Intravascular Ultrasonic Probe Imaging During Core Biopsy Procedures Buroker 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 mm in diameter were manually inserted in the phantom with the probe placed nearby to obtain an image 6 1 Phantom 1 Ultrasonic Gel with Calcifications To 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 for imaging 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 Pulp To 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 phantom and 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 insert To evaluate the effectiveness of the IVUS probe within a core biopsy needle images were taken 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 Gel Calcifications were easy to identify using ultrasound gel containing simulated calcifications Figure 1 No background noise is noted with gel alone while possible simulated calcifications appear as bright spots The surrounding profile located at the edge of the image is the hollow plastic tube Figure 1 Ultrasound gel with probe alone in hollow plastic tube without simulated calcification left and with simulated calcification X right The profile is of the hollow plastic tube is visible near the edge of each image 7 2 Phantom 2 Orange Slices and Pulp Images 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 3 Figure 2 Orange slice with probe alone without simulated calcification left and with simulated calcification X right 7 3 Phantom 3 Water with Suros Needle w wo insert A 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 with plastic insert in water right 7 4 Phantom 4 Turkey Very 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 the inner walls of the biopsy needle when the probe was inserted Figure 4C It was difficult to 4 distinguish 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 5 A B C D E F 6
View Full Document
Unlocking...