Shidong Tong

A three-dimensional ultrasound prostate imaging system.

We have developed a three-dimensional (3D) transrectal ultrasound imaging system, based on using a motorized 5 MHz transducer assembly, rotated under microcomputer control, to collect a series of 100 two-dimensional (2D) images, digitized by a video frame-grabber. These are then reconstructed into a 3D image on a computer workstation, permitting the prostate anatomy to be visualized in three dimensions, and distance and volume measurements to be performed. The accuracy of the distance measurements was assessed with a string test phantom, and that of the volume measurements with balloons of known sizes. Also, the resolution degradation engendered by the reconstruction algorithm was assessed by comparing the full-width at half-maximum (FWHM) of string cross-sectional images in the 3D image to their 2D counterparts. The results show that distance and volume measurements are both accurate to about +/- 1%, and that the reconstruction algorithm increases the mean FWHM by 8 +/- 3% axially and 3 +/- 3% laterally.

Intra- and inter-observer variability and reliability of prostate volume measurement via two-dimensional and three-dimensional ultrasound imaging

We describe the results of a study to evaluate the intra- and inter-observer variability and reliability of prostate volume measurements made from transrectal ultrasound (TRUS) images, using either the (optimal) height-width-length (HWL) method (V = pi/6 HWL) with two-dimensional (2D) TRUS images (obtained as cross-sections of three-dimensional [3D] TRUS images) or manual planimetry of 3D TRUS images (the 3D US method). In this study, eight observers measured 15 prostate images, twice via each method, and an analysis of variance (ANOVA) was performed. This analysis shows that, with the 3D US method, intra-observer prostate volume estimates have 5.1% variability and 99% reliability, and inter-observer estimates have 11.4% variability and 96% reliability. With the HWL method, intra-observer estimates have 15.5% variability and 93% reliability, and inter-observer estimates have 21.9% variability and 87% reliability. Thus, in vivo prostate volume estimates from manual planimetry of 3D TRUS images have much lower variability and higher reliability than HWL estimates from 2D TRUS images.

Accuracy of prostate volume measurements in vitro using three-dimensional ultrasound

RATIONALE AND OBJECTIVES We assessed the ability of a three-dimensional (3D) ultrasound imaging system to measure accurately prostate volume. METHODS Multiple two-dimensional ultrasound images of cadaver prostates scanned in a water bath were reconstructed into three-dimensional (3D) images. The volumes of the prostates were calculated from these 3D images and compared with the actual volumes. Multiple 3D ultrasound volume readings were evaluated for precision. RESULTS The slope of the best-fit line correlating 3D ultrasound estimated volume and true volume was 1.006 +/- 0.007. The average error was 0.36 +/- 1.17 cm3; the coefficient of determination (r2), which is the measure of the straight-line relationship, was .9997; and the standard error was 1.15 cm3. CONCLUSION Three-dimensional ultrasound images accurately reflect true prostate volumes measured in vitro.

Analysis of Linear, Area and Volume Distortion in 3D Ultrasound Imaging

We have developed a three-dimensional (3D) ultrasound imaging system that uses a side-firing probe, axially rotated under computer control, to acquire a series of 2D images, from which the 3D image is reconstructed. For an undistorted reconstruction, the inner radius R0 of the 2D images and the total scanning angle theta must be known accurately. Here, we describe (a) a theoretical analysis of the relative distortion in image shape, length, area, and volume due to an error delta R in R0 or delta theta in theta; (b) measurements of these in simulated and real 3D images; and (c) a method to calibrate R0, theta, and image scale accurately. Theoretically, all four relative distortions vary as P delta R/R + Q delta theta/theta, where magnitude of P < or = 1, magnitude of Q < or = 1, and R is the average distance of the object from the axis. In every case, the simple theoretical formulas for P and Q agree with image measurements to within the measurement uncertainty.

