Three Dimensional Images of the Sternum in Children with Using MDCT

PURPOSE: We wanted to analyze the three dimensional images with using multidetector CT scanning of the sternum in children, and we wanted to compare the CT findings with the children's age. MATERIALS AND METHODS: We studied the three dimensional images of the sternum of 67 children (62 were boys and 5 were girls). The age of the children was 3-15 years old (mean age: 7.5). We evaluated the number of sternal bodies, the presence of the xiphoid process and the bifid shape of each sternal body. RESULTS: The number of sternal bodies was from three to five; 30 patients had 3 bodies, 25 patients had 4 bodies and 5 patients had 2. The number of sternal bodies was 3.4 in Group I, 3.5 in Group II and 3.9 in Group III. As the children's age increased, the number of sternal body was statistically increased. When the number of sternal bodies was three, the mean age of children was 5.4 year; when it was four or five, the mean age of children was 8.1 year. The children's age was increased as the number of sternal bodies increased. The mean age of the children with a xiphoid process was 7.0 years, and the mean age of children without a xiphoid process was 8.1. There was no statistical difference between the two groups with or without xiphoid process. Among the 67 children, 9 had the bifid shape in the 3rd portion of the sternal body, 5 had the bifid shape in 4th portion, 2 had the bifid shape in 2nd portion and 1 had the bifid shape in 5th portion. CONCLUSION: The number of sternal bodies was mostly three or four. The number of sternal bodies was related to the children's age. There is no relationship between children's age and the presence of the xiphoid process. The bifid shapes are mostly shown in the 3rd and 4th portion of the sternal body.

Added Value of Coronal Reformations for Duty Radiologists and for Referring Physicians or Surgeons in the CT Diagnosis of Acute Appendicitis

OBJECTIVE: To assess the added value of coronal reformation for radiologists and for referring physicians or surgeons in the CT diagnosis of acute appendicitis. MATERIALS AND METHODS: Contrast-enhanced CT was performed using 16-detector-row scanners in 110 patients, 46 of whom had appendicitis. Transverse (5-mm thickness, 4-mm increment), coronal (5-mm thickness, 4-mm increment), and combined transverse and coronal sections were interpreted by four radiologists, two surgeons and two emergency physicians. The area under the receiver operating characteristic curve (Az value), sensitivity, specificity (McNemar test), diagnostic confidence and appendiceal visualization (Wilcoxon signed rank test) were compared. RESULTS: For radiologists, the additional coronal sections tended to increase the Az value (0.972 vs. 0.986, p = 0.076) and pooled sensitivity (92% [95% CI: 88, 96] vs. 96% [93, 99]), and enhanced appendiceal visualization in true-positive cases (p = 0.031). For non-radiologists, no such enhancement was observed, and the confidence for excluding acute appendicitis declined (p = 0.013). Coronal sections alone were inferior to transverse sections for diagnostic confidence as well as appendiceal visualization for each reader group studied (p < 0.05). CONCLUSION: The added value of coronal reformation is more apparent for radiologists compared to referring physicians or surgeons in the CT diagnosis of acute appendicitis.

Traumatic Thoracic Injury: The Role of Multidetector-row CT

The introduction of Multidetector-row CT (MDCT) has revolutionized the diagnostic strategy of multitrauma patients. The rapid acquisition of a large scanning volume with a thin slice collimation allows for motion-free images of high spatial resolution, and this enables the application of the multiplanar reformat (MPR) and 3D volume-rendering (VR) images. The MPR images more accurately demonstrate aortic rupture or dissection, diaphragmatic injuries and fracture of vertebrae, sternum and costal cartilages. Diagnosing vascular injuries can be aided by using the MIP images. Rib fracture, trachea and bronchial laceration are more easily detected by the 3D images, while airway and vascular injuries can be detected from performing virtual endoscopy. We introduce our current CT imaging protocol and we present our clinical experience with using MDCT in the assessment of patients with blunt thoracic trauma

Volumetric Measurements of Lung Nodules with Multi-Detector Row CT: Effect of Changes in Lung Volume

