Stereotactic mammography imaging combined with 3D US imaging for image guided breast biopsy.

Stereotactic X-ray mammography (SM) and ultrasound (US) guidance are both commonly used for breast biopsy. While SM provides three-dimensional (3D) targeting information and US provides real-time guidance, both have limitations. SM is a long and uncomfortable procedure and the US guided procedure is inherently two dimensional (2D), requiring a skilled physician for both safety and accuracy. The authors developed a 3D US-guided biopsy system to be integrated with, and to supplement SM imaging. Their goal is to be able to biopsy a larger percentage of suspicious masses using US, by clarifying ambiguous structures with SM imaging. Features from SM and US guided biopsy were combined, including breast stabilization, a confined needle trajectory, and dual modality imaging. The 3D US guided biopsy system uses a 7.5 MHz breast probe and is mounted on an upright SM machine for preprocedural imaging. Intraprocedural targeting and guidance was achieved with real-time 2D and near real-time 3D US imaging. Postbiopsy 3D US imaging allowed for confirmation that the needle was penetrating the target. The authors evaluated 3D US-guided biopsy accuracy of their system using test phantoms. To use mammographic imaging information, they registered the SM and 3D US coordinate systems. The 3D positions of targets identified in the SM images were determined with a target localization error (TLE) of 0.49 mm. The z component (x-ray tube to image) of the TLE dominated with a TLEz of 0.47 mm. The SM system was then registered to 3D US, with a fiducial registration error (FRE) and target registration error (TRE) of 0.82 and 0.92 mm, respectively. Analysis of the FRE and TRE components showed that these errors were dominated by inaccuracies in the z component with a FREz of 0.76 mm and a TREz of 0.85 mm. A stereotactic mammography and 3D US guided breast biopsy system should include breast compression for stability and safety and dual modality imaging for target localization. The system will provide preprocedural x-ray mammography information in the form of SM imaging along with real-time US imaging for needle guidance to a target. 3D US imaging will also be available for targeting, guidance, and biopsy verification immediately postbiopsy.

Prostate boundary segmentation from 2D ultrasound images.

Outlining, or segmenting, the prostate is a very important task in the assignment of appropriate therapy and dose for cancer treatment; however, manual outlining is tedious and time-consuming. In this paper, an algorithm is described for semiautomatic segmentation of the prostate from 2D ultrasound images. The algorithm uses model-based initialization and the efficient discrete dynamic contour. Initialization requires the user to select only four points from which the outline of the prostate is estimated using cubic interpolation functions and shape information. The estimated contour is then deformed automatically to better fit the image. The algorithm can easily segment a wide range of prostate images, and contour editing tools are included to handle more difficult cases. The performance of the algorithm with a single user was compared to manual outlining by a single expert observer. The average distance between semiautomatically and manually outlined boundaries was found to be less than 5 pixels (0.63 mm), and the accuracy and sensitivity to area measurements were both over 90%.

An algorithm for automatic needle localization in ultrasound-guided breast biopsies.

An algorithm was developed in order to reduce operator dependence in ultrasound-guided breast biopsy, by automatically locating the needle in the ultrasound image, and displaying its location on the image for the user. Ultrasound images of a typical breast biopsy needle inserted in a tissue-mimicking agar were obtained to test the algorithm. The resulting images were examined by a group of observers who recorded the values of the angle, intercept and tip coordinates of the needle in the image, and inter- and intra-observer variability studies were performed on the results. The results of the algorithm segmentation were compared to the values recorded by the observers, and physical measurements recorded at the time the images were acquired. The algorithm segmentation was precise enough to successfully (when considering angle and tip segmentation) target 90% of tumors of 4.5 mm in diameter situated at the center of the image.

Variability and accuracy of measurements of prostate brachytherapy seed position in vitro using three-dimensional ultrasound: an intra- and inter-observer study.

This paper is a step in investigating whether three-dimensional (3D) ultrasound can be used intraoperatively to replace Computed Tomography (CT) for localization of brachytherapy seeds. In order to quantify the accuracy and variability of seed localization without introducing effects due to tissues, we first report our results with test phantoms. An inter- and intra-observer study was performed to assess the variability of 2 3D ultrasound scan acquisition methods: Tilt 3D scanning and pull-back 3D scanning. Seven observers measured the positions of gold seed markers in an agar phantom twice in each of the three orthogonal image planes. An analysis of variance (ANOVA) was performed to determine the intra- and inter-observer standard errors of measurement (SEM) and the minimum detectable changes in marker position (deltap). Average intra- and inter-observer SEMs for the tilt scan 3D image were 0.36 and 0.40 mm, respectively. Measurements of the pull-back scan 3D image yielded average intra- and inter-observer SEM of 0.46 and 0.49 mm, respectively. A paired difference analysis showed that the lower SEM for the tilt 3D scan image were statistically significant at a significance level of alpha= 0.05. The accuracy of the US measurements was tested by determining marker coordinates from CT images of the phantom in a stereotactic head frame. CT coordinates were matched to the ultrasound (US) coordinates by means of an affine transform. Average matching errors in x, y, and z were 0.02, 0.10, and -0.02 mm, respectively.

