A hybrid computerized fluoroscopy technique for noninvasive cardiovascular imaging.

The excellent linearity of digital image storage and retrieval permits hybrid analog-digital subtraction to extend the spatial resolution of two previously developed algorithms which employed entirely digital apparatus. A low resolution, time-integrated preinjection digital mask image is reconverted to analog form and subtracted from live analog video images of iodine administered by peripheral intravenous injection to produce a high resolution display of the cardiovascular system with contrast ten times greater than conventional fluoroscopy. Preliminary studies in dogs are compared with images obtained with our digital subtraction algorithms.     

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.     

64层螺旋CT脑动脉、混合脑动静脉和脑静脉血管成像─智能跟踪扫描减影技术

目的:探讨64层螺旋CT智能跟踪扫描减影技术在脑动脉、混合脑动静脉和脑静脉血管成像中的最佳启动扫描阈值和价值。方法:在我院行减影脑血管成像患者共105例,按启动扫描阈值大小分为三组,A组(90HU),共36例;B组(80HU),共34例;C组(70HU),共35例。对整个头部平扫、增强动脉早期和静脉早期扫描获得未减影数据,将动、静脉早期数据减去平扫数据获得减影动脉期、减影混合动静脉期数据,静脉早期数据减去动脉早期数据获得减影静脉期数据。采用VR、MIP重建减影血管图像。根据血管图像质量分为四级并分别记分。结果:(1)三组患者血管密度减影动脉期动脉较静脉显著高,减影混合动静脉期动脉和静脉均较高,减影静脉期静脉较动脉显著高。减影动脉期、减影混合动静脉期和减影静脉期血管密度组间比较相似,但减影动脉期C组动脉密度最低,减影混合动静脉期C组动脉密度最高、静脉密度最低,减影静脉期C组静脉密度最高。(2)减影图像与未减影图像相比去除了动脉、静脉相互的及颅骨的干扰,对脑动、静脉解剖结构显示清楚。①减影动脉期三组脑动脉图像质量均无0分,有诊断价值的病例均占100%,C组较A、B组图像质量稍好;②减影混合动静脉期三组混合脑动静脉图像质量均无0分,有诊断价值的病例均占100%,B、C组较A组图像质量好,B、C组图像质量相似;③减影静脉期A组脑静脉图像质量有诊断价值的病例占69.5%,B组脑静脉图像质量有诊断价值的病例占88.3%,C组脑静脉图像质量有诊断价值的病例占100%,C组图像质量明显好于A、B组。结论:64层螺旋CT智能跟踪扫描减影技术能分别显示脑动静脉、混合脑动静脉和脑静脉,以动脉期启动扫描阈值70HU图像质量最好,全部血管均有诊断价值,特别是对脑静脉的显示,值得临床推广应用。     

对比增强数字减影乳腺恶性肿瘤MR成像

目的 评估增强减影在乳腺恶性肿瘤MRI中的临床应用价值。资料与方法30例乳腺恶性肿瘤患者进行MR增强扫描，MR对比剂采用Gd．DTPA(0．1mmol／kg体重)，然后用T1WI增强后的图像与增强前的图像进行减影。所有病例都与手术或病理结果进行对照。结果 减影图像比增强后的图像显示更清晰、更直观。减影前不能清楚判断是否有增强和／或难以明确增强区域的大小；减影后，所有病灶均能作出明确的判断。结论 MR数字减影技术是一种简便易行而有效的图像后处理方法，而且省时、可靠和成像质量高。对T1wI高信号病灶的增强与否和增强区域大小的判断很有帮助。对用MRI诊断乳腺恶性肿瘤具有重要价值。     

SNR improvement for multiinjection time-resolved high-resolution CE-MRA of the peripheral vasculature.

Peripheral MR angiography (MRA) should ideally provide images over a large field of view with high spatial resolution and adequate temporal resolution to accommodate differences in regional filling times. Image subtraction is usually used to remove background signals. In examination protocols involving multiple injections at multiple sites, previously injected contrast present in the mask image provides a substantial decrease in the subtraction image signal. Bolus chase methods avoid this problem but provide limited time for acquisition of high-resolution images at each station. We present here a technique applied to peripheral angiography that provides high spatial and temporal resolution while maintaining high SNR in multiple injection examinations. Undersampled projection imaging was used to increase spatial resolution relative to a previously reported technique using a Cartesian acquisition technique. Late acquisition of high spatial frequencies and temporal matched-filtering were used to increase spatial resolution and SNR, respectively. Temporal correlation analysis was applied to permit multistation examinations without mask subtraction, thus providing an additional gain in SNR relative to multistation subtraction methods. Quantitative analysis is provided to evaluate the signal and noise behavior in the matched-filtering process due to multiinjection and mask subtraction.     

