Moderne B-Bild-Sonographie der Mamma

Recently, the diagnosis of breast diseases by ultrasound has changed radically. It is no longer a complementary modality to mammography but a separate method to investigate breast disease. Innovative high-resolution ultrasound allows more specific diagnosis of breast tumors. Tissue-harmonic imaging not only uses the transmitted, fundamental frequency to obtain an image but also the harmonic frequency. The harmonic signal is processed by the ultrasound system with the result of better delineation of tissue structures and spatial compounding assembles an image from multiple images taken from different angles of echo waves. The effect is the reduction of artifacts with optimized contrast. Finally the advanced speckle reduction technique is used to smooth and homogenize the image. Additionally continuous advancement of new high-resolution linear transducers is responsible for the essential improvement of image quality. In conclusion, it is recommended to integrate all of the described modalities in order to obtain diagnostically conclusive image quality. This article demonstrates the new techniques and applications exemplified using images.     

Non-linear ultrasound imaging

The recent introduction of non-linear imaging in ultrasound diagnosis could improve image quality by resolving some problems in technically difficult patients allowing a better conspicuity in identification of subtle lesions. Tissue harmonics are generated while the transmitted pulse propagates through tissue. The formation of image by utilising the harmonic signals implies the suppression of fundamental frequency in the received signal. This is achieved by two major processes filtering and pulse inversion imaging. The non-linear properties of contrast agents reinforce the intensity of harmonic signals which could be detected in precise conditions of acoustic power for a non-destructive or destructive imaging. The introduction of this new imaging modality opens new way in ultrasound imaging with precise protocols of acquisition or sequences and possibly in therapy in the near future.     

Digital tomosynthesis aided by low-resolution exact computed tomography

Tomosynthesis reconstructs 3-dimensional images of an object from a significantly fewer number of projections as compared with that required by computed tomography (CT). A major problem with tomosynthesis is image artifacts associated with the data incompleteness. In this article, we propose a hybrid tomosynthesis approach to achieve higher image quality as compared with competing methods. In this approach, a low-resolution CT scan is followed by a high-resolution tomosynthesis scan. Then, both scans are combined to reconstruct images. To evaluate the image quality of the proposed method, we design a new breast phantom for numerical simulation and physical experiments. The results show that images obtained by our approach are clearly better than those obtained without such a CT scan.     

Fortschritte in der pädiatrischen Sonographie

Advances in the field of ultrasound technology and ultrasound contrast media over the past few years have also brought major improvements to pediatric sonography. Accordingly, contrast-enhanced voiding urosonography has become a valuable alternative in the diagnosis of vesicoureteral reflux. It is possible to achieve significant reduction in radiation exposure replacing the conventional radiologic methods used for reflux diagnosis with contrast-enhanced ultrasound. Through the introduction of harmonic imaging, an ultrasound scanning modality with high spatial and contrast resolution has become available. The modality was initially propagated as one to be applied in difficult-to-scan adults. However, initial experiences in pediatric applications are demonstrating the significant improvement it can bring in the ultrasound image quality, for example, in intestinal ultrasound. A further development is three-dimensional [3D] imaging using ultrasound. 3D-ultrasound not only offers an improvement in diagnosis but also in the acceptance of ultrasound in interdisciplinary work and teaching. The first applications of 3D-ultrasound in pediatrics are focusing on brain ultrasound and volume measurement of the kidneys.     

Three-dimensional reconstruction of fine vascularity in ultrasound breast imaging using contrast-enhanced spatial compounding: in vitro analyses

