SPECTRAL TRANSMISSION AND SCATTERING CHARACTERISTICS OF HUMAN SKIN

It is necessary for making the real appearance of human skin sample to deal with not only the spectral reflectance characteristics but also the multi-layer structure and translucency. This paper reported the measurement and analysis of the spectral transmitted and scattering light characteristics. For five subjects, the maximum of transmitted light intensity was resulted at 700 nm near the light source, and decreased with decreasing wavelength. Longer the wavelength, longer the distance which the transmitted light intensity was downing to zero. we defined the average attenuation ratio per unit transmitted light intensity which had the calculation range from 3.5 mm from the light source to the distance that the variation ratio of the transmitted light intensity per unit distance was converged to zero. All subjects’ results showed the peak of the average attenuation ratio at 700 nm and the value were almost 0.5. And they decreased with decreasing wavelength.

Quantitative assessment of HCC wash-out on CT is a predictor of early complete response to TACE

Objectives To investigate the predictive value of four-phase contrast-enhanced CT (CECT) for early complete response (CR) to drug-eluting-bead transarterial chemoembolization (DEB-TACE), with a particular focus on the quantitatively assessed wash-in and wash-out. Methods A retrospective analysis of preprocedural CECTs was performed for 129 HCC nodules consecutively subjected to DEB-TACE as first-line therapy. Lesion size, location, and margins were recorded. For the quantitative analysis, the following parameters were computed: contrast enhancement ratio (CER) and lesion-to-liver contrast ratio (LLC) as estimates of wash-in; absolute and relative wash-out (WOabs and WOrel) and delayed percentage attenuation ratio (DPAR) as estimates of wash-out. The early radiological response of each lesion was assessed by the mRECIST criteria and dichotomized in CR versus others (partial response, stable disease, and progressive disease). Results All quantitatively assessed wash-out variables had significantly higher rates for CR lesions (WOabsp = 0.01, WOrelp = 0.01, and DPAR p = 0.00002). However, only DPAR demonstrated an acceptable discriminating ability, quantified by AUC = 0.80 (95% CI0.73–0.88). In particular, nodules with DPAR ≥ 120 showed an odds ratio of 3.3(1.5–7.2) for CR (p = 0.0026). When accompanied by smooth lesion margins, DPAR ≥ 120 lesions showed a 78% CR rate at first follow-up imaging. No significative association with CR was found for quantitative wash-in estimates (CER and LLC). Conclusions Based on preprocedural CECT, the quantitative assessment of HCC wash-out is useful in predicting early CR after DEB-TACE. Among the different formulas for wash-out quantification, DPAR has the best discriminating ability. When associated, DPAR ≥ 120 and smooth lesion margins are related to relatively high CR rates. Key Points • A high wash-out rate, quantitatively assessed during preprocedural four-phase contrast-enhanced CT (CECT), is a favorable predictor for early radiological complete response of HCC to drug-eluting-bead chemoembolization (DEB-TACE). • The arterial phase of CECT shows great dispersion of attenuation values among different lesions, even when a standardized protocol is used, limiting its usefulness for quantitative analyses. • Among the different formulas used to quantify the wash-out rate (absolute wash-out, relative wash-out, and delayed percentage attenuation ratio), the latter (DPAR), based only on the delayed phase, is the most predictive (AUC = 0.80), showing a significant association with complete response for values above 120.

Comparison between the maximum standard uptake value and the ratio of lymph node to primary tumor attenuation in head and neck cancers: A prospective study

Objective: To investigate the relationship between the ratio of lymph node attenuation to primary lesion attenuation on contrast-enhanced CT and the PET/CT standard uptake value (SUVmax) in head and neck squamous cell cancer (HNSCC). Methods: Volunteers with advanced-stage, histopathologically proven HNSCC indicated to have radiotherapy/chemoradiotherapy were evaluated for CT and PET/CT for radiotherapy planning. The attenuation and SUVmax of the primary lesion and the largest, possibly metastatic lymph node, and the round index and volume of the lymph node were calculated. The relationship between lymph node/primary lesion attenuation and SUVmax ratios was investigated. The differences in CT findings between the SUVmax < and ≥3 groups were examined. Results: Thirty-two cases with adequate diagnostic quality were studied. There was a very strong positive correlation between primary lesion and lymph node attenuation (r=0.817, p<0.001), strong correlation between lymph node volume and SUVmax (r=0.681, p<0.001), and moderate negative correlation between lymph node/primary lesion SUVmax and attenuation (r=-0.503, p=0.004). In patients with ≥3 SUVmax, lymph node volume and lymph node/primary lesion SUVmax were significantly higher, and the attenuation ratio was close to 1 (PPV 94.1, 86.3% respectively). Conclusion: In HNSCC, the lymph node/primary lesion attenuation ratio can be used instead of SUVmax if supported by other conventional CT findings. Metastasis should be considered if lymph node attenuation is similar to primary mass attenuation and excluded if higher. CT attenuation rate can be used as a supportive finding if PET/CT cannot be performed or lymph node SUVmax is close to the acceptable cut-off for metastasis.

