Increasing spiral CT benefits with postprocessing applications

Linea alba 3D morphometric variability by CT scan exploration

PURPOSE

The width of the Linea alba, which is often gauged by inter-rectus distance, is a key risk factor for incisional hernia and recurrence. Previous studies provided limited descriptions with no consideration for width, location variability, or curvature. We aimed to offer a comprehensive 3D anatomical analysis of the Linea alba, emphasizing its variations across diverse demographics.

METHODS

Using open source software, 2D sagittal plane and 3D reconstructions were performed on 117 patients' CT scans. Linea alba length, curvature assessed by the sagitta (the longest perpendicular segment between xipho-pubic line and the Linea alba), and continuous width along the height were measured.

RESULTS

The Linea alba had a rhombus shape, with a maximum width at the umbilicus of 4.4 ± 1.9 cm and a larger width above the umbilicus than below. Its length was 37.5 ± 3.6 cm, which increased with body mass index (BMI) (p < 0.001), and was shorter in women (p < 0.001). The sagitta was 2.6 ± 2.2 cm, three times higher in the obese group (p < 0.001), majorated with age (p = 0.009), but was independent of gender (p = 0.212). Linea alba width increased with both age and BMI (p < 0.001-p = 0.002), being notably wider in women halfway between the umbilicus and pubis (p = 0.007).

CONCLUSION

This study provides an exhaustive 3D description of Linea alba's anatomical variability, presenting new considerations for curvature. This method provides a patient-specific anatomy description of the Linea alba. Further studies are needed to determine whether 3D reconstruction correlates with pathologies, such as hernias and diastasis recti.

Comparison of single coronal thick-slab minimum intensity projection with flexible bronchoscopy for airway compression in children with lymphobronchial tuberculosis

AIM

To generate standardised coronal minimum intensity projection (MinIP) computed tomography (CT) reconstructions, and compare these with flexible bronchoscopy in children with lymphobronchial tuberculosis (LBTB).

MATERIALS AND METHODS

Standardised coronal MinIP reconstructions were performed from CT images in children with LBTB and the findings of three readers were compared with the reference standard, flexible bronchoscopy (FB), regarding airway narrowing. Intraluminal lesions, the site of the stenosis, and the degree of stenosis were also evaluated. The length of stenosis was evaluated by CT MinIP only.

RESULTS

Sixty-five children (38 males; 58.5% and 27 females; 41.5%), with ages ranging from 2.5 to 144 months were evaluated. Coronal CT MinIP demonstrated a sensitivity of 96% and specificity of 89% against FB. The most common site of stenosis was the bronchus intermedius (91%), followed by the left main bronchus (85%), the right upper lobe bronchus RUL (66%), and the trachea (60%).

CONCLUSION

Coronal CT MinIP reconstruction is useful in demonstrating airway stenosis in children with lymphobronchial TB, with high sensitivity and specificity. CT MinIP had additional advantages over FB in that it allowed objective measurement of the diameter of stenosis, measurement of the length of stenosis, and evaluation of post-stenotic segments of the airways and lung parenchymal abnormalities.

Nextmed: Automatic Imaging Segmentation, 3D Reconstruction, and 3D Model Visualization Platform Using Augmented and Virtual Reality

The visualization of medical images with advanced techniques, such as augmented reality and virtual reality, represent a breakthrough for medical professionals. In contrast to more traditional visualization tools lacking 3D capabilities, these systems use the three available dimensions. To visualize medical images in 3D, the anatomical areas of interest must be segmented. Currently, manual segmentation, which is the most commonly used technique, and semi-automatic approaches can be time consuming because a doctor is required, making segmentation for each individual case unfeasible. Using new technologies, such as computer vision and artificial intelligence for segmentation algorithms and augmented and virtual reality for visualization techniques implementation, we designed a complete platform to solve this problem and allow medical professionals to work more frequently with anatomical 3D models obtained from medical imaging. As a result, the Nextmed project, due to the different implemented software applications, permits the importation of digital imaging and communication on medicine (dicom) images on a secure cloud platform and the automatic segmentation of certain anatomical structures with new algorithms that improve upon the current research results. A 3D mesh of the segmented structure is then automatically generated that can be printed in 3D or visualized using both augmented and virtual reality, with the designed software systems. The Nextmed project is unique, as it covers the whole process from uploading dicom images to automatic segmentation, 3D reconstruction, 3D visualization, and manipulation using augmented and virtual reality. There are many researches about application of augmented and virtual reality for medical image 3D visualization; however, they are not automated platforms. Although some other anatomical structures can be studied, we focused on one case: a lung study. Analyzing the application of the platform to more than 1000 dicom images and studying the results with medical specialists, we concluded that the installation of this system in hospitals would provide a considerable improvement as a tool for medical image visualization.

Airway Evaluation with Multidetector Computed Tomography Post-Processing Methods in Asthmatic Patients

Asthma is a chronic inflammatory obstructive airways disease. The disease occurs regardless of age and manifests with cough, attacks of breathlessness, and tightness in the chest. The pathophysiology of asthma is complex and still not fully understood. It is essential to find answers concerning the role of each part of the bronchial tree in asthma, especially the role of small bronchioles. With the development of newer generations of multidetector computed tomography (MDCT) and advanced post-processing methods it is possible to obtain more detailed images and gain insight into further aspects of asthma. MDCT post-processing methods can be divided into two-dimensional (2D) and three-dimensional (3D). In 2D projections, visualized hypodense regions correspond to the airway flow limitations. With the more advanced methods, such as multi planar reconstructions (MPR), images in different planes (axial, coronal, or sagittal) can be created. In the MPR technique only the voxels which are adjacent to each other in the predetermined plane can be extracted from the data set. Using the minimal/maximal intensity projections and shaded surface display, the volume of interest (VOI) can be extracted. High resolution CT scans can be used to create a more advanced imaging tool - the virtual bronchoscopy (VB). Using the VB makes it possible to visualize regions of obturation in the bronchi of up to the 5-8th generation. The MDCT with advanced post-processing methods is likely to assume an important role in the differential diagnosis of asthma, particularly when the diagnosis is dubious or hard to settle due to accompanying other lung diseases.

