An improved Doppler model for obtaining accurate maximum blood velocities

Maximum blood velocity estimates are frequently required in diagnostic applications, including carotid stenosis evaluation, arteriovenous fistula inspection, and maternal-fetal examinations. However, the currently used methods for ultrasound measurements are inaccurate and often rely on applying heuristic thresholds to a Doppler power spectrum. A new method that uses a mathematical model to predict the correct threshold that should be used for maximum velocity measurements has recently been introduced. Although it is a valuable and deterministic tool, this method is limited to parabolic flows insonated by uniform pressure fields. In this work, a more generalized technique that overcomes such limitations is presented. The new approach, which uses an extended Doppler spectrum model, has been implemented in an experimental set-up based on a linear array probe that transmits defocused steered waves. The improved model has been validated by Field II simulations and phantom experiments on tubes with diameters between 2 mm and 8 mm. Using the spectral threshold suggested by the new model significantly higher accuracy estimates of the peak velocity can be achieved than are now clinically attained, including for narrow beams and non-parabolic velocity profiles. In particular, an accuracy of +1.2 ± 2.5 cm/s has been obtained in phantom measurements for velocities ranging from 20 to 80 cm/s. This result represents an improvement that can significantly affect the way maximum blood velocity is investigated today.     

Highly accelerated aortic 4D flow MR imaging with variable-density random undersampling

Purpose

To investigate an effective time-resolved variable-density random undersampling scheme combined with an efficient parallel image reconstruction method for highly accelerated aortic 4D flow MR imaging with high reconstruction accuracy.

Materials and Methods

Variable-density Poisson-disk sampling (vPDS) was applied in both the phase-slice encoding plane and the temporal domain to accelerate the time-resolved 3D Cartesian acquisition of flow imaging. In order to generate an improved initial solution for the iterative self-consistent parallel imaging method (SPIRiT), a sample-selective view sharing reconstruction for time-resolved random undersampling (STIRRUP) was introduced. The performance of different undersampling and image reconstruction schemes were evaluated by retrospectively applying those to fully sampled data sets obtained from three healthy subjects and a flow phantom.

Results

Undersampling pattern based on the combination of time-resolved vPDS, the temporal sharing scheme STIRRUP, and parallel imaging SPIRiT, were able to achieve 6-fold accelerated 4D flow MRI with high accuracy using a small number of coils (N = 5). The normalized root mean square error between aorta flow waveforms obtained with the acceleration method and the fully sampled data in three healthy subjects was 0.04 ± 0.02, and the difference in peak-systolic mean velocity was − 0.29 ± 2.56 cm/s.

Conclusion

Qualitative and quantitative evaluation of our preliminary results demonstrate that time-resolved variable-density random sampling is efficient for highly accelerating 4D flow imaging while maintaining image reconstruction accuracy.     

Evaluation of Marfan patients status post valve-sparing aortic root replacement with 4D flow

Background

Over the past two decades elective valve-sparing aortic root replacement (V-SARR) has become more common in the treatment of patients with aortic root and ascending aortic aneurysms. Currently there are little data available to predict complications in the post-operative population. The study goal was to determine if altered flow patterns in the thoracic aorta, as measured by MRI, are associated with complications after V-SARR.

Methods

Time-resolved three-dimensional phase-contrast MRI (4D flow) was used to image 12 patients with Marfan syndrome after V-SARR. The patients were followed up for an average of 5.8 years after imaging and 8.2 years after surgery. Additionally 5 volunteers were imaged for comparison. Flow profiles were visualized during peak systole using streamlines. Wall shear stress estimates and normalized flow displacement were evaluated at multiple planes in the thoracic aorta.

Results

During the follow-up period, a single patient developed a Stanford Type B aortic dissection. At initial imaging, prior to the development of the dissection, the patient had altered flow patterns, wall shear stress estimates, and increased normalized flow displacement in the thoracic aorta in comparison to the remaining V-SARR patients and volunteers.