双能量减影数字X线摄影技术的应用

目的:用双能量减影数字X线摄影提高肺部小结节病变的检出率。方法:双能量减影摄影可以用两次曝光法和一次曝光法来完成。结果:双能量减影数字化胸部摄影技术作为胸部X线检查的一种辅助手段,它能有效的提高肺部小结节病变的检出率,并能增加鉴别诊断的依据。结论:直接数字化X线摄影(DR)的使用,使两次曝光法得以实行。由于两次曝光法能量差大,它产生的双能量减影图像上组织对比良好,图像信噪比高,比一次曝光法具有更明显的优势。     

Clinical application of hybrid subtraction digital angiography: Preliminary results

The clinical application of hybrid subtraction in digital fluoroscopy of the vasculature is reported in our first 30 patients studied. Hybrid subtraction combines the advantages of temporal and dual energy subtraction techniques to achieve simultaneous elimination of overlying bone, soft tissue, and motion induced artifacts. Hybrid subtraction improved the subjective appearance of an image in 19 of 30 (63%) studies but additional diagnostic information was only revealed in 11 of 30 (37%) patients. This study was supported in part by the General Electric Company Medical Systems Division and the National Heart, Lung, and Blood Institute (Contract #HV-02922)     

Registered image subtraction for CT-, MR- and coronary angiography

Conventional post-processing of digital subtraction angiography (DSA) by 3D spiral CT, 3D MRI and 2D DSA is often hampered by extended artefacts due to patient movements during examination. In this paper an image registration procedure prior to the digital subtraction is introduced allowing an enhanced visualization of the contrast agent. The object displacement is detected by analysis of image deformations in small local regions. The motion pattern is used to compute a new synthetic mask of maximum congruence with the contrast medium image. This new mask image is then used in the subsequent subtraction. The algorithm works fully automatically and does not need any interactive placement of landmarks. Results obtained from subtraction of uncorrected and corrected sequences were compared with each other. The registration procedure provided good results in the suppression of subtraction artefacts and in the enhancement of vascular structures. Results are presented from subtraction of 2D and 3D data from CTA, MR mammography and coronary angiography. Received 10 August 1995; Revision received 18 March 1996; Accepted 12 April 1996     

双能量减影骨组织图像在肋骨骨折诊断上的作用分析

目的:探讨双能量减影骨组织图像在肋骨骨折检查中的应用和诊断价值.方法:搜集171例临床怀疑肋骨骨折的病例,男97例,女74例,年龄7～89岁,平均41岁.运用美国GE公司生产的Revolution XR/d型数字X线成像设备(DR),采用双能量减影法摄正、斜位胸片.结果:在本组病例中,皱折状骨折在骨组织减影图像上的检出率达73.3%,高于常规DR图像的检出率60.0%,而裂隙状骨折及不全性骨折在骨组织减影图像上的检出率低于常规DR图像,完全性骨折在骨组织减影图像和常规DR图像上的检出率相同,骨组织减影图像与常规DR图像两者间总的检出率无显著性差异(P＞0.05);骨组织减影图像正位的检出率为24.1%,斜位的检出率为44.8%,常规DR图像正位的检出率为29.3%,斜位的检出率为48.3%.结论:双能量减影骨组织图像对不同形态骨折的显示程度不同,可提高细小肋骨骨折的检出.摄片体位影响骨折的检出,无论是骨组织减影图像还是常规DR图像斜位较正位更容易显示骨折.     

The influence of tube voltage,X-ray exposure rate and thickness of filter material on image quality with dual-energy subtraction imaging in chest diagnostics

Digital luminescent radiography enables dual-energy subtraction imaging, because this computed system allows susbtraction of imaging data and image post processing, as for example special windowing or edge enhancement. In a special cassette a copper filter is placed between two imaging plates for energy separation by a single X-ray exposure. Image post-processing with subtraction of imaging data permits the elimination of either skeleton or soft tissue structures. The influence of filter thickness, tube voltage and the X-ray exposure dosage on image quality is examined by the use of an anthropomorphic quality is examined by the use of an anthropomorphic phantom of the chest. According to our initial results dual energy subtraction imaging in one-shot-technique seems to be useful in the diagnostics of skeletal lesions and especially pulmonary nodules.     