Liver segmental volume and attenuation ratio (LSVAR) on portal venous CT scans improves the detection of clinically significant liver fibrosis compared to liver segmental volume ratio (LSVR)

Background The aim of this proof-of-concept study was to show that the liver segmental volume and attenuation ratio (LSVAR) improves the detection of significant liver fibrosis on portal venous CT scans by adding the liver vein to cava attenuation (LVCA) to the liver segmental volume ratio (LSVR). Material and methods Patients who underwent portal venous phase abdominal CT scans and MR elastography (reference standard) within 3 months between 02/2016 and 05/2017 were included. The LSVAR was calculated on portal venous CT scans as LSVR*LVCA, while the LSVR represented the volume ratio between Couinaud segments I-III and IV-VIII, and the LVCA represented the density of the liver veins compared to the density in the vena cava. The LSVAR and LSVR were compared between patients with and without significantly elevated liver stiffness (based on a cutoff value of 3.5 kPa) using the Mann–Whitney U test and ROC curve analysis. Results The LSVR and LSVAR allowed significant differentiation between patients with (n = 19) and without (n = 122) significantly elevated liver stiffness (p < 0.001). However, the LSVAR showed a higher area under the curve (AUC = 0.96) than the LSVR (AUC = 0.74). The optimal cutoff value was 0.34 for the LSVR, which detected clinically increased liver stiffness with a sensitivity of 53% and a specificity of 88%. With a cutoff value of 0.67 for the LSVAR, the sensitivity increased to 95% while maintaining a specificity of 89%. Conclusion The LSVAR improves the detection of significant liver fibrosis on portal venous CT scans compared to the LSVR.

Feasibility and diagnostic accuracy of using brain attenuation changes on CT to estimate time of ischemic stroke onset

Purpose CT attenuation of ischemic brain reduces with time after stroke onset. We aimed to quantify this relationship and test the feasibility and accuracy of estimating stroke onset time using only CT attenuation of visible ischemic lesions, the CT-Clock Tool. Methods We selected CT scans with ischemic lesions representing a range of stroke-onset-to-scan times (elapsed time) from a well-defined stroke trial. We measured the attenuation of ischemic lesions and contralateral normal brain to derive attenuation ratio. We assigned scans to development (75%) or test (25%) datasets. We plotted the relationship between attenuation ratio and elapsed time in the development dataset and derived a best-fit curve. We calculated estimated time in the test dataset using only the attenuation ratio curve. We compared estimated time to elapsed time and derived absolute error for estimated time. We assessed area under the receiver operating characteristic (AUROC) curve for identifying scans ≤ 4.5 h elapsed time. Results We included 342 scans from 200 patients (41% male, median age 83 years). Elapsed time range: 22 min to 36 days. Estimation errors were least at early elapsed times (r = 0.82, p < 0.0001): median absolute error was 23, 106, 1030 and 1933 min for scans acquired ≤ 3, > 3–9, > 9–30 and > 30 h from stroke onset, respectively. AUROC was high at 0.955. Conclusions It is feasible to accurately estimate stroke onset time using simple attenuation measures of ischemic brain. Our method was most accurate 0–9 h from onset and may be useful for treatment eligibility assessment, especially where imaging resources are limited.

Temperature Fluctuation Attenuation of Circulating Cooling Water Using Dynamic Thermal Filtering

The Demand for circulating cooling water (CCW) with high temperature stability and a quick response to temperature control is essential for precision engineering, so a dynamic thermal filtering method is proposed in this paper. Some CCW is bypassed, blocked, and used as a thermal capacity medium, and the temperature fluctuation of CCW is significantly reduced by heat exchanging with the medium. The temperature of the medium dynamically follows the set value of the CCW temperature by real time updating, and so realizes a quick CCW temperature control response. The attenuation ratio of temperature fluctuation was derived, theoretically validating the effectiveness of the method. The experimental results indicate that a CCW temperature fluctuation attenuation ratio of tens of dB (−3.47 dB, −6.91 dB, −10.97 dB and −15.28 dB corresponding to temperature fluctuation frequencies of 0.01 Hz, 0.025 Hz, 0.053 Hz and 0.105 Hz, respectively) is achieved by the proposed method. The updating time of thermal capacity medium is 82 s, which means that the temperature fluctuation attenuation remains functionally valid when the set value of CCW changes. The proposed method is low cost in operation and provides an effective approach to satisfy the challenging demand for CCW with high stability and a good dynamic temperature control performance.

Torsion of Wandering Spleen: Importance of Splenic Density and Liver-to- Spleen Attenuation Ratio on CT

Background: Wandering spleen (WS) is a rare clinical condition which may cause fatal complication like torsion with subsequent infarction. Determination of splenic parenchyma viability is very important in deciding whether splenopexy rather than splenectomy is an option. Contrast- enhanced computed tomography (CECT) is important for the diagnosis of WS and assessment of the viability of spleen. Discussion: We reviewed the CT studies of four cases with WS. We measured the mean splenic and liver density and calculated liver-to-spleen attenuation ratio (LSAR). We also assessed the CT findings for each patient. Mean splenic density was measured as 40.77 Hounsfield Unit (HU) in cases with infarction, 127.1 HU in case without infarction. LSAR was calculated as 2.55 in cases with infarction, 0.99 in case without infarction. We detected whirlpool sign, intraperitoneal free fluid, splenic arterial enhancement in all patient, parenchymal and splenic vein enhancement in one patient without infarction, fat rim sign in three patients with infarction, capsular rim sign in one patient with infarction. Conclusion: CECT should be obtained for the diagnosis of WS and assessment of the viability of spleen. CECT could suggest the diagnosis of infarction of the spleen with following findings; absence of parenchymal enhancement, very low density of spleen (<45 HU), and LSAR which is greater than 2.