. The catheter was introduced into multiple regions of the normal lung parenchyma via tunnels that extended 2.5–4 cm from the airway wall, guided by virtual bronchoscopy (Archimedes, Broncus Medical). Animals were euthanized at 2 (n=2) and 13 days (n=2) post-ablation. CT images were acquired immediately post-ablation and on the day of euthanasia. At necropsy, ablated and surrounding lung tissue was excised. Fresh tissue was used to assess the macroscopic extent of the ablation zones following viability staining. Formalin fixed tissue was processed into paraffin for thin sectioning and stained with hematoxylin and eosin for histopathologic examination. RESULTS: No pneumothorax, major bleeding or fistula were observed during and after ablation procedures. All pigs maintained normal appetite and behavior throughout the survival period. On day 2, ablation zone diameters on CT imaging were in the range 18–47 mm, as compared to 10–18 mm on macroscopic analysis. This discrepancy was likely due to edema, inflammation and/or hemorrhage obscuring the ablation boundary on CT assessment. At day 13, ablation zone diameters on CT imaging and macroscopic analysis were in the ranges 16–21 mm and 14–20 mm, respectively. On day 13, the ablation zone was separated from adjacent, aerated, pulmonary parenchyma by a 1-2 mm wide band of granulation tissue (fibrous connective tissue, fibrocytes, and vessels with macrophages and lymphoplasmacytic infiltrates). One of the animals in the 13-day group developed a severe suppurative bronchopneumonia attributed to secondary bacterial infection (the protocol did not include antibiotics). No evidence of emphysema was observed along the transparenchymal tunnels. CONCLUSIONS: We have demonstrated the feasibility of safely delivering virtual bronchoscopy guided transparenchymal MWA in a survival porcine model. CLINICAL IMPLICATIONS: Further evaluation of virtual-bronchoscopy guided transbronchial MWA in human patients in an ablate-and-resect study to assess safety and feasibility is warranted and planned for 2022. DISCLOSURES: No relevant relationships by Warren Beard, source=Web Response No relevant relationships by David Biller, source=Web Response No relevant relationships by Faraz Chamani, source=Web Response No relevant relationships by Pegah Faridi, source=Web Response Employee relationship with phenoMapper Please note: 09/01/2020-now Added 04/30/2021 by Steven Goh, source=Web Response, value=Salary No relevant relationships by Nicholas Hemphill, source=Web Response No relevant relationships by Margaret Highland, source=Web Response No relevant relationships by David Hodgson, source=Web Response No relevant relationships by Stephen Lam, source=Web Response PI ofan investigator-initiated study relationship with Medtronic Please note: >$100000 by Fabien Maldonado, source=Web Response, value=Grant/Research Supportco-I on investigator-initiated studies relationship with Janssen Please note: $20001 - $100000 by Fabien Maldonado, source=Web Response, value=Grant/Research Support Removed 04/19/2021 by Fabien Maldonado, source=Web Response PI on investigator-initiated relationship with Erbe Please note: $5001 - $20000 by Fabien Maldonado, source=Web Response, value=Grant/Research Support Consulting relationship with Medtronic Please note: $5001 - $20000 by Fabien Maldonado, source=Web Response, value=Honorariaco-I industry-sponsored trial relationship with Lung Therapeutics Please note: $5001 - $20000 by Fabien Maldonado, source=Web Response, value=Grant/Research Supportspeaker relationship with Longitudinal lung nodule fellows program - Please note: $1001 - $5000 by Fabien Maldonado, source=Web Response, value=Honoraria Removed 04/19/2021 by Fabien Maldonado, source=Web Response Board of director member relationship with AABIP Please note: $1-$1000 by Fabien Maldonado, source=Web Response, value=Travel No relevant relationships by Renelle Myers, source=Web Response No relevant relationships by Punit Prakash, source=Web Response No relevant relationships by Jan Sebek, source=Web Response No relevant relationships by Abbe Smith, source=Web Response No relevant relationships by Zixuan Wang, source=Web Response Owner/Founder relationship with phenoMapper, LLC Please note: 01/2021-12/2021 Added 04/30/2021 by Henky Wibowo, source=Web Response, value=Grant/Research Support No relevant relationships by Kun-Chang Yu, source=Web Response