CT of facial fracture fixation: an experimental study of artefact reducing methods

OBJECTIVES

This study aimed to determine the optimal post-operative CT imaging method that enables best visualization of facial bony structures in the vicinity of osteosynthesis material.

METHODS

Conducted at Töölö Hospital (Helsinki, Finland), this study relied on scanning a phantom with CBCT, 64-slice CT and high-definition multislice CT with dual-energy scan (providing monochromatic images of 70-, 100-, 120- and 140-keV energy levels) and iterative reconstruction (IR) methods. Two radiologists assessed the image quality, and the assessments were analyzed. In addition, a physicist performed a semi-quantitative analysis of the metal-induced artefacts.

RESULTS

The three subjects most easily assessed were the loose screw and both the bone structure and the fracture further away from the screw and the plate. Soft tissues adjacent to the screw and the plate remained more difficult for assessment. Both image interpreters agreed that the artefacts disturbed their assessments under dual energy. Metal artefacts disturbed the least under multislice CT with IR [adaptive statistical iterative reconstruction (ASiR) and VEO]. Neither interpreter found metal suppression helpful in CBCT.

CONCLUSIONS

CBCT with or without a metal artefact reduction algorithm was not optimal for post-operative facial imaging compared with multislice CT with IR. Multislice CT with ASiR filtering offered good image quality performance with fast image volume reconstruction, representing the current sweet spot in post-operative maxillofacial imaging.

Three-Dimensional Printing: Basic Principles and Applications in Medicine and Radiology

The advent of three-dimensional printing (3DP) technology has enabled the creation of a tangible and complex 3D object that goes beyond a simple 3D-shaded visualization on a flat monitor. Since the early 2000s, 3DP machines have been used only in hard tissue applications. Recently developed multi-materials for 3DP have been used extensively for a variety of medical applications, such as personalized surgical planning and guidance, customized implants, biomedical research, and preclinical education. In this review article, we discuss the 3D reconstruction process, touching on medical imaging, and various 3DP systems applicable to medicine. In addition, the 3DP medical applications using multi-materials are introduced, as well as our recent results.

Implementation of hybrid image fusion technique for feature enhancement in medical diagnosis

Image fusion is used to enhance the quality of images by combining two images of same scene obtained from different techniques. In medical diagnosis by combining the images obtained by Computed Tomography (CT) scan and Magnetic Resonance Imaging (MRI) we get more information and additional data from fused image. This paper presents a hybrid technique using curvelet and wavelet transform used in medical diagnosis. In this technique the image is segmented into bands using wavelet transform, the segmented image is then fused into sub bands using curvelet transform which breaks the bands into overlapping tiles and efficiently converting the curves in images using straight lines. These tiles are integrated together using inverse wavelet transform to produce a highly informative fused image. Wavelet based fusion extracts spatial details from high resolution bands but its limitation lies in the fusion of curved shapes. Therefore for better information and higher resolution on curved shapes we are blending wavelet transform with curvelet transform as we know that curvelet transform deals effectively with curves areas, corners and profiles. These two fusion techniques are extracted and then fused implementing hybrid image fusion algorithm, findings shows that fused image has minimum errors and present better quality results. The peak signal to noise ratio value for the hybrid method was higher in comparison to that of wavelet and curvelet transform fused images. Also we get improved statistics results in terms of Entropy, Peak signal to noise ratio, correlation coefficient, mutual information and edge association. This shows that the quality of fused image was better in case of hybrid method.

The morphology of medial malleolus and its clinical relevance

OBJECTIVE

To provide morphological data of medial malleolus to decrease the possibility of posterior tibial tendon injury and inadvertent ankle penetration.

METHODS

Computed tomography scans of the ankle in 215 patients were reviewed. Then parameters in the 3-D reconstruction images were measured by three independent, qualified observers on two separate occasions.

RESULTS

The average angle between tibia plafond and the articular facet of the medial malleolus was 55.88±4.11°. The distance from the most anterior point of the anterior colliculus to the center of the intercollicular groove was 11.68±1.13 mm. And the average angle between the bimalleolar axis and the articular facet of the medial malleolus was 76.61±2.04°. Significant differences were observed in the distance from the most anterior point of the anterior colliculus to the center of the intercollicular groove between males and females. (P<0.05) All of the parameters exhibited moderate to excellent intra-class correlation coefficient (ICC).

CONCLUSIONS

According to this study, the insertion angle is much smaller than previously believed, and adequate space only exists for two 4.0-mm screws in some large cases. The second screw will probably be near the posterior tibial tendon, especially in some small cases.

Radio-guided sentinel lymph node identification by lymphoscintigraphy fused with an anatomical vector profile: clinical applications

OBJECTIVE

To develop a method to fuse lymphoscintigraphic images with an adaptable anatomical vector profile and to evaluate its role in the clinical practice.

METHODS

We used Adobe Illustrator CS6 to create different vector profiles, we fused those profiles, using Adobe Photoshop CS6, with lymphoscintigraphic images of the patient. We processed 197 lymphoscintigraphies performed in patients with cutaneous melanomas, breast cancer or delayed lymph drainage.

