Temperature elevation in tissue detected in vivo based on statistical analysis of ultrasonic scattered echoes.

It is demanded to monitor temperature in tissue during oncological hyperthermia therapy. In the present study, we non-invasively measured the temperature elevation inside the abdominal cavity and tumour tissue of a living rat induced by capacitive-coupled radiofrequency heating. In the analysis of ultrasound scattered echoes, the Nakagami shape parameter m in each region of interest was estimated at each temperature. The Nakagami shape parameter m has temperature dependence; hence, the temperature increase inside tissue specimens can be detected with the m values. By carrying out in vivo experiments, we visualized the temperature increase inside the abdominal cavity and tumour tissue of living rats using two-dimensional hot-scale images indicating the absolute values of the ratio changes of the m values. In both the abdominal cavity and tumour tissue, the brightness in the hot-scale images clearly increased with increasing temperature. The increases in brightness in the hot-scale images imply the temperature elevations inside the abdominal cavity and tumour tissue of the living rats. The study results prove that the acoustic method we proposed is a promising method for monitoring changes in the internal temperature of the human body under hyperthermia treatment.

Analysis of atherosclerosis by inductively coupled plasma optical emission spectroscopy and scanning acoustic microscopy.

Calcium deposition within the atherosclerotic plaques is the precursor of cardiovascular complications. Therefore, determination of levels of minerals and trace elements in blood plays an important role in assigning the stage of atherosclerosis. In this study, determination of mineral and trace element levels in atherosclerotic patients is aimed. Mineral and trace element levels within serum samples of 12 atherosclerotic patients were evaluated by Inductively Coupled Plasma Optical Emission Spectrometry (ICP-OES) and phosphorous (P), iron (Fe), magnesium (Mg) and calcium (Ca) levels were examined. Human carotid atherosclerotic plaque samples were previously screened by Scanning Acoustic Microscopy (SAM) and sound speed maps of the plaques showed higher sound speed values in the calcified regions, when compared to collagen-rich regions, indicating accumulation of calcium. Element analysis also showed increased Ca levels within serum samples. Therefore, it can be concluded that Ca deposition can be examined by ICP-OES and SAM, indicating that these techniques are confirmatory and may be combined to characterize atherosclerosis in the future.

Subdiffraction-limited second harmonic photoacoustic microscopy based on nonlinear thermal diffusion.

We have developed a second harmonic photoacoustic microscopy (SH-PAM) for subdiffraction-limited imaging based on nonlinear thermal diffusion. When a sine-modulated Gaussian temperature field is introduced by a laser beam, the temperature dependence of the thermal diffusivity induces a nonlinear photoacoustic (PA) effect and thus results in the production of second harmonic PA signals. We demonstrate through both simulation and experiment that the second harmonic PA images can be reconstructed with a lateral resolution exceeding that of conventional optical resolution PA microscopy. The feasibility of SH-PAM was verified on phantom samples. Amphioxus zygotes and germinated pollens have been studied by SH-PAM to demonstrate its biomedical imaging capability. This method expands the scope of conventional PA imaging and opens up new possibilities for super-resolution imaging, prefiguring great potential for biological imaging and material inspection.

Rescue of cortical neurovascular functions during the hyperacute phase of ischemia by peripheral sensory stimulation.

To investigate the potential therapeutic effects of peripheral sensory stimulation during the hyperacute phase of stroke, the present study utilized electrophysiology and photoacoustic imaging techniques to evaluate neural and vascular responses of the rat cortex following ischemic insult. We employed a rat model of photothrombotic ischemia (PTI), which targeted the forelimb region of the primary somatosensory cortex (S1FL), due to its high reproducibility in creating localized ischemic injury. We also established a hybrid, dual-modality system, including six-channel electrocorticography (ECoG) and functional photoacoustic microscopy (fPAM), termed ECoG-fPAM, to image brain functional responses to peripheral sensory stimulation during the hyperacute phase of PTI. Our results showed that the evoked cerebral blood volume (CBV) and hemoglobin oxygen saturation (SO2) recovered to 84±7.4% and 79±6.2% of the baseline, respectively, when stimulation was delivered within 2.5 h following PTI induction. Moreover, neural activity significantly recovered, with 77±8.6%, 76±5.3% and 89±8.2% recovery for the resting-state inter-hemispheric coherence, alpha-to-delta ratio (ADR) and somatosensory evoked potential (SSEP), respectively. Additionally, we integrated the CBV or SO2 with ADR values as a recovery indicator (RI) to assess functional recovery after PTI. The RI indicated that 80±4.2% of neurovascular function was preserved when stimulation was delivered within 2.5h. Additionally, stimulation treatment within this optimal time window resulted in a minimal infarct volume in the ischemic hemisphere (4.6±2.1%). In contrast, the infarct volume comprised 13.7±1.7% of the ischemic hemisphere when no stimulation treatment was applied.