Compensatory Corneal Epithelial Thickness Changes after Myopic Photorefractive Keratectomy Imaged with Ultra High Resolution AnteriorSegment Optical Coherence Tomography

Purpose: To evaluate how corneal epithelium thickness changes after myopic Photorefractive Keratectomy (PRK) relate to the magnitude of myopic correction, the diameter of the Optical Zone (OZ) and the incidence of regression in the early postoperative period. Setting: Tertiary referral center Design: Prospective longitudinal cohort study Methods: Twenty-two eyes of 11 patients with mean manifest spherical equivalent of -4.75 ± 1.69 D underwent PRK between November 2016 and March 2017. Epithelial thickness profiles were evaluated preoperatively and at 1, 3 and 6 month’s postoperatively using ultra-high resolution anterior segment OCT. The relationship between post-operative epithelial thickness changes and the magnitude of myopic correction, the OZ diameter and the refractive outcomes was investigated prospectively. Results: Central epithelial thickening progressed during the first three postoperative months (p=0.045, between first and third postoperative month) and stabilized thereafter (p=0.980, between third and sixth postoperative month). A corresponding myopic shift of 0.13 D and an increase in mean K by 0.65 D were observed at three months postoperatively, which remained stable thereafter and did not affect the final refractive outcomes (mean postoperative spherical equivalent 0.14 ± 0.40 D). Central epithelial thickness increased proportionally with the amount of myopia treated (r=0.41, p=0.04) and reversely with the ablation zone diameter (r=-0.39, p=0.04). Conclusion: Corneal epithelial hyperplasia after myopic PRK is dependent on the preoperative myopic error and ablation zone diameter. Epithelial hyperplasia-induced regression did not have a negative effect on the overall refractive outcome. Synopsis: The degree of epithelial thickening and hyperopic shift post-PRK depends on the preoperative refraction and the optical zone diameter. The subsequent regression does not negatively affect the refractive outcome.

Efficacy and Safety of Thermal Ablation for Solitary T1bN0M0 Papillary Thyroid Carcinoma: A Multicenter Study.

Ultrasound-guided thermal ablation plays an important role in the management of thyroid disease. The objective of this study was to evaluate the feasibility, efficacy, and safety of thermal ablation for patients with solitary T1bN0M0 papillary thyroid carcinoma (PTC) who are ineligible for or unwilling to undergo surgery. Data pertaining to 172 patients (38 males and 134 females) who received thermal ablation therapy at 12 hospitals between April 2015 and March 2020 were retrospectively analyzed. The mean duration of follow-up was 24.9 ± 14.1 months (range, 12-60). The technical feasibility, technical success, efficacy, and safety of treatment were analyzed. Postablation tumor size at various time points was compared with preablation measurement. All patients selected for thermal ablation received enlarged ablation, according to contrast-enhanced ultrasound postablation. The maximum diameter and volume of ablation zone at 6, 12, 18, 24, 36, and 48 months postablation were significantly smaller than those recorded preablation (P < 0.05 for all). At the most recent follow-up, 106 (61.6%) tumors had completely disappeared. The rate of lymph node metastasis was 0.6% (1/172) and the incidence of new tumors was 1.2% (2/172). The overall complication rate was 5.2% (9/172) (major complications: 4.6% [8/172]; minor complications: 0.6% [1/172]). All major complications were relieved within 4 months postablation. Thermal ablation may be a feasible, effective, and safe treatment option for patients with solitary T1bN0M0 PTC who are ineligible for or unwilling to undergo surgery. It may provide a novel treatment option for selected patients.

