Virtual reality (VR) simulation can improve the outcomes of percutaneous nephrolithotomy (PNCL) - a surgery to extract kidney stones using ultrasound (US) or fluoroscopy image guidance. These simulators almost exclusively employ fluoroscopy, and no commercial VR simulator is available for US-guided PNCL (usPCNL). In this paper, we proposed the first step towards developing an usPCNL simulator that integrates a volumetric US model of the patient's anatomy derived from parallel 2D computed tomography (CT) scans. A critical challenge in US image generation from CT scans is that the limited spatial resolution of CT slices may lead to inaccuracies in the simulated US images. The proposed algorithm interpolates successive CT images to create an augmented dataset with increased spatial resolution. Each CT slice is then converted into a US image based on principles of linear acoustics and spatial impulse response. These images are then combined to form two different volumetric US images, one derived from the original sparse CT scans, and one created with the augmented data. From these volumetric US images, new images can be formed along arbitrary imaging planes not captured in the original CT data. The obtained simulated images are compared with their corresponding real US images acquired experimentally, and further evaluated quantitatively using normalized root mean square error (NRMSE) and dice similarity coefficient (DSC). The results reveal an NRMSE of$\mathbf{0.235}\pm \mathbf{0.051}$and a DSC of$\mathbf{0.9139}\pm \mathbf{0.062}$, showcasing a close resemblance between simulated and actual ultrasound images. Additionally, we show that denser CT scan data leads to a 25% improvement in image quality based on peak signal-to-noise ratio compared to the original dataset. This initial work is laying the foundation for the development of the usPCNL simulator, which could potentially have significant benefits for training and enhancing skills in this medical procedure.

Quasi-static elastography (QSE) is a well-known technique, where the ultrasound data acquired before and after a small tissue compression is analyzed to form an image, which is related to the stiffness parameter of the underlying tissue. Most studies have reported the effect of Conventional Focused Beamforming (CFB) transmit scheme on image quality of ultrasound elastography. Recently, Diverging Beam Synthetic Aperture technique (DBSAT) has been shown to improve the image quality of ultrasound images, however, very little is explored of this scheme for elastography application. This research paper presents a novel strategy to obtain better quality elastography images using the DBSAT transmit scheme. The widely used CFB technique is a line-by-line scanning technique that produces one elastogram by processing one pre- compression and one post-compression frame, however, DBSAT being a synthetic aperture approach produces several low-resolution images before summing to obtain one high resolution image. In this experimental work on tissue-mimicking phantom, we demonstrate that estimating 128 low resolution elastograms and summing them to produce one high resolution elastogram is an effective way to reduce noise and increase the elastographic image quality. More than 15dB improvement was found when comparing the image quality metrics of signal-to-noise ratio (SNR) and Contrast-to-noise ratio (CNR) from elastography images obtained from DBSAT vs. that obtained from CFB scheme.

Being a safer modality, ultrasound is used in many imaging applications for diagnostic purposes. Adapting novel ultrasound transmit schemes and beamforming techniques are active areas in the field of ultrasound imaging for further improving the image quality. While Conventional Focused Beam (CFB) is an established technique and available commercially, newer synthetic aperture (SA) techniques have shown promise to overcome several limitations of CFB. However, a significant limitation of these SA techniques is that the imaging depth is much less than that of CFB. Although some works employing SA with increased transmit voltage have been shown to overcome the imaging depth challenge, not much work is reported on their thermal and mechanical indices (TI and MI), which is of prime importance to estimate the safety of ultrasound exposure. This work attempts to analyze and compare the image quality and imaging depth improvements for the different SA schemes for increased input acoustic energy while keeping the MI and TI below that of CFB. Specifically, Synthetic Transmit Aperture (STA) and Diverging Beam with Synthetic Aperture Technique (DB-SAT) are compared with CFB. Contrast ratio (CR) and Contrast to Noise Ratio (CNR) parameters are taken for image quality analysis. The experiments using needle hydrophone were done. The maximum allowable limits for MI and TI values for CFB were taken from IEC 62359 standard report. The result suggests that an additional increase in input voltage to STA and DB-SAT schemes yielded an improvement in contrast ratio and imaging depth, without crossing the safety threshold. Thus, by carefully adopting a higher input voltage for the synthetic aperture schemes, one could be within safe limits of TI and MI and still improve the imaging depth.

