Three-dimensional Volume-rendered Images Research Articles

Value of Multidetector‐row Computed Tomography in Diagnosis of Portal Vein Invasion by Perihilar Cholangiocarcinoma

Although knowledge of cancer invasion of the portal bifurcation is vitally important in planning an operation for perihilar cholangiocarcinoma, the diagnostic capability of multidetector-row computed tomography (MDCT) for this purpose has not been assessed. We evaluated how well MDCT could identify cancer invasion of the portal bifurcation by perihilar cholangiocarcinoma. Between April 2003 and June 2005, perihilar cholangiocarcinoma was resected in 87 patients, 83 of whom underwent MDCT within 1 month before the surgery. Three-dimensional volume-rendered (3DVR) and multiplanar reformation (MPR) images were examined for evidence of portal vein invasion. Agreement with intraoperative and pathologic findings was assessed. Portal bifurcation findings by 3DVR and MPR were classified into no portal vein stenosis, unilateral stenosis, or more extensive stenosis, and also into tumor contact with the bifurcation in no, one of two, or two projections. For macroscopic portal vein invasion, sensitivity, specificity, positive predictive value, negative predictive value, and overall accuracy were 81.5, 91.1, 81.5, 91.1, and 88.0% in 3D portography and 96.3, 92.6, 86.7, 98.1, and 94.0% in MPR, respectively. Findings by both 3DVR and MPR were significantly correlated with depth of cancer invasion (p < 0.001). MDCT is useful in assessing cancer invasion of the portal vein bifurcation by perihilar cholangiocarcinoma.

Retroaortic left renal vein: multidetector computed tomography angiography findings and its clinical importance

To evaluate the appearance, type, frequency, and clinical importance of retroaortic left renal vein (RLRV) in patients examined with multidetector computed tomography (MDCT) angiography. A total of 1856 patients who underwent CT with urological symptoms (hematuria, flank and abdominal pain, left gonadal vein varicocele) (n = 889) or with symptoms other than urological ones (n = 967) were prospectively evaluated for the presence of RLRV. CT was performed with 110 ml of iodinated contrast material through the antecubital vein at a rate of 3.5 ml/s. Late arterial and early venous phase volumetric data sets were acquired at 30 and 65 s, respectively, from the start of the intravenous injection of contrast medium. In addition to axial images, multiplanar reconstructions (MPR), maximum-intensity projection (MIP), and three-dimensional volume-rendering (3D VR) images were used to assess left renal vein anomalies. Left renal vein anomalies were classified into four types according to their appearance: I) RLRV joining the inferior vena cava (IVC) in the orthotopic position; II) RLRV joining the IVC at level L4-L5; III) circumaortic or collar left renal vein; IV) RLRV joining the left common iliac vein. RLRV was detected in 68 (3.6%) of the 1856 patients, with 26, 22, 17, and three of types I, II, III, and IV, respectively. Forty-four of the 68 patients with RLRV (65%) were in the group with urological symptoms, while 24 patients (35%) were in the group without urological symptoms. Compression of the RLRV was found in 16 patients in the urological symptoms group, while compression was detected in only three patients in the other group. This difference was statistically significant (P<0.05). The most common urological symptom was hematuria. The frequency of urological symptoms was higher in groups II and IV compared to the other groups. MDCT angiography with axial, MPR, MIP, and 3D VR images is effective in the detection of vascular renal anomalies such as RLRV. Diagnosing RLRV and differentiating it from other pathologic conditions causing hematuria is important in order to avoid complications during retroperitoneal surgery or interventional procedures.