Topical Cyclosporine in Treatment of Post-LASIK Symptomatic Dry Eye

Purpose: To determine the role of 0.05% topical cyclosporine A (CsA) in treatment of symptomatic dry eye after LASIK (Laser-Assisted in Situ Keratomileusis).&#x0D; Study Design: Interventional Case Series.&#x0D; Place and Duration of Study: Ophthalmology Department, Sir Syed Hospital, Karachi, from July 2018 to Dec. 2019.&#x0D; Methods: Seventy-five patients who underwent LASIK for myopic refractive error and presented with symptomatic dry eye and showed no response to artificial tears therapy after 1 month of LASIK were selected. The patient had ablation zone diameter of 6mm and flap diameter was 8.5mm to 9mm. Cyclisporine A 0.05% ophthalmic preparation was added to treatment regimen and response was observed at 1, 3 and 6 months. OSDI (Ocular Surface Disease Index) scores, Tear film break up time (TBUT), Schirmer's test (ST) values and Best Corrected Visual Acuity (BCVA) were recorded to analyze the treatment response at each visit. The statistical interpretation was done by using SPSS version 21. To interpret the correlation between pre-treatment and 6 month post treatment, Paired sample T test was applied with 95% Confidence Interval; CI and p-value of ≤ 0.05.&#x0D; Results: The mean post-LASIK OSDI score of enrolled patients was 54.25 ± 10.81. After 6 months of treatment mean OSDI score was improved to 21.05 ± 5.13 (p &lt; 0.001). Post-LASIK mean ST value was 5.2 ± 1.2 mm and mean TBUT value was 5.6 ± 1.3 seconds, which changed to 9.8 ± 1.0 mm and 8.9 ± 1.1 seconds respectively. BCVA improved from Log MAR 0.14 ± 0.09 to 0.01 ± 0.03 (p &lt; 0.001).&#x0D; Conclusion: Topical CsA 0.05% was effective in alleviating the symptoms of post-LASIK dry eye.&#x0D; Key Words: LASIK, Dry eye, Ocular Surface Disease Index Score, Cyclosporine A.

Characterization of the ablation zones produced by three commercially available systems from a single vendor for radiofrequency thermoablation in an ex vivo swine liver model.

BackgroundRadiofrequency Ablation (RFA) is rarely performed in veterinary medicine. A rationale exists for its use in selected cases of canine liver tumours. RFA induces ablation zones of variable size and geometry depending on the technique used and on the impedance of the targeted organ.Objectives(a) to describe the geometry and reproducibility of the ablation zones produced by three commercially available systems from a single company, using isolated swine liver parenchyma as a model for future veterinary applications in vivo; (b) to study the effects of local saline perfusion into the ablated parenchyma through the electrode tip and of single versus double passage of the electrode on size, geometry and reproducibility of the ablation zones produced.MethodsSize, and geometry of ablation zones reproduced in six livers with one cooled and perfused (saline) and two cooled and non‐perfused systems, after single or double passage (n = 6/condition), were assessed macroscopically on digitalized images by a blinded operator. Longitudinal and transverse diameters, equivalent diameter, estimated volume and roundness index were measured. Reproducibility was assessed as coefficient of variation.Results and ConclusionsAblation zone reproducibility was higher when expressed in terms of ablation zone diameters than estimated volume. Local saline perfusion of the parenchyma through the electrode tip during RFA increased the ablation zone longitudinal diameter. Ablation zone estimated volume increased with saline perfusion only when double passage was performed. These data may provide useful information for those clinicians who intend to include RFA as an additive tool in veterinary interventional radiology.