OBJECTIVE: To evaluate how changes in lung volume affect volumetric measurements of lung nodules using a multi-detector row CT. MATERIALS AND METHODS: Ten subjects with asthma or chronic bronchitis who had one or more lung nodules were included. For each subject, two sets of CT images were obtained at inspiration and at expiration. A total of 33 nodules (23 nodules > or = 3 mm) were identified and their volume measured using a semiautomatic volume measurement program. Differences between nodule volume on inspiration and expiration were compared using the paired t-test. Percent differences, between on inspiration and expiration, in nodule attenuation, total lung volume, whole lung attenuation, and regional lung attenuation, were computed and compared with percent difference in nodule volume determined by linear correlation analysis. RESULTS: The difference in nodule volume observed between inspiration and expiration was significant (p or = 3 mm. The volume of nodules was measured to be larger on expiration CT than on inspiration CT (28 out of 33 nodules; 19 out of 23 nodules > or = 3 mm). A statistically significant correlation was found between the percent difference of lung nodule volume and lung volume or regional lung attenuation (p or = 3 mm. CONCLUSION: Volumetric measurements of pulmonary nodules were significantly affected by changes in lung volume. The variability in this respiration-related measurement should be considered to determine whether growth has occurred in a lung nodule.

Usefulness of Three Dimensional Reconstructive Images for Thoracic Trauma Induced Fractures

PURPOSE: We wanted to evaluate the usefulness of three-dimensional reconstructive images using multidetector computed tomography (MDCT) for thoracic traumatic patients visiting emergency room. MATERIALS AND METHODS: 76 patients with fractures of the 105 patients who visited our emergency room with complaints of thoracic trauma were analyzed retrospectively. All the patients had thoracic MDCT performed and the three-dimensional reconstructive images were taken. The fractures were confirmed by axial CT, the clinical information, whole body bone scanning and the multiplanar reformation images. Plain x-ray images were analyzed by the fractured sites in a blind comparison of two radiologists' readings, and then that finding was compared with the axial CT scans and the three-dimensional reconstructive images. RESULTS: The fracture sites were rib (n=68), sternum (n=14), clavicle (n=6), scapula (n=3), spine (n=5) and combined fractures (n=14). Plain x-ray and axial CT scans had a correspondency of 0.555 for the rib fractures. Axial CT scans and the three-dimensional reconstructive images had a correspondency of .952. For sternal fractures, those values were 0.692 and 0.928, respectively. The axial CT scans and three-dimensional reconstructive images showed sensitivities of 94% and 91% for rib and other fractures, respectively, and 93% and 100% for sternal fracture, respectively. Three-dimensional reconstructive image had an especially high sensitivity for the diagnosis of sternal fracture. CONCLUSION: While evaluating thoracic trauma at the emergency room, the three-dimensional reconstructive image was useful to easily diagnose the extent of fracture and it was very sensitive for detecting sternal fracture.

Usefulness of Three Dimensional Reconstructive Images for Thoracic Trauma Induced Fractures

PURPOSE: We wanted to evaluate the usefulness of three-dimensional reconstructive images using multidetector computed tomography (MDCT) for thoracic traumatic patients visiting emergency room. MATERIALS AND METHODS: 76 patients with fractures of the 105 patients who visited our emergency room with complaints of thoracic trauma were analyzed retrospectively. All the patients had thoracic MDCT performed and the three-dimensional reconstructive images were taken. The fractures were confirmed by axial CT, the clinical information, whole body bone scanning and the multiplanar reformation images. Plain x-ray images were analyzed by the fractured sites in a blind comparison of two radiologists' readings, and then that finding was compared with the axial CT scans and the three-dimensional reconstructive images. RESULTS: The fracture sites were rib (n=68), sternum (n=14), clavicle (n=6), scapula (n=3), spine (n=5) and combined fractures (n=14). Plain x-ray and axial CT scans had a correspondency of 0.555 for the rib fractures. Axial CT scans and the three-dimensional reconstructive images had a correspondency of .952. For sternal fractures, those values were 0.692 and 0.928, respectively. The axial CT scans and three-dimensional reconstructive images showed sensitivities of 94% and 91% for rib and other fractures, respectively, and 93% and 100% for sternal fracture, respectively. Three-dimensional reconstructive image had an especially high sensitivity for the diagnosis of sternal fracture. CONCLUSION: While evaluating thoracic trauma at the emergency room, the three-dimensional reconstructive image was useful to easily diagnose the extent of fracture and it was very sensitive for detecting sternal fracture.