Conclusions

This is the first follow-up study of patients after 4D flow imaging. An aortic dissection developed in one patient with altered flow patterns and hemodynamic stresses in the thoracic aorta. These results suggest that flow and altered hemodynamics may play a role in the development of post-operative intramural hematomas and dissections.     

In vivo imaging of blood flow in the mouse Achilles tendon using high-frequency ultrasound

Objective

Achilles tendinitis is a common clinical problem with many treatment modalities, including physical therapy, exercise and therapeutic ultrasound. However, evaluating the effects of current therapeutic modalities and studying the therapeutic mechanism(s) in vivo remains problematic. In this study, we attempted to observe the morphology and microcirculation changes in mouse Achilles tendons between pre- and post-treatment using high-frequency (25 MHz) ultrasound imaging. A secondary aim was to assess the potential of high-frequency ultrasound in exploring therapeutic mechanisms in small-animal models in vivo.

Methods

A collagenase-induced mouse model of Achilles tendinitis was adopted, and 5 min treatment of continuous-mode low-frequency (45 kHz) ultrasound with 47 mW/cm² maximum intensity and 16.3 cm² effective beam radiating area was applied. The B-mode images showed no focal hypoechoic regions in normal Achilles tendons either pre- or post-treatment. The Doppler power energy and blood flow rate were measured within the peritendinous space of the Achilles tendon.

Conclusion

An increase in the microcirculation was observed soon after the low-frequency ultrasound treatment, which was due to immediate induction of vascular dilatation. The results suggest that applying high-frequency Doppler imaging to small-animal models will be an invaluable aid in explorations of the therapeutic mechanism(s). Our future work includes using imaging to assess microcirculation changes in tendinitis between before and after treatment over a long time period, which is expected to yield useful physiological data for future human studies.     

Denoising of quadrature ultrasound Doppler signal from bi-directional flow based on matching pursuit

Denoising of Doppler signal is a preliminary and important step in medical ultrasound imaging. To denoise quadrature Doppler signal from bi-directional flow, we propose a novel method based on matching pursuit in this paper. The proposed method is an iterative decomposition algorithm which decomposes the original Doppler signal into a linear expansion of atoms in a time-frequency dictionary. The time-frequency dictionary is similar to Fourier transform domain and the atoms are similar to orthogonal bases in Fourier transform. In each step of the iteration, the atom which gives the largest inner product with the analyzed signal is selected from the dictionary, and the contribution of this atom is subtracted from the Doppler signal. This process is repeated on the residue until the SNR reaches the maximum. The linear expansion of the selected atoms is the denoised signal. Simulations were conducted on a simulation model with a sampling rate of 12.8 kHz. When the original SNRs are 0 dB, 2 dB, 4 dB, 6 dB, 8 dB, 10 dB, the proposed method can improve the SNR for 7.9 dB, 7.8 dB, 7.5 dB, 7.3 dB, 7.05 dB, 6.8 dB respectively, reduce the root mean square error (RMSE) of the mean frequency waveform to 0.0441 kHz, 0.0303 kHz, 0.0245 kHz, 0.0215 kHz, 0.0161 kHz, 0.0125 kHz respectively, and suppress the RMSE of the spectral width waveform to 0.1774 kHz, 0.0591 kHz, 0.0486 kHz, 0.0170 kHz, 0.0145 kHz, 0.0117 kHz respectively. Preliminary in vivo evaluation was also carried out on a healthy 33-year-old male using B-K medical A/S 3535 ultrasound scanner, and the results showed that the proposed method can effectively enhance the Doppler spectrogram.     

Research on laser Doppler velocimeter for vehicle self-contained inertial navigation system

An idea of using laser Doppler velocimeter (LDV) to measure the velocity for the vehicle inertial navigation system was put forward. The principle of measuring its own velocity with laser Doppler technique was elaborated and reference-beam LDV was designed. Then Doppler signal was processed by tracking filter, frequency spectrum refinement and frequency spectrum correction algorithm. The result of theory and experiment showed that the reference-beam LDV solved the problem that dual-beam LDV cannot be used for measuring when the system was out of focus. Doppler signal was tracked so that signal-to-noise ratio was improved, and the accuracy of the system was enhanced by the technology of frequency spectrum refinement and correction. The measurement mean error was less than 1.5% in velocity range of 0-30 m/s.     

