Image analysis methods for diffuse optical tomography

Purpose: The modulation of tissue hemodynamics has important clinical value in medicine for both tumor diagnosis and therapy. As an oncological tool, increasing tissue oxygenation via modulation of inspired gas has been proposed as a method to improve cancer therapy and determine radiation sensitivity. As a radiological tool, inducing changes in tissue total hemoglobin may provide a means to detect and characterize malignant tumors by providing information about tissue vascular function. The ability to change and measure tissue hemoglobin and oxygenation concentrations in the healthy breast during administration of three different types of modulated gas stimuli (oxygen/carbogen, air/carbogen, and air/oxygen) was investigated. Methods: Subjects breathed combinations of gases which were modulated in time. MR‐guided diffuse optical tomography measured total hemoglobin and oxygen saturation in the breast every 30 s during the 16 min breathing stimulus. Metrics of maximum correlation and phase lag were calculated by cross correlating the measured hemodynamics with the stimulus. These results were compared to an air/air control to determine the hemodynamic changes compared to the baseline physiology. Results: This study demonstrated that a gas stimulus consisting of alternating oxygen/carbogen induced the largest and most robust hemodynamic response in healthy breast parenchyma relative to the changes that occurred during the breathing of room air. This stimulus caused increases in total hemoglobin and oxygen saturation during the carbogen phase of gas inhalation, and decreases during the oxygen phase. These findings are consistent with the theory that oxygen acts as a vasoconstrictor, while carbogen acts as a vasodilator. However, difficulties in inducing a consistent change in tissue hemoglobin and oxygenation were observed because of variability in intersubject physiology, especially during the air/oxygen or air/carbogen modulated breathing protocols. Conclusions: MR‐guided diffuse optical imaging is a unique tool that can measure tissue hemodynamics in the breast during modulated breathing. This technique may have utility in determining the therapeutic potential of pretreatment tissue oxygenation or in investigating vascular function. Future gas modulation studies in the breast should use a combination of oxygen and carbogen as the functional stimulus. Additionally, control measures of subject physiology during air breathing are critical for robust measurements.

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“…Previous studies have determined that the spatial resolution of this system is about 5 mm for typical tumor contrasts. 43 …”

Section: Iia Mr-guided Diffuse Optical Imagingmentioning

confidence: 99%

Monitoring of hemodynamic changes induced in the healthy breast through inspired gas stimuli with MR-guided diffuse optical imaging

et al. 2010

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“…A few researchers implemented automated image methods with DOT to identify lesions in a particular subject. [21][22][23] This per-subject analysis, however, neglects information about the common signatures of cancer across a population. Still other researchers pursued hypothesis-driven multiparameter optical metrics with DOS 24,25 and DOT.…”

Section: Ib Limitations Of Current Diffuse Optics Analysismentioning

confidence: 99%

Computer aided automatic detection of malignant lesions in diffuse optical mammography

et al. 2010

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Purpose:Computer aided detection ͑CAD͒ data analysis procedures are introduced and applied to derive composite diffuse optical tomography ͑DOT͒ signatures of malignancy in human breast tissue. In contrast to previous optical mammography analysis schemes, the new statistical approach utilizes optical property distributions across multiple subjects and across the many voxels of each subject. The methodology is tested in a population of 35 biopsy-confirmed malignant lesions. Methods: DOT CAD employs multiparameter, multivoxel, multisubject measurements to derive a simple function that transforms DOT images of tissue chromophores and scattering into a probability of malignancy tomogram. The formalism incorporates both intrasubject spatial heterogeneity and intersubject distributions of physiological properties derived from a population of cancercontaining breasts ͑the training set͒. A weighted combination of physiological parameters from the training set define a malignancy parameter ͑M͒, with the weighting factors optimized by logistic regression to separate training-set cancer voxels from training-set healthy voxels. The utility of M is examined, employing 3D DOT images from an additional subjects ͑the test set͒. Results: Initial results confirm that the automated technique can produce tomograms that distinguish healthy from malignant tissue. When compared to a gold standard tissue segmentation, this protocol produced an average true positive rate ͑sensitivity͒ of 89% and a true negative rate ͑speci-ficity͒ of 94% using an empirically chosen probability threshold. Conclusions: This study suggests that the automated multisubject, multivoxel, multiparameter statistical analysis of diffuse optical data is potentially quite useful, producing tomograms that distinguish healthy from malignant tissue. This type of data analysis may also prove useful for suppression of image artifacts.

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“…Interested readers can find more information from some excellent review articles. 51,52 The concept of absorption and fluorescence spectroscopy as a modality for the diagnosis of disease dates back several decades. 53 In recent years, the potential for spectroscopy to diagnose cancer 54 and to monitor the progress of cancer treatment 55 has been increasingly appreciated.…”

Section: Iib3 Anatomic and Optical Imagingmentioning

confidence: 99%

The role of photodynamic therapy (PDT) physics

2008

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Photodynamic therapy ͑PDT͒ is an emerging treatment modality that employs the photochemical interaction of three components: light, photosensitizer, and oxygen. Tremendous progress has been made in the last 2 decades in new technical development of all components as well as understanding of the biophysical mechanism of PDT. The authors will review the current state of art in PDT research, with an emphasis in PDT physics. They foresee a merge of current separate areas of research in light production and delivery, PDT dosimetry, multimodality imaging, new photosensitizer development, and PDT biology into interdisciplinary combination of two to three areas. Ultimately, they strongly believe that all these categories of research will be linked to develop an integrated model for real-time dosimetry and treatment planning based on biological response.

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Image analysis methods for diffuse optical tomography

Cited by 82 publications

References 135 publications

Monitoring of hemodynamic changes induced in the healthy breast through inspired gas stimuli with MR-guided diffuse optical imaging

Monitoring of hemodynamic changes induced in the healthy breast through inspired gas stimuli with MR-guided diffuse optical imaging

Computer aided automatic detection of malignant lesions in diffuse optical mammography

The role of photodynamic therapy (PDT) physics

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