Quantitative Analysis of a Three-Dimensional Computed Tomography Image Rendering Protocol for Skull Base Applications

Objective: Three-dimensional (3D) volume-rendering image protocols are being utilized at our institution in the development of virtual surgical simulators for improving surgical planning and predicting operative exposures in complex skull base surgery. Image reconstruction protocol validation is essential to verify the accuracy and precision needed for clinical applications. Methods: Three cadaver heads were examined using fine-cut CT. Archived data were transferred to a workstation and, using a 3D visualization and modeling system, high-resolution 3D-CT volumetric reconstructions of the skull base were generated using a specific voxel threshold protocol. Based on conventional craniometric and skull base anatomical landmarks (n = 20), linear anthropomorphic distances (n = 20) were measured on 3D-CT reconstructions. Subsequently, soft tissues were removed from the cadaver heads and linear measurements were repeated manually using digital calipers. All measurements were taken three times, independently, yielding 120 total measurements. Results: No statistically significant difference (p > 0.01) was found between 3D-CT reconstruction and physical cadaver measurements for 19 of 20 linear distances (95%). 3D-CT volumetric reconstructions overestimated one anthropomorphic measurement (glabella to left porion; p = 0.0095) repeatedly. Conclusions: 3D-CT volume-rendered images of the skull base generated using our voxel threshold protocol is both accurate and precise. Virtual 3D skull base models generated using this protocol represent true skull base anatomy. This study represents an essential first step toward the development of a validated and accurate 3D surgical approach assessment model and skull base surgical simulator currently under development at our institution.

Peroneal Tendon Subluxation and Dislocation: Detection on Volume-rendered Images—Initial Experience

Institutional review board approval was received and informed consent was not required for this Health Insurance Portability and Accountability Act-compliant study. The purpose of this study was to retrospectively assess the time efficiency of three-dimensional volume-rendered images obtained from multi-detector row computed tomographic data for the diagnosis of peroneal tendon subluxation or dislocation by using the consensus interpretation of multiplanar reformatted (MPR) images as the reference standard. The reference standard was provided by two musculoskeletal radiologists, and two less experienced readers evaluated 37 images in 32 patients (24 men, eight women; mean age, 41 years; age range, 18-75 years) with acute calcaneal fractures. An analysis of variance was used to compare interpretation time, and the Wilcoxon signed rank test was used to analyze diagnostic difficulty. The average time required for diagnosis was significantly shorter with volume-rendered images than with MPR images (reader 1: 42 vs 78 seconds, P<.001; reader 2: 50 vs 69 seconds, P<.01).

Detection of myocardial bridge and evaluation of its anatomical properties by coronary multislice spiral computed tomography

Background Myocardial bridge (MB) is a common anatomical condition, under which a part of the coronary artery running in the epicardial adipose tissue, is covered with myocardial tissue. It regulates atherosclerosis development and sometimes evokes coronary heart disease through haemodynamic alterations. We attempted to efficiently detect MB and evaluate the anatomical properties of MB by coronary multislice spiral computed tomography (MSCT). Methods Sixteen-row MSCT was conducted on 148 patients with coronary heart disease. MSCT images were reconstructed and reformed with transverse scans, curved planar reformat and three-dimensional volume-rendered images. The MB, over 1.0 mm in thickness, was identified by the presence of the “step-down and step-up” appearance. After “trial and error” essays, we could consistently examine the frequency of MB and evaluate the anatomical properties of MB, especially its thickness, together with coronary wall lesions. Results Twenty-three patients (15.8%) had MB over 1.0 mm in thickness: 21 MBs (87.5%) were located in the left anterior descending artery with a mean thickness and length of 1.8 ± 0.7 and 20.0 ± 8.6 mm. Moreover, although the tunneled segment beneath MB was always free of coronary wall lesions, 79.2% (19/24) of the segments proximal to MB demonstrated coronary wall lesions. Of special significance were three symptomatic MB patients without any atherosclerotic lesion throughout all the coronary arteries. Conclusion Coronary MSCT is a new imaging technique that provides a non-invasive diagnostic tool for MB and yields much better results of MB detection than previous imaging methods.

