A finite element method model to simulate laser interstitial thermo therapy in anatomical inhomogeneous regions

BACKGROUND: Laser Interstitial ThermoTherapy (LITT) is a well established surgical method. The use of LITT is so far limited to homogeneous tissues, e.g. the liver. One of the reasons is the limited capability of existing treatment planning models to calculate accurately the damage zone. The treatment planning in inhomogeneous tissues, especially of regions near main vessels, poses still a challenge. In order to extend the application of LITT to a wider range of anatomical regions new simulation methods are needed. The model described with this article enables efficient simulation for predicting damaged tissue as a basis for a future laser-surgical planning system. Previously we described the dependency of the model on geometry. With the presented paper including two video files we focus on the methodological, physical and mathematical background of the model. METHODS: In contrast to previous simulation attempts, our model is based on finite element method (FEM). We propose the use of LITT, in sensitive areas such as the neck region to treat tumours in lymph node with dimensions of 0.5 cm – 2 cm in diameter near the carotid artery. Our model is based on calculations describing the light distribution using the diffusion approximation of the transport theory; the temperature rise using the bioheat equation, including the effect of microperfusion in tissue to determine the extent of thermal damage; and the dependency of thermal and optical properties on the temperature and the injury. Injury is estimated using a damage integral. To check our model we performed a first in vitro experiment on porcine muscle tissue. RESULTS: We performed the derivation of the geometry from 3D ultrasound data and show for this proposed geometry the energy distribution, the heat elevation, and the damage zone. Further on, we perform a comparison with the in-vitro experiment. The calculation shows an error of 5% in the x-axis parallel to the blood vessel. CONCLUSIONS: The FEM technique proposed can overcome limitations of other methods and enables an efficient simulation for predicting the damage zone induced using LITT. Our calculations show clearly that major vessels would not be damaged. The area/volume of the damaged zone calculated from both simulation and in-vitro experiment fits well and the deviation is small. One of the main reasons for the deviation is the lack of accurate values of the tissue optical properties. In further experiments this needs to be validated

Interventionally implanted port catheter systems for hepatic arterial infusion of chemotherapy in patients with colorectal liver metastases: A phase II-study and historical comparison with the surgical approach

<p>Abstract</p> <p>Background</p> <p>The high complication rates of surgically implanted port catheter systems (SIPCS) represents a major drawback in the treatment of isolated liver neoplasms by hepatic arterial infusion (HAI) of chemotherapy. Interventionally implanted port catheter systems (IIPCS) have evolved into a promising alternative that enable initiation of HAI without laparatomy, but prospective data on this approach are still sparse. Aim of this study was to evaluate the most important technical endpoints associated with the use of IIPCS for the delivery of 5-fluorouracil-based HAI in patients with colorectal liver metastases in a phase 2-study, and to perform a non-randomised comparison with a historical group of patients in which HAI was administered via SIPCS.</p> <p>Methods</p> <p>41 patients with isolated liver metastases of colorectal cancer were enrolled into a phase II-study and provided with IIPCS between 2001 and 2004 (group A). The primary objective of the trial was defined as evaluation of device-related complications and port duration. Results were compared with those observed in a pre-defined historical collective of 40 patients treated with HAI via SIPCS at our institution between 1996 and 2000 (group B).</p> <p>Results</p> <p>Baseline characteristics were balanced between both groups, except for higher proportions of previous palliative pre-treatment and elevated serum alkaline phosphatase in patients of group A. Implantation of port catheters was successful in all patients of group A, whereas two primary failures were observed in group B. The frequency of device-related complications was similar between both groups, but the secondary failure rate was significantly higher with the use of surgical approach (17% vs. 50%, p < 0.01). Mean port duration was significantly longer in the interventional group (19 vs. 14 months, p = 0.01), with 77 vs. 50% of devices functioning at 12 months (p < 0.01). No unexpected complications were observed in both groups.</p> <p>Conclusion</p> <p>HAI via interventionally implanted port catheters can be safely provided to a collective of patients with colorectal liver metastases, including a relevant proportion of preatreated individuals. It appears to offer technical advantages over the surgical approach.</p

MR fluoroscopy in vascular and cardiac interventions (review)