癫痫发作期与发作间期脑血流灌注显像减影法定位致痫灶的价值

目的:研究癫痫发作期与发作间期脑血流灌注显像减影法定位致癫灶的价值.材料和方法:14例癫痫患者在癫痫发作期和发作间期分别进行脑血流灌注显像,两次所得图像进行空间匹配后相减得到减影像,并与EEG、MRI、手术结果及临床表现比较.结果:与发作间期相比,13/14例发作期局部脑血流有不同程度的增高,减影像可显示血流改变的具体部位及形态;1例发作期血流低于发作间期,但病灶区表现明显.手术后病灶病理诊断包括胶质细胞增生、疤痕组织及胶质细胞瘤.术后13例患者发作次数明显减少,1例效果不显著.结论:发作期与发作间期显像减影法定位致痫灶有较高的准确性,有助于术前制定合理的手术方案.     

Assessment of pulmonary perfusion in a single shot using SEEPAGE

PURPOSE: To present a single-shot perfusion imaging sequence that does not require contrast agents or a subtraction of a tag and a control image to create the perfusion-weighted contrast. The proposed method is based on SEEPAGE. MATERIALS AND METHODS: Experiments with healthy volunteers were performed to qualitatively and quantitatively obtain pulmonary perfusion values in coronal as well as sagittal orientation. In addition, a first experiment with a lung cancer patient was performed to explore the potentials of SEEPAGE in a clinical application. RESULTS: All experiments clearly showed a perfusion-weighted contrast, providing clinical quality images with high spatial resolution. The quantified perfusion rates were consistent in the different imaging orientations and covered the interval of 1.00-4.00 mL/min/mL. In addition, the gravitational dependence of pulmonary perfusion, the influence of adiabatic pulse duration on signal intensity, and the tracer saturation effect were examined. In the patient examination the presented technique provided additional information of the lung deficiency compared to a conventional anatomical image. CONCLUSION: SEEPAGE has proved to be a robust and reproducible technique for obtaining perfusion-weighted images in a single measurement and for quantifying pulmonary perfusion using an additional reference scan. Furthermore, the proposed method shows promise for future clinical application.     

Three-phase dynamic breast magnetic resonance imaging with two-way subtraction

OBJECTIVE: This study was undertaken to introduce a new breast magnetic resonance (MR) imaging technique, 3-phase dynamic MR imaging with 2-way subtraction, and to examine the morphologic and kinetic features of malignant and benign breast lesions using this technique. METHODS: In 99 breasts from 89 consecutive women with suspicious breast lesions (age range: 32-72 years, mean = 48.2 years), MR imaging was performed using a fat-saturated, sagittal, gradient-echo sequence in 3 phases (1 precontrast and 2 postcontrast scans). Two-way subtraction was performed: standard subtraction (early postcontrast minus precontrast scans) and reverse subtraction (early postcontrast minus late postcontrast scans). A radiologist interpreted all the images, described the breast lesions (using the Breast Imaging Reporting and Data System MR lexicon), and assessed the lesions prospectively as being benign or malignant. The lesions with at least 1 malignant feature were classified as malignant. The MR classifications were compared with the biopsy or follow-up results. RESULTS: Sixty-five (65.7%) breast lesions were malignant, and 34 (34.3%) were benign. Forty-two (97.7%) of the 43 cases of microinvasive or invasive ductal cancer showed malignant morphologic features, and 38 (88.4%) showed washout kinetics. Eighteen (81.8%) of the 22 cases of ductal carcinoma in situ showed malignant morphologic features, and 11 (50.0%) showed washout kinetics. Twenty-nine (85.3%) of the 34 benign lesions showed neither malignant morphologic features nor washout kinetics. The sensitivity and specificity were 92.3% and 91.2% by morphologic analysis and 93.8% and 85.3% by the combined method (morphology plus kinetic analysis), respectively. CONCLUSIONS: This study demonstrated that 3-phase dynamic breast MR imaging with 2-way subtraction and a maximum intensity projection (MIP) image is a simple and useful technique for identifying breast lesions. Although the addition of the kinetic criteria enhanced the sensitivity at the cost of specificity, radiologists can diagnose a malignant lesion showing non-mass-like enhancement more confidently using reverse subtraction imaging. Therefore, this study proposes 3-phase dynamic imaging with 2-way subtraction and an MIP image as one of the standard protocols of breast MR imaging.     