Six modes of corneal topography for evaluation of ablation zones after small-incision lenticule extraction and femtosecond laser-assisted in situ keratomileusis

To evaluate the ablation zone diameter (AZD) using six modes of corneal topography after small-incision lenticule extraction (SMILE) and femtosecond laser-assisted in situ keratomileusis (FS-LASIK) for myopia and to compare the programmed and postoperative AZDs METHODS: This retrospective comparative study included 86 right eyes in 86 patients who underwent SMILE or FS-LASIK at the Shandong Eye Institute between June 2016 and August 2017. Data were collected preoperatively and at 1, 3, and 6months postoperatively using the Pentacam system. The AZD was determined using six modes of corneal topography: postoperative axial curvature topography (PACT), postoperative tangential curvature topography (PTCT), difference-axial curvature topography (DACT), difference-tangential curvature topography (DTCT), postoperative front elevation topography (PFET), and difference-corneal thickness topography (DCTT). The difference between the programmed and postoperative AZDs was compared between the groups of two surgical procedures. At 3months, the AZDs measured by PTCT, DTCT, and PFET after SMILE showed a significant decrease, while the AZD by DACT revealed an increase (P < 0.001), and the AZDs measured by PACT, PTCT, DACT, DTCT, PFET, and DCTT after FS-LASIK were all significantly decreased (P < 0.001), as compared with the programmed ablation zone values. The AZDs measured by DACT and DTCT after 3months were larger in the SMILE group (P < 0.001); likewise, the differences between the programmed and postoperative AZDs were lower in the SMILE group (P < 0.001). Furthermore, PACT, PTCT, DACT, DTCT, and PFET indicated acceptable inter-observer reliability (ICC > 0.75). In the treatment of myopia, the achieved topographic ablation zones after FS-LASIK were smaller than the theoretically designed ones. The AZDs after SMILE were larger than those after FS-LASIK, with an equivalent programmed value. The DACT may be more suitable for measuring postoperative ablation zones in clinic with clearer borders and favorable repeatability. This method may be potential for the measurement of ablation zones and further research on the visual quality after refractive surgery.

Abstract No. 504 Ex vivo evaluation of the effect of multiple electrode radiofrequency needle tip convergence on size of ablation zone

Radiofrequency ablation (RFA) is an established therapy for treatment of malignancy in several organs, including the liver. One commonly used system, the Cool-tip Cluster Electrode, uses three parallel needles fixed in a triangular geometry. However, upon insertion, the final geometry of the needle tips can vary. In the case of converging needles, ablation volumes have been anecdotally observed to be smaller than expected. The study objective is to determine whether needle tip convergence significantly affects ablation zone in a bovine liver model. Cool-tip Cluster Electrodes were used to perform RFA in an ex vivo bovine liver using a 3D-printed guide to produce: no, partial or full convergence of the electrode needle tips. Ablation time was 12 minutes. Cone beam computed tomography scans were obtained to verify needle positions. Time to first roll off and period between roll-offs was recorded. Gross pathology was performed to estimate ablation zone volumes. Preliminary results from the initial pilot experiment found partial needle tip convergence decreased ablation zone volume by 6.13 cm3 (40.3%), time to first roll-off by 5.16 minutes (36.1%), and average time between roll-offs by 16 seconds (25.5%) compared to no convergence. Full convergence resulted in ablation zone volume decrease by 10.3 cm3 (67.7%), time to first roll-off decreased by 5.45 minutes (39.5%), and the average time between roll-offs decreased by 13 seconds (31.4%) compared to no convergence. Preliminary results suggest significant decrease in ablation volume and faster roll-off as the electrode tips increasingly converge. Further experiments are planned to test the study hypothesis with statistical significance. If confirmed, these results suggest confirmation of needle tip geometry prior to ablation should be performed clinically in order to ensure adequate ablation volumes when using Cool-tip Cluster electrodes.Tabled 1Distance Between Electrodes (mm)Diameter of Ablation Zone (cm)Ablation Volume (cm3)Time to First Roll-Off (min)Average Time Between Roll-Offs (sec)44.415.218.535133.49.083.373802.54.913.0835 Open table in a new tab