Role of 3D CT in the Evaluation of the Temporal Bone

In recent years, three-dimensional (3D) multiplanar reformatted images from conventional cross-sectional computed tomographic (CT) data have been increasingly used to better demonstrate the anatomy and pathologic conditions of various organ systems. Three-dimensional volume-rendered (VR) CT images can aid in understanding the temporal bone, a region of complex anatomy containing multiple small structures within a relatively compact area, which makes evaluation of this region difficult. These images can be rotated in space and dissected in any plane, allowing assessment of the morphologic features of individual structures, including the small ossicles of the middle ear and the intricate components of the inner ear. The use of submillimeter two-dimensional reconstruction from CT data in addition to 3D reformation allows depiction of microanatomic structures such as the osseous spiral lamina and hamulus. Furthermore, 3D VR CT images can be used to evaluate various conditions of the temporal bone, including congenital malformations, vascular anomalies, inflammatory or neoplastic conditions, and trauma. The additional information provided by 3D reformatted images allows a better understanding of temporal bone anatomy and improves the ability to evaluate related disease, thereby helping to optimize surgical planning.

Multichannel CT: Evaluating the Spine in Postoperative Patients with Orthopedic Hardware

Evaluating the spine in patients with metal orthopedic hardware is challenging. Although the effectiveness of conventional computed tomography (CT) can be limited by severe beam-hardening artifacts, the evolution of multichannel CT in recent years has made available new techniques that can help minimize these artifacts. Multichannel CT allows faster scanning times, resulting in reduced motion artifacts; thinner sections, with which it is possible to create a scanned volume of isotropic voxels with equivalent image resolution in all planes; and the generation of a higher x-ray tube current, which may result in better penetration of metal hardware and reduction of artifacts. Although 140 kVp and high milliamperage-second exposure are recommended for imaging patients with hardware, caution should always be exercised, particularly in children, young adults, and patients undergoing multiple examinations. The acquisition of multiplanar reformatted images in the axial, sagittal, coronal, and oblique planes and of three-dimensional volume-rendered images optimizes image interpretation. Wide window settings are best for reviewing images when hardware is present. The integrity of hardware is best assessed with multiplanar average intensity projection. Soft-tissue structures are best visualized by interactively varying the window width and level settings. Implementation of these techniques can yield diagnostic-quality images and aid in patient treatment.

Image-guided microneurosurgical management of vascular lesions using navigated computed tomography angiography. an advanced IGS technology application

Image-guided neurosurgery has become a standard practice in the last few years, with more than 2000 surgical navigation stations installed worldwide. In the same time several reports have also demonstrated the efficacy and accuracy of computed tomography angiography (CTA) in assessing cerebral vascular pathologies. Therefore, the CTA data have recently been implemented into the different navigation systems available on the market, making this new technique widely applied. The objective of this paper is to discuss and evaluate the clinical usefulness of navigated CTA in planning and performing surgery of neurovascular lesions. Raw images acquired from an helical CTA are automatically post-processed on an independent workstation by using a three-dimensional (3D) volume-rendering images engine and/or using thresholding and drawing tools. The data obtained provide useful information in the preoperative stage by reconstructing the vascular tree with regard to lesion volume, aneurysm neck, dome projection, perforating vessels and their relationship with the lesion and the surrounding anatomy. Furthermore, it can help in the identification of an arteriovenous malformation (AVM) nidus and recognition of its feeding and draining vessels. This fascinating technique can give some invaluable advantages on the management of cerebral vascular lesions and provides excellent information not always available on traditional digital subtraction angiography investigation. It has also proved to be very accurate, particularly regarding the correlation between the 3D volume-rendered CT angiography and the intraoperative findings.