Number of siblings and intellectual development. The resource dilution explanation.

The resource dilution model posits that parental resources are finite and that as the number of children in the family increases, the resources accrued by any one child necessarily decline. Siblings are competitors for parents' time, energy, and financial resources and so the fewer the better. Even one sibling is too many. The author describes the general elements of the dilution position and assesses its merits for explaining the effect of siblings on one component of the educational process--tests of intellectual development. The author identifies critical flaws in recent critiques of the dilution position and concludes that dilution continues to provide the most promising explanation for why children with few siblings score higher on tests of cognitive skills than children with many siblings.

Three-dimensional ultrasound imaging.

Ultrasound is an inexpensive and widely used imaging modality for the diagnosis and staging of a number of diseases. In the past two decades, it has benefited from major advances in technology and has become an indispensable imaging modality, due to its flexibility and non-invasive character. In the last decade, research investigators and commercial companies have further advanced ultrasound imaging with the development of 3D ultrasound. This new imaging approach is rapidly achieving widespread use with numerous applications. The major reason for the increase in the use of 3D ultrasound is related to the limitations of 2D viewing of 3D anatomy, using conventional ultrasound. This occurs because: (a) Conventional ultrasound images are 2D, yet the anatomy is 3D, hence the diagnostician must integrate multiple images in his mind. This practice is inefficient, and may lead to variability and incorrect diagnoses. (b) The 2D ultrasound image represents a thin plane at some arbitrary angle in the body. It is difficult to localize the image plane and reproduce it at a later time for follow-up studies. In this review article we describe how 3D ultrasound imaging overcomes these limitations. Specifically, we describe the developments of a number of 3D ultrasound imaging systems using mechanical, free-hand and 2D array scanning techniques. Reconstruction and viewing methods of the 3D images are described with specific examples. Since 3D ultrasound is used to quantify the volume of organs and pathology, the sources of errors in the reconstruction techniques as well as formulae relating design specification to geometric errors are provided. Finally, methods to measure organ volume from the 3D ultrasound images and sources of errors are described.

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.

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.

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.

Three-dimensional ultrasound-guided core needle breast biopsy.

A new core needle breast biopsy system guided by 3-D ultrasound (US) is proposed. Our device provides rapid imaging and real-time guidance, as well as breast stabilization and a needle guidance apparatus using 3-D imaging. The targeting accuracy of our device was tested by inserting a 14-gauge biopsy needle into agar phantoms under 3-D US guidance. A total of 18 0.8-mm stainless-steel beads embedded in the phantoms defined each of the four target positions tested. Positioning accuracy was calculated by comparing needle tip position to the preinsertion bead position, as measured by three observers three times each on 3-D US. The interobserver standard error of measurement was no more than 0.14 mm for the beads and 0.27 mm for the needle tips. A 3-D principal component analysis was performed to obtain the population distribution of needle tip position relative to the target beads for the four target positions. The 3-D 95% confidence intervals were found to have total widths ranging from 0.43 to 1.71 mm, depending on direction and bead position.

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.

The development and evaluation of a three-dimensional ultrasound-guided breast biopsy apparatus.

We have designed a prototype three-dimensional ultrasound guidance (3D USB) apparatus to improve the breast biopsy procedure. Features from stereotactic mammography and free-hand US-guided biopsy have been combined with 3D US imaging. This breast biopsy apparatus accurately guides a needle into position for the sampling of target tissue. We have evaluated this apparatus in three stages. First, by testing the placement accuracy of a needle in a tissue mimicking phantom. Second, with tissue mimicking phantoms that had embedded lesions for biopsy. Finally, by comparison to free-hand US-guided biopsy, using chicken breast phantoms. The first two stages of evaluation quantified the mechanical biases in the 3D USB apparatus. Compensating for these, a 96% success rate in targeting 3.2 mm "lesions" in chicken breast phantoms was achieved when using the 3D USB apparatus. The expert radiologists performing biopsies with free-hand US guidance achieved a 94.5% success rate. This has proven an equivalence between our apparatus, operated by non-experts, and free-hand biopsy performed by expert radiologists, for 3.2 mm lesions in vitro, with a 95% confidence.