RESULTS

Our models can be adapted to every patient attitude or position and contain different levels of anatomical details ranging from external body profiles to the internal anatomical structures like bones, muscles, vessels, and lymph nodes. If needed, more new anatomical details can be added and embedded in the profile without redrawing them, saving a lot of time. Details can also be easily hidden, allowing the physician to view only relevant information and structures. Fusion times are about 85 s. The diagnostic confidence of the observers increased significantly. The validation process showed a slight shift (mean 4.9 mm).

CONCLUSIONS

We have created a new, practical, inexpensive digital technique based on commercial software for fusing lymphoscintigraphic images with built-in anatomical reference profiles. It is easily reproducible and does not alter the original scintigraphic image. Our method allows a more meaningful interpretation of lymphoscintigraphies, an easier recognition of the anatomical site and better lymph node dissection planning.

Technical developments in postprocessing of paediatric airway imaging

CT postprocessing allows more scan information to be viewed at one time allowing an accurate diagnosis to be made more efficiently, and is particularly important in paediatric practice where invasive clinical diagnostic tools can be replaced or at least assisted by modern postprocessing techniques. Four visualization techniques in clinical use are described in this paper including the advantages and disadvantages of each: multiplanar reformation, maximum and minimum intensity projections, shaded surface display and volume rendering. Volume-rendered internal visualization in the form of virtual endoscopy is also discussed. In addition, the clinical usefulness in paediatric practice of demonstrating airway compression and its causes are discussed. Advanced postprocessing techniques that must still find their way from the biomedical research environment into clinical use are introduced with specific reference to computer-aided diagnosis.

Technical considerations for lower limb multidetector computed tomographic angiography

Multidetector computed tomography (MDCT) enables imaging of the entire arterial tree non-invasively. Optimal technical considerations for performing MDCT angiography (MDCTA) are essential for accurate diagnosis and atherosclerotic disease stratification. This review article focuses on the various technical aspects necessary for peripheral computed tomographic angiography (CTA) acquisition. Common clinical indications for peripheral MDCTA and the latest scan protocols are described. The essential issue of radiation dose reduction is discussed, along with methods of optimal contrast bolus detection and delivery. Post-processing techniques are also presented. Previously, digital subtraction angiography was the only established reliable imaging technique to quantify atherosclerotic disease load; however, MDCTA may now challenge this old gold standard, along with other non-invasive techniques such as magnetic resonance angiography (MRA).

Assessment of pancreatic tumor resectability with multidetector computed tomography: semiautomated console-generated images versus dedicated workstation-generated images

RATIONALE AND OBJECTIVES

The purpose of this retrospective study was to compare the maximum intensity projection (MIP) images generated at a multidetector computed tomography (MDCT) scanner console using advanced tools at a three-dimensional (3D) workstation for assessment of pancreatic tumor resectability.

MATERIALS AND METHODS

Institutional review board approval and informed consent wavier were obtained for this retrospective study. The intraoperative findings were used as reference standard. Two radiologists assessed console MIPs that were created using computed tomographic (CT) data sets of 30 patients (17 men and 13 women; age range, 35-79 years; mean age, 58 years) operated for pancreatic tumors. Semi-automated MIP images were created on a separate MDCT console. Two blinded radiologist (R1, R2) and surgeons (S1, S2) evaluated the image data independently for vascular involvement and tumor resectability. The image quality and diagnostic confidence for MIPs were graded on a 5-point scale (1 = poor, 2 = suboptimal, 3 = intermediate, 4 = good; 5 = excellent) and comparison was made with 3D workstation image scores.

RESULTS

The findings revealed greater than 90% sensitivity, specificity, and accuracy for detecting involvement of peripancreatic vessels by pancreatic tumor with an excellent interobserver agreement (kappa = 0.87-1.00). The findings of console-generated MIPs were same as the findings of 3D workstation images. The mean of image quality and diagnostic confidence grading for console MIPs by assessors were 4.4 and 4.2, respectively. The average time to generate simple MIPs at the console was 3.4 minutes (range, 2.3-4.4) compared to 26 minutes (range, 18-33) to create images at the 3D workstation.

CONCLUSION

Semi-automated MIPs generated from an MDCT scanner console is an excellent alternative to 3D workstation images for assessing resectability of pancreatic tumor based on vascular involvement. Console MIPs can be quickly generated during the time of scan and thus can improve CT workflow.

Semiautomated MIP Images Created Directly on 16-Section Multidetector CT Console for Evaluation of Living Renal Donors

Institutional Review Board approval was obtained and informed consent was waived for this HIPAA-compliant study. The aim of this study was to retrospectively compare the accuracy of semiautomated maximum intensity projection (MIP) images created at a 16-section multidetector CT console with three-dimensional (3D)-workstation-generated images for the definition of renal donor anatomy, with intraoperative findings as a reference standard. In examining 40 renal donors (21 men and 19 women; age range, 24-56 years; mean age, 40.4 years), the sensitivity and accuracy for mapping donor anatomy by two readers were greater than 95%, interobserver agreement was excellent (kappa = 0.89-1.00). The 95% confidence interval for sensitivity was also calculated. Simple MIPs compared well with 3D-workstation images. MIPs from a predesigned protocol on the scanner console were generated more quickly than similar images from 3D workstations; postprocessing demands (eg, for renal donors) can be quickly fulfilled at the scanner console itself. The average time to generate simple MIPs at the console was 3.4 minutes (range, 1.7-4.4 minutes), and 22.3 minutes (range, 15-30 minutes) to create images at the 3D workstation.