Diagnostic Importance of 3D CT Images in Klippel-Feil Syndrome with Multiple Skeletal Anomalies: A Case Report

We present here the case of a 12-year-old boy who had Klippel-Feil syndrome with renal, cardiac and multiple skeletal anomalies, and we show the relevent three-dimensional computed tomography images. Our patient had a triple renal pelvis, mitral valve prolapsus, multiple cervical vertebrae fusions, cervical ribs, hypoplasia of the right thumb, spina bifida of L5, lumbalization at the right side of S1 and a sacral curved defect. In this study, we discuss the atypical clinical features and the diagnostic value of three-dimensional CT for evaluating the skeletal anomalies of the Klippel-Feil syndrome cases.

Three Dimensional Volume Rendering Virtual Endoscopy of the Ossicles Using a Multi-Row Detector CT: Applications and Limitations

PURPOSE: This study was conducted to know the applications and limitations of three dimensional volume rendering virtual endoscopy of the ossicles using a multi-row detector CT. MATERIALS AND METHODS: This study examined 25 patients who underwent temporal bone CT using a 16-row detector CT as a result of hearing problems or trauma. The axial CT scan of the temporal bone was performed with a 0.6 mm collimation, and a reconstruction was carried out with a U70u Sharp of kernel value, a 1 mm thickness and 0.5-1.0 mm increments. After observing the ossicles in the axial and coronal images, virtual endoscopy was performed using a three dimensional volume rendering technique with a threshold value of -500 HU. The intra-operative otoendoscopy was performed in 12 ears, and was compared with the virtual endoscopy findings. RESULTS: Virtual endoscopy of the 29 ears without hearing problems demonstrated hypoplastic or an incomplete depiction of the stapes superstructures in 25 ears and a normal depiction in 4 ears. Virtual endoscopy of 21 ears with hearing problems demonstrated no ossicles in 1 ear, no malleus in 3 ears, a malleoincudal subluxation in 6 ears, a dysplastic incus in 5 ears, an incudostapedial subluxation in 9 ears, dysplastic stapes in 2 ears, a hypoplastic or incomplete depiction of the stapes in 16 ears and no stapes in 1 ear. In contrast to the intra-operative otoendoscopy, 8 out of 12 ears showed a hypoplastic or deformed stapes in the virtual endoscopy. CONCLUSION: Volume rendering virtual endoscopy using a multi-row detector CT is an excellent method for evaluation the ossicles in three dimension, even though the partial volume effect for the stapes superstructures needs to be considered.

Role of CT Venography in the Diagnosis and Treatment of Benign Thoracic Central Venous Obstruction

OBJECTIVE: To evaluate the role of CT venography in the diagnosis and treatment of benign thoracic central venous obstruction. MATERIALS AND METHODS: Eighteen patients who had undergone both CT venography and digital subtraction venography were prospectively enrolled in this study. The following features were analyzed by two observers: the cause, degree, and extent of venous obstruction; associated thrombosis; and implications for the planning of treatment. CT venography and digital subtraction venography were compared in defined venous segments, and the degree of obstruction, and correlation was expressed using Spearman's rank correlation coefficient. RESULTS: In all patients, CT venography depicted the causes of obstruction, including extrinsic compression of the left brachiocephalic vein, and mediastinal inflammatory pseudotumor. Interobserver agreement regarding classification of the degree of obstruction was judged as good for CT venography (k=0.864), and in evaluating this, there was significant correlation between CT venography and digital subtraction venography (reader 1: Rs = 0.58, p < 0.01; reader 2: Rs = 0.56, p < 0.01). In evaluating the status of central veins proximal to long segmental obstruction, and associated thrombosis, CT venography was superior to digital subtraction venography. In half of all patients, the findings of CT venography led to changes in the treatment plan. CONCLUSION: The findings of CT venography correlated closely with those of digital subtraction venography, and the former accurately depicted the degree and extent of benign venous obstruction.