Ultrasonic distance and velocity measurement using a pair of LPM signals for cross-correlation method: improvement of Doppler-shift compensation and examination of Doppler velocity estimation

Real-time distance measurement of a moving object with high accuracy and high resolution using an ultrasonic wave is difficult due to the influence of the Doppler effect or the limit of the calculation cost of signal processing. An over-sampling signal processing method using a pair of LPM signals has been proposed for ultrasonic distance and velocity measurement of moving objects with high accuracy and high resolution. The proposed method consists of cross correlation by single-bit signal processing, high-resolution Doppler velocity estimation with wide measurement range and low-calculation-cost Doppler-shift compensation. The over-sampling cross-correlation function is obtained from cross correlation by single-bit signal processing with low calculation cost. The Doppler velocity and distance of the object are determined from the peak interval and peak form in the cross-correlation function by the proposed method of Doppler velocity estimation and Doppler-shift compensation. In this paper, the proposed method of Doppler-shift compensation is improved. Accuracy of the determined distance was improved from approximately within ±140 μm in the previous method to approximately within ±10 μm in computer simulations. Then, the proposed method of Doppler velocity estimation is evaluated. In computer simulations, accuracy of the determined Doppler velocity and distance were demonstrated within ±8.471 mm/s and ±13.87 μm. In experiments, Doppler velocities of the motorized stage could be determined within ±27.9 mm/s.     

High-overtone self-focusing acoustic transducers for high-frequency ultrasonic Doppler

This work reports the potential use of high-overtone self-focusing acoustic transducers for high-frequency ultrasonic Doppler. By using harmonic frequencies of a thick bulk Lead Zirconate Titanate (PZT) transducer with a novel air-reflector Fresnel lens, we obtained strong ultrasound signals at 60 MHz (3rd harmonic) and 100 MHz (5th harmonic). Both experimental and theoretical analysis has demonstrated that the transducers can be applied to Doppler systems with high frequencies up to 100 MHz.     

Suitability of laser Doppler velocimetry for the calibration of pressure microphones

The details of a new approach for absolute calibration of microphones, based on the direct measurement of acoustic particle velocity using laser Doppler velocimetry (LDV), are presented and discussed. The calibration technique is carried out inside a tube in which plane waves propagate and closed by a rigid termination. The method developed proposes to estimate the acoustic pressure with two velocity measurements and a physical model. Minimum theoretical uncertainties on the estimated pressure and minimum measurable pressure are calculated from the Cramer Rao bounds on the estimated acoustic velocity amplitude and phase. These uncertainties and the minimum measurable pressure help to optimize the experimental set up. Acoustic pressure estimations performed with LDV are compared with acoustic pressures obtained with a reference microphone. Measurements lead to a minimum bias of 0.006 dB and a minimum uncertainty of 0.013 dB on the acoustic pressure estimation for frequencies 1360 Hz and 680 Hz.     

High resolution diffusion weighted magnetic resonance imaging of the pancreas using reduced field of view single-shot echo-planar imaging at 3 T

Diffusion weighted magnetic resonance imaging (DWI) has been mostly acquired using single-shot echo-planar imaging (ss EPI) to minimize motion induced artifacts. The spatial resolution, however, is inherently limited in ss EPI especially for abdominal imaging, even with the advances in parallel imaging. A novel method of reduced Field of View ss EPI (rFOV ss EPI) has achieved high resolution DWI in human carotid artery, spinal cord with reduced blurring and higher spatial resolution than conventional ss EPI, but it has not been used to pancreas imaging. In the work, comparisons between the full FOV ss-DW EPI and rFOV ss-DW EPI in image qualities and ADC values of pancreatic tumors and normal pancreatic tissues were performed to demonstrate the feasibility of pancreatic high resolution rFOV DWI. There were no significant differences in the mean ADC values between full FOV DWI and rFOV DWI for the 17 subjects using b = 600 s/mm² (P = 0.962). However, subjective scores of image quality was significantly higher at rFOV ss DWI (P = 0.008 and 0.000 for b-value = 0 s/mm² and 600 s/mm² respectively). The spatial resolution of DWI for pancreas was increased by a factor of over 2.0 (from almost 3.0 mm/pixel to 1.25 mm/pixel) using rFOV ss EPI technique. Reduced FOV ss EPI can provide good DW images and is promising to benefit applications for pancreatic diseases.     

