Optical coherence tomography of the esophagus in radiation therapy

Esophageal cancer is the eight most common type of cancer worldwide and the sixth leading cause of cancer-related death with a five-year survival rate of 15-25%. Prominent histopathological types of cancer are squamous cell carcinoma and adenocarcinoma. Currently, the clinical guidelines for esophageal cancer patients (>T2) involves neoadjuvant chemo-radiation therapy (nCRT) followed by esophagectomy. The main objective during radiation therapy (RT) is to precisely deliver the radiation dose to the tumor and tumor-involved lymph nodes while sparing surrounding healthy tissue. Although image-guided RT enhances the local tumor control, detailed knowledge of the tumor extent is limited and improvements are required. Computed tomography (CT) and recently magnetic resonance imaging (MRI) are the main imaging modalities used for RT planning. CT and MRI are limited in terms of resolution to visualize the tumor extent, and therefore endoscopic ultrasound (EUS) is used to assess the longitudinal extent of the tumor. However, EUS has a low soft-tissue contrast and suffers from understaging due to the limited resolution of EUS to visualize microscopic tumor extent and overstaging since it is unable to distinguish tumor infiltration from inflammatory changes. Such uncertainties require a large expansion of the gross tumor volume (GTV) into the clinical target volume (CTV) during RT planning. Optical coherence tomography (OCT) with a 10-fold higher resolution than EUS may potentially better visualize the tumor extent, which can reduce CTV margins. The aim of this thesis was to adopt OCT for image-guided RT of esophageal cancer and diagnostics of radiation-induced esophageal damages during RT of thoracic and head and neck cancer

Optical coherence tomography of the esophagus in radiation therapy

Esophageal cancer is the eight most common type of cancer worldwide and the sixth leading cause of cancer-related death with a five-year survival rate of 15-25%. Prominent histopathological types of cancer are squamous cell carcinoma and adenocarcinoma. Currently, the clinical guidelines for esophageal cancer patients (>T2) involves neoadjuvant chemo-radiation therapy (nCRT) followed by esophagectomy. The main objective during radiation therapy (RT) is to precisely deliver the radiation dose to the tumor and tumor-involved lymph nodes while sparing surrounding healthy tissue. Although image-guided RT enhances the local tumor control, detailed knowledge of the tumor extent is limited and improvements are required. Computed tomography (CT) and recently magnetic resonance imaging (MRI) are the main imaging modalities used for RT planning. CT and MRI are limited in terms of resolution to visualize the tumor extent, and therefore endoscopic ultrasound (EUS) is used to assess the longitudinal extent of the tumor. However, EUS has a low soft-tissue contrast and suffers from understaging due to the limited resolution of EUS to visualize microscopic tumor extent and overstaging since it is unable to distinguish tumor infiltration from inflammatory changes. Such uncertainties require a large expansion of the gross tumor volume (GTV) into the clinical target volume (CTV) during RT planning. Optical coherence tomography (OCT) with a 10-fold higher resolution than EUS may potentially better visualize the tumor extent, which can reduce CTV margins. The aim of this thesis was to adopt OCT for image-guided RT of esophageal cancer and diagnostics of radiation-induced esophageal damages during RT of thoracic and head and neck cancer

Computational Re-Entry Vulnerability Index Mapping to Guide Ablation in Patients With Postmyocardial Infarction Ventricular Tachycardia

Background: Ventricular tachycardias (VTs) in patients with myocardial infarction (MI) are often treated with catheter ablation. However, the VT induction during this procedure does not always identify all of the relevant activation pathways or may not be possible or tolerated. The re-entry vulnerability index (RVI) quantifies regional activation-repolarization differences and can detect multiple regions susceptible to re-entry without the need to induce the arrhythmia. Objectives: This study aimed to further develop and validate the RVI mapping in patient-specific computational models of post-MI VTs. Methods: Cardiac magnetic resonance imaging data from 4 patients with post-MI VTs were used to induce VTs in a computational electrophysiological model by pacing. The RVI map of a premature beat in each patient model was used to guide virtual ablations. We compared our results with those of clinical ablation in the same patients. Results: Single-site virtual RVI-guided ablation prevented VT induction in 3 of 9 cases. Multisite virtual ablations guided by RVI mapping successfully prevented re-entry in all cases (9 of 9). Overall, virtual ablation required 15-fold fewer ablation sites (235.5 ± 97.4 vs 17.0 ± 6.8) and 2-fold less ablation volume (5.34 ± 1.79 mL vs 2.11 ± 0.65 mL) than the clinical ablation. Conclusions: RVI mapping allows localization of multiple regions susceptible to re-entry and may help guide VT ablation. RVI mapping does not require the induction of arrhythmia and may result in less ablated myocardial volumes with fewer ablation sites.Medical Instruments & Bio-Inspired Technolog