Andinet Enquobahrie attended the 28th International Congress and Exhibition for Computer Assisted Radiology and Surgery (CARS) in Fukuoka, Japan, from June 25-28. The CARS congress is an annual event for scientists, engineers, and physicians to present and discuss innovations in radiology and surgery. The conference had multiple tracks focusing on image- and model-guided intervention, medical imaging, image processing and visualization, decision and support system in surgical management, computer aided diagnosis, medical simulation, virtual training, surgical navigation and robotics, and model-guided and personalised medicine.
In the "CT and PET-CT" session of the conference, Kitware's work in image-guided application using low-radiation dose amplitude gated phase-matched PET-CT images was presented. This effort is part of the PET/CT guided biopsy project that is currently going on in collaboration with Georgetown University and Children's National Medical Center. The overall goal of the project is to improve the clinical effectiveness of liver lesion biopsy by fusing respiratory-compensated PET-CT with CT images in the interventional CT suite (Clinical workflow is shown in the figure below).
In this project, we are developing an algorithm and software for PET/CT-fused needle biopsy guidance. PET imaging provides information on functional or metabolic characteristics of tumors, whereas CT predominately assesses tumor’s anatomical and morphological features. Given the ability of PET to localize malignancies in situations where the same tumors do not have a CT correlate, PET/CT guided biopsy helps to improve the diagnostic yield of liver lesion biopsies.
The approach presented at the conference focused on acquiring low-radiation dose amplitude gated phase-matched PET/CT images. The protocol was developed in collaboration with the Molecular Image PET group at Siemens Healthcare and Prof. Paul Kinahan at University of Washington. In this approach, gated PET images are obtained. The amplitude level of the PET gating is then used to obtain phase-matched amplitude gated prospective CT images. During the CT acquisition, the patient is exposed to radiation only during the amplitude gating. Thus, the total radiation exposure for the patient is limited to low levels. By acquiring gated amplitude-matched PET/CT images, motion artifacts due to the PET acquisition process are significantly reduced. During the biopsy procedure, the intra-operative CT images are also obtained at peak inspiration. Thus, the pre-interventional PET images can be fused with the CT images to provide tumor localization during biopsy. To test the approach, we used the Anzai respiratory gating and respiratory phantom shown below.
This phantom consists of a cylinder that moves at a constant speed and a line source attached to the cylinder visible in both CT and PET images. We used the Siemens mCT 64 detector PET/CT machine with the VG40 software to acquire the images. The line source is visible in both CT and PET images. During the image acquisition, we collected four sets of data: 1) attenuation-correction CT, 2) regular PET, 3) Gated PET, and 4) gated prospective CT. As shown in the figure below, the regular PET/CT fusion (left in the figure below) suffers from the cylinder motion resulting in a curved trace as compared to the crisp amplitude gated phase-matched PET/CT fusion (right). Also, the variation of the functionally active part in the image is more in the regular image as compared to the gated PET/CT image, where the functionally active image pixels closely stick to the outline of the line detector.
This work is published in the conference proceedings.
Cleary K,, Khare R., Enquobahrie A.,Kinahan P.,Esposito G., Banovac F., “Evaluation of a method using low-radiation dose amplitude gated phase matched PET-CT images for guided liver biopsy”, Computer Assisted Radiology and Surgery: Proceedings of the 28th International Congress and Exhibition (CARS 2014), Vol. 9, No. 1 Suppl, pp 8-9 Fukuoka, Japan, June 25 – 28, 2014.
This phantom study is part of the effort to get the software ready for a clinical feasibility study that will start soon. For the clinical feasibility study, we have implemented an application using the 3D Slicer framework. The development is centered around a work-flow based module that includes data loading, registration, tracking connection, and visualization steps. Software, user and developer documentation, and other information about the project can be found in the Wiki page.
Research reported in this publication was supported by the National Cancer Institute of the National Institutes of Health under Award Number R42CA153488. The content is solely the responsibility of the authors and does not necessarily represent the official views of the National Institutes of Health.