CT-Koronarangiographie bei Patienten mit Vorhofflimmern

Reliable visualization of the coronary arteries with multislice spiral CT angiography (MSCTA) in patients with atrial fibrillation (AF) remains a challenge despite retrospective ECG gating. A recently developed new algorithm automatically compensates dynamic changes in the heart rate during the scan, thus reducing misregistration and motion artifacts. The HeartBeat-RT algorithm combines a fixed-percent delay determined from the first R wave and the fixed offset delay based on the second R wave in the ECG cycle. The purpose of this study was to find out the optimal reconstruction window in MSCTA in patients with AF for each of the three major coronary arteries during the cardiac cycle. 20 patients with permanent AF were imaged on a 16-slice scanner (slice collimation: 16 x 0.75 mm; rotation time 0.42 s; 140 kV; 380 mAs; 120 ml Ultravist 370 (R) i.v.). The patients had not received any previous drugs for heart frequency regulation. Acquisition was started after bolus tracking of a biphasic bolus of 120 ml Ultravist 370 injected intravenously. Each coronary segment was reconstructed at 0 % - 90 % of the cardiac cycle in increments of 10 %. For image analysis we used coronary segments as defined by the American Heart Association. Two blinded independent readers assessed the image quality in terms of visibility and artifacts (five-point rating scale 1 = very poor, 2 = poor, 3 = fair, 4 = good and 5 = excellent) and the degree of stenosis (five-point rating scale 1 = 0 %, 2 = 1 % - 49 %, 3 = 50 % - 74 %, 4 = 75 % - 99 %, 5 = 100 %) on axial slices, multiplanar reconstructions and three-dimensional volume-rendered images. The heart rate during examination ranged between 42 and 156 beats per minute, the average heart rate was 78 +/- 23. Each of the two readers evaluated 300 segments in 20 patients. Visualization of all coronary artery segments was superior at 40 % (mean score of the image quality 2.79) as compared to the standard diastolic reconstruction window at 80 % (image quality 2.33). The second best image quality (2.57) was acquired at 0 % of the cardiac cycle. The use of a frequency adapted delay algorithm with the choice of an end-systolic reconstruction window provided diagnostically valuable images in patients with AF.

Dehiscence of the superior and/or posterior semicircular canal: delineation on T2-weighted axial three-dimensional turbo spin-echo images, maximum intensity projections and volume-rendered images

The purpose of this study was to compare the ability of T2-weighted three-dimensional turbo spin-echo (TSE) images, maximum intensity projections and three-dimensional volume-rendered images for delineation of semicircular canal dehiscence. In 26 patients with dehiscence of the superior and/or posterior semicircular canal and 26 control patients, TSE images were obtained with two different resolutions and maximum intensity projection (MIP) and 3D volume-rendered images reconstructed. All images were evaluated by two radiologists in consensus regarding the visualization of anatomical structures and dehiscence of the semicircular canals. Computed tomography was used to confirm or exclude dehiscence. Dehiscence of the semicircular canals was delineated on axial MR images and on 3D volume-rendered images, but not on MIP images. The number of false positive cases was reduced from 3 to 0 with an increase in matrix, rendering results similar to those obtained with CT. Dehiscence of the semicircular canals can be assessed on high resolution MR images. Volume-rendered 3D images allow for immediate perception of the location of defects in semicircular canal dehiscence. These images may facilitate understanding of the extent and location of the defects.

Constrictive pericarditis with persistent left superior vena cava flow into right atria through coronary sinus demonstrated by multislice computed tomography

A 28-year-old male with history of childhood tuberculosis and protein-losing enteropathies with ascites and edema in lower extremities presented with abnormal chest X-ray showing calcification around the heart. To evaluate the heart and the pericardium, enhanced multislice CT (Light Speed Ultra 16, General Electric, Milwaukee, WI) was performed after injection of contrast with a 1.25-mm slice thickness, (helical pitch 6.00) with retrospective ECGgated reconstruction. Data were transferred to a workstation (Virtual Place Office Azemoto, Tokyo). Axial source image showed multiple spots indicating severe calcifications around the whole heart (arrowheads Fig. 1a). Three-dimensional volume-rendered images revealed an enlarged right ventricle (RV) surrounded by localized severe calcification (arrowheads Fig. 1b,c).