RATIONALE AND OBJECTIVES: Ultrasound image quality can be improved by imaging an object (here: the female breast) from different viewing angles in one image plane. With this technique, which is commonly referred to as spatial compounding, a more isotropic resolution is achieved while speckle noise and further artifacts are reduced. We present results obtained from a combination of spatial compounding with contrast-enhanced ultrasound imaging in three dimensions to reduce contrast specific artifacts (depth dependency, shadowing, speckle) and reconstruct vascular structures. MATERIALS AND METHODS: We used a conventional ultrasound scanner and a custom made mechanical system to rotate an ultrasound curved array probe around an object (360 degrees , 36 transducer positions). For 10 parallel image planes, ultrasound compound images were generated of a flow-mimicking phantom consecutively supplied with water and contrast agent. These compound images were combined to form a volume dataset and postprocessed to obtain a sonographic subtraction angiography. RESULTS: Image quality was significantly improved by spatial compounding for the native (ie, without contrast agent), and, in particular, for the contrast-enhanced case. After subtracting the native images from the contrast-enhanced ones, only structures supplied with contrast agent remain. This technique yields much better results for compound images than for conventional ultrasound images because speckle noise and an anisotropic resolution affect the latter. CONCLUSIONS: With the presented approach contrast specific artifacts can be eliminated efficiently, and a subtraction angiography can be computed. A speckle reduced three-dimensional reconstruction of submillimeter vessel structures was achieved for the first time. In the future, this technique can be applied in vivo to image the vascularity of cancer in the female breast.     

Contrast-enhanced harmonic imaging for the diagnosis of vesicoureteral reflux in pediatric patients.

OBJECTIVE: Harmonic imaging using phase or pulse inversion technology is a new sonographic diagnostic modality that has the potential to produce images of a higher quality than can be obtained with the conventional method. The aim of this study was to compare both types of harmonic modalities--tissue and contrast harmonic imaging--with the fundamental imaging mode in contrast-enhanced B-mode sonographic diagnosis of vesicoureteral reflux. SUBJECTS AND METHODS: Fifty-four children presenting for diagnostic examination of vesicoureteral reflux underwent standard sonography of the urinary tract in the fundamental mode, followed by intravesical administration of a galactose-based contrast medium containing microbubbles. The contrast-enhanced sonography was conducted by scanning the bladder and each kidney in transverse and longitudinal planes, from ventral and dorsal views, consecutively in B-mode using fundamental, contrast harmonic, and tissue harmonic imaging modalities. Soft-touch buttons on the console screen were used to alternate between the three imaging options, so that switching from one modality to the other could be done almost instantaneously. For comparison, in each patient, we selected one set of contrast-enhanced images of the bladder and two sets, one ventral and one dorsal, of the kidney. In a series, the images were compared and ranked from 1 to 3, with 1 being the best, with regard to sonomorphology (demarcation of the retrovesical space and renal pelvis as the potential sites to look for vesicoureteral reflux) and reflux detection and conspicuity, if present. RESULTS: In all, 248 sets of images were available for comparison. The delineation of both the retrovesical space and the renal pelvis was found to be best with tissue harmonic imaging in 84% and 96% of the image sets, respectively (p < 0.01). Forty-one sets of images were compared from 27 kidney-ureter image units of 22 children (41%) with reflux. The refluxing microbubbles were much more conspicuous in the harmonic imaging mode (tissue harmonic, 100%; contrast harmonic, 93%) than in the fundamental mode (p < 0.01). In eight kidney-ureter units, the reflux was detected only by using the harmonic imaging modalities. CONCLUSION: Visualization of the urinary tract and detection of ultrasound contrast media is significantly improved by the use of the harmonic imaging modalities. When both fundamental and harmonic imaging options are available, we recommend harmonic imaging for contrast-enhanced sonographic diagnosis of vesicoureteral reflux.     

新型乳腺机X线摄影技术临床应用探讨

目的:探讨新型乳腺机X线摄影技术临床应用价值。方法:用新型乳腺机摄取乳腺X线照片,找出获得最佳影像质量的摄影方法。结果:所摄取乳腺片符合影像诊断要求。结论:选用新型乳腺机0.5mm铝滤线器可显著降低X线照射量(mAs),对图像仍保持较好的诊断质量。     