The preliminary evaluation of a 1 MHz ultrasound probe for measuring the elastic anisotropy of human cortical bone

Our objective is to evaluate an ultrasound probe for measurements of velocity and anisotropy in human cortical bone (tibia). The anisotropy of cortical bone is a known and mechanically relevant property in the context of osteoporotic fracture risk. Current in vivo quantitative ultrasound devices measuring the velocity of ultrasound in long bones can only be applied in the axial direction. For anisotropy measurements a second direction for velocity measurements preferably perpendicular to the axial direction is necessary. We developed a new ultrasound probe which permits axial transmission measurements with a simultaneous second perpendicular direction (tangential). Anisotropy measurements were performed on isotropic and anisotropic phantoms and two excised human female tibiae (age 63 and 82). Anisotropy ratios (AI; ratio of squared ultrasound velocities in the two directions) were for the isotropic phantom 1.06 ± 0.01 and for the anisotropic phantom 1.14 ± 0.03 (mean ± standard deviation). AI was 1.83 ± 0.29 in the tibia from the older donor and 1.37 ± 0.18 in the tibia from the younger donor. The AIs were in the expected range and differed significantly (p < 0.05, t-test) between the tibiae. Measured sound velocities were reproducible (mean standard deviation of short time precision of both channels for phantom measurements 31 m/s) and in agreement with reported velocities of the phantom material. Our results document the feasibility of anisotropy measurements at long bones using a single probe. Further improvements in the design of the probe and tests in vivo are warranted. If this approach can be evaluated in vivo an additional tool for assessing the bone status is available for clinical use.     

Velocity changing collisions in the laser saturation spectra of Rb D2 F″ = 2

The saturation absorption technique is applied to the ⁸⁷Rb ²S_1/2 F″ = 2 → ²P_3/2 F′ = 1, 2 and 3 transitions to study the effect of velocity changing collisions (VCC). The VCC caused Doppler pedestal increases with argon pressure from 0 to 110 mTorr and decreases with modulation frequencies of 700-3200 Hz. The resonances of the velocity selective, saturated optical pumping are washed out for pressure of 110 mTorr. The magnitude of the Doppler pedestal relative to the homogeneous features, yields a rate for velocity changing collisions of 6.5 ± 0.2 × 10⁻¹⁰ cm³ s⁻¹.     

Intravoxel incoherent motion diffusion-weighted imaging in head and neck squamous cell carcinoma: Assessment of perfusion-related parameters compared to dynamic contrast-enhanced MRI

Purpose

To investigate the correlation between perfusion-related parameters obtained with intravoxel incoherent motion (IVIM) and classical perfusion parameters obtained with dynamic contrast-enhanced (DCE) magnetic resonance imaging in patients with head and neck squamous cell carcinoma (HNSCC), and to compare direct and asymptotic fitting, the pixel-by-pixel approach, and a region of interest (ROI)-based approach respectively for IVIM parameter calculation.

