hard disc (540MB, SyQuest, Nomai, Iomega Jazz) for later re-rendering and analysis. 2 RESULTS. 2. 1 3DUS Images of Structures and Lesions Con-.
Journal of Tongji Medical University ffl: ~ fg ~ ~ ~ ~[ ( ~b 3~ I~ ) 20 (2): 159-162, 2000
159
Clinical Application of Surface Mode on Three-dimensional U! trasonography: A Preliminary Stud . XU Huixiong (/~g~lt), ZHANG Qingping (~K'~'~), ZHOU Yuqing (gl ~i~-), LE Guir0ng (,~..//~-), WANG Yuanfang ( ~ L - ~ ) Department of Ultrasound, Tongfi Hospital, Tongji Medical University, Wuhan 430030
Summary: To investigate the methodology and evaluate the clinical value of surface mode on three-dimensional ultrasonography (3DUS) in static anatomical structures, 62 patients with various diseases were studied. The equipment used here was Voluson 530D 3DUS imaging system and 3D volume transducer with frequency being 3.0--5. 0 MHz. The 3DUS rendering method was surface mode. The results showed that: 1) Surface mode of 3DUS could demonstrate clearly the anatomical characteristics of the region-of-interest (ROD and the inner wall of lesions or organs that contained fluid. The anatomic details, such as location, size, shape, and number of the ROI, could be visualized intuitively; 2) The outer anatomic features (e. g. contour, edge, configuration, etc. ) of some organs or lesions surrounded by fluid could be displayed clearly. It could be concluded thai surface mode on 3DUS could provide more diagnostic information than two-dimensional ultrasonography (2DUS) in some cases and could served as a beneficial supplement to 2DUS in clinical practice. Key words: three-dimensional ultrasonography; surface mode; volume transducer In recent years, more and more physicians and sonographers have accepted three-dimensional ultrasonography ( 3 D U S ) as a beneficial supplement to 2DUS and a developing trend of diagnostic ultrasound. Along with the rapid, development of related computer technology and image-processing technolog y , 3DUS is now widely applied in more and more clinical fields and remains as a state-of-art imaging technology, and three-dimensional reconstruction of ultrasound images has become a widespread option in clinical unitCt-ak 3DUS could provide more "spatial anatomical information than 2DUS, which compensate for some insufficiency of 2DUS. Integration of views obtained over a region of a patient with 3DUS may permit better visualization in some situations and allow for a more accurate diagnosis to be made. The newly developed 3DUS imaging system of Voluson 530D has greatly shortened the time spent in data acquiring and data processing to several seconds because the technologies of 3DUS volume transducer and the related were adapted, which makes great progress when compared to the previous 3DUS imaging system. Recently, our group conducted some clinical research work of surface mode on 3DUS by using this newly developed equipment, and the results were reported as follows. 1
M A T E R I A L S AND METHODS
1.1
Subjects A total of 62 cases including 46 men and 16 women with various diseases were involved in this study, who were 13 to 72 years old with a mean age of 37.4 years. Of the 62 patients, 20 cases were diagnosed as having ascite (including 10 secondary to liver cirrhosis, 4 secondary to congestive liver, 3 secondary to tuberculous peritonitis, 3 secondary to ovary t u m o r s ) , 5 having gallbladder stone, 8 having gallbladder polyp, 10 having different ocular diseases (5 retinal detachment, 3 vitreous organization, 2 XU Huixiong, male, born in 1972, Doctor in Charge
retinoblastoma ) , 9 pregnant women in secondtrimester, 4 having bladder t u m o r , 4 having hydrocele of tunica vaginalis and 2 having ulcerative carcinoma of stomach.
1.2
Equipment
T h e 3DUS imaging system of Voluson 530D (Kreztechnik-Medison, Zipf, Austria) was used in this study. The probe applied was 3D transabdominal annular volume transducer with a frequency range of 3. 5 - - 5 . 0 M H z , which consisted of an assembly of 2D and a small mechanical driven device. T h e volume transducer acquired a volume as a series of slices at slightly different orientations. After each slice, the transducer plane was moved by the driven device. As a result, the relative angle between slices was exactly k n o w n , eliminating distortion in the resultant scan.
