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Richard A Robb

Publications and source records attributed to Richard A Robb.

24 records · Page 2Linked to original sources
PubMed2004

Prostate brachytherapy seed localization by analysis of multiple projections: identifying and addressing the seed overlap problem.

Intraoperative three-dimensional reconstruction of seed locations during prostate brachytherapy for purposes of immediate computation of radiation dosimetry is an active area of current investigation, including methods which use multiple fluoroscopic projections. A simulation study using seed locations extracted from clinical CT data was performed; the result showed that on average one quarter of the seeds had a projection image overlapping with other seeds. The average percentage of non-overlapping seeds for the prostate implants and seed types investigated was 74.5% with a range of 56.9%-92.9%. The distribution of seeds in different cluster sizes was analyzed as well as the distribution of pixel counts of connected components. A statistical classifier was developed to determine the number of seed images in a self-connected component in the segmented images. The classifier was tested with simulation data, and the error rate was below 2%. A method to determine seed image position is also provided. A modified three-film technique was used to reconstruct 3-D seed locations. The algorithm allows unequal number of seed images for each projection as input while current methods require the same number of seed images detected in all projections. An accuracy analysis based on angular and positional uncertainty was performed. The reconstruction and seed localization algorithms were tested with simulation data, and the mean distance error of the reconstructed results was 0.61 mm. A phantom study was performed to validate the seed localization method. Three false positive seeds, 4.7% of the total, in the reconstruction result were observed in this study.

Algorithms↗
PubMed2003

Measurement of the ultrasound backscatter signal from three seed types as a function of incidence angle: application to permanent prostate brachytherapy.

PURPOSE: To measure the relative ultrasound backscatter of different seed types as a function of seed orientation and to evaluate the corresponding images of these seeds. METHODS AND MATERIALS: Three seed types were evaluated: OncoSeed (standard), EchoSeed (corrugated), and RAPID Strand(RS). Ultrasound images for angles of incidence varying from 90 degrees (perpendicular) to 20 degrees at 5MHz and 7.5MHz were produced by raster scanning the seeds in a degassed water bath. Seed images were visually inspected and analyzed using the integrated-optical-density (IOD) method. RESULTS: Corrugated seeds appear as contiguous objects over the range of frequencies and orientations examined, whereas standard seeds appear as contiguous objects from 90 degrees to 80 degrees only. The ranges and means of the backscattered IOD ratio of the seeds from 85 degrees to 20 degrees were: (corrugated vs. standard) 1.48 to 3.72 (2.32 +/- 0.62) for 5 MHz and 1.26 to 3.77 (2.19 +/- 0.84) for 7.5 MHz and (corrugated vs. RS) 1.21 to 9.53 (2.98 +/- 2.48) for 5 MHz and 1.008 to 10.86 (2.79 +/- 3.08) for 7.5 MHz. Backscattered signal increase ranged from 1.66 dB to 20.7 dB for the corrugated seed as compared to the other seeds. CONCLUSIONS: Corrugated seeds produce greater backscatter signal and a more readily identifiable seed image over a large range of seed orientation as compared with standard brachytherapy seeds.

Brachytherapy↗
PubMed2003

Parametric visualization methods for the quantitative assessment of myocardial motion.

RATIONALE AND OBJECTIVES: The authors performed this study to evaluate three-dimensional (3D) and four-dimensional (4D) techniques for quantifying and visualizing myocardial motion. MATERIALS AND METHODS: The 4D method was performed by using 3D reconstructions of the complete, in vivo, canine heart before and after acute myocardial infarction. Images were obtained with the Dynamic Spatial Reconstructor (1-3) at 15 time points throughout one cardiac cycle. The authors used 0.75-mm-thick sections to allow creation of deformable models at each time point. For the 3D method, electron-beam computed tomographic reconstructions were obtained in anesthetized pigs from eight adjacent short-axis sections of the left ventricle. Data were acquired before and after selective microembolization of the left anterior descending coronary artery at 11 time points throughout one complete cardiaccycle. The authors used 8-mm-thick sections, which did not enable the use of the volumetric 4D approach with deformable models. For the 3D method, images were processed by radially dividing the tomographic images into small circumferential sectors. Color encoding was used for the derived local magnitudes of wall dynamics. RESULTS: The 4D method provided endocardial peak velocities, excursions, and strains throughout systole and diastole. The 3D method provided regional thickness or regional rates of left ventricular wall thickening throughout the cardiac cycle. CONCLUSION: Functional parametric maps of disturbances in regional contractility and relaxation facilitate appreciation of the effect of altered structure-to-function relationships in the myocardium.

