Analysis Of Tissue Perfusion Research Articles

Colour Doppler Ultrasonographic Tissue Perfusion Analysis in Peri-Implant Mucosa with and Without Low-Level Laser Therapy: A Prospective Randomized Double-Blind Clinical Trial

Colour Doppler Ultrasonographic Tissue Perfusion Analysis in Peri-Implant Mucosa with and Without Low-Level Laser Therapy: A Prospective Randomized Double-Blind Clinical Trial

Technical and functional design considerations for a real-world interpretable AI solution for NIR perfusion analysis (including cancer)

Near infrared (NIR) analysis of tissue perfusion via indocyanine green fluorescence assessment is performed clinically during surgery for a range of indications. Its usefulness can potentially be further enhanced through the application of interpretable artificial intelligence (AI) methods to improve dynamic interpretation accuracy in these and also open new applications. While its main use currently is for perfusion assessment as a tissue health check prior to performing an anastomosis, there is increasing interest in using fluorophores for cancer detection during surgical interventions with most research being based on the paradigm of static imaging for fluorophore uptake hours after preoperative dosing. Although some image boosting and relative estimation of fluorescence signals is already inbuilt into commercial NIR systems, fuller implementation of AI methods can enable actionable predictions especially when applied during the dynamic, early inflow-outflow phase that occurs seconds to minutes after ICG (or indeed other fluorophore) administration. Already research has shown that such methods can accurately differentiate cancer from benign tissue in the operating theatre in real time in principle based on their differential signalling and could be useful for tissue perfusion classification more generally. This can be achieved through the generation of fluorescence intensity curves from an intra-operative NIR video stream. These curves are processed to adjust for image disturbances and curve features known to be influential in tissue characterisation are extracted. Existing machine learning based classifiers can then use these features to classify the tissue in question according to prior training sets. The use of this interpretable methodology enables accurate classification algorithms to be built with modest training sets in comparison to those required for deep learning modelling in addition to achieving compliance with medical device regulations. Integration of the multiple algorithms required to achieve this classification into a desktop application or medical device could make the use of this method accessible and useful to (as well as useable by) surgeons without prior training in computer technology. This document details some technical and functional design considerations underlying such a novel recommender system to advance the foundational concept and methodology as software as medical device for in situ cancer characterisation with relevance more broadly also to other tissue perfusion applications.

Cover Image

The cover image is based on the Original Article Ultrasonographic Tissue Perfusion Analysis at Implant and Palatal Donor Sites Following Soft Tissue Augmentation: A Clinical Pilot Study by Lorenzo Tavelli et al., https://doi.org/10.1111/jcpe.13424.

Ultrasonographic tissue perfusion analysis at implant and palatal donor sites following soft tissue augmentation: A clinical pilot study

To describe the application of power Doppler Ultrasonography (US) for evaluating blood flow at implant and palatal donor sites following soft tissue augmentation with the connective tissue graft (CTG). Five patients exhibiting a peri-implant soft tissue dehiscence received treatment with a coronally advanced flap and corresponding CTG. Power Doppler US was used for assessing blood volume at baseline, 1week, 1month, 6months and 12months post-surgery for assessing blood-flow dynamics at the implant and palatal donor sites. The speed-weighted and power-weighted colour pixel density (CPPD) were computed from colour velocity (CV) and colour power (CP), respectively. A mean increase in CV of 199.25% was observed at the midfacial region of the implant sites after 1week compared to baseline. CV and CP were increased in all sites at 1week and 1month. At 6 and 12months, the mean CV appeared lower than baseline at the implant sites. CCPD was increased at the palatal donor sites and at the great palatine foramen areas at the 1-week and 1-month post-operative evaluations. Power Doppler US is a non-invasive and valuable tool for estimating tissue perfusion and CPPD variation during different phases of intra-oral soft tissue graft healing.

Intraoperative Perfusion Assessment in Enhanced Reality Using Quantitative Optical Imaging: An Experimental Study in a Pancreatic Partial Ischemia Model.