Cochlear implantation in a child with severe cochlear hypoplasia

The child was identified as having bilateral profound hearing loss at the age of 2 years. He had bilateral hearing aids and continued aural habilitation until the age of 9 years 6 months, but his speech-perception skills didn’t improve. Preoperative pure-tone audiogram revealed hearing thresholds of 104 dB HL in his right ear and 110 dB HL in his left ear. Preoperative computed tomography (CT) and magnetic resonance imaging (MRI) with the three-dimensional volume-rendering image of the inner ear revealed bilateral severe cochlear hypoplasia with rudimentary cochlear bud (Figure 1). Promontory stimulation test (PST) revealed auditory perception bilaterally. Promontory stimulation electrical auditory brainstem response (PS-EABR) demonstrated auditory response to electrical stimulation with the right ear response better than the left. He underwent right-side cochlear implantation (Nucleus CI24R ST) at the age of 9 years 6 months. Cochleostomy was tried by drilling on the cochlear bud, but the cochlear lumen was not identified. Therefore 12 electrodes were inserted into the vestibule through the oval window niche after stapedectomy. No surgical complications occurred postoperatively. 210 Cochlear Implants International, 5(Supplement 1), 2004 ©Whurr Publishers Ltd

Volume Visualization of the Cervical Spine: Principles, Techniques, and Clinical Applications

Multidetector computed tomography (CT) offers important advantages over conventional imaging modalities in the evaluation of the cervical spine. It allows for faster scanning times by a factor of 4 to 16 over conventional CT scanning, which is critical for triaging patients after trauma. Faster scanning times help to eliminate motion artifacts, and the newest multidetector scanners allow for thinner collimation and the ability to achieve an isotropic data set that can be reformatted in any plane without loss of spatial resolution. In addition, three-dimensional volume-rendered reconstructions of images obtained using multidetector scanners can provide additional information in defining the extent of injury or neoplasm, allowing neurosurgeons to see fractures or tumors in any plane, simulating intraoperative views. Three-dimensional volume-rendered images also can significantly reduce streak artifact and beam-hardening artifact that can occur with two-dimensional images in the presence of metal surgical hardware. Three-dimensional volume-rendered multidetector CT represents an advance in CT technology and can help to ensure rapid, accurate evaluation of cervical spine pathology. In this article, the authors demonstrate the utility of three-dimensional volume-rendered images in evaluating cervical spine trauma, neoplasm, and postoperative conditions, with the majority of images presented being obtained with multidetector CT scanners.

Multislice spiral computed tomography in diagnosis and staging of pancreatic carcinoma: preliminary experience

Background. Computed tomography has become the modality of choice for preoperative evaluation of patients with suspected pancreatic carcinoma, although some limitations are well known. Aims. To evaluate use of multislice spiral computed tomography in preoperative assessment of patients with suspected pancreatic carcinoma using volume-rendering as image reconstruction algorithm. Patients. A total of 27 patients with suspected pancreatic carcinoma underwent multislice spiral computed tomography examination. Methods. All studies were performed on a multislice computed tomography scanner with the following parameters: slice collimation, 1 mm; slice thickness, 1.25 mm; reconstruction interval, 1 mm; scan time, 22–25 sec; mAs, 165. Scans were acquired with a biphasic technique with a 30-sec (pancreatic phase) and a 70-sec (portal venous phase) delay time after start of contrast material injection. Diagnostic confirmation was obtained with surgical exploration, percutaneous biopsy, or with a combination of follow-up imaging studies. Results. Multislice spiral computed tomography yielded correct diagnosis of pancreatic carcinoma in 20 cases (sensitivity, 95%; specificity, 100%). Positive predictive values for resectability and unresectability were 80% and 93.3%, respectively. Three-dimensional volume-rendered images improved diagnostic confidence in the depiction of major vascular structures. Two cases of anomalous origin of hepatic artery were also identified with volume-rendered images. Conclusions. Multislice technology improves accuracy of spiral computed tomography for diagnosis and staging of pancreatic carcinoma.