Three-dimensional ultrasound and magnetic resonance imaging of pelvic anatomy: potential for complications from minimally invasive procedures.

OBJECTIVE: Several new minimally invasive therapies have recently been popularized for both malignant and benign prostate disorders, including interstitial implantation of radioactive seeds and high-radiofrequency wires, cryoablation, transurethral thermotherapy, and laser prostatectomy. Complications can be incurred during the various procedures, often as a result of injury to adjacent anatomic structures. Some of the complications are inadvertent, whereas others are inherent in the particular treatment process. We hope to increase awareness and understanding of some of the potential complications. METHODS AND MATERIALS: Magnetic resonance (MR) and three-dimensional transrectal ultrasonography (TRUS) imaging were utilized to illustrate the relevant pelvic anatomy in, respectively, a healthy volunteer and four patients undergoing evaluation for prostate symptoms. In addition, data from the Visible Human dataset (the Visible Human Project is part of the National Library of Medicine 1986 Long-Range Plan) were used. RESULTS: The potential complications relating to urinary sphincter and anal sphincter control, sexual function, pelvic musculature, and pelvic nerve physiology could be explained on the basis of the MR and TRUS findings using cryoablation for illustrative purposes. CONCLUSION: A clear understanding of the relevant anatomy and physiology is essential for the physician to provide patient counseling preoperatively regarding anticipated sequelae and to avoid preventable intraoperative complications related to minimally invasive therapeutic procedures for the prostate.

Perineal prostate cancer seeding along needle tract following cryosurgery.

We report a case of tumor seeding along the path of a cryoprobe during cryotherapy for prostate cancer. Seeding was reported as a potential problem in the era of transperineal biopsies, but we suspect that it may again resurface in modern minimally invasive surgical treatments that develop a transperineal tract. Minimizing prostate trauma and bleeding during minimally invasive therapies such as cryosurgery and brachytherapy may decrease the risk of tumor seeding. We believe that the perineum of all patients who have undergone transperineal procedures should be thoroughly checked during follow-up.

Receiver operating characteristic (ROC) curve analysis of transrectal ultrasonographic prostate cancer detection.

PURPOSE: To provide an overview of receiver operating characteristics (ROC) curve theory and create an ROC curve describing transrectal ultrasound (TRUS) detection of prostate cancer (PCa). METHODS: One hundred thirty-two patients with either an abnormal digital rectal exam (DRE) or a prostate-specific antigen (PSA) above 4 ng/ml or both underwent TRUS and biopsy of the peripheral zone (PZ) of each quadrant. ROC software was used to create an ROC curve. RESULTS: One hundred seventy-nine of 528 quadrants (34%) harbored PCa. The performance of TRUS in detection of PCa as defined by the area below the ROC is 0,809. CONCLUSIONS: Future investigators are encouraged to employ ROC analysis of TRUS to permit more meaningful comparisons of performance.

3D ultrasound guided breast biopsy system.

Stereotactic X-ray mammography (SM) and ultrasound (US) guidance are commonly used techniques for breast biopsy. While SM provides 3D targeting information and US provides real-time guidance, both techniques have limitations. SM is a long and uncomfortable procedure and the US guided procedure is inherently 2D, requiring a skilled physician for both safety and accuracy. We have developed a 3D US-guided biopsy system to integrate with SM. The dual modality breast biopsy system combines the advantages of both approaches with 3D US and SM targeting, near real-time 3D and real-time 2D US guidance, breast stabilisation and a confined needle trajectory. Our goal is to be able to biopsy a larger percentage of suspicious masses using ultrasound, by clarifying ambiguous structures with mammographic imaging. Using breast phantoms, we have shown that our ultrasound guided biopsy system was capable of targeting artificial lesions that were 3.2 mm in diameter, with a 96% success rate. Through this study, we also demonstrated that our system was equivalent to current clinical practice, for an in vitro biopsy task. Metal beads in known relative positions allowed us to determine the geometry of the SM system, so that stereotactic mammography could be registered to 3D US images. The target registration error was found to be 1.6 mm. This error was dominated by positioning error in the vertical direction (perpendicular to the film surface). As an adjunct to SM, we propose that 3D US could provide more complete imaging information for target identification and real-time monitoring of needle insertion, as well as providing a means for rapid confirmation of biopsy success.