Article

Digital-signal-processor-based dynamic imaging system for optical tomography

Department of Biomedical Engineering, Columbia University, 351 Engineering Terrace MC8904, New York, NY 10027, USA.
Review of Scientific Instruments (Impact Factor: 1.58). 09/2007; 78(8):083706. DOI: 10.1063/1.2769577
Source: PubMed

ABSTRACT In this article, we introduce a dynamic optical tomography system that is, unlike currently available analog instrumentation, based on digital data acquisition and filtering techniques. At the core of this continuous wave instrument is a digital signal processor (DSP) that collects, collates, processes, and filters the digitized data set. The processor is also responsible for managing system timing and the imaging routines which can acquire real-time data at rates as high as 150 Hz. Many of the synchronously timed processes are controlled by a complex programmable logic device that is also used in conjunction with the DSP to orchestrate data flow. The operation of the system is implemented through a comprehensive graphical user interface designed with LABVIEW software which integrates automated calibration, data acquisition, data organization, and signal postprocessing. Performance analysis demonstrates very low system noise (approximately 1 pW rms noise equivalent power), excellent signal precision (<0.04%-0.2%) and long term system stability (<1% over 40 min). A large dynamic range (approximately 190 dB) accommodates a wide scope of measurement geometries and tissue types. First experiments on tissue phantoms show that dynamic behavior is accurately captured and spatial location can be correctly tracked using this system.

0 Bookmarks
 · 
153 Views
  • [Show abstract] [Hide abstract]
    ABSTRACT: We present a dynamic contact-free continuous-wave diffuse optical tomography system for the detection and monitoring of peripheral arterial disease (PAD) in the foot. Peripheral Arterial Disease (PAD) is the narrowing of the functional area of the artery generally due to atherosclerosis. It affects between 8-12 million people in the United States and if untreated this can lead to ulceration, gangrene and ultimately amputation. Contact-Free imaging is highly desirable, due to the presence of ulcerations and gangrene in many patients affected by PAD. The system uses an electron multiplying charge coupled device (EMCCD) camera for detection to achieve a dynamic range of 86 dB with a frame rate of 1 Hz using 20 collimated source fibers and 2 wavelengths. We present first clinical results showing 3D images of total hemoglobin changes in response to a dynamic thigh cuff.
    Conference on Optical Tomography and Spectroscopy of Tissue X; 03/2013
  • [Show abstract] [Hide abstract]
    ABSTRACT: Peripheral Arterial Disease (PAD) is the narrowing of the functional area of the artery generally due to atherosclerosis. It affects between 8-12 million people in the United States and if untreated this can lead to ulceration, gangrene and ultimately amputation. The current diagnostic method for PAD is the ankle-brachial index (ABI). The ABI is a ratio of the patient’s systolic blood pressure in the foot to that of the brachial artery in the arm, a ratio below 0.9 is indicative of affected vasculature. However, this method is ineffective in patients with calcified arteries (diabetic and end-stage renal failure patients), which falsely elevates the ABI recording resulting in a false negative reading. In this paper we present our results in a pilot study to deduce optical tomography’s ability to detect poor blood perfusion in the foot. We performed an IRB approved 30 patient study, where we imaged the feet of the enrolled patients during a five stage dynamic imaging sequence. The patients were split up into three groups: 10 healthy subjects, 10 PAD patients and 10 PAD patients with diabetes and they were imaged while applying a pressure cuff to their thigh. Differences in the magnitude of blood pooling in the foot and rate at which the blood pools in the foot are all indicative of arterial disease.
    Conference on Optical Tomography and Spectroscopy of Tissue X; 03/2013
  • [Show abstract] [Hide abstract]
    ABSTRACT: Vascular optical tomographic imaging (VOTI) is a novel imaging modality that is capable of detecting hemoglobin concentrations in tissue. VOTI is non-invasive, non-ionizing and does not require contrast injection. This technology was applied to the diagnosis of peripheral arterial disease (PAD) within lower extremities of diabetic patients with calcified arteries. This could be of substantial benefit as these patients suffer from comorbidities such as arterial incompressibility, which complicates diagnosis and monitoring. Forty individuals (10 non-diabetic patients with PAD, 10 diabetic patients with PAD, and 20 healthy volunteers) were enrolled in a diagnostic pilot study using the VOTI system. The patients were imaged during a thigh pressure cuff occlusion. The VOTI system was capable of quantifying the blood volume changes within the foot during the thigh cuff occlusion and outputting diagnostic parameters, such as change in hemoglobin concentration, enabling the assessment of foot perfusion. This study resulted in a statistically significant difference between the healthy cohort and both the non-diabetic and the diabetic PAD cohorts (p = .006, p = .006). Receiver operating characteristic (ROC) curve analysis showed that PAD diagnosis could be made with over 80% sensitivity or specificity depending on the characteristic cutoff point. In addition, VOTI was capable of providing the locations of under-perfused regions within the foot and evaluating the severity of arterial disease, even within diabetic patients with calcified arteries, who are traditionally difficult to diagnose. VOTI can effectively diagnose PAD independently of arterial compressibility, making it very useful for assessing vascular disease in diabetic patients. Copyright © 2014 European Society for Vascular Surgery. Published by Elsevier Ltd. All rights reserved.
    European Journal of Vascular and Endovascular Surgery 11/2014; 49(1). DOI:10.1016/j.ejvs.2014.10.010 · 3.07 Impact Factor

Full-text (2 Sources)

Download
61 Downloads
Available from
May 23, 2014