Primary Interpretation of Thoracic MDCT Images Using Coronal Reformations

OBJECTIVE

The objective of this study was to evaluate the accuracy and efficiency of primary interpretation of thoracic MDCT using coronal reformations as compared with transverse images.

SUBJECTS AND METHODS

Fifty patients (18 females, 32 males; age range, 15-93 years; mean age, 63.6 years) underwent 4-MDCT of the chest (detector width, 1 mm; beam pitch, 1.5). Contrast material was administered in 20 of the 50 patients. Coronal and transverse sections were reformatted into 5-mm-thick sections at 3.5-mm intervals. All available image and clinical data consensually reviewed by two thoracic radiologists served as the reference standard. Subsequently, three other thoracic radiologists independently evaluated reformatted coronal and transverse images at two separate review sessions. Each image set was assessed in 58 categories for abnormalities of the lungs, mediastinum, pleura, chest wall, diaphragm, abdomen, and skeleton. Interpretation times and number of images assessed were recorded. Sensitivity, specificity, and interobserver concordance were calculated. Differences in mean sensitivities and specificities were evaluated with Wilcoxon's signed rank test.

RESULTS

The most common findings identified were pulmonary nodules (n = 73, transverse images; n = 72, coronal images) and emphysema (n = 45, transverse; n = 40, coronal). The mean detection sensitivity of all lesions was significantly (p = 0.001) lower on coronal (44% +/- 26% [SD]) than on transverse (51% +/- 22%) images, whereas the mean detection specificity was significantly (p = 0.005) higher (96% +/- 5% vs 95% +/- 6%, respectively). Reporting findings for significantly (p < 0.001) fewer coronal images (mean, 63.0 +/- 4.6 images) than transverse images (mean, 91.9 +/- 8.8 images) took significantly (p = 0.025) longer (mean, 263 +/- 56 sec vs 238 +/- 45 sec, respectively).

CONCLUSION

Primary interpretation of thoracic MDCT is less sensitive and more time-consuming using 5-mm-thick coronal reformations as compared with transverse images.

OsiriX: an open-source software for navigating in multidimensional DICOM images

A multidimensional image navigation and display software was designed for display and interpretation of large sets of multidimensional and multimodality images such as combined PET-CT studies. The software is developed in Objective-C on a Macintosh platform under the MacOS X operating system using the GNUstep development environment. It also benefits from the extremely fast and optimized 3D graphic capabilities of the OpenGL graphic standard widely used for computer games optimized for taking advantage of any hardware graphic accelerator boards available. In the design of the software special attention was given to adapt the user interface to the specific and complex tasks of navigating through large sets of image data. An interactive jog-wheel device widely used in the video and movie industry was implemented to allow users to navigate in the different dimensions of an image set much faster than with a traditional mouse or on-screen cursors and sliders. The program can easily be adapted for very specific tasks that require a limited number of functions, by adding and removing tools from the program's toolbar and avoiding an overwhelming number of unnecessary tools and functions. The processing and image rendering tools of the software are based on the open-source libraries ITK and VTK. This ensures that all new developments in image processing that could emerge from other academic institutions using these libraries can be directly ported to the OsiriX program. OsiriX is provided free of charge under the GNU open-source licensing agreement at http://homepage.mac.com/rossetantoine/osirix.

CT Angiography for Evaluation of Living Renal Donors: Comparison of Four Reconstruction Methods

OBJECTIVE

We sought to compare various reconstruction methods for CT angiographic images in evaluating living renal donors.

MATERIALS AND METHODS

In 76 patients who underwent donor nephrectomy, vascular phase CT data were obtained using an MDCT scanner (detector array, 1.25 mm x 4; beam pitch, 1.5). Two radiologists independently reconstructed CT angiographic images using thick-slab volume rendering, thick-slab maximum intensity projection (MIP), sliding thin-slab volume rendering, and sliding thin-slab MIP. The radiologists counted the number of renal arteries, early branching arteries, and renal veins. We compared the accuracy rates for the detection of vessels achieved with the four types of reconstructed images, using the surgical findings as the gold standard. Agreement between the two observers and between the surgical and CT angiographic findings was evaluated.

RESULTS

The sensitivity for detecting the supernumerary artery was significantly greater with sliding thin-slab volume rendering and sliding thin-slab MIP (97%) than with thick-slab volume rendering (59%) (p = 0.039). No significant difference between the other comparison pairs of reconstruction methods was found. The interobserver agreement for detecting supernumerary and early branching arteries with sliding thin-slab volume rendering and MIP was excellent (kappa = 0.820-0.859) and good for renal veins (kappa = 0.698-0.724), whereas the agreement of thick-slab volume rendering and MIP was good for arteries (kappa = 0.706-0.791) and moderate for veins (kappa = 0.443-0.579). The agreement between CT angiographic reconstructed images and surgical findings for detection of vessels was better with sliding thin-slab volume rendering and MIP (kappa = 0.793-1.000) than in thick-slab volume rendering and MIP (kappa = 0.306-0.613).

CONCLUSION

For CT angiographic evaluation of living renal donors, sliding thin-slab reconstruction is superior to thick-slab reconstruction.

Multidetector CT angiography of arterial inflow and runoff in the lower extremities: a challenge in data acquisition and evaluation

PURPOSE

To show the feasibility of acquiring homogenous 3-dimensional datasets with high temporal and spatial resolution from computed tomographic angiographic (CTA) scans of the lower extremities and to assess automated vessel-tracking techniques for vascular evaluation.