Materials and methods

Seventeen patients with HNSCC were included in this retrospective study. All magnetic resonance (MR) scanning was performed using a 3 T MR unit. Acquisition of IVIM was performed using single-shot spin-echo echo-planar imaging with three orthogonal gradients with 12 b-values (0, 10, 20, 30, 50, 80, 100, 200, 400, 800, 1000, and 2000). Perfusion-related parameters of perfusion fraction ‘f’ and the pseudo-diffusion coefficient ‘D*’ were calculated from IVIM data by using least square fitting with the two fitting methods of direct and asymptotic fitting, respectively. DCE perfusion was performed in a total of 64 dynamic phases with a 3.2-s phase interval. The two-compartment exchange model was used for the quantification of tumor blood volume (TBV) and tumor blood flow (TBF). Each tumor was delineated with a polygonal ROI for the calculation of f, f ? D* performed using both the pixel-by-pixel approach and the ROI-based approach. In the pixel-by-pixel approach, after fitting each pixel to obtain f, f ? D* maps, the mean value in the delineated ROI on these maps was calculated. In the ROI-based approach, the mean value of signal intensity was calculated within the ROI for each b-value in IVIM images, and then fitting was performed using these values. Correlations between f in a total of four combinations (direct or asymptotic fitting and pixel-by-pixel or ROI-based approach) and TBV were respectively analyzed using Pearson's correlation coefficients. Correlations between f ? D* and TBF were also similarly analyzed.

Results

In all combinations of f and TBV, f ? D* and TBF, there was a significant correlation. In the comparison of f and TBV, a moderate correlation was observed only between f obtained by direct fitting with the pixel-by-pixel approach, whereas a good correlation was observed in the comparisons using the other three combinations. In the comparison of f ? D* and TBF, a good correlation was observed only with f ? D* obtained by asymptotic fitting with the ROI-based approach. In contrast, moderate correlations were observed in the comparisons using the other three combinations.

Conclusion

IVIM was found to be feasible for the analysis of perfusion-related parameters in patients with HNSCC. Especially, the combination of asymptotic fitting with the ROI-based approach was better correlated with DCE perfusion.     

Effect of dual-frequency clutter suppression in harmonic Doppler detection

Background

High-frequency Doppler imaging is highly potential for detection of blood flow in microcirculation. In a swept-scan system, however, the spectral broadening of tissue clutter limits the detectability of low-velocity flow signal. Conventionally, the scanning speed of transducer has to be reduced to alleviate the clutter interference but at the cost of imaging frame rate. For example, the blood velocity of 0.5 mm/s becomes detectable only with a scanning speed lower than 1 mm/s. In this study, an alternative method is examined by suppressing the clutter magnitude to reduce the interference to flow signal without sacrificing scanning speed.

Methods

The method of third harmonic (3f₀) transmit phasing can suppress the tissue harmonic clutter by transmitting at the fundamental and the additional 3f₀ frequencies to achieve mutual cancellation between the frequency-sum and the frequency-difference components of the second harmonic signal. With 3f₀ transmit phasing, the cut-off frequency of wall filtering can be reduced to preserve low-velocity flow without compromising the frame rate.

Results

Our results indicate that the 3f₀ transmit phasing effectively reduces the harmonic clutter magnitude and thus improves the flow signal-to-clutter ratio. Compared to the conventional counterpart, the clutter-suppressed color flow and power Doppler images show fewer clutter artifacts and is capable of detecting more low-velocity flow of microbubbles. The resultant color-pixel-density also improves with clutter suppression.

Conclusion

For the swept-scan high-frequency (>20 MHz) system, 3f₀ transmit phasing is capable of providing effective clutter suppression. With the same achievable scanning speed, the resultant Doppler image has higher sensitivity for low-velocity flow and is less susceptible to clutter artifacts.     

Diffusion-weighted MR imaging for assessing synovitis of wrist and hand in patients with rheumatoid arthritis: A feasibility study

