Two types of signal acquisition methods using CMOS sensor array coated with piezoelectric material
(PE-CMOS) were studied. The laboratory projection-reflection ultrasound prototypes featuring a
PE-CMOS ultrasound sensing array and an acoustic compound lens were employed to image pork bones
with fractures in vitro. We found that the projection-reflection ultrasound prototypes are capable of
revealing hairline bone fractures with skin in tact. However, the image characteristics generated from these
C-scan prototypes are somewhat different because they were equipped with two different senor array models.
The signal acquired by the first sensor model is based on an integrated signal (IS) at a given time interval.
But the signal acquired by the second sensor model is based on peak signal (PS) with a time gating function
controllable by the user. We found that both systems can detect bone fracture as small as 0.5mm shown as a
strip of ultrasound signal. However, images obtained from the IS sensor show more speckles with a greater
blooming effect on the fractures. On the other hand, images obtained from the PS sensor show less contrast
with less speckles. When the beam position is slightly tilted from the normal direction, the blooming effect
of the ultrasound image would become dark on the fracture region with both acquisition modes.
In this study, we investigated the characteristics of the ultrasound reflective image obtained by a CMOS sensor
array coated with piezoelectric material (PE-CMOS). The laboratory projection-reflection ultrasound prototype
consists of five major components: an unfocused ultrasound transducer, an acoustic beam splitter, an acoustic
compound lens, a PE-CMOS ultrasound sensing array (Model I400, Imperium Inc. Silver Spring, MD), and a
readout circuit system. The prototype can image strong reflective materials such as bone and metal. We found
this projection-reflection ultrasound prototype is able to reveal hairline bone fractures with and without intact skin
and tissue. When compared, the image generated from a conventional B-scan ultrasound on the same bone
fracture is less observable. When it is observable with the B-scan system, the fracture or crack on the surface
only show one single spot of echo due to its scan geometry. The corresponding image produced from the
projection-reflection ultrasound system shows a bright blooming strip on the image clearly indicating the fracture
on the surface of the solid material. Speckles of the bone structure are also observed in the new ultrasound
prototype. A theoretical analysis is provided to link the signals as well as speckles detected in both systems.
In the projection geometry, the detected ultrasound energy through a soft-tissue is mainly attributed to the attenuated primary intensity and the scatter intensity. In order to extract ultrasound image of attenuated primary beam out of the detected raw data, the scatter component must be carefully quantified for restoring the original image. In this study, we have designed a set of apparatus to modeling the ultrasound scattering in soft-tissue. The employed ultrasound imaging device was a C-Scan (projection) prototype using a 4th generation PE-CMOS sensor array (model I400, by Imperium Inc., Silver Spring, MD) as the detector. Right after the plane wave ultrasound transmitting through a soft-tissue mimicking material (Zerdine, by CIRS Inc., Norfolk, VA), a ring aperture is used to collimate the signal before reaching the acoustic lens and the PE-CMOS sensor. Three sets of collimated ring images were acquired and analyzed to obtain the scattering components as a function of the off-center distance. Several pathological specimens and breast phantoms consisting of simulated breast tissue with masses, cysts and microcalcifications were imaged by the same C-Scan imaging prototype. The restoration of these ultrasound images were performed by using a standard deconvolution computation. Our study indicated that the resultant images show shaper edges and detailed features as compared to their unprocessed counterparts.
In this study, we have tested the ability of four imaging modalities to investigate foreign objects in soft tissue. We inserted wood, plastic, glass, and aluminum objects into a pork sample to simulate traumatized soft tissue. Each object was inserted into the skin, then passed through the fat tissue layer and penetrated into the muscle layer. We then took images of the pork sample using four different modalities: (1) a C-Scan imaging prototype which consists of an unfocused transducer, a compound acoustic lens, and a 2D ultrasound sensor array based on the piezoelectric sensing complementary metal-oxide semiconductor (PE-CMOS) technology; (2) a portable B-Scan ultrasound system; (3) a conventional X-ray system; (4) and a computed radiography (CR) X-ray system. We found that the aluminum and glass objects were clearly visible in both conventional X-ray and CR X-ray images with good contrast-to-noise ratio (CNR); however, the wood and plastic objects could not be clearly seen using these modalities. However, we found that the wood, plastic, and glass objects, as well as the thicker aluminum object, were clearly visible in the C-Scan ultrasound images. Furthermore, the fold fibro structures of the fat and muscle tissues in the pork were observable using this modality. The C-Scan prototype images produce neither speckle nor geometry distortion. Both of these issues are commonly seen in B-Scan ultrasound. The results of this study also indicate that the C-Scan images have better CNRs for most foreign objects when compared to other imaging modalities.
The purpose of this study is to investigate the imaging capability of a CMOS (PE-CMOS) ultrasound sensing array coated with piezoelectric material. There are three main components in the laboratory setup: (1) a transducer operated at 3.5MHz-7MHz frequency generating unfocused ultrasound plane waves, (2) an acoustic compound lens that collects the energy and focuses ultrasound signals onto the detector array, and (3) a PE-CMOS ultrasound sensing array (Model I400, Imperium Inc. Silver Spring, MD) that receives the ultrasound and converts the energy to analog voltage followed by a digital conversion. The PE-CMOS array consists of 128×128 pixel elements with 85μm per pixel. The major improvement of the new ultrasound sensor array has been in its dynamic range. We found that the current PE-CMOS ultrasound sensor (Model I400) possesses a dynamic range up to 70dB. The system can generate ultrasound attenuation images of soft tissues which are similar to digital images obtained from an x-ray projection system. In the paper, we also show that the prototype system can image bone fractures using reflective geometry.
The purpose of this study is to investigate the feasibility of generating 3D projection ultrasound computed tomography images using a transmission ultrasound system via a piezoelectric material coated CMOS ultrasound sensing array. There are four main components in the laboratory setup: (1) a transducer operated at 5MHz frequency generating unfocused ultrasound plane waves, (2) an acoustic compound lens that collects the energy and focuses ultrasound signals onto the detector array, and (3) a CMOS ultrasound sensing array (Model I100, Imperium Inc. Silver Spring, MD) that receives the ultrasound and converts the energy to analog voltage followed by a digital conversion, and (4) a stepping motor that controls the rotation of the target for each projection view. The CMOS array consists of 128×128 pixel elements with 85μm per pixel. The system can generate an ultrasound attenuation image similar to a digital image obtained from an x-ray projection system. A computed tomography (CT) study using the ultrasound projection was performed. The CMOS array acquired ultrasound attenuation images of the target. A total of 400 projections of the target image were generated to cover 180o rotation of the CT scan, each with 0.45° increment. Based on these 400 projection views, we rearranged each line profile in the corresponding projection views to form a sinogram. For each sinogram, we computed the cross section image of the target at the corresponding slice. Specifically, the projection ultrasound computed tomography (PUCT) images were reconstructed by applying the filtered back-projection method with scattering compensation technique. Based on the sequential 2D PUCT images of the target, we generated the 3D PUCT image.