Contrast-enhanced magnetic resonance angiography in peripheral arterial disease: improving image quality by automated image registration

In peripheral arterial disease, contrast-enhanced MR angiography (MRA) is a noninvasive imaging alternative for catheter-based digital subtraction angiography (DSA). In DSA, final images are generated by subtracting a native mask image from subsequent contrast-enhanced images. Image quality is routinely improved by digitally shifting the mask image prior to subtraction if the patient has moved during angiography. This study investigated whether such image registration may also help to improve the image quality of MRA. In all, 545 MRA examinations of pelvic and leg arteries in patients with symptoms of peripheral arterial disease were studied retrospectively. Standard nonregistered MRA was compared to automatically linear, affine, and warp registered MRA by visual analysis and by three image quality parameters, including vessel detection probability (VDP) of angiographic maximum intensity projections. Most MRA of pelvic and upper leg arteries showed good nonregistered image quality. However, the 15% of lower legs with a body shift of 1 mm or more had relatively low nonregistered image quality, which improved significantly with image registration (VDP gain more than 18%, P < 0.05). The visual analysis gave similar results. In conclusion, image registration can improve image quality of MRA in peripheral arterial disease, especially in the lower legs.     

不完全投影医学图像的多目标向量优化重建算法

目的解决少数据投影图像重建中分辨率差、伪影严重等问题。方法提出了一种基于多目标决策的交叉熵向量优化图像重建算法。算法中折衷考虑了图像重建中最小交叉熵、范数极小化以及最大熵3个目标,并建立了一种新的动态权系数迭代法。应用该算法对模拟的有噪声投影数据和SIEMENS SOMATOM DR3的头部实际扫描数据分别进行了重建。结果文中算法较传统的重建算法．如卷积反投影法、代数重建法以及单目标优化算法,在误差、平滑性以及分辨率方面均有显著改善。结论本算法将对采用迭代法求解少数据投影重建问题产生一定的影响。     

64层螺旋CT分别脑动脉、脑动静脉和脑静脉成像—不同能量扫描比较研究

目的探讨64层螺旋CT同序列分别行脑动脉、脑动静脉、脑静脉的成像方法和最佳扫描能量（kV）。方法在我院行减影脑血管成像研究患者共220例,按扫描仟伏值大小随机分为三组,A组（120kV）,共59例;B组（100kV）,共85例;C组（80kV）,共76例。对整个头部平扫、动脉期和静脉期扫描（智能跟踪阈值70HU启动扫描）,将动、静脉期数据减去平扫数据获得减影动脉期、减影动静脉期数据,静脉期数据减去动脉期数据获得减影静脉期数据。采用容积再现（VR）、最大密度投影（MIP）重建减影血管图像。测量A、B、C组减影后血管密度和翼内肌SD噪声（客观噪声）,根据血管图像质量分为四级并分别记分。结果 1血管密度：A、B、C三组患者血管组内比较减影动脉期动脉较静脉密度显著高,差异有统计学意义（P〈0.05）,减影动静脉期动脉和静脉密度相似,差异无统计学意义（P〉0.05）,减影静脉期动脉较静脉密度显著低,差异有统计学意义（P〈0.05）。三组减影动脉期、减影动静脉期和减影静脉期血管密度组间比较随能量降低密度升高,差异有统计学意义（P〈0.05）;2图像质量：A、B、C三组减影脑动脉全部有诊断价值,组间两两比较差异有统计学意义（P〈0.05）;三组减影动静脉全部有诊断价值,Ⅰ级图像以C组减影脑动静脉图像质量最高,BC组间两两比较差异无统计学意义（P〉0.05）,AC和BC组间两两比较差异有统计学意义（P〈0.05）;三组减影脑静脉少数无诊断意义,Ⅰ级图像以B组最高,AC组间两两比较差异无统计学意义（P〉0.05）,AB和BC组间两两比较差异有统计学意义（P〈0.05）;3辐射剂量和噪声：三组辐射剂量随能量的降低而明显下降,三组噪声随能量的降低而明显增加（P〈0.05）。结论 64层螺旋CT同序列能分别脑动脉、脑动静脉和脑静脉成像,脑动脉、脑动静脉全部有诊断价值,仅     

