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PulseCam: a camera-based, motion-robust and highly sensitive blood perfusion imaging modality.

ABSTRACT: Blood carries oxygen and nutrients to the trillions of cells in our body to sustain vital life processes. Lack of blood perfusion can cause irreversible cell damage. Therefore, blood perfusion measurement has widespread clinical applications. In this paper, we develop PulseCam - a new camera-based, motion-robust, and highly sensitive blood perfusion imaging modality with 1 mm spatial resolution and 1 frame-per-second temporal resolution. Existing camera-only blood perfusion imaging modality suffers from two core challenges: (i) motion artifact, and (ii) small signal recovery in the presence of large surface reflection and measurement noise. PulseCam addresses these challenges by robustly combining the video recording from the camera with a pulse waveform measured using a conventional pulse oximeter to obtain reliable blood perfusion maps in the presence of motion artifacts and outliers in the video recordings. For video stabilization, we adopt a novel brightness-invariant optical flow algorithm that helps us reduce error in blood perfusion estimate below 10% in different motion scenarios compared to 20-30% error when using current approaches. PulseCam can detect subtle changes in blood perfusion below the skin with at least two times better sensitivity, three times better response time, and is significantly cheaper compared to infrared thermography. PulseCam can also detect venous or partial blood flow occlusion that is difficult to identify using existing modalities such as the perfusion index measured using a pulse oximeter. With the help of a pilot clinical study, we also demonstrate that PulseCam is robust and reliable in an operationally challenging surgery room setting. We anticipate that PulseCam will be used both at the bedside as well as a point-of-care blood perfusion imaging device to visualize and analyze blood perfusion in an easy-to-use and cost-effective manner.

SUBMITTER: Kumar M

PROVIDER: S-EPMC7075982 | biostudies-literature |

REPOSITORIES: biostudies-literature

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Project description:PurposeTo present and assess an automatic nonrigid image registration framework that compensates motion in cardiac magnetic resonance imaging (MRI) perfusion series and auxiliary images acquired under a wide range of conditions to facilitate myocardial perfusion quantification.Materials and methodsOur framework combines discrete feature matching for large displacement estimation with a dense variational optical flow formulation in a multithreaded architecture. This framework was evaluated on 291 clinical subjects to register 1.5T and 3.0T steady-state free-precession (FISP) and fast low-angle shot (FLASH) dynamic contrast myocardial perfusion images, arterial input function (AIF) images, and proton density (PD)-weighted images acquired under breath-hold (BH) and free-breath (FB) settings.ResultsOur method significantly improved frame-to-frame appearance consistency compared to raw series, expressed in correlation coefficient (R2 = 0.996 ± 3.735E-3 vs. 0.978 ± 2.024E-2, P < 0.0001) and mutual information (3.823 ± 4.098E-1 vs. 2.967 ± 4.697E-1, P < 0.0001). It is applicable to both BH (R2 = 0.998 ± 3.217E-3 vs. 0.990 ± 7.527E-3) and FB (R2 = 0.995 ± 3.410E-3 vs. 0.968 ± 2.257E-3) paradigms as well as FISP and FLASH sequences. The method registers PD images to perfusion T1 series (9.70% max increase in R2 vs. no registration, P < 0.001) and also corrects motion in low-resolution AIF series (R2 = 0.987 ± 1.180E-2 vs. 0.964 ± 3.860E-2, P < 0.001). Finally, we showed the myocardial perfusion contrast dynamic was preserved in the motion-corrected images compared to the raw series (R2 = 0.995 ± 6.420E-3).ConclusionThe critical step of motion correction prior to pixel-wise cardiac MR perfusion quantification can be performed with the proposed universal system. It is applicable to a wide range of perfusion series and auxiliary images with different acquisition settings.Level of evidence3 Technical Efficacy: Stage 1 J. Magn. Reson. Imaging 2017;46:1060-1072.

Project description:Essentials The best imaging modality for joint blood detection in hemophilia is unknown. Blood appearance and detection thresholds were studied with ultrasound and conventional MRI. Ultrasound is sensitive to low volume and concentration of blood, whereas conventional MRI is not. The findings establish the validity of ultrasound for rapid bleed detection in hemophilia care. SUMMARY:Background There is increasing demand for musculoskeletal ultrasound (MSKUS) to detect hemophilic joint bleeding, but there is uncertainty regarding blood detection concentration thresholds or if magnetic resonance imaging (MRI) is more accurate. Aims Compare the sensitivity of blood detection by MSKUS and MRI. Methods Increasing blood concentrations in plasma were imaged with MSKUS and MRI 1-2 h, 3-4 days and 7 days after blood withdrawal in vitro, and after injection into cadaveric pig joints. Additionally, effusions in the joints of two patients with hemophilia joints were imaged, followed by aspiration. MSKUS was performed using an 8-18-MHz linear transducer; MRI was performed at 3T using T1-weighted and T2-weighted fat-suppressed sequences. Images were reviewed by a hematologist certified in MSKUS and a musculoskeletal radiologist. Results MSKUS permitted the detection of blood in vitro and in pig joint spaces at concentrations as low as 5%, demonstrated by the presence of echogenic signals that were absent with plasma alone. In contrast, no differences between fluids were discernible on the T1-weighted or T2-weighted MRI images. Results were confirmed in the two patients with hemophilia. Blood clots demonstrated varying and dynamic echogenicity patterns over time and, using MRI, were visualized best with T2 sequences. Conclusion MSKUS is extremely sensitive in detecting low concentrations of intra-articular blood and in discriminating between bloody and non-bloody fluid, whereas conventional MRI is not. These observations demonstrate the advantages of MSKUS over MRI in detecting intra-articular blood, and show that MSKUS is ideal for rapid bleed detection in the clinic.

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PulseCam: a camera-based, motion-robust and highly sensitive blood perfusion imaging modality.

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