Ablation zone geometry after CT-guided hepatic microwave ablation: evaluation of a semi-automatic software and comparison of two different ablation systems

Purpose The aims of this study were to evaluate a semi-automatic segmentation software for assessment of ablation zone geometry in computed tomography (CT)-guided microwave ablation (MWA) of liver tumors and to compare two different MWA systems. Material and Methods 27 patients with 40 hepatic tumors (primary liver tumor n = 20, metastases n = 20) referred for CT-guided MWA were included in this retrospective IRB-approved study. MWA was performed using two systems (system 1: 915 MHz; n = 20; system 2: 2.45 GHz; n = 20). Ablation zone segmentation and ellipticity index calculations were performed using SAFIR (Software Assistant for Interventional Radiology). To validate semi-automatic software calculations, results (2 perpendicular diameters, ellipticity index, volume) were compared with those of manual analysis (intraclass correlation, Pearson’s correlation, Mann–Whitney U test; p < 0.05 deemed significant. Results Manual measurements of mean maximum ablation zone diameters were 43 mm (system 1) and 34 mm (system 2), respectively. Correlations between manual and semi-automatic measurements were r = 0.72 and r = 0.66 (both p < 0.0001) for perpendicular diameters, and r = 0.98 (p < 0.001) for volume. Manual analysis demonstrated that ablation zones created with system 2 had a significantly lower ellipticity index compared to system 1 (mean 1.17 vs. 1.86, p < 0.0001). Results correlated significantly with semi-automatic software measurements (r = 0.71, p < 0.0001). Conclusion Semi-automatic assessment of ablation zone geometry using SAFIR is feasible. Software-assisted evaluation of ablation zones may prove beneficial with complex ablation procedures, especially for less experienced operators. The 2.45 GHz MWA system generated a significantly more spherical ablation zone compared to the 915 MHz system. The choice of a specific MWA system significantly influences ablation zone geometry.

Effectiveness of the Goldmann Applanation Tonometer, the Dynamic Contour Tonometer, the Ocular Response Analyzer and the Corvis ST in Measuring Intraocular Pressure following FS-LASIK

ABSTRACTPurpose: To test the performance of the four tonometers in providing IOP measurements that were free of the effects of corneal biomechanics changes caused by refractive surgery.Methods: Four tonometers were employed to provide IOP measurements for 65 participants who accepted Femtosecond laser-assisted LASIK (FS-LASIK). The measurements included GAT-IOP by the Goldmann Applanation Tonometer, DCT-IOP by the Dynamic Contour Tonometer, Goldmann-correlated IOP (ORA-IOPg) and corneal-compensated IOP (ORA-IOPcc) by the Ocular Response Analyzer, and uncorrected IOP (CVS-IOP) and biomechanically corrected IOP (CVS-bIOP) by the Corvis ST. Statistical analyses were performed to assess the association of the differences in IOP caused by FS-LASIK with central corneal thickness (CCT), mean corneal curvature (Km), age, refractive error correction (REC), optical zone diameter (OZD), ablation zone diameter (AZD), residual stromal bed thickness (RSB) and RSB ratio (RSB/CCT). Multiple linear regression models were constructed to explore factors influencing IOP changes.Results: All four tonometers exhibited significant differences between IOP measurements taken pre and post-surgery except for CVS-bIOP in the low to moderate myopia group (t = 1.602, p = .12). CVS-bIOP, followed by DCT-IOP, provided the best agreement between pre and post-FS-LASIK measurements with the lowest differences in IOP and the narrowest limits of agreement. The pre-post IOP differences were also significantly associated with the reduction in CCT in only GAT-IOP, ORA-IOPg, and CVS-IOP. CVS-bIOP and ORA-IOPcc were the only measurements that were not correlated with CCT, Km or age both before and after FS-LASIK.Conclusions: The biomechanically corrected bIOP from the Corvis ST provided post-FS-LASIK measurements that were in closest agreement with those obtained before surgery. In comparison, GAT-IOP, ORA-IOPg, ORA-IOPcc, and CVS-IOP appeared to be more influenced by the changes in corneal biomechanics caused by FS-LASIK.