METHODS

Eighteen men (mean age 67.0 years, range 43-83) with aneurysmal or occlusive vascular diseases underwent contrast-enhanced CTA of the lower limb arteries utilizing a 16-row CT imager. Curved multiplanar reformations were generated by manual selection of vessel centerlines in the infrarenal aorta and the arterial vasculature in the pelvis, thigh, and calf based on volume-rendering techniques. For each vessel, opacification and depiction were quantitatively evaluated. The manually segmented images were compared to datasets processed with automated vessel-tracking strategies by 5 radiologists, who evaluated diagnostic reliability and image quality. A Differential Receiver Operating Characteristic (DROC) analysis was performed.

RESULTS

An increase in the temporal and spatial resolution led to acquisition of high quality CTA datasets. Significant homogeneity of the vascular contrast-to-noise ratios was achieved in the pelvic (coefficient of variance 1.5% to 10.1%), thigh (0.1% to 9.4%), and calf (3.3% to 19.2%) vessels. The assessment of vascular delineation revealed full-width-at-half-maximum contrast values of 96.4%, 95.5%, and 111.3% in the pelvis, thigh, and calf, respectively. Observers were not able to distinguish between manual and automated vascular segmentation, as represented by a 0.56 value for the area under the DROC curve.

CONCLUSIONS

High-resolution CTA lower extremity datasets were acquired successfully, presenting vascular signal intensities of high homogeneity suitable for automated vessel-tracking techniques. Automated 3D visualization tools produced reliable, reproducible, and time-efficient centerline extractions that were comparable to manually defined centerlines.

Effects of ECG Gating and Postprocessing Techniques on 3D MDCT of the Bronchial Tree

OBJECTIVE

Our goal was to determine the impact of ECG gating and different postprocessing techniques on 3D imaging of the bronchial tree. SUBJECTS AND METHODS. Retrospective ECG-gated MDCT and non-ECG-gated MDCT of the chest were performed in 25 patients. ECG-gated MDCT data were reconstructed mid diastole using a fixed interval of -400 msec in 25 patients and then additionally at -200, -300, and -500 msec in 10 of those patients. Shaded surface display and volume rendering of the bronchial tree combined with virtual bronchoscopy were performed using all data sets. The extent of bronchial tree visualization in shaded surface display-virtual bronchoscopy and volume rendering-virtual bronchoscopy and the presence of artifacts in volume-rendered images were scored by three blinded reviewers. The effective radiation doses of the ECG-gated and nongated acquisitions were compared.

RESULTS

The summary scores of all bronchial segments for gated shaded surface display-virtual bronchoscopy and gated volume rendering-virtual bronchoscopy did not differ significantly. The summary scores for nongated shaded surface display-virtual bronchoscopy and nongated volume rendering-virtual bronchoscopy were not significantly different. Non-gated acquisition yielded significantly better visualization of the bronchial tree for both post-processing techniques, regardless of the time interval used for reconstruction of the ECG-gated series. Artifact scores in volume-rendered images were significantly higher for ECG-gated MDCT compared with nongated MDCT. Effective radiation dose was significantly higher for the ECG-gated acquisition.

CONCLUSION

Given the advantage of volume rendering for representing the entire data set and given the lower radiation dose and better 3D image quality of nongated acquisition, volume rendering performed on nongated MDCT data is the method of choice for 3D visualization of the bronchial tree.

Multi-detector computed tomography and 3-dimensional imaging in a multi-vendor picture archiving and communications systems (PACS) environment

RATIONALE AND OBJECTIVES

To show the impact of the introduction of multi-detector computed tomography (CT) on radiologic workflow and to demonstrate how this reflects on picture archiving and communications systems (PACS) requirements.

MATERIALS AND METHODS

Production measurements were obtained from different CT scanners (first two single-slice CT scanners; from December 2001 single and 4-slice CT; from April 2002 single and 16-slice CT) in number of patients from the radiologic information system. Implications on our PACS were recorded in terms of images and studies stored. Furthermore, our PACS design was made so that optimal use of 3-dimensional imaging within the radiologic workflow was possible. Finally, the number of non-diagnosed studies were recorded every day since the start of the transition to a filmless radiology department.

RESULTS

This PACS design achieved a high level of integration between simple viewing and advanced 3-dimensional imaging and is optimized for handling large amounts of data. Overall increase of patients scanned with CT from January 2002-December 2003 was 54%. The number of series increased by 286% from December 2001-April 2003 and by 130% from April 2002-December 2003. From January 2002-February 2003, the number of images per patient increased from 175 to 450 (157%). Non-diagnosed studies decreased from about 100-120 before to practically zero after PACS implementation.

CONCLUSION

PACS significantly increases productivity because of availability of the images and elimination of certain manual tasks. These results show that although the amount of examinations increases significantly with the introduction of MDCT, simultaneous introduction of PACS and filmless operation allows radiologists to handle the growth in workload.

Multidetector row computed tomography of the aorta and peripheral arteries

MDCT represents a significant advance on SDCT and the advantages it brings are particularly clear in CTA applications. It allows cost effective assessment of longer segments of vascular territories to be imaged with higher spatial, contrast, and temporal resolution. It has replaced SDCT as the new CT standard and its technical abilities are rapidly approaching the temporal resolution of EBCT. With 3-D post processing tools its main benefit is in imaging studies customized to the patient's pathology, with greater measurement accuracy and reliable longitudinal assessment. MDCTA is increasingly applied not to individual vascular territories but to a complete assessment dictated by the pathology, such as the entire aorta and branch vessels in aneurysm evaluation and the aorta and the coronary arteries in dissection cases or the vascular and non-vascular chest in acute chest pain. Greater accuracy of vessel assessment will lead to a refinement of interventional and surgical techniques for an individual patient and facilitates conservative management of conditions that can be reliably monitored non-invasively and the development of intervention criteria. MDCTA will continue to increase its major role in peripheral vascular evaluation in the future though its reliability in assessing small vessels below the knee and in the foot remains to be conclusively proven to obviate the need for diagnostic catheter angiography.

