Purpose
Our previous studies demonstrate that the variation in ultrasonic envelope statistics is correlated with the temperature change inside scattering media. This variation is identified as the ...change in the scatterer structure during thermal expansion or contraction. However, no specific evidence has been verified to date. This study numerically reproduces the change in the scatterer distribution during thermal expansion or contraction using finite element simulations and also investigates how the situation is altered by different material properties.
Methods
The material properties of a linear elastic solid depend on the thermal expansion coefficient, thermal conductivity, specific heat, and initial scatterer number density. Three‐dimensional displacements, calculated in the simulation, were sequentially used to update the positions of the randomly distributed scatterers. Ultrasound signals from the scatterer distribution were generated by simulating a 7.5‐MHz linear array transducer whose specifications were the same as those in the experimental measurements of several phantoms and excised porcine livers. To represent the change in the envelope statistical feature, the absolute value of the ratio change in the logarithmic Nakagami (NA) parameter, Δm, at each time was calculated as a value normalized with the initial NA parameter.
Results
The change in the scatterer number density relates to the volume change during temperature elevation. The magnitude of the Δm shift against the temperature change increases depending on the higher thermal expansion coefficient. In contrast, the relationship between Δm and the scatterer number density is similar with any material property. Additionally, the changes in Δm obtained by several experimental phantoms with low to high scatterer number densities are comparable with the numerical simulation results.
Conclusions
The change in Δm is indirectly related to the change in the scatterer number density owing to the volume change during thermal expansion or contraction.
Abstract
Motion compensation was applied in the envelope statistical analysis to develop robust thermometry for in vivo situations. Numerical data were reproduced with the temporal change in the ...scatterer distribution due to thermal expansion and arbitrary translational motions, and experimental phantom data were obtained under heating with the probe motion. Additionally, the case under respiratory motion was evaluated using the data collected from in vivo rat tumor. Ultrasound signals were acquired using a 7.5 MHz linear probe, and their misalignments of envelopes due to the motions were compensated by a block-matching-based motion estimator. The absolute change in the Nakagami shape parameter,
Δ
m
,
in each frame was calculated by normalizing with the initial frame to indicate the temperature change. The uncompensated
Δ
m
with physical motions deviated from that without motion, whereas the motion-compensated numerical and experimental data suppressed the rapid or gradual
Δ
m
change and showed the same trend of
Δ
m
without motion.
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.
Abstract
In an RF ablation procedure for treating hepatocellular carcinoma and metastatic liver cancer, plucking out an ablation antenna from incompletely cauterized tumor tissues can cause ...neoplastic seeding; hence, it is demanded to properly evaluate the thermal denaturation of tumor tissue before plucking out the antenna. In the present ex vivo study, we show that the degree of thermal denaturation inside porcine liver tissue induced with RF current heating can be evaluated by binarized two-dimensional Nakagami parametric image indicating the weighted average of the Nakagami shape parameter
m
. Moreover, we present that the pre-Rayleigh distribution is dominant in ultrasonic backscattered envelopes obtained from incompletely cauterized liver tissue, whereas the Rayleigh distribution is dominant in those obtained from completely cauterized liver tissue which has coagulative necrosis region. The result indicates that the change in scatterer distribution would be occurred inside liver tissue by coagulative necrosis caused by RF current heating in this study.
The oryzapsin genes
opsA
and
opsB
in
Aspergillus oryzae
encoding glycosylphosphatidylinositol (GPI)-anchored aspartic endopeptidase are homologs of
Saccharomyces cerevisiae
yapsins. We recently found ...another homolog,
opsC
, in the
A. oryzae
genome database, which was suggested to be a pseudogene. However, the profiles and roles of the proteins encoded by these genes have not yet been clarified. Toward this end, we first produced
opsA
- and
opsB-
overexpression strains and performed enzymatic analyses, revealing that OpsA and OpsB can attack sites other than the carboxyl-terminal peptide bonds of basic amino acids. Moreover, OpsA and OpsB were confirmed to bind to the cell membrane with a GPI anchor. Second,
opsA
and
opsB
single-deletion and double-deletion strains (Δ
opsA
, Δ
opsB
, and Δ
opsA
Δ
opsB
) were constructed to explore the expected roles of oryzapsins in cell wall synthesis, similar to the role of yapsins. The transcription level of
mpkA
in the cell wall integrity pathway was increased in Δ
opsB
and Δ
opsA
Δ
opsB
strains, suggesting that OpsB might be involved in processing cell wall synthesis-related proteins. Treatment with an ergosterol biosynthesis inhibitor reduced the growth of the Δ
opsA
Δ
opsB
strain. Moreover, the mRNA levels of Ao
erg1,
Ao
erg3-1,
Ao
erg3-2,
Ao
erg7b,
Ao
erg11,
and Ao
hmg1,2
showed a decreasing tendency in the Δ
opsA
Δ
opsB
strain, and the ergosterol content in the membrane was reduced in the Δ
opsA
Δ
opsB
strain. These results suggest that oryzapsins exist in the cell membrane and play roles in the formation of cell membranes. This is the first report of the involvement of GPI-anchored aspartic endopeptidases in ergosterol biosynthesis.