Sequential and Simultaneous 4-Antenna Microwave Ablation in an Ex Vivo Bovine Liver Model.

To determine the sizes and shapes of ablation zones in 4-antenna microwave ablation in ex vivo bovine liver model under different conditions of power delivery patterns, antenna spacings, and ablation durations, for further using of multi-antenna MWA strategies in the treatment of large hepatocellular carcinoma. We tested protocols of eight ablations each on ex vivo bovine livers, involving simultaneous or sequential activation of four microwave antennas, spaced either 3 cm, 4 cm, or 5 cm apart, for either 10 or 15min, at 60-W power. We determined the diameters, shapes, and temperatures of the ablation zones. Compared to sequential power delivery, simultaneous power delivery resulted in significantly larger ablation zone diameters (P < .001). The temperatures in ablation zones were significantly higher for simultaneous than for sequential power delivery. The largest ablation diameter (7.45 ± 0.06cm) resulted from simultaneous delivery for 15min using 4-cm antenna spacing. Simultaneous 4-antenna microwave ablation results in larger ablation zones than sequential ablation, and 4-cm antenna spacing with a 15-minute ablation duration creates the largest ablation zone. This information may provide multi-antenna MWA strategies for large HCC in the further clinical practice.

Radiofrequency ablation of atypical cartilaginous tumors in long bones: a retrospective study

Purpose: To determine the size of the ablation zone after radiofrequency ablation (RFA) of atypical cartilaginous bone tumors (ACT) using temperature-controlled 20 and 30 mm RFA straight non-cooled electrodes.Materials and methods: Sixteen patients with ACT in their long bones, who had undergone a single-session single-application CT-guided temperature-controlled RFA, were included retrospectively in the study. Tumors with a diameter of 10–25 mm were treated with 20 mm electrodes (n = 10), and tumors of 25–35 mm, with 30 mm electrodes (n = 6). The ablated zone was measured after three months on MRI images.Results: All the tumors were within the ablated zone on the 3-month follow-up MRI scan. The mean ablation time with the electrode, at a target temperature of 90 °C, was 7.6 minutes (range 6–10). The median of the largest ablation diameters, on applying the 20 and 30 mm electrodes, were 42 mm (IQR 8.5, range 30–51 mm) and 44.5 mm (IQR 4.5, range 42–63 mm), respectively.Conclusions: All the retrospectively viewed tumors in the long bones of ACT patients treated with RFA were completely ablated. The ablation zone diameters in the bones were larger than expected, when compared to other tissues, such as the liver.

Safety and complications after three different surface ablation techniques with mitomycin C: a retrospective analysis of 2757 eyes.

To evaluate the safety and spectrum of complications of three excimer laser surface ablation techniques (SATs) with an intraoperative application of mitomycin C (MMC) 0.02%. A retrospective, non-comparative large case series. SATs were performed on 2757 eyes with a preoperative spherical equivalent (SE) of - 4.41 ± 2.44 and a Wavelight Allegretto 200 platform. Ablation zone diameters between 6.0 and 7.0mm were used according to mesopic pupil size. All patients were treated with an intraoperative application of MMC for 30 to 90s depending on refractive error. The mean follow-up time was > 3months (107 ± 24days). Complication range and incidence were analyzed retrospectively and safety index was calculated. Two thousand seven hundred and fifty-seven eyes met the inclusion criteria for surface ablation. Two thousand five hundred and seventy-three eyes were assigned to alcohol-assisted photorefractive keratectomy (APRK), 135 eyes to transepithelial photorefractive keratectomy (TPRK), and 49 eyes to off-flap epithelial laser in situ keratomileusis (EpiLASIK/EpiK). Overall, the safety index was 1.06 ± 0.28. Haze was graded according to the Fantes scale. Haze incidence rates were highest in the TPRK group (14.81%) and comparably low in APRK (2.95%) and EpiK (4.08%) groups. Intraoperative topical application of MMC (0.02%) results in good safety and no severe side effects. However, highest incidence of haze was observed after TPRK. The more frequent peripheral localization of haze might be attributed to large ablation zones and the wavefront optimized ablation profile especially in the PTK modus of the laser platform.

