Investigation of prostate cancer using diffusion-weighted intravoxel incoherent motion imaging

Purpose

The objective of this work was to evaluate the diagnostic performance of the intravoxel incoherent motion (IVIM) model to differentiate between healthy and malignant prostate tissue.

Materials and Methods

Regions of interest were drawn in healthy and cancerous tissue of 13 patients with histologically proven prostate carcinoma and fitted to a monoexponential model [yielding the apparent diffusion coefficient (ADC)] and the IVIM signal equation (yielding the perfusion fraction f, the diffusion constant D and the pseudodiffusion coefficient of perfusion D?). Parameter maps were calculated for all parameters.

Results

The ADC, D and f were significantly (P<.005) lowered in cancerous tissue (1.01±0.22 μm²/ms, 0.84±0.19 μm²/ms and 14.27±7.10%, respectively) compared to benign tissue (1.49±0.17 μm²/ms, 1.21±0.22 μm²/ms and 21.25±8.32%, respectively). Parameter maps of D and f allowed for a delineation of the tumor, but showed higher variations compared to the ADC map.

Conclusion

Apparent diffusion coefficient maps provide better diagnostic performance than IVIM maps for tumor detection. However, the results suggest that the reduction of the ADC in prostate cancer stems not only from changes in cellularity but also from perfusion effects. IVIM imaging might hold promise for the diagnosis of other prostatic lesions.     

MRI检查无责任病灶脑后循环缺血患者的CT灌注成像研究

目的探讨MRI检查显示无责任病灶的脑后循环缺血(PCI)患者的局部脑血流灌注情况,探索PCI患者早期诊断的有效方法.方法选取符合PCI临床诊断的24例患者行头颅MRI检查,对未发现责任病灶的患者进一步行CT灌注成像(CTPI)检查.在CTPI图像上手绘感兴趣区域(ROI),记录病灶区与对照区的灌注参数,包括局部脑血流量(rCBF)、局部脑血容量(rCBV)、平均通过时间(MTT)和达峰时间(TTP).结果 CTPI检查发现异常灌注18例(阳性率75%),缺血灶共26处,其中小脑10处(38.5%),枕叶7处(26.9%),颞叶3处(11.5%),脑干6处(23.1%).TTP发现异常15例,且均与临床症状相对应,rCBF发现异常13例,rCBV发现异常8例.脑梗死前期分期:玉1期4例,玉2期1例,域1期5例,域2期8例.病灶区的rCBF、rCBV、MTT及TTP与对照区相比较,差异均有统计学意义(P<0.01或0.05).结论 CTPI检查通过对PCI患者进行ROI半定量分析,可客观评价脑后循环脑血流灌注情况,发现头颅MRI检查所未能发现的缺血灶,为临床诊治PCI提供依据.     

Engineered 3D tissue models for cell-laden microfluidic channels

Delivery of nutrients and oxygen within three-dimensional (3D) tissue constructs is important to maintain cell viability. We built 3D cell-laden hydrogels to validate a new tissue perfusion model that takes into account nutrition consumption. The model system was analyzed by simulating theoretical nutrient diffusion into cell-laden hydrogels. We carried out a parametric study considering different microchannel sizes and inter-channel separation in the hydrogel. We hypothesized that nutrient consumption needs to be taken into account when optimizing the perfusion channel size and separation. We validated the hypothesis by experiments. We fabricated circular microchannels (r = 400 μm) in 3D cell-laden hydrogel constructs (R = 7.5 mm, volume = 5 ml). These channels were positioned either individually or in parallel within hydrogels to increase nutrient and oxygen transport as a way to improve cell viability. We quantified the spatial distribution of viable cells within 3D hydrogel scaffolds without channels and with single- and dual-perfusion microfluidic channels. We investigated quantitatively the cell viability as a function of radial distance from the channels using experimental data and mathematical modeling of diffusion profiles. Our simulations show that a large-channel radius as well as a large channel to channel distance diffuse nutrients farther through a 3D hydrogel. This is important since our results reveal that there is a close correlation between nutrient profiles and cell viability across the hydrogel. Young Seok Song and Richard L. Lin have contributed equally to this contribution     

Analytical procedure for mapping the distribution of B and Tc markers in cryo-sections of animal tissue samples by secondary ion mass spectrometry

The development of a complete, standard analytical procedure for a quantitative use of secondary ion mass spectrometry to map the distribution in animal tissues of exogenous isotopes presents difficulties inherently related to sample preparation and preservation, as well as to the specific application being considered. We have tested in two very different cases a procedure based on the cryo-preparation of samples and calibration standards. The applications under investigation were the mapping of ¹⁰B in mouse brain tissue, with relevance to the boron neutron capture therapy, and of the perfusion tracer ⁹⁹Tc in mouse heart tissue, with relevance to the study of microcirculation and cardiovascular pathologies. Scanning electron microscopy and inductively coupled mass spectrometry analysis were used as reference techniques for secondary ion mass spectrometry images and analyte measurements, respectively. Cryo-preparation of tissue sections for ion microscopy proved to be simple and efficient (in terms of structural and chemical integrity) for both brain and heart samples derived from fresh organs. This technique, however, turned out to be reliable only on the brain tissue when applied to the preparation of standards, which required chemical fixation of portions of organs. Brain and heart tissues showed a totally different response to chemical fixation, from both a structural and an analytical point of view. On the one hand, we were able to estimate a relative sensitivity factor for ¹⁰B in the cryo-sectioned brain matrix; on the other hand, even without the possibility of an absolute quantification of the ⁹⁹Tc signal and notwithstanding the presence of an isobaric interference, secondary ion mass spectrometry mapping however proved to be capable to resolve the specific response of the cardiac tissue to the perfusion mechanism.     