Vascular and cardiac disease remains a leading cause of morbidity and mortality in developed and emerging countries. Vascular and cardiac interventions require extensive fluoroscopic guidance to navigate endovascular catheters. X-ray fluoroscopy is considered the current modality for real time imaging. It provides excellent spatial and temporal resolution, but is limited by exposure of patients and staff to ionizing radiation, poor soft tissue characterization and lack of quantitative physiologic information. MR fluoroscopy has been introduced with substantial progress during the last decade. Clinical and experimental studies performed under MR fluoroscopy have indicated the suitability of this modality for: delivery of ASD closure, aortic valves, and endovascular stents (aortic, carotid, iliac, renal arteries, inferior vena cava). It aids in performing ablation, creation of hepatic shunts and local delivery of therapies. Development of more MR compatible equipment and devices will widen the applications of MR-guided procedures. At post-intervention, MR imaging aids in assessing the efficacy of therapies, success of interventions. It also provides information on vascular flow and cardiac morphology, function, perfusion and viability. MR fluoroscopy has the potential to form the basis for minimally invasive image–guided surgeries that offer improved patient management and cost effectiveness

Transsplenic tract closure after transsplenic portalvenous access using gelfoam-based tract plugging

Abstract Background To assess the feasibility and safety of a gelfoam torpedo plugging technique for embolization of the transsplenic access channel in adult patients following transvenous portal vein interventions. Materials and methods Between 09/2016 and 08/2021, an ultrasound guided transsplenic portalvenous access (TSPVA) was established in twenty-four adult patients with a 21-G needle and 4-F microsheath under ultrasound guidance. Afterwards, sheaths ranging from 4-F to 8-F were inserted as needed for the procedure. Following portal vein intervention, the splenic access tract was embolized with a gelfoam-based tract plugging (GFTP) technique. TSPVA and GFTP were performed twice in two patients. Patients’ pre-interventional and procedural characteristics were analyzed to assess the feasibility and safety of the plugging technique according Cardiovascular and Interventional Radiological Society of Europe (CIRSE) classification system. Values are given as median (minimum;maximum). Subgroup analysis of intercostal vs. subcostal puncture site for TSPVA was performed using the two-sided Mann–Whitney-U test or Student’s t-test and Fisher’s exact test. Level of significance was p < 0.05. Results The study population’s age was 56 (29;71) years and 54% were female patients. Primary liver disease was predominantly liver cirrhosis with 62% of the patients. Pre-interventional model for end-stage liver disease score was 9 (6;25), international normalized ratio was 1.15 (0.86;1.51), activated partial thromboplastin time was 33s (26s;52s) and platelet count was 88.000/µL (31.000;273.000/µL). Ascites was present in 76% of the cases. Craniocaudal spleen diameter was 17cm (10cm;25cm). Indication for TSPVA was assisted transjugular intrahepatic portosystemic shunt placement in 16 cases and revision in two cases, portal vein stent placement in five cases and variceal embolization in three cases. TSPVA was successfully established in all interventions; interventional success rate was 85% (22/26). The splenic access time was 33min (10min;133min) and the total procedure time was 208min (110min;429min). Splenic access was performed with a subcostal route in 11 interventions and with an intercostal route in 15 interventions. Final sheath size was 4-F in 17 cases, 5-F in three cases, 6-F in five cases, 7-F in two cases and 8-F in one case. A median of two gelfoam cubes was used for GFTP. TSPVA- and GFTP-related complications occurred in 4 of 26 interventions (15%) with a subcapsular hematoma of the spleen in two patients (CIRSE grade 1), access-related infection in one patient (CIRSE grade 3) and both in one patient (CIRSE grade 3). In detail, one access-related complication occurred in a patient with subcostal TSPVA (CIRSE grade 1 complication) and the other three complications occurred in patients with intercostal TSPVA (one CIRSE grade 1 complication and two CIRSE grade 3 complication) (p = 0.614). No patient required interventional or surgical treatment due to puncture tract bleeding. Conclusion Gelfoam-based plugging of the puncture tract was feasible and safe for transsplenic access in adult patients undergoing percutaneous portal vein interventions. The lack of major bleeding complications and complete absorption of the gelatine sponge make it a safe alternative to transjugular and transhepatic access and re-interventions via the splenic route