1.3
Data Acquisition
Conventional 2DUS were performed as a routine to the organs and structures of interest. Various parameters (e. g. gain, T G C , power etc) were adjusted to optimize 2D images. The volume transducer was then placed on the body skin with no movement during the course of volume scanning. Volume of different size could be obtained according to the size of R O I , and the sample box angle and the volume angle could be selected to determine the size of the data volume. Following these steps, the 2DUS image of three orthogonal planes appeared instantaneously on the monitor of the main unit, and the 3DUS data volume was obtained. Five to ten seconds would be required for the whole course of data acquisition. 1.4 3D Rendering T h e 3DUS images could be rendered soon after the data acquisition. Firstly, select the surface rendering mode, then place the cursor on the R O I , and rotate around the X, Y , or Z axis to choose the optimal viewing direction. Secondly, adjust the size of the editing box (or viewing b o x ) so that the ROI could be included in the data volume, and the unwanted organs or structures could be eliminated. Thirdly, grey scale threshold was set to obtain the 3D images in desire. Also, the 3D images could be
160 displayed dynamically in order to observe them from different orientations and demonstrate the spatial an~,tomical relationship between different structures. 1, 5 Data Storing The volume data and the rendered 3D images were stored in digitized form on removable cartridge hard disc (540MB, SyQuest, Nomai, Iomega Jazz) for later re-rendering and analysis. 2
RESULTS
2. 1 3DUS Images of Structures and Lesions Containing Fluid Rendered by Surface Mode 3DUS surface mode could show the subtle anatomic characteristics of ROI and internal wall in lesions or structures containing fluid. The anatomic details of the ROI, such as location, size, shape, number, surface feature, and relationship to the wall, could be visualized well. The shape, size, location and number cot/ld be
]Fig. 1 The 3D image of gallstone 2. 2 3DUS Surface Images of Structures and Lesions Surrounded by Fluid The outer anatomic featores of the structures and lesions surrounded by fluid, such as contour, edge, shape, surface feature (smooth or n o t ) , and fibrin adhersion to the surface, could be obtained by surface mode. 3DUS could show the region of interest as a continuous structure, and the spatial relationship between ROI and adjacent anatomic structures could also be determined. In 10 cases of liver cirrhosis, surface mode depicted abnormal configuration, sharp edge and irregular surface of the overall liver, and also the small nodular changes diffused in the liver could be visualized projecting from the liver surface. Simultaneously, the thickened and floweredge-shape wall of the gallbladder could be displayed. The 3DUS images were apt to understanding and were intuitive when compared to 2DUS images (fig. 3, 4). In 4 cases of congestive liver, the plump configuration and blunt edge of the liver could be detected. In the cases of ascite, the intestine (fig. 5) as
Journal of Tongii Medical University 20 (2) .. 159-162, 2000 displayed clearly in 5 cases of gallbladder stone by using the surface mode (fig. 1). Besides the location, shape, number and size, the continuity between the base of mass and inner wall, as well as the range of the base, could be demonstrated in 8 cases of gallbladder polyp (fig. 2) and 4 cases of bladder tumor, which could provide helpful information for differentiating the benign lesions from the malignant ones. Vitreum was anaechoic in 2DUS images, the surface mode could show the stereo-shape of organization in the vitreum and its relationship to the ocular wall, which may be helpful to the differentiation of the in: tra-vitreum band-like diseases. The configuration, range and relationship to the peripheral anatomic structures could be depicted. When the stomach was filled with air-free water, surface mode could show the surface fheatures of the ulcerative lesions and gastric tumors. The characteristics of the internal wall of dilated bileduct and portal vein could also be visualized.
Fig. 2 The 3D image of gallbladder polyp
well as uterine and its appendages (fig. 6) floating in the ascite could be clearly seen. It was helpful to depict the anatomic surface feature (e. g. existence of nodular structure) of the intestine and pelvic organs. Adhesion between the intestines, as well as fibrin de position to the surface may be visualized, which could be helpful to the differentiation of the character of the ascite. In 4 cases of hydroeele of tunica vaginalis, the surface feature (nodular structures or not, fibrin deposit or not) could be clearly demonstrated (fig. 7). The face anatomic structures in 9 normal second-trimester fetuses could be obtained, which was helpful to diagnose the congenital anomaly of fetal face. Rendering of the fetal face provided an easily recognized view of the face to the physicians, facilitating understanding of possible anomalies such as cleft lip/palate. The stereo-shape of limb and genitalia could also be seen (fig. 8), which may assist the physicians to evaluate the anomalies such as hexadactyly, absence of a finger, skeletal dysplasis, hermaphroditism or mieropenis.