Curved-slab maximum intensity projection: method and evaluation

The authors developed and evaluated a method to produce curved-slab maximum intensity projections (MIPs) through blood vessels that semiautomatically excludes soft tissue and bone. Results obtained with the algorithm were compared with those obtained with rectangular-slab MIPs by using computed tomographic (CT) data from four patients with abdominal aortic aneurysms. Curved-slab MIPs exhibited increased mean vessel-to-perivascular tissue contrast of 55.1 HU (36%), allowed a 10% increase in contrast-to-noise ratio, and decreased apparent vessel narrowing by 0.12-1.09 mm, without increasing processing time. Curved-slab MIPs may also include multiple vessels in a single image, thereby improving interpretation efficiency by reducing the number of MIPs required in these patients from eight to three.

Three-dimensional volume rendering of multidetector-row CT data: applicable for emergency radiology

Multidetector-row computed tomography (MD-CT) not only creates new opportunities but also challenges for medical imaging. Isotropic imaging allows in-depth views into anatomy and disease but the concomitant dramatic increase of image data requires new approaches to visualize, analyze and store CT data. The common diagnostic reviewing process slice by slice becomes more and more time consuming as the number of slice increases, while on the other hand CT volume data sets could be used for three-dimensional visualization. These techniques allow for comprehensive interpretation of extent of fracture, amount of dislocation and fragmentation in a three-dimensional highly detailed setting. Further more, using minimal invasive techniques like CT angiography, new opportunities for fast emergency room patient's work up arise. But the most common application is still trauma of the musculoskeletal system as well as face and head. The following is a brief review of recent literature on volume rendering technique and some exemplary applications for the emergency room.

Peripancreatic masses that simulate pancreatic disease: spectrum of disease and role of CT

A number of entities can simulate pancreatic disease at computed tomography (CT), which may lead to misdiagnosis. Common pitfalls include peripancreatic lesions of the foregut, adrenal gland, and kidney as well as disease of the mesentery and neurovascular structures. Optimal design and application of multi-detector row CT protocols with multiplanar reformation and maximum-intensity-projection and volume-rendering postprocessing improves the specificity of image interpretation. In most cases, helical CT is highly accurate for distinguishing primary disease of the pancreas from adjacent disease, although there are cases in which the differential diagnosis is more challenging and the potential for misdiagnosis still exists. Familiarity with some of the entities that can simulate pancreatic disease, careful attention to scanning protocol and contrast material administration, use of the full potential of multi-detector row CT data sets, and judicious application of postprocessing tools may help avoid some of the pitfalls caused by peripancreatic lesions.

Four-channel multidetector CT in facial fractures: do we need 2 x 0.5 mm collimation?

OBJECTIVE

Our aim was to optimize acquisition protocols and multiplanar reformation algorithms for the evaluation of facial fractures using multidetector CT (MDCT) and to determine whether 2 x 0.5 mm collimation is necessary.

MATERIALS AND METHODS

A cadaveric head with artificial blunt facial trauma was examined using a four-channel MDCT scanner. The influence of acquisition parameters (collimation, 2 x 0.5 mm, 4 x 1 mm, 4 x 2.5 mm; tube current, 120 mAs, 90 mAs, 60 mAs), image reconstruction algorithms (standard vs ultra-high-resolution modes; reconstructed slice thicknesses, 0.5 mm, 1 mm, 3 mm; increment, 0.3 mm, 0.6 mm, 1.5 mm), and reformation algorithms (slice thicknesses, 0.5 mm, 1 mm, 3 mm; overlap, 0.5 mm, 1 mm, 3 mm) on detectability of facial fractures in multiplanar reformations with MDCT was analyzed.

RESULTS

Fracture detection was significantly higher with thin multiplanar reformations (0.5 and 0.5 mm, 1 and 0.5 mm, and 1 and 1 mm) (p < or = 0.014) acquired with 2 x 0.5 mm collimation (p < or = 0.046) in ultra-high-resolution mode (p < 0.0005) with 120 mAs (p < or = 0.025). Interobserver variability showed very good agreement (kappa > or = 0.942). Non-ultra-high-resolution mode, lower milliampere-seconds, and thick multiplanar reformations (3 and 0.5 mm, 3 and 1 mm, and 3 and 0.5 mm) showed significantly decreased fracture detectability.

CONCLUSION

Although thin multiplanar reformations obtained from thin collimation (2 x 0.5 mm) are statistically superior for the detection of subtle fractures, 4 x 1 mm collimation is sufficient for routine diagnostic evaluation. Ultra-high-resolution mode with 120 mAs is mandatory for detection of clinically relevant fractures.

Incremental benefit of maximum-intensity-projection images on observer detection of small pulmonary nodules revealed by multidetector CT

OBJECTIVE

Our purpose was to assess the incremental effect of maximum-intensity-projection (MIP) image processing on the ability of various observers to detect small (<1 cm in diameter) central and peripheral lung nodules revealed by multidetector CT.

MATERIALS AND METHODS

We retrospectively identified 25 patients with metastatic disease, each having from two to nine nodules that were 3-9 mm in diameter. Two senior and three junior reviewers interpreted all images on a workstation. The observers first reviewed axial images (3.75-mm collimation, 3-mm reconstruction interval, multidetector acquisition) in cine and sequential fashion and recorded the size, lobe, and central or peripheral (within 1 cm of the edge of lung) location of each nodule. MIP images (10-mm slab, 8-mm interval) were then reviewed, and additional nodules detected were recorded. Final counts were established by consensus.

