Three-dimensional finite-element based deformable image registration for evaluation of pleural cavity irradiation during photodynamic therapy

Our plain-English summary of Three-dimensional finite-element based deformable image registration for evaluation of pleural cavity irradiation during photodynamic therapy, by R. Penjweini, M.M. Kim, T.C. Zhu (Medical Physics, 2017).

The study

• Authors: R. Penjweini, M.M. Kim, T.C. Zhu
• Journal: Medical Physics
• Published: 2017;44(7):3767-3775
• Cited by: 2 articles, as counted by NIH iCite
• Read it: PubMed · Publisher · Free full text

Abstract

Purpose: Photodynamic therapy (PDT) is used after surgical resection to treat the microscopic disease for malignant pleural mesothelioma and to increase survival rates. As accurate light delivery is imperative to PDT efficacy, the deformation of the pleural volume during the surgery is studied on its impact on the delivered light fluence. In this study, a three-dimensional finite element-based (3D FEM) deformable image registration is proposed to directly match the volume of lung to the volume of pleural cavity obtained during PDT to have accurate representation of the light fluence accumulated in the lung, heart and liver (organs-at-risk) during treatment.

Methods: A wand, comprised of a modified endotrachial tube filled with Intralipid and an optical fiber inside the tube, is used to deliver the treatment light. The position of the treatment is tracked using an optical tracking system with an attachment comprised of nine reflective passive markers that are seen by an infrared camera-based navigation system. This information is used to obtain the surface contours of the plural cavity and the cumulative light fluence on every point of the cavity surface that is being treated. The lung, heart, and liver geometry are also reconstructed from a series of computed tomography (CT) scans of the organs acquired in the same patient before and after the surgery. The contours obtained with the optical tracking system and CTs are imported into COMSOL Multiphysics, where the 3D FEM-based deformable image registration is obtained. The delivered fluence values are assigned to the respective positions (x, y, and z) on the optical tracking contour. The optical tracking contour is considered as the reference, and the CT contours are used as the target, which will be deformed. The data from three patients formed the basis for this study.

Results: The physical correspondence between the CT and optical tracking geometries, taken at different times, from different imaging devices was established using the 3D FEM-based image deformable registration. The volume of lung was matched to the volume of pleural cavity and the distribution of light fluence on the surface of the heart, liver and deformed lung volumes was obtained.

Conclusion: The method used is appropriate for analyzing problems over complicated domains, such as when the domain changes (as in a solid-state reaction with a moving boundary), when the desired precision varies over the entire domain, or when the solution lacks smoothness. Implementing this method in real-time for clinical applications and in situ monitoring of the under- or over- exposed regions to light during PDT can significantly improve the treatment for mesothelioma.

© 2017 American Association of Physicists in Medicine.

In plain English

This was a technical methods study from the University of Pennsylvania. It did not study asbestos exposure. It concerned photodynamic therapy, a light-activated drug treatment given after surgery for malignant pleural mesothelioma. The authors built a computer method, called three-dimensional finite-element deformable image registration. It reshapes the lung outline from CT scans taken after surgery to match the shape of the opened pleural cavity, which an infrared tracking system recorded during treatment. The aim was to estimate how much treatment light reached the lung, heart and liver. The method was tested on data from three patients. The matching error was at most 0.95 cm, with a largest standard deviation of 0.40 cm, both in case 3. Light delivered to the pleural cavity ranged from 54.6 to 73.6 J/cm2, against a prescribed 60 J/cm2. About 22-31% of the heart surface and 11-22% of the liver surface received the full 60 J/cm2. The authors described this as part of the treatment target. The authors concluded that the accuracy of the transformation was very good for the three patients studied.

We wrote this plain-English summary from the full article with the help of AI, and a second AI model checked each sentence against the article. It is not the authors' wording; the abstract and the article are their own account.

What the study did and found

• Design: Technical methods-development study applying a computer image-matching (finite-element deformable image registration) method to treatment and CT data from three patients
• Who was studied: Three mesothelioma patients, drawn from patients aged 27 to 81 who had surgical resection plus photodynamic therapy at the Hospital of the University of Pennsylvania from 2004 to 2016. The article does not say whether the 27 to 81 age range applies to these three patients specifically.
• Exposure: No asbestos exposure was studied. The exposure examined was photodynamic therapy treatment light: porfimer sodium (Photofrin II), 2 mg per kg body weight, given 24 hours before 630 nm laser light, with a prescribed dose of 60 J/cm2.
• Main results:
  • Across the three patients, the pleural cavity measured by optical tracking during treatment ranged from 2176 to 9027 cm3 in volume and from 924 to 2210 cm2 in surface area.
  • Matching the CT lung to the optical tracking volume: the largest maximum error (0.95 cm) and the largest standard deviation (0.40 cm) were both in case 3.
  • In an additional check for case 1, matching the pre-treatment CT lung to the post-treatment CT lung gave a maximum error of 0.71 cm and a standard deviation of 0.29.
  • Delivered light fluence on the pleural cavity ranged from 54.6 to 73.6 J/cm2.
  • About 22-31% of the heart surface area and 11-22% of the liver surface area received the full 60 J/cm2 light fluence.
• The authors' conclusion: The authors concluded that the post-surgery CT lung volume can be deformed with their model to overlap the optical tracking geometry, and that the transformation accuracy was very good for the three patients studied.

Topics

The National Library of Medicine indexes this study under subjects our site covers: Mesothelioma.

Medical terms in this study, explained in our Lexicon: Pleural Cavity, Surgical Resection, Pleural Mesothelioma, Mesothelioma.

Related studies

• Real-time light dosimetry for intra-cavity photodynamic therapy: Application for pleural mesothelioma treatment — N. Betrouni, C. Munck, et al. (2017)
• Malignant pleural mesothelioma segmentation for photodynamic therapy planning — W. Brahim, M. Mestiri, et al. (2018)
• Intrapleural Photodynamic Therapy for Mesothelioma: What Place and Which Future? — C. Munck, S.R. Mordon, et al. (2015)
• A Novel Prospective Study Assessing the Combination of Photodynamic Therapy and Proton Radiation Therapy: Safety and Outcomes When Treating Malignant Pleural Mesothelioma — S.R. Rice, Y.R. Li, et al. (2019)
• Phase III randomized trial of surgery with or without intraoperative photodynamic therapy and postoperative immunochemotherapy for malignant pleural mesothelioma — H.I. Pass, B.K. Temeck, et al. (1997)
• Radical pleurectomy and intraoperative photodynamic therapy for malignant pleural mesothelioma — J.S. Friedberg, M.J. Culligan, et al. (2012)

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