Combination Therapies: Quantifying the Effects of Transarterial Embolization on Microwave Ablation Zones

PurposeTo quantify the effect of transarterial embolization on microwave (MW) ablations in an in vivo porcine liver model. Materials and MethodsHepatic arteriography and cone-beam computed tomography (CT) scans were performed in 6 female domestic swine. Two lobes were embolized to an endpoint of substasis with 100–300-μm microspheres. MW ablations (65 W, 5 min) were created in embolized (n = 15) and nonembolized (n = 12) liver by using a 2.45-GHz system and single antenna. Cone-beam CT scans were obtained to monitor the ablations, document gas formation, and characterize arterial flow. Ablation zones were excised and sectioned. A mixed-effects model was used to compare ablation zone diameter, length, area, and circularity. ResultsCombined transarterial embolization and MW ablation zones had significantly greater area (mean ± standard deviation, 11.8 cm2 ± 2.5), length (4.8 cm ± 0.5), and diameter (3.1 cm ± 0.6) compared with MW only (7.1 cm2 ± 1.9, 3.7 cm ± 0.6, and 2.4 cm ± 0.3, respectively; P = .0085, P = .0077, and P = .0267, respectively). Ablation zone circularity was similar between groups (P = .9291). The larger size of the combined ablation zones was predominantly the result of an increase in size of the peripheral noncharred zone of coagulation (1.3 cm ± 0.4 vs 0.8 cm ± 0.2; P = .0104). Cone-beam CT scans demonstrated greater gas formation during combined ablations (1.8 cm vs 1.1 cm, respectively). Mean maximum temperatures 1 cm from the MW antennas were 86.6°C and 68.7°C for the combined embolization/ablation and MW-only groups, respectively. ConclusionsCombining transarterial embolization and MW ablation increased ablation zone diameter and area by approximately 27% and 66%, respectively, in an in vivo non–tumor-bearing porcine liver model. This is largely the result of an increase in the size of the peripheral ablation zone, which is most susceptible to local blood flow.

Automated trajectory planning for laser interstitial thermal therapy in mesial temporal lobe epilepsy

SummaryObjectiveSurgical resection of the mesial temporal structures brings seizure remission in 65% of individuals with drug‐resistant mesial temporal lobe epilepsy (MTLE). Laser interstitial thermal therapy (LiTT) is a novel therapy that may provide a minimally invasive means of ablating the mesial temporal structures with similar outcomes, while minimizing damage to the neocortex. Systematic trajectory planning helps ensure safety and optimal seizure freedom through adequate ablation of the amygdalohippocampal complex (AHC). Previous studies have highlighted the relationship between the residual unablated mesial hippocampal head and failure to achieve seizure freedom. We aim to implement computer‐assisted planning (CAP) to improve the ablation volume and safety of LiTT trajectories.MethodsTwenty‐five patients who had previously undergone LiTT for MTLE were studied retrospectively. The EpiNav platform was used to automatically generate an optimal ablation trajectory, which was compared with the previous manually planned and implemented trajectory. Expected ablation volumes and safety profiles of each trajectory were modeled. The implemented laser trajectory and achieved ablation of mesial temporal lobe structures were quantified and correlated with seizure outcome.Results CAP automatically generated feasible trajectories with reduced overall risk metrics (P < .001) and intracerebral length (P = .007). There was a significant correlation between the actual and retrospective CAP‐anticipated ablation volumes, supporting a 15 mm diameter ablation zone model (P < .001). CAP trajectories would have provided significantly greater ablation of the amygdala (P = .0004) and AHC (P = .008), resulting in less residual unablated mesial hippocampal head (P = .001), and reduced ablation of the parahippocampal gyrus (P = .02).SignificanceCompared to manually planned trajectories CAP provides a better safety profile, with potentially improved seizure‐free outcome and reduced neuropsychological deficits, following LiTT for MTLE.

