scholarly journals Biomedical photoacoustic imaging

2011 ◽  
Vol 1 (4) ◽  
pp. 602-631 ◽  
Author(s):  
Paul Beard
Keyword(s):  
Optical Imaging ◽  
Ultrasound Imaging ◽  
Spatial Resolution ◽  
Breast Imaging ◽  
Clinical Medicine ◽  
Blood Oxygenation ◽  
Whole Body ◽  
Practical Implementation ◽  
Wide Range

Photoacoustic (PA) imaging, also called optoacoustic imaging, is a new biomedical imaging modality based on the use of laser-generated ultrasound that has emerged over the last decade. It is a hybrid modality, combining the high-contrast and spectroscopic-based specificity of optical imaging with the high spatial resolution of ultrasound imaging. In essence, a PA image can be regarded as an ultrasound image in which the contrast depends not on the mechanical and elastic properties of the tissue, but its optical properties, specifically optical absorption. As a consequence, it offers greater specificity than conventional ultrasound imaging with the ability to detect haemoglobin, lipids, water and other light-absorbing chomophores, but with greater penetration depth than purely optical imaging modalities that rely on ballistic photons. As well as visualizing anatomical structures such as the microvasculature, it can also provide functional information in the form of blood oxygenation, blood flow and temperature. All of this can be achieved over a wide range of length scales from micrometres to centimetres with scalable spatial resolution. These attributes lend PA imaging to a wide variety of applications in clinical medicine, preclinical research and basic biology for studying cancer, cardiovascular disease, abnormalities of the microcirculation and other conditions. With the emergence of a variety of truly compelling in vivo images obtained by a number of groups around the world in the last 2–3 years, the technique has come of age and the promise of PA imaging is now beginning to be realized. Recent highlights include the demonstration of whole-body small-animal imaging, the first demonstrations of molecular imaging, the introduction of new microscopy modes and the first steps towards clinical breast imaging being taken as well as a myriad of in vivo preclinical imaging studies. In this article, the underlying physical principles of the technique, its practical implementation, and a range of clinical and preclinical applications are reviewed.

scholarly journals Is the resting rate of oxygen consumption of locomotor muscles in crustaceans limited by the low blood oxygenation strategy?

2001 ◽  
Vol 204 (5) ◽  
pp. 933-940 ◽  
Author(s):  
J. Forgue ◽  
A. Legeay ◽  
J.C. Massabuau
Keyword(s):  
Blood Oxygenation ◽  
Whole Body ◽  
Blood Gas ◽  
Astacus Leptodactylus ◽  
Night Time ◽  
Arterial Blood ◽  
Rate Of Oxygen Consumption ◽  
Locomotor Muscles

Numerous water-breathers exhibit a gas-exchange regulation strategy that maintains O(2) partial pressure, P(O2), in the arterial blood within the range 1–3 kPa at rest during the daytime. In a night-active crustacean, we examined whether this could limit the rate of O(2)consumption (M(O2)) of locomotor muscles and/or the whole body as part of a coordinated response to energy conservation. In the crayfish Astacus leptodactylus, we compared the in vitro relationship between the M(O2) of locomotor muscles as a function of the extracellular P(O2) and P(CO2) and in vivo circadian changes in blood gas tensions at various values of water P(O2). In vitro, the M(O2) of locomotor muscle, either at rest or when stimulated with CCCP, was O(2)-dependent up to an extracellular P(O2) of 8–10 kPa. In vivo, the existence of a night-time increase in arterial P(O2) of up to 4 kPa at water P(O2) values of 20 and 40 kPa was demonstrated, but an experimental increase in arterial P(O2) during the day did not lead to any rise in whole-body M(O2). This suggested that the low blood P(O2) in normoxia has no global limiting effect on daytime whole-body M(O2). The participation of blood O(2) status in shaping the circadian behaviour of crayfish is discussed.