The purpose of this study was to investigate the feasibility of diffusion-weighted imaging (DWI) in detecting synovitis of wrist and hand in patients with rheumatoid arthritis (RA) and evaluate its sensitivity, specificity and accuracy as compared to T₂-weighted imaging (T2WI) with short tau inversion recovery (STIR) with the reference standard contrast-enhanced magnetic resonance imaging (CE-MRI). Twenty-five patients with RA underwent MR examinations including DWI, T2WI with STIR and CE-MRI. MR images were reviewed for the presence and location of synovitis of wrist and hand. The sensitivity, specificity and accuracy of DWI and T2WI with STIR were calculated respectively and then compared. All patients included in this study completed MR examinations and yielded diagnostic image quality of DWI. For individual joint, there was good to excellent inter-observer agreement (k = 0.62–0.83) using DWI images, T2WI with STIR images and CE-MR images, respectively. There was a significance between DWI and T2WI with STIR in analyzing proximal interphalangeal joints II–V, respectively (P < 0.05). The k-values for the detection of synovitis indicated excellent overall inter-observer agreements using DWI images (k = 0.86), T2WI with STIR images (k = 0.85) and CE-MR images (k = 0.91), respectively. Overall, DWI demonstrated a sensitivity, specificity and accuracy of 75.6%, 89.3% and 84.6%, respectively, for detection of synovitis, while 43.0%, 95.7% and 77.6% for T2WI with STIR, respectively. DWI showed positive lesions much better and more than T2WI with STIR. Our results indicate that DWI presents a novel non-invasive approach to contrast-free imaging of synovitis. It may play a role as an addition to standard protocols.     

Photodissociation of iodocyclohexane at 266 and 277 nm: Energy partitioning and curve crossing analysis

The photodissociation dynamics of iodocyclohexane (C₆H₁₁I) at 266 and 277 nm has been investigated by ion velocity imaging technique. The velocity distributions, angular distributions and relative quantum yields are obtained for I (²P_3/2) (denoted I) and I (²P_1/2) (denoted I*) fragments. The energy partitioning shows that about 70% of the available energy goes into the internal excitation of the photofragments for both dissociation channels. From the angular distributions, we found the value of the anisotropy parameter β for I* at the corresponding excitation wavelength was less than that for I. Based on the measured angular distributions and relative quantum yields, the relative fractions of each excited state to the products are determined. The curve crossing probabilities between the ³Q₀ and ¹Q₁ states are determined 0.503 at 266 nm and 0.443 at 277 nm.     

A novel algorithm in buildings/shadow detection based on Harris detector

A novel method based on corner detectors is proposed in detecting shadow and buildings in this paper. Its most outstanding point is employing Harris corner detector in region-based detection, despite that Harris detector traditionally used to select pixels as final results. Different densities of buildings are generally influenced by different features for recognition. First time, images are self-grouped into two groups according to the distribution of buildings, and two specifical algorithms are ready for detection specifically. A region-based method is used in comparison with our algorithm, and the results indicate that the new idea works not only more robustly, but also more effectively. It is a fast and simple method, which needs average 3.28 × 10⁻⁵ s to run per square image.     

Contrast enhanced maximum intensity projection ultrasound imaging for assessing angiogenesis in murine glioma and breast tumor models: A comparative study

The purpose of this study was to prospectively compare noninvasive, quantitative measures of vascularity obtained from four contrast enhanced ultrasound (US) techniques to four invasive immunohistochemical markers of tumor angiogenesis in a large group of murine xenografts. Glioma (C6) or breast cancer (NMU) cells were implanted in 144 rats. The contrast agent Optison (GE Healthcare, Princeton, NJ) was injected in a tail vein (dose: 0.4 ml/kg). Power Doppler imaging (PDI), pulse-subtraction harmonic imaging (PSHI), flash-echo imaging (FEI), and Microflow imaging (MFI; a technique creating maximum intensity projection images over time) was performed with an Aplio scanner (Toshiba America Medical Systems, Tustin, CA) and a 7.5 MHz linear array. Fractional tumor neovascularity was calculated from digital clips of contrast US, while the relative area stained was calculated from specimens. Results were compared using a factorial, repeated measures ANOVA, linear regression and z-tests. The tortuous morphology of tumor neovessels was visualized better with MFI than with the other US modes. Cell line, implantation method and contrast US imaging technique were significant parameters in the ANOVA model (p < 0.05). The strongest correlation determined by linear regression in the C6 model was between PSHI and percent area stained with CD31 (r = 0.37, p < 0.0001). In the NMU model the strongest correlation was between FEI and COX-2 (r = 0.46, p < 0.0001). There were no statistically significant differences between correlations obtained with the various US methods (p > 0.05). In conclusion, the largest study of contrast US of murine xenografts to date has been conducted and quantitative contrast enhanced US measures of tumor neovascularity in glioma and breast cancer xenograft models appear to provide a noninvasive marker for angiogenesis; although the best method for monitoring angiogenesis was not conclusively established.     