The discernment of the gender of the fetus during obstetric ultrasound has played a major in sex-selective abortions. Researchers have shown that in India, there are approximately 50,000 to 100,000 abortions per year. Though there are laws on female feticide, poor awareness and difficulty in implementing technological solutions has made it difficult to effectively dissuade such practice. In the current scenario, B-scans are displayed on monitor screens in real time, which can lead to the unnecessary display of frames that reveal the gender of the fetus. This workflow adds undue burden on the operator to take further precautions to prevent leak of the gender information. Our work not only focuses on automatically detecting ultrasound frames that contain gender but also identify the specific region of the frame that indicated the gender, so that it can be obscured during real-time display.

The most common means of treating a cancerous tumor is using radiation therapy that involves a combination of both external and internal radiation treatments. To aid the clinician to plan for the treatment, image-guided radiotherapy is used, in which computed tomography (CT) images are acquired multiple times during treatment. This puts the patient at unnecessary risk of additional radiation exposure. Simulating pseudo-CT scans have been proposed as an alternative to acquiring CT scans, thereby reducing the risks related to radiation exposure. In this study, we propose a methodology in which pseudo-CT images can be simulated from the pre-radiotherapy CT and ultrasound and pre-brachytherapy ultrasound images. The primary step in this is the registration between pre-radiotherapy and pre-brachytherapy ultrasound images. In this study, the performance of the demons deformable registration algorithm and mid-space independent image registration algorithm on ultrasound images of a cervical cancer patient are evaluated. The resultant deformation field obtained from the registration step is used to simulate the pseudo-CT image, which is then compared with the ground-truth CT image. The results show very little variability in the similarity metrics between the algorithms, indicating the feasibility of the proposed methodology.

Radiation therapy is often used to treat cancerous tumors, with most cases involving a combination of external and internal radiation treatments. To aid the clinician to plan for the treatment, image-guided radiotherapy is used, in which computed tomography (CT) images are acquired multiple times during treatment. This puts the patient at unnecessary risk of additional radiation exposure. Simulating pseudo-CT scans at some time points that would obviate acquiring CT scans has the potential to reduce the risks related to radiation exposure. In this study, we propose a methodology in which pseudo-CT images for brachytherapy planning can be simulated from the pre-radiotherapy CT and ultrasound and pre-brachytherapy ultrasound images. The primary step in this is the registration between pre-radiotherapy and pre-brachytherapy ultrasound images. In this study, the performance of the demons deformable registration algorithm and mid-space independent image registration algorithm on ultrasound images obtained from a tissue-mimicking phantom are evaluated. The resultant deformation field obtained from the registration step is used to simulate the pseudo-CT image, which is then compared with the ground-truth CT image acquired from the same phantom. The results show very little variability in the similarity metrics between the algorithms, indicating the feasibility of the proposed methodology.

High energy solid state lasers such as Nd:YAG are most commonly used as source of illumination in Photoacoustic (PA) imaging. However, recently, pulsed laser diodes (PLD)are being increasingly explored as a potential alternative to solid state sources due to its advantages such as portability, high pulse repetition rate and affordability. However, PLD has low energy per pulse which results in weaker signal, especially, from deep-seated photoacoustic targets. Hence, additional noise from external sources, such as, electronic noise, jitter, etc. have more pronounced detrimental effect on the quality of the reconstructed PA images resulting in low Signal-to-Ratio (SNR) values. Recently, several works have been reported to reduce the effect of noise by taking advantage of the high pulse-repetition rate offered by PLD and performing averaging. In this work we demonstrate that by strategically employing noise-reduction filter on the raw data prior to reconstruction stage yields significant improvement in SNR compared to mere averaging (~61%) in PLD-based PAT systems.