Classification of breast ultrasound images using fractal feature

Fractal analyses have been applied successfully for the image compression, texture analysis, and texture image segmentation. The fractal dimension could be used to quantify the texture information. In this study, the differences of gray value of neighboring pixels are used to estimate the fractal dimension of an ultrasound image of breast lesion by using the fractal Brownian motion. Furthermore, a computer-aided diagnosis (CAD) system based on the fractal analysis is proposed to classify the breast lesions into two classes: benign and malignant. To improve the classification performances, the ultrasound images are preprocessed by using morphology operations and histogram equalization. Finally, the k-means classification method is used to classify benign tumors from malignant ones. The US breast image databases include only histologically confirmed cases: 110 malignant and 140 benign tumors, which were recorded. All the digital images were obtained prior to biopsy using by an ATL HDI 3000 system. The receiver operator characteristic (ROC) area index AZ is 0.9218, which represents the diagnostic performance.     

Wideband harmonic imaging: a novel contrast ultrasound imaging technique

A novel ultrasonic imaging method, wideband harmonic imaging, for nonlinear imaging of microbubble contrast agents is evaluated. In wideband harmonic mode, two pulses of alternate phase are send out. The image is then processed from the sum of both pulses, resulting in an image of nonlinear scatterers such as microbubbles. A prototype ultrasound system, Siemens Elegra, was evaluated with in vitro investigations and animal trials, using conventional, harmonic and wideband harmonic settings with the galactose based ultrasound contrast agent Levovist. Wideband harmonic imaging offers superior sensitivity for ultrasound contrast agents compared to conventional imaging and harmonic imaging. At low transmit power settings (MI 0. 1-0.5) the nonlinear response is already sufficient to generate a image of the blood pool distribution of Levovist in the rabbit kidney including the microvasculature, with clear delineation of vessels and perfused parenchyma. At high transmit amplitudes, nonlinear tissue response reduced the apparent image contrast between contrast agent and tissue. The results suggest that wideband harmonic imaging is currently the most sensitive contrast imaging technique, maintaining highest spatial resolution. This may add to image quality and offer new clinical potential for the use of ultrasound contrast agents such as Levovist.     

Fat suppression with spectrally selective inversion vs. high spectral and spatial resolution MRI of breast lesions: qualitative and quantitative comparisons

PURPOSE: To compare conventional fat-suppressed MR images of the breast to images derived from high spectral and spatial resolution MR data. Image quality and the level of fat suppression are compared qualitatively and quantitatively. MATERIALS AND METHODS: Women with suspicious breast lesions found on X-ray mammography were imaged on 1.5 Tesla GE SIGNA scanners. High spectral and spatial resolution (HiSS) data were acquired using echo-planar spectroscopic imaging. Images with intensity proportional to the water signal peak height in each voxel were synthesized. Conventional fat-suppressed images were acquired using a frequency selective inversion method. The experimental (HiSS) and conventional images were compared by experienced radiologists to evaluate the quality of fat suppression. In addition, fat suppression and image quality were evaluated quantitatively. RESULTS: Fat suppression, tumor edge delineation, lesion conspicuity, and image texture were improved in the peak height images derived from HiSS data. CONCLUSION: The results demonstrate that the water peak height images obtained from HiSS data potentially could improve the quality of fat suppression, detection and diagnosis of breast cancer. HiSS allowed detection of lesions and evaluation of lesion morphology prior to contrast media injection. J. Magn. Reson. Imaging 2006. (c) 2006 Wiley-Liss, Inc.     

Research in digital mammography and tomosynthesis at the University of Toronto

There have been major advances in the field of breast cancer imaging since the early 1970s, both in technological improvements and in the use of the methods of medical physics and image analysis to optimize image quality. The introduction of digital mammography in 2000 provided a marked improvement in imaging of dense breasts. In addition, it became possible to produce tomographic and functional images on modified digital mammography systems. Digital imaging also greatly facilitated the extraction of quantitative information from images. My laboratory has been fortunate in being able to participate in some of these exciting developments. I will highlight some of the areas of our research interest which include modeling of the image formation process, development of high-resolution X-ray detectors for digital mammography and investigating new methods for analyzing image quality. I will also describe our more recent work on developing new applications of digital mammography including tomosynthesis, contrast-enhanced mammography, and measurement of breast density. Finally, I will point to a new area for our research—the application of the techniques of medical imaging to making pathology more quantitative to contribute to use of biomarkers for better characterizing breast cancer and directing therapeutic decisions.     