Three Dimensional Digital Rotational Imaging in the Evaluation of the Fractures

PURPOSE: To evaluate the usefulness and the application of three dimensional digital rotational imaging (3D DRI) by the evaluation of fractures. MATERIALS AND METHODS: Sixteen patients with clinically diagnosed or suspicious fracture were involved in this study. The lesion or suspicious sites of all 16 cases were spines (n=7), pelvis (n=3) and so on (n=6; knee, elbow, ankle, wrist and foot). In all cases, conventional radiography, multiplanar 2D (slice thickness/pitch=3 or 5 mm/1:1)and volume rendering 3D reconstructed single detector helical CT (HiSpeed Advantage, GE Medical Systems, Milwaukee, WIS) scans and 3D DRI (Integris V-5000,Philips Medical Systems, The Netherlands) with multiplanar intersection and gray scaling as postprocessing technique were performed. 3D DRI was evaluated and compared with conventional radiography, multiplanar 2D CT and volume rendering 3D CT. RESULTS: 3D DRI provided more detail and additional information in 14 cases (88%), comparing with 2D and 3D CT scans. Two fractures were revealed only on 3D DRI other than conventional radiography and CT scans and one case was revealed on 2D CT and 3D DRI. In all cases, we could acquired more detail and additional information from 3D DRI than from 3D CT in the acquisition of 3D imaging. 3D DRI didn't change the classification of fracture in 12 of 13 cases (92%),which revealed the fracture on the conventional radiography or CT. CONCLUSION: 3D DRI can diagnose and evaluate the fracture rapidly and easily with anatomical and spatial resolution by acquisition of 3D imaging with postprocessing using DRI.

Measurement of Normal Size of Styloid Process with 3D Reconstruction CT

PURPOSE: To measure the normal size of the styloid process using 3D (three-dimensional) reconstruction CT. MATERIALS AND METHODS: We retrospectively analyzed 3D reconstruction images obtained after coronal and axial CT scanning of the temporal bone or neck of 115 patients. The length and shape of both sides of the styloid process, the location of its tip, and calcification of the stylohyoid ligament were retrospectively analysed. RESULTS: The mean length of the styloid process was 26.6 (+/-7.9)mm on the right side, and 26.4(+/-8.3)mm on the left, a statistically insignificant difference (p=0.694). Its mean length was 26.2 (+/-8.5)mm in men and 26.7 (+/-7.2)mm in women, a statically in significant difference (p=0.733). As for variation with age, mean length tended to increase until the third decade, but not beyond. Segmental type (104/230, 45.2%) and fragmental type (73/230, 31.7%) were more commonly seen in shape of styloid process, and tapering tip of styloid process (156/230, 67.9%) is more commonly seen than clubbing tip of it (74/230, 32.1%). The process was angulated in six cases (2.6%); its tip was more frequently located between the internal and external carotid artery (211 cases, 91.7%) than more medially (19 cases, 8.3%). In the former location, the length of the process was 26.2(+/- 7.2)mm, and in the latter, 37.0(+/-6.0)mm. The difference was statistically significant (p=0.000). Calcification had occurred in 33 cases (14.3%). CONCLUSION: The length of a normal styloid process was 18-32 mm. There were no statistically significant differences between its two sides, or between the sexes. Length tended to increase until the third decade, but not beyond. Predominantly the tip was located between the internal and external carotid artery, though the process was longer when its tip was located medially.

The Quality of Reconstructed 3D Images in Multidetector-Row Helical CT: Experimental Study Involving Scan Parameters

OBJECTIVE: To determine which multidetector-row helical CT scanning technique provides the best-quality reconstructed 3D images, and to assess differences in image quality according to the levels of the scanning parameters used. MATERIALS AND METHODS: Four objects with different surfaces and contours were scanned using multidetector-row helical CT at three detector-row collimations (1.25, 2.50, 5.00 mm), two pitches (3.0, 6.0), and three different degrees of overlap between the reconstructed slices (0%, 25%, 50%). Reconstructed 3D images of the resulting 72 sets of data were produced using volumetric rendering. The 72 images were graded on a scale from 1 (worst) to 5 (best) for each of four rating criteria, giving a mean score for each criterion and an overall mean score. Statistical analysis was used to assess differences in image quality according to scanning parameter levels. RESULTS: The mean score for each rating criterion, and the overall mean score, varied significantly according to the scanning parameter levels used. With regard to detector-row collimation and pitch, all levels of scanning parameters gave rise to significant differences, while in the degree of overlap of reconstructed slices, there were significant differences between overlap of 0% and of 50% in all levels of scanning parameters, and between overlap of 25% and of 50% in overall accuracy and overall mean score. Among the 18 scanning sequences, the highest score (4.94) was achieved with 1.25 mm detector-row collimation, 3.0 pitch, and 50% overlap between reconstructed slices. CONCLUSION: Comparison of the quality of reconstructed 3D images obtained using multidetector-row helical CT and various scanning techniques indicated that the 1.25 mm, 3.0, 50% scanning sequence was best. Quality improved as detector-row collimation decreased; as pitch was reduced from 6.0 to 3.0; and as overlap between reconstructed slices increased.