Ultrasound Imaging Characterization of Soft Tissue Dynamics of the Seated Human Body

2020 ◽  
Vol 142 (6) ◽  
Author(s):  
Daisuke Yamada ◽  
Alperen Değirmenci ◽  
Robert D. Howe
Keyword(s):  
Ultrasound Imaging ◽  
Human Body ◽  
Human Subjects ◽  
Excitation Amplitude ◽  
Whole Body ◽  
Ultrasound Images ◽  
Body Dynamics ◽  
Excitation Pattern

Abstract To characterize the dynamics of internal soft organs and external anatomical structures, this paper presents a system that combines medical ultrasound imaging with an optical tracker and a vertical exciter that imparts whole-body vibrations on seated subjects. The spatial and temporal accuracy of the system was validated using a phantom with calibrated internal structures, resulting in 0.224 mm maximum root-mean-square (r.m.s.) position error and 13 ms maximum synchronization error between sensors. In addition to the dynamics of the head and sternum, stomach dynamics were characterized by extracting the centroid of the stomach from the ultrasound images. The system was used to characterize the subject-specific body dynamics as well as the intrasubject variabilities caused by excitation pattern (frequency up-sweep, down-sweep, and white noise, 1–10 Hz), excitation amplitude (1 and 2 m/s2 r.m.s.), seat compliance (rigid and soft), and stomach filling (empty and 500 mL water). Human subjects experiments (n = 3) yielded preliminary results for the frequency response of the head, sternum, and stomach. The method presented here provides the first detailed in vivo characterization of internal and external human body dynamics. Tissue dynamics characterized by the system can inform design of vehicle structures and adaptive control of seat and suspension systems, as well as validate finite element models for predicting passenger comfort in the early stages of vehicle design.

scholarly journals In Vivo Resolution of Multiexponential Decays of Multiple Near-Infrared Molecular Probes by Fluorescence Lifetime-Gated Whole-Body Time-Resolved Diffuse Optical Imaging

2007 ◽  
Vol 6 (4) ◽  
pp. 7290.2007.00020 ◽  
Author(s):  
Walter Akers ◽  
Frederic Lesage ◽  
Dewey Holten ◽  
Samuel Achilefu
Keyword(s):  
Optical Imaging ◽  
Fluorescence Lifetime ◽  
Fluorescence Intensity ◽  
Near Infrared ◽  
Molecular Probes ◽  
Whole Body ◽  
Diffuse Optical Imaging ◽  
Fluorescence Lifetimes ◽  
Time Resolved

The biodistribution of two near-infrared fluorescent agents was assessed in vivo by time-resolved diffuse optical imaging. Bacteriochlorophyll a (BC) and cypate-glysine-arginine-aspartic acid-serine-proline-lysine-OH (Cyp-GRD) were administered separately or combined to mice with subcutaneous xenografts of human breast adenocarcinoma and slow-release estradiol pellets for improved tumor growth. The same excitation (780 nm) and emission (830 nm) wavelengths were used to image the distinct fluorescence lifetime distribution of the fluorescent molecular probes in the mouse cancer model. Fluorescence intensity and lifetime maps were reconstructed after raster-scanning whole-body regions of interest by time-correlated single-photon counting. Each captured temporal point-spread function (TPSF) was deconvolved using both a single and a multiexponental decay model to best determine the measured fluorescence lifetimes. The relative signal from each fluorophore was estimated for any region of interest included in the scanned area. Deconvolution of the individual TPSFs from whole-body fluorescence intensity scans provided corresponding lifetime images for comparing individual component biodistribution. In vivo fluorescence lifetimes were determined to be 0.8 ns (Cyp-GRD) and 2 ns (BC). This study demonstrates that the relative biodistribution of individual fluorophores with similar spectral characteristics can be compartmentalized by using the time-domain fluorescence lifetime gating method.

Total marrow and lymphoid irradiation with helical tomotherapy: A practical implementation report

2020 ◽  
Author(s):  
Srinivas Chilukuri ◽  
Sham Sundar ◽  
Rajesh Thiyagarajan ◽  
Jose Easow ◽  
Mayur Sawant ◽  
...  
Keyword(s):  
Helical Tomotherapy ◽  
Organs At Risk ◽  
Conditioning Regimen ◽  
Ct Scanning ◽  
Whole Body ◽  
Patient Specific ◽  
Practical Implementation ◽  
Allogenic Bone ◽  
Megavoltage Ct