A Review of Vibro-acoustography and its Applications in Medicine

In recent years, several new techniques based on the radiation force of ultrasound have been developed. Vibro-acoustography is a speckle-free ultrasound based imaging modality that can visualize normal and abnormal soft tissue through mapping the acoustic response of the object to a harmonic radiation force induced by ultrasound. In vibro-acoustography, the ultrasound energy is converted from high ultrasound frequencies to a low acoustic frequency (acoustic emission) that is often two orders of magnitude smaller than the ultrasound frequency. The acoustic emission is normally detected by a hydrophone. In medical imaging, vibroacoustography has been tested on breast, prostate, arteries, liver, and thyroid. These studies have shown that vibro-acoustic data can be used for quantitative evaluation of elastic properties. This paper presents an overview of vibro-acoustography and its applications in the areas of biomedicine.     

Precision imaging—its impact on image quality and diagnostic confidence in breast ultrasound examinations

Objective:

To determine the effect of noise-reducing innovation—precision imaging (PI)—on image quality and diagnostic efficacy in breast ultrasound.

Methods:

The study, which assessed four levels of PI from zero to three, consisted of two parts: image quality assessment and diagnostic efficacy evaluation. For the first part, 247 sets of ultrasound images displayed at each PI level were evaluated by 6 experienced breast imaging observers, by rating image quality using visual grading analysis on a 1–4 scale. For the diagnostic efficacy part 51 breast lesions were displayed at each PI level and scored 1–6 to generate a receiver operating characteristic (ROC) curve. These images were evaluated by radiologists and sonographers. Analyses were performed using non-parametric Friedman and Wilcoxon signed rank tests and a multireader multicase methodology.

Results:

Statistically, higher scores of image quality were observed with increased levels of PI than with the zero setting (p < 0.001). The ROC analysis did not demonstrate any significant change in diagnostic efficacy, with mean scores for all observers being 0.79, 0.80, 0.81 and 0.81 for settings zero, one, two and three, respectively.

Conclusion:

This study suggested a perceived improvement in image quality with increasing levels of PI; however, no changes in diagnostic efficacy were noted. The importance of looking at the impact of new imaging technologies in a multifaceted way is emphasized.

Advances in knowledge:

To our knowledge, this is the first article investigating the impact of the PI algorithm on ultrasound image quality and breast lesion characterization.     

Sensitivity, resolution and image quality with a multi-head SPECT camera.

This investigation sought to determine which collimation factors were most important in providing superior image quality with a three-headed SPECT device. The relationship between sensitivity, resolution and SPECT image quality was studied. Two different sets of parallel-hole collimators were used. The ultrahigh-resolution collimators have higher spatial resolution (8.9 versus 11.0 mm), but only 55% of the sensitivity of the high-resolution collimators. A phantom with hot rods was imaged with both collimator sets. Observers compared images with the ultrahigh-resolution collimators to images of varying counts with the high-resolution collimators and determined which high-resolution images matched the ultrahigh-resolution images in image quality. Eleven patient studies were acquired with both collimator sets for equal time, and observers chose which image set they preferred. Transverse images of brain and liver studies were simulated with varying resolution and counts and subjectively compared. The phantom study indicated that the improvement in resolution led to image quality comparable to increasing the number of counts by a factor of 2.5 to 3.4. The clinical studies showed that the ultrahigh-resolution collimators were preferred in a large majority of the cases. These trends were also seen in the simulation study. These results confirm that higher resolution collimators should be used with multihead SPECT devices. The improvement in resolution more than compensates for the loss in sensitivity, leading to an overall improvement in image quality.     