Assessment of Hepatic Arterial Variation Using Multidetector Helical CT-Angiography

PURPOSE: To evaluate the anatomy of the hepatic artery and normal variants using oblique thick-slab maximal intensity projection (MIP) 3-D CT angiography and multidetector helical CT technology. MATERIALS AND METHODS: In 70 patients, axial three-phase CT together with multidetector helical CT and a non-ionic contrast agent was used to evaluate liver disease. During the early arterial phase, the parameters were as follow: slice thickness, 2.5 mm; table speed, 15 mm/rotation, pitch, 6; contrast material, 4 ml/sec; total 120 ml. Using the MIP technique and an Advantage window voxtal 3.03 system (GE), the images obtained were reconstructed as 3D angiograms. In each case, the arterial anatomy and its variants were recorded. RESULTS: A typical anatomy was found in 53 cases (75.7 %). Common variants were a left hepatic artery arising from the left gastric artery(8 cases, 11.4 %) and a right hepatic artery arising from the superior mesenteric artery(3 cases, 4.3 %). Other variant cases were a right hepatic artery arising from the gastroduodenal artery(2 cases, 2.9%), a proper hepatic artery arising from the left gastric artery (1 case, 1.4%), a hepatomesenteric trunk (1 case), a hepatogastric / splenomesenteric trunk(1 case), and a celiomesenteric trunk (1 case). CONCLUSION: 3-D hepatic angiography using multidetector helical CT technology is non-invasive and as accurate as conventional angiography for the evaluation of hepatic arterial anatomy. It is thus considered that 3-D CT angiography is very helpful for the evaluation of hepatic arterial anatomy prior to liver surgery such as transplantation or the treatment of hepatocellular carcinoma.

Congenital Anomalies of Aortic Arch: CT Angiography

Aortic arch anomalies result from the failure of an embryonic vascular structure to persist and regress in the usual manner during formation of the aortic arch. The anomalous aortic arch may encircle and compress the trachea and esophagus as a form of a vascular ring. The diagnosis of aortic arch anomaly and the recognition of airway compression are important because they are conditions which complicate the natural and surgical course of related diseases. CT can demonstrate the nature of anatomic structures such as the trachea and esophagus not revealed by angiography, simultaneously disclosing the relationship of stenotic airways and offending mediastinal vessels. Volumetric data acquisition by means of spiral CT enables three dimensional reconstruction,which can provide easy global understanding of the complex anatomy and spatial relationship of airway and cardiovascular structures. Three dimensional imaging is very useful for the physician and surgeon who are not accustomed to mentally reconstructing axial images, and can facilitate surgical planning.

A study of Parameters in Spiral CT Volumetry Using Balloon Phantoms

PURPOSE: To evaluate the effects of threshold values, reconstruction interval, slice thickness and table speed on the spiral CT volumetry. MATERIALS AND METHODS: Two phantoms made of a balloon and diluted contrast media underwent spiral CT scanning with section thicknesses of 5, 7 and 10 mm and table speeds of 5, 8 and 10 mm with scans of 5 mm section thickness, 7, 10, and 14 mm with scans of 7 mm section thickness, and 10, 15, and 20 mm with scans of 10 mm section thickness. The volumetric values of phantom A and B were obtained at varying threshold values and a reconstruction interval of 5 and 10 mm for all scans. Volumes were also determined with the threshold value fixed and a reconstruction interval of 1, 5, 7 and 10 mm, respectively. Three-dimensional display and volumetric measurements were obtained using reconstructed images. The effects of threshold value, reconstruction interval, slice thickness and table speed on volumetry were analyzed. RESULTS: Volumetric values varied according to threshold values. Where a threshold value was low, value increased as pitch increased, but where a the threshold value was high, value decreased as pitch increased. With varying threshold values, measurement errors in hydrostatic volumetry were between 0.19 and 27.98%; at a fixed threshold value, measurement errors in CT volumetry were 1.6 to 9.0%. Volume decreased as reconstruc-tion interval increased. Where the table speed/ slice thickness ratio was constant, volume was constant though slice thickness differed. At fixed threshold values, variation in the reconstruction interval was statistically more significant than variation in slice thickness or table speed ( p<0.05, Kruskal-Wallis one-way ANOVA). CONCLUSION: Among serveral spiral scanning and image reconstruction parameters including threshold value, reconstruction interval, slice thickness, and table speed, threshold value most affected the result obtained. At fixed threshold values, the reconstruction interval usded had more effect on CT volumetry than other parameters.