To reduce the risk of pancreatic fistula after pancreatectomy, a satisfactory blood flow at the pancreatic stump is considered crucial. Our group has developed and validated a real-time computational imaging analysis of tissue perfusion, using fluorescence imaging, the fluorescence-based enhanced reality (FLER). Hyperspectral imaging (HSI) is another emerging technology, which provides tissue-specific spectral signatures, allowing for perfusion quantification. Both imaging modalities were employed to estimate perfusion in a porcine model of partial pancreatic ischemia. Perfusion quantification was assessed using the metrics of both imaging modalities (slope of the time to reach maximum fluorescence intensity and tissue oxygen saturation (StO2), for FLER and HSI, respectively). We found that the HSI-StO2 and the FLER slope were statistically correlated using the Spearman analysis (R = 0.697; p = 0.013). Local capillary lactate values were statistically correlated to the HSI-StO2 and to the FLER slope (R = −0.88; p < 0.001 and R = −0.608; p = 0.0074). HSI-based and FLER-based lactate prediction models had statistically similar predictive abilities (p = 0.112). Both modalities are promising to assess real-time pancreatic perfusion. Clinical translation in human pancreatic surgery is currently underway.

Acellular Dermal Matrix–sparing Direct-to-implant Prepectoral Breast Reconstruction

Refined mastectomy techniques, the advent of new technologies and materials such as acellular dermal matrix (ADM), cohesive gel silicone implants, and intraoperative tissue perfusion analysis, have fueled a resurgence in prepectoral breast reconstruction. This article aims to compare an immediate direct-to-implant prepectoral ADM-sparing approach with the traditional subpectoral 2-stage immediate reconstruction. A cost analysis within a Canadian-run single-payer system is also presented. A retrospective 2-group comparative chart review study was performed (June 2015-January 2017) to identify all patients who underwent prepectoral direct-to-implant breast reconstruction using an ADM-sparing technique. The comparison group consisted of patients having undergone traditional 2-stage subpectoral reconstruction with ADM. All countable variables were included in the cost analysis, which was performed in Canadian dollars. A total of 77 patients (116 reconstructed breasts) were included. Both the prepectoral and subpectoral groups were comparable in size, demographics including age, diabetic and smoking status, and receiving neoadjuvant chemotherapy and postmastectomy radiotherapy. Patients having undergone direct-to-implant prepectoral reconstruction benefited from fewer follow-up visits (3.8 vs 5.4, respectively) and from less complications (24.7% vs 35.6%, respectively) including animation deformity. In addition, direct-to-implant prepectoral reconstruction costs 25% less than the 2-stage subpectoral reconstruction when all associated costs were considered. Prepectoral implant placement avoids many of the disadvantages of the traditional 2 stage subpectoral reconstruction, including pectoralis muscle dissection, animation deformity, and multiple surgeries. As the first comparative cost analysis study on the subject, our ADM-sparing direct-to-implant prepectoral reconstruction method costs 25% less than the traditional 2-stage subpectoral reconstruction with a comparable complication profile.

Assessment of lower extremity ischemia using smartphone thermographic imaging

Conventional diagnostic modalities for assessing arterial circulation or tissue perfusion include blood pressure measurement, ultrasound evaluation, and contrast-based angiographic assessment. An infrared thermal camera can detect infrared radiation energy from the human body, which generates a thermographic image to allow tissue perfusion analysis. We describe a smartphone-based miniature thermal imaging system that can be used as an adjunctive imaging modality to assess tissue perfusion. This smartphone-based camera device is noninvasive, simple to use, and cost-effective in assessing patients with lower extremity tissue perfusion. Assessment of patients with lower extremity arterial ischemia can be performed by a variety of diagnostic modalities, including ankle-brachial index, absolute systolic ankle or toe pressure, transcutaneous oximetry, arterial Doppler waveform, arterial duplex ultrasound, computed tomography scan, arterial angiography, and thermal imaging. We herein describe a noninvasive imaging modality using smartphone-based infrared thermography.