Moderne Ultraschalldiagnostik der Beinvenenthrombose bei unklarer Genese der Lungenembolie

PURPOSE: We compared innovative ultrasound techniques such as tissue harmonic imaging (THI) and cross-beam technique with speckle reduction imaging (SRI) to conventional fundamental B scan in the diagnosis of deep vein thrombosis. MATERIAL AND METHODS: We investigated a total number of 185 patients with clinical symptoms of acute vein thrombosis. We documented the thrombosis in the patients using multifrequency ultrasound probes (5-7 MHz, 6-9 MHz, 9-14 MHz, Logig 9, GE) and recorded ultrasound sequences in fundamental B scan, THI, and cross-beam technique with SRI (grade 2). Three blinded ultrasound investigators ranked the marking of the thrombosis in each of these image modalities and graded them with the numbers 5 = weak, 4 = moderate, 3 = satisfactory, 2 = good, and 1 = excellent. We calculated the median and a t-test for each of these image modalities. RESULTS: We diagnosed 115 thromboses (62%) in 185 investigated patients. This group could be divided as follows: 11 patients (6%) with three-level thrombosis, 37 patients (20%) with two-level thrombosis, and 67 (36%) with one-level thrombosis. The one-level thrombosis group included five (3%) patients with muscle vein thromboses, seven (4%) cases of thrombophlebitis without involvement of the deep vein system, and three (2%) cases of thrombophlebitis with involvement of the deep vein system. The t-test for unconnected samples showed significant differences (p <0.05) in iliac veins and highly significant differences (p <0.001) in the veins of the lower extremity due to the superior capabilities for detection of thrombosis using the cross-beam technique with SRI compared to THI and the fundamental B scan. CONCLUSION: The use of high-resolution linear ultrasound probes with the concomitant application of THI and cross-beam technique with SRI facilitates the diagnosis of deep vein thrombosis. The employment of these new ultrasound modalities is an advantage in distinguishing the veins from the surrounding tissue structures and helps in evaluating the compressibility of venous vessels.     

Supine breast MRI

Purpose:

To achieve high‐quality unilateral supine breast magnetic resonance imaging (MRI) as a step to facilitate image aiding of clinical applications, which are often performed in the supine position. Contrast‐enhanced breast MRI is a powerful tool for the diagnosis of cancer. However, prone patient positioning typically used for breast MRI hinders its use for image aiding.

Materials and Methods:

A fixture and a flexible four‐element receive coil were designed for patient‐specific shaping and placement of the coil in close conformity to the supine breast. A 3D spoiled gradient sequence was modified to incorporate compensation of respiratory motion. The entire setup was tested in volunteer experiments and in a pilot patient study.

Results:

The flexible coil design and the motion compensation produced supine breast MR images of high diagnostic value. Variations in breast shape and in tissue morphology within the breast were observed between a supine and a diagnostic prone MRI of a patient.

Conclusion:

The presented supine breast MRI achieved an image quality comparable to diagnostic breast MRI. Since supine positioning is common in many clinical applications such as ultrasound‐guided breast biopsy or breast‐conserving surgery, the registration of the supine images will aid these applications. J. Magn. Reson. Imaging 2011;. © 2011 Wiley Periodicals, Inc.     

High-field,high-resolution,susceptibility-weighted magnetic resonance imaging: improved image quality by addition of contrast agent and higher field strength in patients with brain tumors

Introduction To demonstrate intratumoral susceptibility effects in malignant brain tumors and to assess visualization of susceptibility effects before and after administration of the paramagnetic contrast agent MultiHance (gadobenate dimeglumine; Bracco Imaging), an agent known to have high relaxivity, with respect to susceptibility effects, image quality, and reduction of scan time. Methods Included in the study were 19 patients with malignant brain tumors who underwent high-resolution, susceptibility-weighted (SW) MR imaging at 3 T before and after administration of contrast agent. In all patients, Multihance was administered intravenously as a bolus (0.1 mmol/kg body weight). MR images were individually evaluated by two radiologists with previous experience in the evaluation of pre- and postcontrast 3-T SW MR images with respect to susceptibility effects, image quality, and reduction of scan time. Results In the 19 patients 21 tumors were diagnosed, of which 18 demonstrated intralesional susceptibility effects both in pre- and postcontrast SW images, and 19 demonstrated contrast enhancement in both SW images and T1-weighted spin-echo MR images. Conspicuity of susceptibility effects and image quality were improved in postcontrast images compared with precontrast images and the scan time was also reduced due to decreased TE values from 9 min (precontrast) to 7 min (postcontrast). Conclusion The intravenous administration of MultiHance, an agent with high relaxivity, allowed a reduction of scan time from 9 min to 7 min while preserving excellent susceptibility effects and image quality in SW images obtained at 3 T. Contrast enhancement and intralesional susceptibility effects can be assessed in one sequence.     