Virtual Endoscopy Using Spiral CT in Patients with Carcinomas of the Hypopharynx and Larynx

PURPOSE: To compare the usefulness of virtual endoscopy using spiral CT with that of laryngoscopy in the detection and evaluation of laryngeal and pharyngeal carcinomas. MATERIALS AND METHODS: Twenty-four patients with pathologically proven laryngeal and pharyngeal carcinomas underwent laryngoscopy and virtual endoscopy using spiral CT. Eleven of the carcinomas were supraglottic, five were glottic, and eight were hypopharyngeal. Source images obtained by spiral CT were transmitted to an independent workstation and virtual endoscopic images were obtained using Navigator software. These were graded according to their quality (good, fair, bad), and were interpreted by two radiologists who were blinded to the conventional endoscopic findings. These latter were subsequently compared with the virtual endoscopic findings in terms of similarity to laryngoscopic examination and detectability of lesions. RESULTS: The overall image quality of virtual endoscopy was good in 16 cases (67%), fair in eight (33%), and bad in no case. Among the 11 supraglottic carcinomas, image quality was good in seven cases (64%), and fair in four (36%). In four of the five glottic carcinomas (80%) quality was good, and in one case (20%) it was fair, while among the eight hypopharyngeal carcinomas, quality was good in five cases (63%), and fair in three (37%). Overall, detection of the lesion was possible in 23 cases (96%). Due to the small size of the lesion, the CONCLUSION: Virtual endoscopy using spiral CT is a safe and noninvasive method, and also successfully detects laryngeal and pharygenal lesions, with good image quality. For the evaluation of laryngeal and hypopharyngeal carcinoma, its use may complement that of axial CT.

Evaluation of Tracheobronchial Diseases: Comparison of Different Imaging Techniques

OBJECTIVE: To compare the clinical utility of the different imaging techniques used for the evaluation of tracheobronchial diseases. MATERIALS AND METHODS: Forty-one patients with tracheobronchial diseases [tuberculosis (n = 18), bronchogenic carcinoma (n = 10), congenital abnormality (n = 3), post-operative stenosis (n = 2), and others (n = 8)] underwent chest radi-ography and spiral CT. Two sets of scan data were obtained: one from routine thick-section axial images and the other from thin-section axial images. Multiplanar reconstruction (MPR) and shaded surface display (SSD) images were obtained from thin-section data. Applying a 5-point scale, two observers compared chest radiography, routine CT, thin-section spiral CT, MPR and SSD imaging with regard to the detection, localization, extent, and characterization of a lesion, information on its relationship with adjacent structures, and overall information. RESULTS: SSD images were the most informative with regard to the detection (3.95 +/-0.31), localization (3.95 +/-0.22) and extent of a lesion (3.85 +/-0.42), and overall information (3.83 +/-0.44), while thin-section spiral CT scans provided most information regarding its relationship with adjacent structures (3.56 +/-0.50) and characterization of the lesion (3.51 +/-0.61). CONCLUSION: SSD images and thin-section spiral CT scans can provide valuable information for the evaluation of tracheobronchial disease.