RESULTS

The reviewers found 122 nodules (71 peripheral, 51 central) in the 25 patients. The addition of MIP slabs significantly enhanced reviewer detection of central nodules (p < 0.001) and junior reviewer detection of peripheral nodules (p < 0.001). MIP slabs also reduced the effects of reviewer experience, particularly for peripheral nodules.

CONCLUSION

MIP processing reduces the number of overlooked small nodules, particularly in the central lung. Observer nodule detection remains imperfect even when lesions are clearly depicted on images.

Automated generation of curved planar reformations from volume data: method and evaluation

The authors developed and evaluated a method to automatically create interactive vascular curved planar reformations with computed tomographic (CT) angiographic data. The method decreased user interaction time by 86%, from 15 to 2 minutes. Expert reviewers were asked to indicate their confidence in differentiating automatically created images from clinical-quality manually produced images. The area under the receiver operating characteristic curve was 0.45 (95% CI: 0.39, 0.51), and a test of equivalency indicated that reviewers could not distinguish between images. They also graded image quality as equivalent to that with manual methods and found fewer artifacts on automatically created images. Automatic methods rapidly produce curved planar reformations of equivalent quality with reduced time and effort.

Three-dimensional computed tomographic volume rendering techniques in endoscopic thoracoplasty

BACKGROUND CONTEXT

Thoracoplasty is occasionally necessary to achieve an acceptable cosmetic result in the presence of a rib hump, especially in previously fused young adults with scoliosis. This usually requires the resection of four to five rib segments, and the morbidity associated with open posterior resection or of open anterior resection by means of thoracotomy is often considerable, apart from leaving an unsightly scar. We thought the use of an endoscopic internal rib resection technique would achieve the desired result with less morbidity. Our experience with using the technique of three-dimensional (3-D) computed tomographic (CT) volume rendering to plan our portals and releases for endoscopic scoliosis correction led us to believe the same techniques could be adapted to plan and endoscopically carry out the thoracoplasty.

PURPOSE

To define the utility of 3-D CT volume rendering of the spine and thorax in the preoperative planning of endoscopic rib resection.

STUDY DESIGN

A prospective evaluation of the utility of 3-D CT volume rendering for preoperative planning in patients with scoliosis undergoing endoscopic thoracoplasty for correction of rib humps.

PATIENT SAMPLE

Four consecutive patients with previously fused scoliotic spines and pronounced right-sided rib humps requiring operative correction were selected.

OUTCOME MEASURES

Outcome was assessed at a minimum follow-up of 6 months by clinical examination, patient satisfaction with the clinical result, and repeat helical CT scanning with 3-D reconstruction.

METHODS

Four patients with previously fused scoliotic spines and pronounced rib humps underwent helical CT scanning with 3-D volume rendering, prior to endoscopic corrective surgery. All four patients had right-sided rib humps requiring corrective rib resection for cosmetic reasons. Using the technique of 3-D volume rendering, a vector plane was created to mirror the left scapula, and its intersections on the right chest wall were noted. The ribs to be resected were marked, and the length of rib resection was measured from the vector plane's intersection points with the ribs. In this way an estimate of the resection required to achieve the desired final position of the right elevated scapula could be determined. Entry portals were also estimated with vector lines to achieve optimal access to each rib. During surgery, the portal sites were assessed for access to the selected ribs. Also, the extent of rib resections was compared with the estimates. The final clinical outcome was assessed by clinical examination, patient satisfaction with the cosmetic result, and repeat helical CT scanning with 3-D reconstruction.

RESULTS

The male to female ratio was 1:3, and the average age was 21 years. Our average estimated blood loss was 307 ml and average hospital stay was 4.75 days. The estimated portal sites were accurate and did provide for direct access to each selected rib involved in the deformity. We were able to resect the ribs at the points suggested by 3-D CT volume rendering, with the lengths of our resected segments matching our preoperative estimates. In all cases the elevated right scapula did descend into the rib resection bed, thus balancing the shoulder heights. An excellent cosmetic result was achieved in all cases as evaluated by clinical examination, patient's perception, and repeat helical CT scanning.

CONCLUSION

The technique of 3-D CT volume rendering with vector plane estimates provides a reliable estimate of the rib resection required to achieve a cosmetically acceptable correction of the rib hump through minimally invasive techniques.

From maximum intensity projection to volume rendering

Three-dimensional medical images can be generated with a variety of computer algorithms from computed tomography and magnetic resonance data sets. The most commonly used techniques are maximum intensity projection (MIP) and shaded surface display (SSD). Recently, volume rendering (VR) has become available on dedicated workstations, providing the possibility of interaction with data sets. All 3D rendering techniques represent a volume of data in 1 or more 2-dimensional (2D) planes, conveying the spatial relationships inherent in the data with the use of visual depth cues. Techniques and artefacts regarding MIP, SSD, and VR are described here, along with several models of clinical application.