Three-dimensional ultrasound imaging system for prostate cancer diagnosis and treatment

Prostate cancer is the most commonly diagnosed cancer in men in North America. Although two-dimensional (2-D) transrectal ultrasound imaging is widely used for the evaluation of prostate disease, it suffers from limitations that limit its use in diagnosis and therapy of prostate cancer. The use of conventional ultrasound requires that the diagnosticians mentally integrate a series of 2-D images in order to develop an impression of the three-dimensional (3-D) anatomy, and to estimate the volume of the prostate. This approach depends of the expertise of the physician resulting in variability. We have developed a 3-D ultrasound imaging approach that overcomes this problem. In this paper, we describe a 3-D ultrasound imaging system for use in prostate imaging and report on its performance. The system consists of a conventional ultrasound machine, a microcomputer with a video frame grabber, and a custom-built assembly for rotating the ultrasound transducer. A typical scan of 100 2-D B-mode images takes 8 s. These images are then reconstructed into a 3-D image, which can be displayed and interactively manipulated using 3-D visualization software. We also show that manual planimetry of prostates in the 3-D images can be used to estimate volumes in vitro with an accuracy of 2.6%, and a precision of 2.5%; and in vivo with 5.1% intra-observer variability and 11.4% interobserver variability. Thus, 3-D ultrasound imaging overcomes some of the limitations of conventional imaging of the prostate, and has great potential as a tool in the diagnosis and treatment of prostate disease.

Three-dimensional ophthalmic contact B-scan ultrasonography of the posterior segment.

Purpose: A system to produce three‐dimensional computer reconstructions of ophthalmic contact B‐scan ultrasound was developed and investigated. Methods: Investigators used ocular phantoms to measure the accuracy and reproduc‐ibility of linear, area, and volume measurements. Results: In vitro calibration tests of linear and area measurements demonstrate accurate and reproducible findings throughout the imaged space. Phantom volume tests also show reasonable accuracy and reproducibility. Conclusions: Three‐dimensional ultrasonography is effective in measuring length, area, and volume in an experimental model. The in vitro accuracy and reproducibility of measure‐ments warrants further investigation into the clinical utility of this method in posterior segment tumors and other posterior segment pathology.

Three-dimensional ultrasound imaging

Ultrasound is an inexpensive and widely used imaging modality for the diagnosis and staging of a number of diseases; nevertheless, technical improvements are needed before its full potential is realized. We believe that 2-D viewing of the 3-D anatomy, using conventional ultrasound procedures, limits our ability to quantify, diagnose and stage a number of diseases because: conventional ultrasound images are 2-D, multiple images must be integrated in the diagnosticians mind to develop a 3-D impression of the anatomy leading to a time-consuming process with increased operator variability; the patients anatomy or orientation sometimes restricts the image angle, resulting in the optimal image plane necessary for diagnosis being unavailable; and, it is difficult to localize the conventional 2-D image plane and reproduce it at a later time, making it suboptimal for monitoring of therapy. Our efforts have focused on overcoming these deficiencies by developing 3-D ultrasound imaging techniques that are capable of acquiring B-mode, color Doppler and power Doppler images from existing ultrasound instruments, reconstructing the information in 3-D, and then allowing interactive viewing of 3-D ultrasound images on inexpensive desktop computers.

Development and evaluation of a 3D ultrasound imaging system

The use of a 3D ultrasound imaging to perform a prostate examination will overcome the limitations of conventional 2D transrectal ultrasound (TRUS) and permit the estimation of prostate and tumor volumes with greater accuracy and and consistency. In this way, the diagnosis and staging of prostate cancer can be made more accurate and less operator dependent. With a 3D ultrasound imaging system, the patients prostate can be scanned in only a few seconds and the resulting 3D image can be later manipulated and viewed interactively on a computer, after the patient has departed, and prostate and tumor volumes can be measured with better accuracy and reproducibility. The authors developed a 3D TRUS system to image the prostate.