The Usefulness of Virtual Cystoscopy with Spiral CT in Evaluating Bladder Tumor

PURPOSE: To compare the role and clinical usefulness of virtual and convetional cys-t o s c o py in patientswith known bladder tumors. MATERIALS AND METHODS: S eventeen patients with a known bladder tumor underwentvirtual and conventional cystoscopy. As a result of conventional cystoscopy and s u r g e r y, 32 tumors weredetected. Prior to examination, each patient lay supine on the CT table, and the urinary bladder was catheterized,drained of all urine, and inflated with air. Spiral CT of the pelvis was then performed. CT data were transferredto a separate workstation and three-dimensional and virtual cystoscopic images were reconstructed. The latter wereinterpreted by two radiologists, who recorded the number, size, morphology, and exact location of the massesobserve d. The results of virtual CT cystoscopy were correlated with conventional cystoscopic findings. RESULTS:Twenty - two (69%) of 32 bladder tumors detected during conventional cystoscopy were visualized by virtualcystoscopy. Four (36%) of 11 tumors measured 0.5 cm or less, 15 (83%) of 18 measured 0.5 -3 cm and all (100%) oftumors measured 3 cm or more. With regard to tumor morphology, six (86%) of seven sessile tumors and 16 (64%) of25 which were pedunculated were detected. The procedure was well tol-erated by all patients, and no complicationswere reported. CONCLUSION: Due to its intrinsic weakness, virtual cystoscopy cannot replace itscon-ventional counterpart, though by developing data scan and acquisition techniques and software, and on thebasis of clinical experience, the latter can be used in the future for the diagnosis and follow up ofbladder tumors.

Helical CT of a Tracheobronchial Phantom: Angle and Optimal Window Affecting Size Measurements of ThreeDimensional Images

PURPOSE: To determine the effect of angle variation, relative to scan plan and optimal window setting, on thesize of three dimensional spiral CT images of a tracheobronchial tree using a phantom. MATERIALS AND METHODS:Spiral CT[collimation(mm)/table speed(mm/sec): 3/3; reconstruction interval:1.5 mm] was performed on atracheobronchial phantom consisting of a box filled with saline solution containing air-filled 5cc syringesoriented at varying angles relative to the scan plan. The diameter of three dimensional images was measured ateach window(minimal threshold value; -1000 HU; maximaml threshold value: from -300 HU to -500 HU; 50 HU interval). RESULTS: The inner diamenter of syringes used for tracheobronchial phantom was 12.55 +/-3.19mm. At all windows,as the angle became more perpendicular, the diameter of three-dimensional images increased, and at all angles, asmaxinal HU increased, measured diameter also increased(p<0.0001). In particular, at a maximal value of -500HU,measured values were closest to control values at all angles. CONCLUSION: Diameter can be measured close tocontrol value from three dimensional spiral CT images at maximal HU of -500 window, regardless of angle.

Virtual Bronchoscopy: An Experimental Study on Parameters Affecting Apparent Sizes of Simulated EndobronchialLesions

PURPOSE: To evaluate the scanning parameters affecting the apparent sizes of endoluminal lesions of thetracheobronchial tree, as seen on virtual bronchoscopy(VB), and to determine the optimal CT parameters fordemonstrating the real sizes of endobronchial lesions. MATERIALS AND METHODS: Spherical beads of 8 mm - 10 mmdiameter were randomly placed in the airways of fixed pig lung. CT scans were obtained with collimation and pitchof 3 mm/1, 3 mm/1.5, and 5mm/1, respec-tively. Volumetric data were reconstructed with 1mm-, 1.5 mm-, and2mm-collimation for each parameter. VBs were reconstructed with shaded-surface technique and soft tissuealgorithm. A 10mm-sized bead in the trachea and two 8 mm-sized beads in the left main bronchus were selected andtheir longest diameters were measured on VB at varying thresholds from -800 to -2 00HU. RESULTS: When themeasured diameters of beads on VB were recorded as the percentage of real sizes, they were 1) 78.9 %, 77.5%, and73.7% at collimations and pitches of 3 mm/1, 3mm/1.5, and 5 mm/1, respectively; 2) 77.9 %, 76.9 %, and 75.1 % at 1mm, 1.5 mm and 2 mm reconstructions, respectively; 3) 86.2 % / 83.4% / 80.4% / 77.0% / 74.8% / 70.2% / 64.5% atisosurface thresholds of -8 0 0 /-7 0 0 /-6 0 0 /-5 0 0 /-4 0 0 /-3 0 0 /-200HU, re-spectively; 4) 85.6 %, 75.0 %,69.3% at 23 mm, 17 mm and 11mm luminal diameters of lesion location, respectively. CONCLUSION: Overall, thediameters of endobronchial lesions are underestimated on VB. As the isosurface threshold values, collimations,pitches and reconstruction interuals decrease in size, the measured diameters approach to real diameter of thebeads. Beads in peripheral airways appear smaller than those in proximal airways.