Abstract Objective To standardize the technique and resources for total marrow and lymphoid irradiation (TMLI) as part of the conditioning regimen before allogenic bone marrow transplantation (ABMT) using helical tomotherapy.Methods We used this technique in our first 5 patients requiring TMLI. Patients were immobilized using a mask and a whole-body vacuum cushion. CT scanning was performed in head first supine (HFS) and feet first supine (FFS) orientations with an overlap at mid-thigh. Target consisted of the entire skeleton, spleen, sanctuary sites and major lymphatics whereas lungs, kidneys, aero-digestive tract, bowel, parotids, heart and liver were defined as organs at risk (OAR). Treatment was performed in two parts based on 2 different plans generated in HFS and FFS orientations with an overlap at the mid thigh. Patients along with the immobilization device were manually rotated by 180° to change the orientation after the delivery of HFS plan. The dose at the junction was contributed by a complementary dose gradient from each of the plans. Plan was to deliver 95% of 12Gy to 98% of CTV with dose heterogeneity < 10% and pre-specified OAR doe constraints. Megavoltage-CT was used for position verification before each fraction. Patient specific quality assurance and an in-vivo film dosimetry to verify junction dose were performed in all patients.Results Treatment was delivered in two daily fractions of 2Gy each for 3 days with at least 8-hours gap between each fraction. The target coverage goals were met in all the patients. The average person-hours per patient were 16.5, 21.5 and 25.75 for radiation oncologist, radiation therapist and medical physicist respectively. Average in-room time per patient was 9.25 hours with an average beam-on time of 3.32 hours for all the six fractions. Conclusion This report comprehensively describes technique and resource requirements for TMLI and would serve as a practical guide for departments keen to start this service. Despite being time and labor intensive, it can be implemented safely and robustly. We will be using this methodology in a prospective phase II trial to study safety and feasibility of dose escalated TMLI as part of conditioning regimen before ABMT.

Liposomal Encapsulation of a Near-Infrared Fluorophore Enhances Fluorescence Quenching and Reliable Whole Body Optical Imaging Upon Activation In Vivo

Small ◽  
2013 ◽  
Vol 9 (21) ◽  
pp. 3659-3669 ◽  
Author(s):  
Felista L. Tansi ◽  
Ronny Rüger ◽  
Markus Rabenhold ◽  
Frank Steiniger ◽  
Alfred Fahr ◽  
...  
Keyword(s):  
Fluorescence Quenching ◽  
Optical Imaging ◽  
Near Infrared ◽  
Whole Body

Abstract T P114: Insulin Resistance in Skeletal Muscle of Chronic Stroke

Stroke ◽  
2015 ◽  
Vol 46 (suppl_1) ◽  
Author(s):  
Alice S Ryan ◽  
Heidi Ortmeyer ◽  
Frederick Ivey ◽  
Charlene Hafer-Macko
Keyword(s):  
Insulin Resistance ◽  
Skeletal Muscle ◽  
Insulin Sensitivity ◽  
Glucose Tolerance ◽  
Insulin Action ◽  
Glycogen Synthase ◽  
Chronic Stroke ◽  
Whole Body ◽  
Wide Range

Risk of glucose intolerance and diabetes increases in chronic stroke. The purpose of this study was to assess insulin sensitivity and glycogen synthase (GS), a known benchmark index of insulin action in skeletal muscle, and to compare the activity of this important regulatory enzyme between paretic (P) and non-paretic (NP) skeletal muscle in chronic stroke. We measured insulin sensitivity (M) and bilateral GS fractional activity (ratio of independent to total activity), in lyophilized microdissected muscle samples obtained after an overnight fast and 2 hrs into a 3-hr 80 mU . m -2. min -1 hyperinsulinemic-euglycemic clamp in 21 stroke survivors (n=15 men, n=6 women) (age: 59±2 yrs, BMI: 31±2 kg/m 2 , X±SEM). All had hemiparetic gait after ischemic stroke (>6 months), low aerobic capacity (VO 2 peak, 19.7±1.3 ml/kg/min), and wide range of %body fat (11-48%). Leg lean mass was lower in P than NP (9.3±0.5 vs. 10.0±0.5 kg, P<0.001). Subjects had either normal glucose tolerance (n=7), impaired glucose tolerance (n=7), or diabetes (n=7) and insulin resistance (M: 38.5±2.6 umol/kgFFM/min). Insulin robustly increased GS fractional activity (basal vs. insulin) in P (2.8±0.4 vs.7.5±0.8%, P<0.00001) and NP (2.7±0.4 vs. 9.1±1.1%, P<0.00001) muscle. The %change was greater in NP than P (213±32 vs. 296±36%, P=0.04). The effect of in vivo insulin to increase GS fractional activity was associated with M in P and NP muscle (r=0.59 and r=0.49, P<0.05). In conclusion, muscle atrophy and a reduction in insulin action in paretic muscle likely contribute to whole body insulin resistance in chronic stroke.