Perfusion Imaging in Clinical Practice: A Multimodality Approach to Tissue Perfusion Analysis

327 Objectives Due to their electron-rich aromatic structure, nucleophilic fluorination of pyridines is challenging, especially at the meta position. Methods that generally work well for making ortho and para fluorinated pyridines do not work for meta substituted pyridines. Meta substitutions are possible through precursors such as iodonium salts and iodonium ylides, which are often difficult to prepare. In this project, we produce meta fluorinated 3-fluoro-4-aminopyridine (a brain radiotracer currently under investigation for multiple sclerosis) by direct nucleophilic fluorination of an off-the-shelf N-oxide precursor. Methods - Standard techniques in organic synthesis and radiochemistry - Solid phase extraction, radioHPLC and radioTLC - Automation of the synthesis using Synthera (IBA Radiopharmacy solutions) is currently ongoing Results [18F]3F4AP was produced in two steps by direct fluorination of 3-bromo-4-nitropyridine N-oxide followed by reduction using hydrogen gas catalyzed by 10% Pd/C. The fluorination reaction resulted in 25 ± 4% decay-corrected yield (n = 6) and the hydrogenation of the intermediate resulted in 55 ± 11% decay-corrected yield (n = 6). Fluorination was conducted at room temperature for 15 min. Total synthesis time including HPLC purification and quality control was 2 h and the overall radiochemical yield was 2.5% non-decay-corrected with most of the activity lost during the multiple purifications and transfers. Automation of this process should further increase the yield. Conclusions The use of pyridine N-oxides as substrates in fluorination reactions is unprecedented in the chemical literature. While the corresponding pyridine preferentially reacts at the ortho and para positions, the pyridine N-oxide preferentially reacts at the meta position. This is probably due to the strong electron-withdrawing effects of the N-oxide, which drastically changes the reactivity of the pyridine. The widespread availability of N-oxides and ease of reduction of the N-oxide group makes this reaction a promising new method for the production of meta fluorinated pyridines and other electron rich aromatics. $$graphic_9ADF8554-E16D-48C9-88C4-582F95C31044$$

Contrast-enhanced ultrasound analysis of tissue perfusion in tumor-bearing mice following treatment with endostatin combined with radiotherapy.

The aim of this study was to observe the effects of Endostar (recombinant human endostatin) and radiotherapy, singly or in combination, on blood flow in mouse tumour tissue using ultrasound imaging. The ultrasound contrast agent, SonoVue, was used for the contrast-enhanced ultrasound examinations. SonoLiver software was used to analyse dynamic vascular patterns (DVPs) in the contrast process. Blood perfusion data were collected and statistical analysis was performed for data processing. Results were presented as DVP curves and quantitative parameters. Quantitative parameters showed statistically significant (P<0.05) differences in peak strength, rise time, time to peak and mean transit time among the various treatment groups. Changes in tumour blood perfusion were quantified by the assessment of contrast-enhanced ultrasound parameters. The results indirectly reflected the degree of change in angiogenesis in the tumour following experimental intervention. Ultrasound contrast imaging effectively showed the extent of the changes in vascularity and flow state. Therefore, contrast-enhanced ultrasound is suitable for use as an indicator of blood flow changes in an experimental model.

Muscle-based pharmacokinetic modeling of marrow perfusion for osteoporotic bone in females.

The pharmacokinetic model has been widely used in tissue perfusion analysis, such as bone marrow perfusion. In the modeling process, the arterial input function is important to guarantee the reliability of the fitting result. However, the arterial input function is variable and hard to control, which makes it difficult to compare results across different studies. The purpose of this study was to establish a muscle-based pharmacokinetic model for bone marrow perfusion without using arterial input function. Erector spinae muscle around the vertebral body was selected as the reference region. The study was carried out in elderly females with different bone mineral densities (normal, osteopenia, and osteoporosis). Quantitative parameters were extracted from the pharmacokinetic model. Parameter K trans,BM (contrast agent extravasation rate constants for blood perfusion of the bone marrow) showed a significant reduction in subjects with lower bone mineral density, which is consistent with previous studies. However, muscle perfusion parameters remained unchanged among different groups. The results indicated that the muscle-based model was stable for bone marrow perfusion modeling. Additionally, nonsignificant change in muscle parameters indicated that the diminished perfusion is only a local rather than a systematic change in the bone marrow for osteoporosis.