彩色多普勒超声对小乳腺癌与乳腺增生的诊断价值研究

目的研究彩色多普勒超声对小乳腺癌与乳腺增生的诊断价值。方法收集我院经手术和病理活检确诊的乳腺增生与小乳腺癌患者各73例,比较分析其病灶形态的彩色多普勒超声二维声像图特征及血流信号图特征。对各指标率的变化进行统计分析。结果小乳腺癌和乳腺增生病灶形态的二维声像图特征及彩色血流图的比较,具有统计学意义（P〈0.05）。结论彩色多普勒超声检查可以根据病灶形态及血流信号的二维声像图特征对乳腺疾病进行有效的鉴别检查。     

Hepatic sonography: comparison of tissue harmonic and standard sonography techniques.

OBJECTIVE: This study was performed to compare tissue harmonic sonography of the liver with conventional sonography of the liver. SUBJECTS AND METHODS: Forty-eight patients underwent tissue harmonic and conventional sonography of the liver, using a randomized imaging sequence. Imaging parameters were standardized, but gain varied. Techniques were compared using predetermined impact analysis categories. If a finding was revealed by only one sonographic technique, additional confirmation was obtained by another imaging technique or by surgery. In a separate image quality analysis, masked images were reviewed by two experienced radiologists to evaluate fluid-solid differentiation, near-field, far-field, and overall image quality. Rankings were correlated with field of view of images and body habitus of patients as determined by body mass index. RESULTS: Tissue harmonic sonography provided the same information as conventional sonography in 34 patients (71%) and added information in 14 patients (29%). The findings from tissue harmonic sonography resulted in altered treatment in five patients (10%). Eight patients (17%) had lesions revealed by tissue harmonic sonography only. Four patients (8%) had inadequate far-field visualization by both techniques. Both observers ranked tissue harmonic sonography the same as or better than standard sonography in 46 patients (96%) for fluid-solid differentiation, in 46 patients (96%) for near-field image quality, and in 45 patients (94%) for overall image quality. For far-field image quality, one observer ranked tissue harmonic sonography the same as or better than conventional sonography in 40 patients (83%), and the second observer, in 41 patients (85%). Image quality ratings showed no correlation with body habitus of the patients or field of view of images. CONCLUSION: Tissue harmonic sonography of the liver provides more information and better image quality than does conventional sonography of the liver.     

Dose-image optimisation in digital radiology with a direct digital detector: an example applied to pelvic examinations

In diagnostic radiology increasing attention has been focused on dose reduction while maintaining a clinically good image quality. With the use of digital detectors balancing dose vs image quality is done differently than in film-screen radiography, since dose and image brightness are uncoupled in digital imaging. In this study a new direct digital detector (flat-panel detector) was used in a dose-image optimisation of a simulated pelvic examination. X-ray images were taken with a direct digital detector (DDD), of the pelvic of a phantom using varying tube current (varying stochastic noise). The entrance surface dose was measured for each image. These images were scored by two radiologists according to EU guidelines. A dose comparison was made with an older PCR system (storage phosphor plates). With decreasing tube current the noise in the images increased and the image with the lowest dose and still acceptable image quality was identified. The results showed that the entrance surface dose using the DDD decreased from 1.4 mGy (PCR value) to 0.48 mGy (DDD standard settings). Through the optimisation the dose could be further decreased to 0.24 mGy while still maintaining an acceptable image quality. A substantial dose reduction was obtained with this new direct digital detector. This simple but efficient optimisation approach is easily applicable to other examinations and both DDD and storage phosphor plate detectors.