Sinais e sintomas de doença da superfície ocular em usuários de hipotensores oculares tópicos / Signs and symptoms of ocular surface disease in patients on topical intraocular pressure-lowering therapy

OBJETIVO: determinar a prevalência de sinais e sintomas de doença da superfície ocular (OSD) em pacientes em uso crônico de hipotensores oculares tópicos. MÉTODOS: Neste estudo transversal, foram recrutados 40 pacientes consecutivos, provenientes do ambulatório de glaucoma de um hospital público localizado no Rio de Janeiro, Brasil. Os mesmos deveriam apresentar: idade maior ou igual a 18 anos, diagnóstico de hipertensão ocular ou glaucoma primário de ângulo aberto e deveriam estar em uso da mesma terapia hipotensora ocular há pelo menos seis meses. Foram considerados: sexo, idade, medicação utilizada e duração do tratamento. Todos os pacientes foram submetidos à avaliação da superfície ocular que incluiu: entrevista por meio do questionário Ocular Surface Disease Index® (OSDI®), tempo de rotura do filme lacrimal, biomicroscopia, avaliação da superfície ocular com fluoresceína e com rosa Bengala. RESULTADOS: A média de pontuação do OSDI® foi 24,6 ± 20,7. A maioria dos pacientes (67,5%) apresentou uma pontuação anormal no questionário do OSDI®. Em 25% dos pacientes, a pontuação foi compatível com sintomas leves, em 12,5% com sintomas moderados e em 30% com sintomas graves. Blefarite e ceratite ponteada foram diagnosticadas em 42,5% e 20% dos pacientes respectivamente. Instabilidade do filme lacrimal foi observada em 75% dos pacientes, enquanto que alteração da superfície ocular foi evidenciada pelo teste de rosa bengala em 35% dos pacientes. Foi encontrada correlação positiva (r=0,4) estatisticamente significativa (p=0,01) entre a pontuação do OSDI® e o tempo de duração do tratamento com hipotensores oculares tópicos. CONCLUSÃO: Pacientes em uso crônico de hipotensores oculares tópicos apresentam alta prevalência de sinais e sintomas de OSD. Existe correlação significativa entre a duração do tratamento e a gravidade dos sintomas de OSD.

PURPOSE: To determine the prevalence of signs and symptoms of ocular surface disease (OSD) in patients using topical intraocular pressure-lowering therapy. METHODS: In this cross-sectional study, 40 patients were consecutively recruited from the glaucoma clinic of a public hospital located in Rio de Janeiro, Brazil. Eligible patients were 18 years of age or older, with primary open-angle glaucoma or ocular hypertension and on the same topical ocular therapy for at least 6 months. The following data were considered: sex, age, medication history and number of years on topical intraocular pressure-lowering therapy. All patients underwent an evaluation of the ocular surface which included: an interview using the Ocular Surface Disease Index® (OSDI®) questionnaire, break-up time, biomicroscopy, fluorescein corneal staining and rose Bengal ocular surface staining. RESULTS: The mean OSDI® score was 24.6 ± 20.7. Most patients (67.5%) had an abnormal score on the OSDI® questionnaire. In 25% of patients, the score was consistent with mild symptoms, 12.5% ​​with moderate symptoms and 30% with severe symptoms. Blepharitis and punctate keratitis were diagnosed in 42.5% and 20% of patients respectively. Tear film instability was observed in 75% of patients and ocular surface staining with rose Bengal in 35%. A positive statistically significant correlation (r=0.4; p=0.01) was found between OSDI® scores and the duration of topical intraocular pressure-lowering therapy. CONCLUSION: Patients with primary open-angle glaucoma or ocular hypertension on topical intraocular pressure-lowering therapy have high prevalence of OSD. Longer duration since diagnosis is significantly correlated with worsening of OSD symptoms.

Single-cell photoacoustic thermometry.

A novel photoacoustic thermometric method is presented for simultaneously imaging cells and sensing their temperature. With three-seconds-per-frame imaging speed, a temperature resolution of 0.2°C was achieved in a photo-thermal cell heating experiment. Compared to other approaches, the photoacoustic thermometric method has the advantage of not requiring custom-developed temperature-sensitive biosensors. This feature should facilitate the conversion of single-cell thermometry into a routine lab tool and make it accessible to a much broader biological research community.