CMR2009: 8.06: DCIMS: a DCE‐imaging‐simulator for optimization of contrast agent injection and tissue perfusion analysis. Application to contrast agents of different molecular weights and lesion types

CMR2009: 8.06: DCIMS: a DCE‐imaging‐simulator for optimization of contrast agent injection and tissue perfusion analysis. Application to contrast agents of different molecular weights and lesion types

Thrombin promotes arteriogenesis and hemodynamic recovery in a rabbit hindlimb ischemia model

Compared with angiogenesis, arteriogenesis is a distinct process based on the remodeling and maturation of pre-existing arterioles into large conductance arteries. Therapeutic angiogenesis has been proposed as a potential treatment for ischemic atherosclerotic diseases. Since a variety of angiogenic factors have been tested with inconsistent so far clinical results, the challenge remains in identifying the factor(s) that will stimulate functional neovascularization. Thrombin has been reported to play a pivotal role in the initiation of angiogenesis by regulating and organizing a network of angiogenic mediators. Also, it was recently demonstrated that thrombin is a potent anti-apoptotic factor for endothelial cells, providing evidence on a potential role of thrombin in vascular protection and maintenance of vessel integrity. Based on these observations, we hypothesized that thrombin may promote the development of mature functional blood vessels. Seventy-four (n=74) rabbits underwent bilateral femoral artery surgical excision. On the 20th postsurgical day increasing doses of VEGF or bFGF or thrombin were injected in one ischemic limb per rabbit and an equal volume of normal saline to the contralateral control limbs. Quantification of newly developed collateral vessels (diameter >500 mum) was performed by transauricular intra-arterial subtraction angiography. Computerized quantitative analysis of collateral vessels in angiography images was based on the concept of multiscale structural tensor. Perfusion analysis of an in vivo dynamic computed tomography study was performed to investigate hemodynamic recovery of the distal ischemic limbs. Tissue perfusion analysis was performed with the semiquantitative slope methodology, which focuses on the first-pass arterial phase. A single administration of thrombin exhibited a dose-dependent increase of arteriogenic outcome. Thrombin at 5000 IU induced a 30.2 +/- 7.4% (P < 0.05) increase of total collateral area and length. Both VEGF and bFGF were without any significant effect at the concentrations used. Functional estimation of limb perfusion showed a statistically significant increase of blood flow recovery only for thrombin. The semiquantitative slope method perfusion score differed significantly in the 5000 IU thrombin treated limbs (5.7 +/- 0.3 vs 5.0 +/- 0.3 in control ischemic limbs; P < .05), and was not significantly inferior from the score of normal nonoperated limbs (6.5 +/- 0.3) suggesting a trend towards hemodynamic recovery of distal limb perfusion. In a rabbit hindlimb ischemia model, thrombin promoted the formation of large collateral vessels and improved the perfusion of distal ischemic tissue. These results provide new insights in understanding the involvement of thrombin in vascular formation and point to a novel role of thrombin in arteriogenesis.

Regularized Estimation of Contrast Agent Attenuation to Improve the Imaging of Microbubbles in Small Animal Studies

Quantitative analysis of tissue perfusion using contrast-enhanced ultrasound is still limited by shadowing, which is caused by inadequate compensation for microbubble contrast agent attenuation. Many previous methods have been developed for attenuation correction in soft tissues. However, no method has been proposed to correct for microbubble attenuation in vivo. In this article, a model to estimate microbubble attenuation is presented, using the time-intensity variation in a highly echogenic distal area without contrast uptake. This model is based on the assumption that a linear relationship holds between local microbubble attenuation and local backscatter. The model was applied to 12 murine renal perfusion studies. Parametric images of microbubble attenuation were generated, corresponding to dynamic contrast agent-specific sequences without shadowing. Contrast uptake kinetics consistent with the physiology were retrieved in all perfused areas. This method therefore proved to be of potential interest in the quantification of tissue perfusion in small animal studies. (E-mail: sebastien.mule@imed.jussieu.fr)