Intravascular Ultrasonic Probe Imaging DuringCore Biopsy ProceduresBuroker, M., Johnson, K., Simatic, N., and Zechlinski, J.§6. Methods and Materials Tests were conducted under the direction Dr. Jim Zebzeski from the Department of Medical Physics located in the Medical Sciences building. All testing was done using 40 MHz Discovery probes attached to an electric control and image reconstruction system. Testing protocol was developed according to the regulations regarding the use of the IVUS system. In order to prevent motor burnout, the probe was turned on just long enough to obtain a steady image, and then turned off until the next image. The probe system was always flushed with water to ensure that the ultrasonic sound waves would pass through the catheter to image the surrounding area. The gain on the ultrasound machine was checked so that the signals furthest away from the probe were being amplified more than the objects closest to the probe. This eliminates much of the noise created by the needle. All testing was recorded continuously on VHS tape, with digital video and images being captured using a computer. In nearly all cases, the probe was first inserted into an untreated phantom and images were obtained. Calcifications were then mimicked using “8 in 1: Sun Ripened Fruit Mineral Treat,” which contained 22.5 to 27% calcium by weight. Small pieces, approximately 3 to 4 mmin diameter, were manually inserted in the phantom with the probe placed nearby to obtain an image. §6.1 Phantom #1 Ultrasonic Gel with CalcificationsTo evaluate the raw imaging power of the IVUS system, an imaging test was first performed using a hollow plastic tube filled with ultrasonic gel. The ultrasonic gel allowed forimaging of a homogeneous system, and allowed the sole imaging of individual calcifications without background interference. In triplicate, images were taken of the probe in a pure ultrasonic gel and then compared to images taken from a solution with intermixed calcifications .5-2mm in diameter. §6.2 Phantom #2 Orange Slices and PulpTo evaluate the effectiveness of IVUS detection of calcification in a medium with significant interference an imaging test was done using an orange. A fresh navel orange was ground into a pulp and put into a hollow plastic tube. Images were taken of the baseline phantomand a phantom with calcification interlaced in triplicate. Images were also taken of individual slices from the orange with and without simulated calcifications.§6.3 Phantom #3 Water with Suros Needle w/wo insertTo evaluate the effectiveness of the IVUS probe within a core biopsy needle, images weretaken of water with the probe inside a needle. The needle used was an 11gauge MRI compatible vacuum assisted core biopsy needle manufactured by Suros Surgical. Three trials were taken for each of the following conditions: probe alone, probe inside needle, and probe inside the needle with plastic insert. §6.4 Phantom #4 Turkey As an all inclusive phantom, images were taken under many conditions of a turkey breast. Turkey breasts are accurate models of a human breast, and have similar acoustical impedance. Trials were taken in triplicate of both a normal and a calcified turkey breast under the following conditions: probe alone, probe with needle, and probe inside needle with plastic insert.2§7. Results §7.1 Phantom #1 Ultrasonic GelCalcifications were easy to identify using ultrasound gel containing simulatedcalcifications (Figure 1). No background noise is noted with gel alone, while possible simulatedcalcifications appear as bright spots. The surrounding profile located at the edge of the image isthe hollow plastic tube. Figure 1. Ultrasound gel with probe alone in hollow plastic tube without simulatedcalcification (left) and with simulated calcification (X) (right). The profile is of the hollowplastic tube is visible near the edge of each image.§7.2 Phantom #2 Orange Slices and PulpImages from orange slices were inconclusive. Phantoms containing simulated calcifications appeared extremely similar to those without (Figure 2). Exact location of simulated calcifications was difficult if not impossible to determine. It is possible that fresh orange tissue contains enough calcium to cause background noise. It is not known how well fresh orange simulates breast tissue.3Figure 2. Orange slice with probe alone without simulated calcification (left) and with simulatedcalcification (X) (right). §7.3 Phantom #3 Water with Suros Needle w/wo insertA strong, sharp profile of the biopsy needle is visible when the plastic insert is not used; no other background noise is visible (Figure 3). Addition of the plastic insert reduces needle artifact.Figure 3. Probe alone in water (left). Probe in needle in water (center). Probe in needle withplastic insert in water (right). §7.4 Phantom #4 TurkeyVery little background noise was noted with the probe alone in raw turkey breast, and simulated calcifications were easy to detect (Figure 4A, 4B). Strong reflection occurred from theinner walls of the biopsy needle when the probe was inserted (Figure 4C). It was difficult to 4distinguish the cutaway portion of the needle opening from the remainder of its profile. Calcifications were still visible (Figure 4D). Needle artifact is greatly reduced when the plastic insert is used, and calcifications stand out more against the black background (Figure 4E, 4F). The plastic insert is weakly visible. In some tests the very edges of the needle opening remain highly visible, but in all cases the remainder of the needle profile is faint. The location of the needle can be determined by identifying these bright edges in some images. In general, distinguishing the needle profile from the cutaway portion (where tissue is located) was much easier in video footage versus a static image. As the probe was fed in and out through the tissue, the cutaway portion of the image changed greatly as tissue passed by the transducer, while the portion of the image showing the needle profile remained nearly static.56A BC DE
View Full Document
Unlocking...