Key points
•
The oryzapsins have wider substrate specificity than yaspins in S. cerevisiae.
•
Unlike the yapsins, the oryzapsins might not be involved in the main structure synthesis of the cell wall.
•
The oryzapsins would be involved in ergosterol biosynthesis.
XlnR is a Zn(II)₂Cys₆ transcriptional activator of xylanolytic and cellulolytic genes in Aspergillus. Overexpression of the aoxlnR gene in Aspergillus oryzae (A. oryzae xlnR gene) resulted in ...elevated xylanolytic and cellulolytic activities in the culture supernatant, in which nearly 40 secreted proteins were detected by two-dimensional electrophoresis. DNA microarray analysis to identify the transcriptional targets of AoXlnR led to the identification of 75 genes that showed more than fivefold increase in their expression in the AoXlnR overproducer than in the disruptant. Of these, 32 genes were predicted to encode a glycoside hydrolase, highlighting the biotechnological importance of AoXlnR in biomass degradation. The 75 genes included the genes previously identified as AoXlnR targets (xynF1, xynF3, xynG2, xylA, celA, celB, celC, and celD). Thirty-six genes were predicted to be extracellular, which was consistent with the number of proteins secreted, and 61 genes possessed putative XlnR-binding sites (5′-GGCTAA-3′, 5′-GGCTAG-3′, and 5′-GGCTGA-3′) in their promoter regions. Functional annotation of the genes revealed that AoXlnR regulated the expression of hydrolytic genes for degradation of β-1,4-xylan, arabinoxylan, cellulose, and xyloglucan and of catabolic genes for the conversion of d-xylose to xylulose-5-phosphate. In addition, genes encoding glucose-6-phosphate 1-dehydrogenase and l-arabinitol-4-dehydrogenase involved in d-glucose and l-arabinose catabolism also appeared to be targets of AoXlnR.
Mammals possess a unique signaling system based on the proteolytic mechanism of a disintegrin and metalloproteinases (ADAMs) on the cell surface. We found two genes encoding ADAMs in Aspergillus ...oryzae and named them admA and admB. We produced admA and admB deletion strains to elucidate their biological function and clarify whether fungal ADAMs play a similar role as in mammals. The ∆admA∆admB and ∆admB strains were sensitive to cell wall-perturbing agents, congo red, and calcofluor white. Moreover, the two strains showed significantly increased weights of total alkali-soluble fractions from the mycelial cell wall compared to the control strain. Furthermore, ∆admB showed MpkA phosphorylation at lower concentration of congo red stimulation than the control strain. However, the MpkA phosphorylation level was not different between ∆admB and the control strain without the stimulation. The results indicated that A. oryzae AdmB involved in the cell wall integrity without going through the MpkA pathway.
Non-invasive monitoring of temperature elevations inside tumor tissue is imperative for the oncological thermotherapy known as hyperthermia. In the present study, two cancer patients, one with a ...developing right renal cell carcinoma and the other with pseudomyxoma peritonei, underwent hyperthermia. The two patients were irradiated with radiofrequency current for 40 min during hyperthermia. We report the results of our clinical trial study in which the temperature increases inside the tumor tissues of patients with right renal cell carcinoma and pseudomyxoma peritonei induced by radiofrequency current irradiation for 40 min could be detected by statistical analysis of ultrasonic scattered echoes. The Nakagami shape parameter m varies depending on the temperature of the medium. We calculated the Nakagami shape parameter m by statistical analysis of the ultrasonic echoes scattered from the tumor tissues. The temperature elevations inside the tumor tissues were expressed as increases in brightness on 2-D hot-scale maps of the specific parameter αmod, indicating the absolute values of the percentage changes in m values. In the αmod map for each tumor tissue, the brightness clearly increased with treatment time. In quantitative analysis, the mean values of αmod were calculated. The mean value of αmod for the right renal cell carcinoma increased to 1.35 dB with increasing treatment time, and the mean value of αmod for pseudomyxoma peritonei increased to 1.74 with treatment time. The increase in both αmod brightness and the mean value of αmod implied temperature elevations inside the tumor tissues induced by the radiofrequency current; thus, the acoustic method is promising for monitoring temperature elevations inside tumor tissues during hyperthermia.
In the present study, the variation of the Nakagami shape parameter m of the probability distribution of amplitudes of ultrasonic echoes from soft tissue due to a temperature increase is shown to ...exhibit initial m-value dependence. The change of the Nakagami shape parameter m due to the temperature rise increased with increasing the initial m-value. In order to measure the temperature distribution in soft tissue, we propose a parameter that indicates the absolute values of ratio changes of m values with the multiplying factor varying as a function of the initial m-value. In the hot-scale images indicating the absolute values of ratio changes of m values with the consideration of the initial m-value dependence, the temperature distribution in soft tissue was visualized clearly.
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