Animals↗
PubMed2002

Three-dimensional visualization and analysis in prostate cancer.

Current and emerging three- and four-dimensional medical imaging modalities, along with development of efficient 3-D computer rendering and modeling of multidimensional volume image data and image-guided navigation, are significantly advancing our capabilities for improved and minimally invasive diagnosis and treatment of prostate cancer, obviating the need for exploratory surgery, physical dissection, blind biopsies and mental reconstruction of anatomy and pathology. Currently, both diagnostic and therapeutic procedures require x-ray fluoroscopy, transrectal ultrasound, CT and/or MRI for assessing the condition of the prostate and/or the outcome of any therapeutic procedure. New imaging approaches based on three-dimensional ultrasound transducers placed on catheters for easy insertion into the urethra are demonstrating significant promise for improved diagnosis and treatment of prostate disease. Microwave thermal ablation shows promise for reduction of prostate size and tumor volume, and preliminary data from cryosurgery suggests improvements in tumor reduction and/or management while minimizing the risk of serious complications. Prostate brachytherapy is becoming a more popular and effective alternative to surgery. All of these methods, either independently or combined through image fusion, are providing an exciting and rapid evolution in capabilities for visualizing the prostate and its anatomic environment, extending from physical to functional forms and from macro to micro orders of scale. Traversing the scale distances between these imaged objects within the prostate and its environs will be made automatic and instantaneous in the near future with the expected advances in miniaturization of powerful computing and electronic sensing elements. Imaging devices will continue to improve in resolution, speed and affordability and will be deployed harmlessly within the body, as well as outside of it. Diagnosis and therapy of prostate disease will become fully noninvasive and synchronous.

Adult↗
PubMedDate not supplied

3D visualization, analysis, and treatment of the prostate using trans-urethral ultrasound.

In the year 2000, it is estimated that over 20,000 men underwent transperineal interstitial permanent prostate brachytherapy (TIPPB) for treatment of prostate cancer. Trans-urethral ultrasound (TUUS) is a new interactive, real-time 3D imaging method that may be effective in therapy-guidance during and after TIPPB. TUUS provides higher resolution than trans-rectal ultrasound (TRUS). TUUS can be used to accurately localize radioactive seeds and therefore contribute to more accurate determination of radiation dose distribution throughout the tissue after the completion of the procedure, similar to information currently provided by expensive and offline CT scans. A TUUS catheter can be used to acquire 2D section images or 3D volume images for detailed analyses of the prostate and associated tissue. Initial development of TUUS imaging was carried out on an ultrasound-equivalent prostate phantom with cylindrical dummy radiation sources. This was followed by preliminary studies in animals and then in patients. Both CT and TRUS data were acquired in these studies for comparative purposes. Segmentation of the prostate capsule and radioactive seeds was carried out using several semi-automated 3D algorithms and image processing techniques. Presentation of the data to the clinician is provided by a variety of complementary 2D and 3D display methods. In comparison with the CT data, TUUS data provided both greater spatial resolution and better soft tissue differentiation. In comparison to the TRUS data, TUUS data provided greater resolution and better seed localization. Combining these advantages suggests the possibility of TUUS becoming the exclusive imaging method in prostate cancer brachytherapy.

Humans↗