XU Huixiong et al. Surface Mode on Three-dimensional Ultrasonography
Fig. 3 Fig. 4
161
The 3D image of liver and gallbladder in liver cirrhosis. The sharp edge and irregular surface could be demonstrated, and small nodular changes could be seen projecting from the liver surface. The thickened wall of gallbladder could also be delineated The 3D image of liver cirrhosis accompanied by small hepatocellular carcinoma. The rough surface of the liver and the small hepatocellular carcinoma (arrow) could be described
Fig. 6
The 3D image of uterine and bilateral ovary cyst in ascite
Fig. 5
The 3D image of intestine in ascite
Fig. 7 Fig. 8
The 3D image of testis and epididy in the case of hydrocele of tunica vaginalis The 3D image of male genitalia of a futus in 28-week pregnancy
162
3
DISCUSSION
At present, there are several rendering modes based on 3DUS- multiplanar mode, transparent mode and surface mode ~vz. The 3DUS multiplanar mode without requiring reconstruction of the 3D images mainly obtained the echo information of coronal plane (C plane) parallel to the transducer surface that could not be obtained in 2DUS due to anatomical constraints. Also, three orthogonal tomographic images (coronal, saggital and axial plane) could be visualized simultaneously by multiplanar mode. The muttiplanar mode has been reported to have some special advantages over 2DUS in diagnosing the anomaly of uterine, differentiating the benign endometrial lesions from malignant ones. The 3D volume measurement was also based on the multiplanar mode. The work in this area has been done little inland, and some attention should be paid to it. The transparent mode could be divided into severaltypes (minimal mode, maximal mode, X ray mode and mixed m o d e ) , which were suitable for different diagnostic purposes. The clinical application value of it has been evaluated in our previous research ~3. In this article, the clinical value of the 3DUS surface mode was emphatically studied. As to the principle of the 3DUS surface mode, the surface mode only receives the nearest echo information to the transducer, so it was compatible to view the anatomic surface information of the ROI. When 3DUS surface mod~ was applied to rendering, there is a former condition that the ROI should be surrounded by fluid or contain fluid, thus enough echo contrast between ROI and surroundings could be obtained, and then the 3D surface rendering could be conducted. Through our preliminary clinical practice, we think some attention should be paid to the rendering method. Firstly, the grey scale contrast between ROI and the peripheral structures should be adjusted as high as possible before 3DUS volume scanning, thus makes it possible that the surface contour of the ROI be visualized cleai'ly. If some noise existed in front of the surface of ROI due to wrong adjusted gain or other reasons, the grey scale threshold setting can be applied to clear away the unwanted echo information. It was always found that the echo information scale of noise was often lower than that of the surface of ROI. Secondly, the quality of 2DUS images should be guaranteed before 3D volume scanning. The 3D volume transducer should be placed on the body skin with no movement when scanning, at the same time the breath of the patients should be held. Through these methods, the artifact due to the movement of organ and abdominal wall during
Journal of Tongji Medical University 20 (2) : 159-162, 2000 breathing could be prevented. Thirdly, adequate coupling gel should be applied to the subjects lest absence of images. Simultaneously, optimal 2D images should be obtained by adjusting the related parameters, and all possible artifacts should be eliminated. As we all know that the quality of 2DUS image is the foundation of 3DUS. Fourthly, the selection of viewing direction is also important to 3D rendering, which can be conducted by rotating the 3D data set. Because of the limitation of imaging principle and technology available today, optimal 3D images could not be obtained in some view orientation and will not be helpful to make correct diagnosisE8l; With regard to its clinical application, 3DUS surface mode has showed clinical implications in two aspects: ( 1 ) Surface mode could demonstrate the anatomic surface characteristics of ROI and inner wall of lesions or structures containing fluid. Morphologie features such as range, size, location, number, shape of ROI could be obtained; (2) Outer anatomic details of the structures surrounded by fluid could be attained. The contour, edge, configuration and other surface features could be visualized. The features of coherent structures could be demonstrated continuously. Some of these morphologic parameters (e. g. echo information of the coronal plane) could not be obtained by 2DUS, others that can be attained are not precise or intuitive enough in 2DUS. Therefore, 3DUS could provide more diagnostic information than 2DUS. It is of great significance for the physicians to evaluate the patient's overall situation .and make correct diagnosis. At the same time, the intuitive demonstration of the inner features of the lesions and the spatial relationship between the lesions and peripheral structures would facilitate the physicians to make a reasonable scheme of treatment. REFERENCES
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