Computer-aided surgical planning for implantation of hearing aids based on CT data in a VR environment

A study was undertaken to assess the feasibility of a preoperative fitting test for an implantable hearing aid in a virtual reality (VR) environment. High-resolution spiral computed tomography (CT) of the mastoid bone was performed, and the results of a mastoidectomy were simulated with manual segmentation on a standard medical workstation. CT was also performed on a temporal bone specimen obtained at real mastoidectomy, and the bone margins were segmented automatically with threshold-based techniques. A triangulated surface representation of the bone structures including the mastoid cavity was generated. These data as well as the computer-aided design (CAD) files of the medical devices were transferred into a VR environment. The CAD components of the hearing aid were manipulated to simulate the surgical implantation procedure. Merging CAD data of an implantable hearing aid with CT data of the temporal bone in a VR environment was shown to be a feasible method of providing three-dimensional information for the presurgical determination of fit and mountability. Advances in hardware and software are expected to improve the usability of this method. Although clinical studies are needed, these results may serve as an impetus for exploring the use of low-cost, widely available VR computer equipment in a potentially broad field of clinical applications.

Clinical applications of 2D and 3D CT imaging of the airways--a review

Hardware and software evolution has broadened the possibilities of 2D and 3D reformatting of spiral CT and MR data set. In the study of the thorax, intrinsic benefits of volumetric CT scanning and better quality of reconstructed images offer us the possibility to apply additional rendering techniques to everyday clinical practice. Considering the large number and redundancy of possible post-processing imaging techniques that we can apply to raw CT sections data, it is necessary to precisely set a well-defined number of clinical applications of each of them, by careful evaluation of their benefits and possible pitfalls in each clinical setting. In diagnostic evaluation of pathological processes affecting the airways, a huge number of thin sections is necessary for detailed appraisal and has to be evaluated, and information must then be transferred to referring clinicians. By additional rendering it is possible to make image evaluation and data transfer easier, faster, and more effective. In the study of central airways, additional rendering can be of interest for precise evaluation of the length, morphology, and degree of stenoses. It may help in depicting exactly the locoregional extent of central tumours by better display of relations with bronchovascular interfaces and can increase CT/bronchoscopy sinergy. It may allow closer radiotherapy planning and better depiction of air collections, and, finally, it could ease panoramic evaluation of the results of dynamic or functional studies, that are made possible by increased speed of spiral scanning. When applied to the evaluation of peripheral airways, as a completion to conventional HRCT scans, High-Resolution Volumetric CT, by projection slabs applied to target areas of interest, can better depict the profusion and extension of affected bronchial segments in bronchiectasis, influence the choice of different approaches for tissue sampling by better evaluation of the relations of lung nodules with the airways, or help to detect otherwise overlooked slight pathological findings. In the exploration of the air-spaces of the head and neck, targeted multiplanar study can now be performed without additional scanning by retro-reconstructed sections from original transverse CT slices. Additional rendering can help in surgical planning, by simulation of surgical approaches, and allows better integration with functional paranasal sinuses endoscopic surgery, by endoscopic perspective rendering. Whichever application we perform, the clinical value of 2D and 3D rendering techniques lies in the possibility of overcoming perceptual difficulties and 'slice pollution', by easing more efficient data transfer without loss of information. 3D imaging should not be considered, in the large majority of cases, as a diagnostic tool: looking at reformatted images may increase diagnostic accuracy in only very few cases, but an increase in diagnostic confidence could be not negligible. The purpose of the radiologist skilled in post-processing techniques should be that of modifying patient management, by more confident diagnostic evaluation, in a small number of patients, and, in a larger number of cases, by simplifying communication with referring physicians and surgeons. We will display in detail possible clinical applications of the different 2D and 3D imaging techniques, in the study of the tracheobronchial tree, larynx, nasal cavities and paranasal sinuses by Helical CT, review relating bibliography, and briefly discuss pitfalls and perspectives of CT rendering techniques for each field.

Diagnostic potential of virtual bronchoscopy: advantages in comparison with axial CT slices, MPR and mIP?

The aim of this study was to evaluate the diagnostic potential of virtual endoscopy (VE) and to compare it with axial CT slices, multiplanar reconstructions (MPR), minimal intensity projections (mIP), and bronchoscopy in patients diagnosed with bronchogenic carcinoma. Thirty patients underwent a spiral CT. Axial CT images were transferred to an Onyx workstation (Silicon Graphics, Sun Microsystems, Mountain View, Calif.) for performing virtual endoscopy. Accuracy for this procedure was tested by three radiologists on a monitor in comparison with axial CT slices, MPR, mIP, and bronchoscopy concerning the localization and degree of stenoses. Endoluminal tumors were identified by virtual bronchoscopy with no statistically significant difference of localization or grading of stenosis in comparison with bronchoscopy, axial CT slices, MPR and mIP. Axial CT slices, MPR, and mIP showed poorer results with over- or underestimation of stenoses compared with VE and bronchoscopy. Passing of stenoses was only possible with VE in 5 patients. Virtual endoscopy is a non-invasive method for identification of endoluminal tumors and is comparable to real bronchoscopy.

Cone-beam CT angiography of the thorax: an experimental study

The authors recently developed a cone-beam computed tomography (CT) scanner and this report presents their evaluation of its potential for thoracic vascular imaging. An X-ray tube and a video-fluoroscopic system were rotated around the objects and 360 projected images were collected in a 12-s scan. Each image was digitized and a 3 dimensional (D) image (256x256x256 voxel volume with a voxel dimension of 0.9x0.9x0.9 mm) was reconstructed. Two different 3D-CT angiographies were investigated in 2 pigs: right atriography and thoracic aortography. Each pig was anesthetized, mechanically ventilated and positioned within the scanner. Contrast agent was infused through the right atrium or the aortic root at a rate of 3 ml/s during the scan. The right atriography scan clearly delineated the anatomy of the pulmonary artery, heart chambers and thoracic aorta. The thoracic aortography scan also clearly delineated the aortic anatomy including the internal thoracic and intercostal arteries. In conclusion, cone-beam CT angiography is potentially useful for thoracic vascular imaging.