MR-guided microwave ablation in hepatic tumours: initial results in clinical routine.

Evaluation of the technical success, patient safety and technical effectiveness of magnetic resonance (MR)-guided microwave ablation of hepatic malignancies. Institutional review board approval and informed patient consent were obtained. Fifteen patients (59.8years ± 9.5) with 18 hepatic malignancies (7 hepatocellular carcinomas, 11 metastases) underwent MR-guided microwave ablation using a 1.5-T MR system. Mean tumour size was 15.4mm ± 7.7 (7-37mm). Technical success and ablation zone diameters were assessed by post-ablative MR imaging. Technique effectiveness was assessed after 1month. Complications were classified according to the Common Terminology Criteria for Adverse Events (CTCAE). Mean follow-up was 5.8months ± 2.6 (1-10months). Technical success and technique effectiveness were achieved in all lesions. Lesions were treated using 2.5 ± 1.2 applicator positions. Mean energy and ablation duration per tumour were 37.6kJ ± 21.7 (9-87kJ) and 24.7min ± 11.1 (7-49min), respectively. Coagulation zone short- and long-axis diameters were 31.5mm ± 10.5 (16-65mm) and 52.7mm ± 15.4 (27-94mm), respectively. Two CTCAE-2-complications occurred (pneumothorax, pleural effusion). Seven patients developed new tumour manifestations in the untreated liver. Local tumour progression was not observed. Microwave ablation is feasible under near real-time MR guidance and provides effective treatment of hepatic malignancies in one session. • Planning, applicator placement and therapy monitoring are possible without using contrast enhancement • Energy transmission from the generator to the scanner room is safely possible • MR-guided microwave ablation provides effective treatment of hepatic malignancies in one session • Therapy monitoring is possible without applicator retraction from the ablation site.

Experimental measurement of microwave ablation heating pattern and comparison to computer simulations

Introduction: For computational models of microwave ablation (MWA), knowledge of the antenna design is necessary, but the proprietary design of clinical applicators is often unknown. We characterised the specific absorption rate (SAR) during MWA experimentally and compared to a multi-physics simulation.Methods: An infrared (IR) camera was used to measure SAR during MWA within a split ex vivo liver model. Perseon Medical’s short-tip (ST) or long-tip (LT) MWA antenna were placed on top of a tissue sample (n = 6), and microwave power (15 W) was applied for 6 min, while intermittently interrupting power. Tissue surface temperature was recorded via IR camera (3.3 fps, 320 × 240 resolution). SAR was calculated intermittently based on temperature slope before and after power interruption. Temperature and SAR data were compared to simulation results.Results: Experimentally measured SAR changed considerably once tissue temperatures exceeded 100 °C, contrary to simulation results. The ablation zone diameters were 1.28 cm and 1.30 ± 0.03 cm (transverse), and 2.10 cm and 2.66 ± −0.22 cm (axial), for simulation and experiment, respectively. The average difference in temperature between the simulation and experiment were 5.6 °C (ST) and 6.2 °C (LT). Dice coefficients for 1000 W/kg SAR iso-contour were 0.74 ± 0.01 (ST) and 0.77 (± 0.03) (LT), suggesting good agreement of SAR contours.Conclusion: We experimentally demonstrated changes in SAR during MWA ablation, which were not present in simulation, suggesting inaccuracies in dielectric properties. The measured SAR may be used in simplified computer simulations to predict tissue temperature when the antenna geometry is unknown.