In vivo n.m.r. imaging in medicine: the Aberdeen approach, both physical and biological

1980 ◽  
Vol 289 (1037) ◽  
pp. 519-533 ◽  
Keyword(s):  
Pulse Sequence ◽  
The Body ◽  
Spin Lattice Relaxation ◽  
Surrounding Tissue ◽  
Whole Body ◽  
Spin Concentration ◽  
Stage Of Development ◽  
Wide Range

A novel magnetic field and radio frequency (1.7 MHz) pulse sequence is described for a whole body n.m.r. imaging machine under construction. Selective excitation is used to obtain signals from successive lines of proton spins (water) across the body to build up an image of a transverse section. The images display spin concentration and spin-lattice relaxation time, T 1 , separately. For a 50 % change in T 1 to be discerned in the human trunk, a spatial resolution of 2 cm 3 is expected for a 2 min scan and 0.5 cm 3 for a 30 min scan. Very preliminary images at the present incomplete stage of development show the geometrical accuracy and T 1 discrimination: an in vivo image demonstrates some of the difficulties to be overcome. In vitro measurements of normal rabbit tissue samples have been made at 24 MHz to map the T 1 distributions that can be expected from normal subjects. The transposition of this information from rabbit to man, and from 24 MHz to 2.5 MHz have been checked and the comparison shown to be meaningful. Of pathological samples, human breast tumour and human liver metastases offer a good contrast to their surrounding tissue, and an experimental investigation has shown that tissue immediately surrounding a tumour also has an elevated T 1 value. A wide range of abnormalities that are associated with abnormal fluid formation in the body may be amenable to imaging by the n.m.r. technique. Potential hazards are believed to be small in the present generation of equipment.

Discrimination and Quantification of Spectrally Similar Near-Infrared Probes by Time-Domain (TD) Optical Imaging in Acute Myeloid Leukemia Mouse Models.

Blood ◽  
2007 ◽  
Vol 110 (11) ◽  
pp. 4319-4319
Author(s):  
Emmet McCormack ◽  
Alexandre Belankov ◽  
Maja Mujic ◽  
Pierre Couture ◽  
Bjorn T. Gjertsen
Keyword(s):  
Optical Imaging ◽  
Fluorescence Lifetime ◽  
Time Domain ◽  
Spectral Properties ◽  
Near Infrared ◽  
Leukemic Cells ◽  
Whole Body ◽  
Single Wave ◽  
Optical Absorbance

Abstract The use of whole-body optical imaging in the near-infrared (NIR) spectrum (650–1100 nm) employing fluorescently labelled reagents recognising cell-specific biomarkers of leukemia has become a standard modality in preclinical models of the human disease. A particular challenge is represented by leukemic infiltrates in liver and spleen, organs with high optical absorbance. While there are increasingly impressive arrays of fluorescently labelled biomolecules available for exploitation via optical imaging, the number of commmercially availible fluorophores for NIR imaging remain limited. In particular, simultaneous imaging of disease progression and functional imaging of more specific biological processes within the same sample is complicated by the requiste for multiple filtersets for fluorophores with similar spectral properties. Subsequent “bleeding” fluorescence through filtersets is unavoidable precluding ones ability to quantify specific fluorophores based on fluorescence. Similarly, descrimination of in vivo autofluorescence of similar spectral properties to commonly employed NIR dyes, consequent of ingested food comlicates contrast even further. More recently spectral imaging techniques have aided discrimination of fluorophores of similar spectral profiles however, these techniques attenuate much of the light reaching the detector. Time-domain (TD) optical imaging through the use of pulsed laser diodes and time resolved detector system, typically a photo-multiplier tube (PMT), has previously been demonstrated to distinguish between changes in physiological processes such as; tissue pH or calcuim concentration, based on changes in fluorescence lifetime of a fluorescently labelled probe. Here we demonstrate employing a single wave lenght TD optical imaging (eXplore Optix™, ART Inc) the potential to discriminate and quantify combinations of diverse NIR probes of spectrally similar properties but differing fluorescence lifetime on the basis of fluorescence lifetime in appropriate in vitro phantoms. Similarly, we illustrate the ability of this technique to discriminate between endogenous autofluorescence from administered fluorophores in vivo of leukemic cells in liver and spleen, and subsequent distinction of mixtures these fluorophores via their inherent fluorescent lifetimes in vivo.

Detection of experimental prostate cancer skeletal metastases in vivo whole body optical imaging

2003 ◽  
Vol 2 (1) ◽  
pp. 61
Author(s):  
G. Thalmann ◽  
A. Wetterwald ◽  
G. Van der Plujim ◽  
M. Karperien ◽  
C. Löwik ◽  
...  
Keyword(s):  
Prostate Cancer ◽  
Optical Imaging ◽  
Whole Body ◽  
Skeletal Metastases
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