Effect of B-value in revealing postinfarct myocardial microstructural remodeling using MR diffusion tensor imaging

Nonmonoexponential diffusion behavior has been previously reported to exist in some biological tissues, making quantification of diffusion tensor imaging (DTI) indices dependent on diffusion sensitivity of b-value. This study aims to investigate the effect of b-value in revealing postinfarct myocardial microstructural remodeling in ex vivo hearts. DTI scans were performed on heart samples 1, 3, 5, and 7 days after infarction induction as well as intact controls with b-values of 500 to 2500 s/mm². DTI indices, including fractional anisotropy (FA), and mean and directional diffusivities, were measured in infarct, adjacent and remote regions with zero and each non-zero b-values respectively using conventional DTI analysis. Experimental results showed that these DTI indices decreased gradually with b-values in all regions and groups. Optimal b-values were found to vary with targeted DTI indices, and could strengthen DTI ability in revealing myocardium degradation with using conventional DTI approach. Specifically, FA showed the most sensitive detection of fiber integrity degradation at moderate b-values (≈ 1500 to 2000 s/mm²), and the greatest ability of mean and directional diffusivities in monitoring diffusivity alteration occurred at relatively small b-values (≤ 1500 s/mm²) during the necrotic and fibrotic phases. These findings may provide useful information for DTI protocol parameter optimization in assessing heart microstructures at other pathological or in vivo states in the future.     

Semiquantitative perfusion combined with diffusion-weighted MR imaging in pre-operative evaluation of endometrial carcinoma: Results in a group of 57 patients

Purpose

To evaluate the semiquantitative DCE and quantitative DWI parameters in endometrial cancer, in order to assess the presence of neoplastic tissue and normal myometrium and to ascertain a potential relationship with tumor grade.

Methods and materials

A total of 57 patients with biopsy-proven endometrial adenocarcinoma who underwent MR imaging examination for staging purposes were retrospectively evaluated. Imaging protocol included multiplanar T₁- and T₂-weighted TSE, DCE T₁-weighted (THRIVE; 0, 30, 90 and 120 seconds after intravenous injection of gadolinium) and DWIBS sequences (b values = 0 and 1000 mm²/s). Color perfusion and ADC maps were automatically generated on dedicated software. Relative enhancement (RE, %), maximum enhancement (ME, %), maximum relative enhancement (MRE, %), time to peak (TTP, s) and mean apparent diffusion coefficient (ADC) were calculated by manually drawing a region of interest (ROI) both on the neoplastic tissue and the normal myometrium. Histopathology was used as reference standard.

Results

Histopathological analysis confirmed the presence of endometrial carcinoma in all patients. Neoplastic tissue demonstrated significantly lower (P < 0.001) values of RE (%) 63.92 ± 35.68; ME (%) 864.91 ± 429.54 and MRE (%) 75.97 ± 38.26 as compared to normal myometrium (RE (%) 151.43 ± 55.99; ME (%) 1800.73 ± 721.32; MRE (%) 158.28 ± 54.05). TTP was significantly higher (P < 0.05) in tumor lesion (385.51 ± 1630.27 vs 195.44 ± 78.69). Mean ADC value of neoplastic tissue (775.09 ± ?220.73 × 10^− 3 mm²/s) was significantly lower (P < 0.05) than in myometrium (1602.37 ± 378.54 × 10^− 3 mm²/s). The analysis of perfusion and diffusion parameters classified according to tumor grades, showed a statistically significant difference only for RE (P = 0.043) and ME (P = 0.007).

Conclusions

Perfusion parameters and mean ADC differ significantly between endometrial cancer and normal myometrium, potentially reflecting the different microscopical features of cellularity and vascularity; however a significant relationship with tumor grade was not found in our series.