Photoacoustic imaging is a hybrid imaging modality that is based on the detection of acoustic waves generated by absorption of pulsed light by tissue chromophores such as hemoglobin in blood. Serial photoacoustic imaging has been performed over a 10-day period after subcutaneous inoculation of pancreatic tumor cells in a rat. The images were obtained from ultrasound generated by absorption in hemoglobin of short laser pulses at a wavelength of 1064 nm. The ultrasound signals were measured in reflection mode using a double-ring photoacoustic detector. A correction algorithm has been developed to correct for scanning and movement artifacts during the measurements. Three-dimensional data visualize the development and quantify the extent of individual blood vessels around the growing tumor, blood concentration changes inside the tumor and growth in depth of the neovascularized region.

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X-ray coronary angiography is widely used to determine the presence of a stenosis. This paper discusses an approach towards the detection of the functional severity of a stenosis using the relative velocity of the contrast agent. The velocity of the contrast is measured using the arrival time at several locations on a coronary artery. This is done by placing multiple Regions Of Interest(ROI) equally spaced on the artery. The location of these ROIs varies in time because of the cardiac motion. Therefore, an artery tracing and tracking algorithm is used to estimate the location of the ROIs in time. The arrival time of the contrast can be estimated by measuring the image intensity in these ROIs. Using the arrival times in several ROIs, a qualitative velocity can be estimated. Altering the velocity of the blood pharmacologically, by inducing hyperemic conditions, results in a qualitative change in velocity detected by the algorithm. 1 No change in velocity may indicate a severe flow limiting stenosis.

Photoacoustic imaging is used to obtain a range of three-dimensional images representing tumor neovascularization over a 10-day period after subcutaneous inoculation of pancreatic tumor cells in a rat. The images are reconstructed from data measured with a double-ring photoacoustic detector. The ultrasound data originates from the optical absorption by hemoglobin of 14 ns laser pulses at a wavelength of 1064 nm. Three-dimensional data is obtained by using two dimensional linear scanning. Scanning and motion artifacts are reduced using a correction method. The data is used to visualize the development of the individual blood vessels around the growing tumor, blood concentration changes inside the tumor and growth in depth of the neovascularized region. The three-dimensional vasculature reconstruction is created using VTK, which enables us to create a composition of the vasculature on day seven, eight and ten and to interactively measure tumor growth in the near future.