The 10 MHz ultrasonic near-field: calculations, hydrophone and optical diffraction tomography measurements

The near-field from a 10 MHz ultrasound transducer has been studied using three different techniques; theoretical calculations, miniature hydrophone measurements and optical diffraction tomography (ODT). The motive was twofold; to evaluate the measurement possibilities of ODT for high-frequency ultrasound and to verify the calculated complexity of near-fields from real ultrasound transducers designed for use in blood perfusion measurements. Calculations of the field from an ideal piston transducer were done with surface integrals of the Kirchhoff function and the measured transducer was designed to approximate this ideal. Contour maps, from the three methods, of pressure amplitude from 1 to 30 mm along the beam are presented with beam profiles at 5 and 45 mm. The results imply that ODT has an increased spatial resolution compared with the 0.5 and 1.0 mm hydrophones. However, even better spatial resolution is needed to draw definite conclusions regarding the complexity of the near-field of the 10 MHz transducer.     

一个用于肿瘤研究中灌流和扩散成像参数分析的应用软件

A software package has been developed to process perfusion, relaxation times and diffusion MRI dat a acquired in cancer research. This software package was written on MATLAB platf orm (Version 6.0). Parameter maps, such as permeability, apparent diffusion coef ficient and T₁ were generated from original MRI data. The features of para metric analysis include ROI analysis, contrast adjust, statistical information generat ion, false color image and zoom in display. Since it was written in Matlab fun ct ions, this package can be used on almost all operation systems (Microsoft window s, Unix, Mac OS & Linux) and it is easy to expand the features.     

High-density hybridoma perfusion culture

Because our earlier work indicated a strong correlation between specific antibody productivity and cell density in perfusion culture, we conducted experiments to determine the optimum means of increasing cell density while mainitaining high antibody productivity. The rates of medium supply and waste removal were varied to determine whether cell density was limited or inhibited, and whether a diffusable substance could be responsible for the correlation between antibody productivity and cell density. Nutrient supply was found to be a stronger determinant of cell density than waste removal; however, the rate of waste removal had a greater effect on cell growth at lower cell densities. Even at noninhibitory levels of ammonia and lactate, cellular metabolism was regulated to minimize their concentrations at lowered rates of waste removal. Separate step changes in glucose and glutamine resulted in increased cell density and antibody concentration. Specific antibody productivity increased following the step in glutamine, but not glucose. Both steps caused changes in cellular metabolism that prevented the levels of lactate and ammonia from reaching toxic levels.     

Biochemical Studies in Perfundates and Homogenates of Isolated Porcine Kidneys after Flushing with Zinc or Zinc–Prolactin Modified Preservation Solution Using a Static Cold Storage Technique

Zinc is an effective anti-inflammatory and antioxidant trace element. The aim of this study was to analyse the protective effect of zinc and zinc–prolactin systems as additives of preservation solutions in the prevention of nephron damage caused during ischemia. The study used a model for storing isolated porcine kidneys in Biolasol^®. The solution was modified with the addition of Zn at a dose of 1 µg/L and Zn: 1 µg/L with prolactin (PRL): 0.1 µg/L. After 2 h and 48 h of storage, the levels of alanine aminotransferase, aspartate aminotransferase, lactate dehydrogenase, sodium, potassium, creatinine and total protein were determined. Zinc added to the Biolasol^® composition at a dose of 1 µg/L showed minor effectiveness in the protection of nephrons. In turn, Zn²⁺ added to Biolasol + PRL (PRL: 0.1 µg/L) acted as a prolactin inhibitor. We do not recommend the addition of Zn(II) (1 µg/L) and Zn(II) (1 µg/L) + PRL (0.1 µg/L) to the Biolasol solution.     

肿瘤射频热疗SAR场与瞬时温度分布模拟

本文针对非侵入性射频热疗的SAR场及瞬态温度分布进行建模和数值模拟计算。采用了能正确反映电磁波在生物组织中衰减的电磁场模型。在温度场模拟中考虑了血液灌流项随组织温度变化和肿瘤区低血液灌流的特点,这些措施使模拟计算结果更加符合临床实际。还对射频热疗电磁能量分布和温度分布的特点及其影响因素等作了细致的分析和讨论。     

Validation study of a pulsed arterial spin labeling technique by comparison to perfusion computed tomography

Abnormalities in cerebral blood flow (CBF) are believed to play a significant role in the development of major neonatal neuropathologies. One approach that would appear ideal for measuring CBF in this fragile age group is arterial spin labeling (ASL) since ASL techniques are noninvasive and quantitative. The purpose of this study was to assess the accuracy of a pulsed ASL method implemented on a 3-T scanner dedicated to neonatal imaging. Cerebral blood flow was measured in nine neonatal piglets, the ASL–CBF measurements were acquired at two inversion times (TI) (1200 and 1700 ms), and CBF was measured by perfusion computed tomography (pCT) for validation. Perfusion CT also provided images of cerebral blood volume, which were used to identify large blood vessels, and contrast arrival time, which were used to assess differences in arterial transit times between gray and white matter. Good agreement was found between gray matter CBF values from pCT (76±1 ml/min per 100 g) and ASL at TI=1700 ms (73±1 ml/min per 100 g). At TI=1200 ms, ASL overestimated CBF (91±2 ml/min per 100 g), which was attributed to substantial intravascular signal. No significant differences in white matter CBF from pCT and ASL were observed (average CBF=60±1 ml/min per 100 g), nor was there any difference in contrast arrival times for gray and white matter (0.95±0.04 and 0.99±0.03 s, respectively), which suggests that the arterial transit times for ASL were the same in this animal model. This study verified the accuracy of the implemented ASL technique and showed the value of using pCT to study other factors that can affect ASL–CBF measurements.