Acute subarachnoid Haemorrhage: 3D time-of-flight MR angiography versus intra-arterial digital angiography

To evaluate the efficacy and reliability of 3D time-of-flight MR angiography (TOF MRA) as a noninvasive procedure, 27 patients with acute subarachnoid haemorrhage (SAH) were studied with MRA immediately before or after intra-arterial digital subtraction angiography (DSA). 3DTOF MRA was performed with an axial slab of 60 mm centred on the circle of Willis and isotropic voxels. DSA showed 22 aneurysms and 1 dural arteriovenous fistula in 21 patients; the aneurysms ranged in size from 2 to 8 mm. MRA failed to show 2 small aneurysms, at the origin of the posterior and anterior communicating arteries. The 3D display of the intracranial vessels obtained with maximum intensity projection (MIP) or targetted MIP sometimes rendered the aneurysms better than DSA. However, due to its high spatial resolution, DSA more clearly defined the overall anatomy of the walls of the normal and abnormal vessels.1992 Scientific Award of the ESNR     

Separating arterial and venous components from 3D dynamic contrast-enhanced MRI studies using factor analysis.

Dynamic contrast-enhanced MRI has been used extensively for angiography but in order to generate separate arterial and venous images some form of postprocessing is required. This typically involves the subtraction of one image in a dynamic sequence from another in order to suppress unwanted signal; however, this also has the effect of decreasing the signal-to-noise ratio (SNR) of the image. In this study, factor analysis, a technique related to eigenimage filtering, is used to separate arterial and venous components from dynamic contrast-enhanced images of the legs acquired with a temporal resolution of 30 sec. The SNR of the venous and arterial images extracted from a series of 20 patients using conventional single subtraction, a double subtraction method, and factor analysis were compared. Results show that the use of factor analysis improved the SNR in the venous images by a factor of 2.3 compared with the use of simple subtraction. A subjective comparison of the maximum intensity projection images generated from the venous images was also carried out and showed a significant preference for those generated using factor analysis over those generated using other subtraction methods.     

Adaptive subtraction as an aid in MR-guided placement of catheters and guidewires

PURPOSE: To demonstrate the utility of mask subtraction optimization in magnetic resonance (MR)-guided placement of catheters and guidewires. MATERIALS AND METHODS: MR-guided positioning of magnetically prepared catheters and guidewires was done by dynamically imaging a single thick slab at two frames per second. Selective visualization of the prepared parts of the devices was achieved by the use of a conventional baseline subtraction technique and by the use of an adaptive subtraction technique. In the latter, the best reference image is automatically selected from a fixed or a sliding subset of hitherto acquired dynamic images. The efficacy of both approaches was compared by tracking experiments in a flow phantom and in the aortoiliac arteries of a pig. RESULTS: Baseline subtraction produced adequate visualization of paramagnetic markers in the absence of subject motion and for fixed scan conditions. The sensitivity to subject motion and interactive modification of the scan parameters was greatly reduced by using adaptive subtraction. Adaptive subtraction images, other than conventional subtraction images, appeared to be insensitive to slow periodic motion, e.g., respiratory motion, and were only transiently affected by gross subject motion and interactive alterations of the scan parameters. CONCLUSION: Adaptive subtraction is superior to baseline subtraction for guiding the manipulation of catheters and guidewires in the presence of gross and periodic subject motion and whenever scan parameters are modified in the course of a procedure.     

Comparison of spatial resolution in high-resolution multislice computed tomography and digital subtraction angiography using renal specimens

OBJECTIVE: To compare maximum spatial resolution in multislice computed tomography (MS-CT) and digital subtraction angiography (DSA) using an arterial tree model for canine kidney specimens. METHODS: Twenty-three isolated fox terrier kidneys were catheterized with a 4F catheter and underwent contrast-enhanced MS-CT with a maximum spatial resolution of 0.23-mm isotropic voxel size in an early arterial phase. In addition, a digital subtraction angiogram was performed on all kidneys. The kidneys were segmented semiautomatically, and each parenchymal vessel that was identified in the kidney was marked. The maximum intensity projections of arterial vessels in the CT datasets were evaluated in a comparison with the DSA datasets. RESULTS: No significant difference in vessel delineation and count was found at any level up to the fourth level of intrarenal branching. CONCLUSION: MS-CT has the potential of replacing DSA in the diagnosis of intrarenal arteries.