Reconstructions in limited‐view thermoacoustic tomography

Abstract

The limited-view problem is studied for thermoacoustic tomography, which is also referred to as photoacoustic or optoacoustic tomography depending on the type of radiation for the induction of acoustic waves. We define a ''detection region,'' within which all points have sufficient detection views. It is explained analytically and shown numerically that the boundaries of any objects inside this region can be recovered stably. Otherwise some sharp details become blurred. One can identify in advance the parts of the boundaries that will be affected if the detection view is insufficient. If the detector scans along a circle in a two-dimensional case, acquiring a sufficient view might require covering more than a -, or less than a -arc of the trajectory depending on the position of the object. Similar results hold in a three-dimensional case. In order to support our theoretical conclusions, three types of reconstruction methods are utilized: a filtered backprojection ͑FBP͒ approximate inversion, which is shown to work well for limited-view data, a local-tomography-type reconstruction that emphasizes sharp details ͑e.g., the boundaries of inclusions͒, and an iterative algebraic truncated conjugate gradient algorithm used in conjunction with FBP. Computations are conducted for both numerically simulated and experimental data. The reconstructions confirm our theoretical predictions.

Imaging of high‐intensity focused ultrasound‐induced lesions in soft biological tissue using thermoacoustic tomography

“…In the following experiments, we reconstructed the image with full (panoramic) view data, which were collected by scanning the ultrasonic transducer around the tissue sample in a full circle. In practice, we often can obtain only limited-view data and then must use the limitedview algorithm discussed previously 20 to reconstruct the image.…”

“…20 An approximate two-dimensional filtered backprojection algorithm was applied to obtain an energy deposition image first. To emphasize the sharp details in the reconstructed image, we then used a local-tomography-type reconstruction algorithm that was also studied in the paper referenced above.…”

Exact series reconstruction in photoacoustic tomography with circular integrating detectors

“…In the reconstructed images one notices some blurred boundaries which are limited data artifacts [20,24,29] arising from the finite height of the stack of circular integrating detectors. Moreover the images reconstructed with (4.4) are less sensitive to noise.…”

Photoacoustic Tomography

“…The most well developed example is the Thermoacoustic Tomography (TAT) (also abbreviated as TCT) [19]. Let us provide a brief description of the TAT procedure (also see [11,18,19,22,35] and [40]- [45]). …”