Development of a dual-modal tissue diagnostic system combining time-resolved fluorescence spectroscopy and ultrasonic backscatter microscopy.

We report a tissue diagnostic system which combines two complementary techniques of time-resolved laser-induced fluorescence spectroscopy (TR-LIFS) and ultrasonic backscatter microscopy (UBM). TR-LIFS evaluates the biochemical composition of tissue, while UBM provides tissue microanatomy and enables localization of the region of diagnostic interest. The TR-LIFS component consists of an optical fiber-based time-domain apparatus including a spectrometer, gated multichannel plate photomultiplier, and fast digitizer. It records the fluorescence with high sensitivity (nM concentration range) and time resolution as low as 300 ps. The UBM system consists of a transducer, pulser, receiving circuit, and positioning stage. The transducer used here is 45 MHz, unfocused, with axial and lateral resolutions 38 and 200 microm. Validation of the hybrid system and ultrasonic and spectroscopic data coregistration were conducted both in vitro (tissue phantom) and ex vivo (atherosclerotic tissue specimens of human aorta). Standard histopathological analysis of tissue samples was used to validate the UBM-TRLIFS data. Current results have demonstrated that spatially correlated UBM and TR-LIFS data provide complementary characterization of both morphology (necrotic core and calcium deposits) and biochemistry (collagen, elastin, and lipid features) of the atherosclerotic plaques at the same location. Thus, a combination of fluorescence spectroscopy with ultrasound imaging would allow for better identification of features associated with tissue pathologies. Current design and performance of the hybrid system suggests potential applications in clinical diagnosis of atherosclerotic plaque.

Photoacoustic imaging and temperature measurement for photothermal cancer therapy.

Photothermal therapy is a noninvasive, targeted, laser-based technique for cancer treatment. During photothermal therapy, light energy is converted to heat by tumor-specific photoabsorbers. The corresponding temperature rise causes localized cancer destruction. For effective treatment, however, the presence of photoabsorbers in the tumor must be ascertained before therapy and thermal imaging must be performed during therapy. This study investigates the feasibility of guiding photothermal therapy by using photoacoustic imaging to detect photoabsorbers and to monitor temperature elevation. Photothermal therapy is carried out by utilizing a continuous wave laser and metal nanocomposites broadly absorbing in the near-infrared optical range. A linear array-based ultrasound imaging system is interfaced with a nanosecond pulsed laser to image tissue-mimicking phantoms and ex-vivo animal tissue before and during photothermal therapy. Before commencing therapy, photoacoustic imaging identifies the presence and spatial location of nanoparticles. Thermal maps are computed by monitoring temperature-induced changes in the photoacoustic signal during the therapeutic procedure and are compared with temperature estimates obtained from ultrasound imaging. The results of our study suggest that photoacoustic imaging, augmented by ultrasound imaging, is a viable candidate to guide photoabsorber-enhanced photothermal therapy.

Real-time optoacoustic monitoring of vascular damage during photodynamic therapy treatment of tumor.

The optoacoustic technique is a noninvasive imaging method with high spatial resolution. It potentially can be used to monitor anatomical and physiological changes. Photodynamic therapy (PDT)-induced vascular damage is one of the important mechanisms of tumor destruction, and real-time monitoring of vascular changes can have therapeutic significance. A unique optoacoustic system is developed for neovascular imaging during tumor phototherapy. In this system, a single-pulse laser beam is used as the light source for both PDT and for concurrently generating ultrasound signals for optoacoustic imaging. To demonstrate its feasibility, this system is used to observe vascular changes during PDT treatment of chicken chorioallantoic membrane (CAM) tumors. The photosensitizer used in this study is protoporphyrin IX (PpIX) and the laser wavelength is 532 nm. Neovascularization in tumor angiogenesis is visualized by a series of optoacoustic images at different stages of tumor growth. Damage of the vascular structures by PDT is imaged before, during, and after treatment. Rapid, real-time determination of the size of targeted tumor blood vessels is achieved, using the time difference of positive and negative ultrasound peaks during the PDT treatment. The vascular effects of different PDT doses are also studied. The experimental results show that a pulsed laser can be conveniently used to hybridize PDT treatment and optoacoustic imaging and that this integrated system is capable of quantitatively monitoring the structural change of blood vessels during PDT. This method could be potentially used to guide PDT and other phototherapies using vascular changes during treatment to optimize treatment protocols, by choosing appropriate types and doses of photosensitizers and doses of light.