Spiral Computed Tomography Imaging Research Articles

Three dimensional spiral CT imaging of the musculoskeletal system: Application and advantages

Background: Clinical applications of spiral computed tomography (CT) have increased extensively over the past decade and continue to widen rapidly. The introduction of three-dimensional(3-D) reconstruction in CT technology has revolutionized medical imaging. This advancement has been possible due to the combination of spiral computed tomography and various 3-D reconstruction protocols which have permitted rapid and comprehensive examination of all regions of the body. It has unequivocal advantages in the preoperative planning of craniofacial surgery, assessment of complex fractures of the skeletal system especially pelvis and in the surgical treatment of dysplastic hips in children. Methods: 3-D spiral CT imaging of various parts of the musculoskeletal system was carried out in 60 cases using available protocols, at the CT scan center of a large tertiary care service hospital. Results: The study provided a new approach in the analysis of complex anatomic relationships of the musculoskeletal system. Therapeutic planning whether surgical or medical was to a great extent aided by the anatomic information available from these images. Conclusion: 3-D CT imaging is a rapid, non-invasive and accurate technique for diagnosis, pre-operative evaluation as well as post-operative assessment of a large number of musculoskeletal diseases. 3-D CT studies have come to stay and with continued improvement in CT technology it has now become an integral part of imaging studies of the musculoskeletal system.

CT Perfusion Cerebral Blood Flow Imaging in Neurological Critical Care

Computed tomography (CT) perfusion imaging is a technique for the measurement of cerebral blood flow, cerebral blood volume, and time-to-peak or mean transit time. The technique involves the administration of a single-bolus dose of iodinated contrast material, followed by spiral CT imaging during the passage of the contrast bolus through the cerebral vasculature. CT perfusion is a fast and inexpensive brain imaging modality for use in the management of patients with various neurological disorders, ranging from acute stroke to subarachnoid hemorrhage. This article reviews the technique of CT perfusion and presents several illustrative cases in which this imaging modality was used effectively in the critical care of patients with neurological disorders.

Multislice spiral computed tomography coronary angiography in patients with stable angina pectoris

Since its introduction, spiral computed tomography (CT) technology underwent a continuous and fast technical and clinical development. In particular, spatial and temporal resolutions were constantly increased during the last decade. The main breakthrough for clinical application was the introduction of multislice technology, first with 2-row and 4-row equipment and more recently with 16-row scanners. A high-resolution sub-millimeter CT dataset can be acquired easily, although with an increased x-ray exposure for the patient. The high speed of the scan requires up-to-date and careful protocol optimization. Scanner technology and geometry affect image formation procedure and imaging protocols should be adapted accordingly. The technical foundations of spiral CT imaging and the main scan and reconstruction parameters are described in this article. Updated protocols and clinical examples of the latest applications are also discussed.

Sixteen-Row multislice computed tomography: basic concepts, protocols, and enhanced clinical applications

Since its introduction, spiral computed tomography (CT) technology underwent a continuous and fast technical and clinical development. In particular, spatial and temporal resolutions were constantly increased during the last decade. The main breakthrough for clinical application was the introduction of multislice technology, first with 2-row and 4-row equipment and more recently with 16-row scanners. A high-resolution sub-millimeter CT dataset can be acquired easily, although with an increased x-ray exposure for the patient. The high speed of the scan requires up-to-date and careful protocol optimization. Scanner technology and geometry affect image formation procedure and imaging protocols should be adapted accordingly. The technical foundations of spiral CT imaging and the main scan and reconstruction parameters are described in this article. Updated protocols and clinical examples of the latest applications are also discussed.

Value of CT Volume Imaging for Optimal Placement of Radiofrequency Ablation Probes in Liver Lesions

To determine the value of multiplanar and volume-rendered modes of analysis versus axial imaging for the optimal placement of probes in spiral image computed tomography (CT)-guided radiofrequency (RF) ablation of liver lesions. Thirty-two malignant hepatic lesions in 21 patients with hepatocellular carcinoma (n = 10) or metastases (n = 11) were treated with percutaneous RF ablation. After axial CT-guided placement (biopsy mode) of the probe in the tumor, a contrast-enhanced spiral image set was obtained and data were viewed in contiguous axial sections and the multiplanar and volume-rendered modes. The position of the probe was characterized as "central," "marginal," or "outside," corresponding with its position in the lesion. Outside positioning was corrected before ablation was performed and, in cases of "marginal" positioning, the probe was redirected after initial ablative therapy in the same session. Multiplanar and volume-rendered analysis reclassified the needle position before 14 of 32 RF ablation procedures (44%; P =.0034, McNemar test). In 10 cases, probe positions considered "central" on biopsy-mode images were found to be "marginal" with multiplanar/volume-rendered analysis. In three cases, probe positions considered "marginal" on biopsy-mode images were found to be "outside" with multiplanar/volume-rendered analysis. In one lesion, multiplanar/volume-rendered analysis upgraded the probe position from "marginal" to "central." Comparison of multiplanar and volume-rendered analysis revealed no difference in probe positioning. The time requirements to obtain additional data were 159 seconds +/- 49 for multiplanar analysis and 434 seconds +/- 78 for volume-rendered analysis. A contrast-enhanced spiral CT image data set with multiplanar reformations to verify an optimal probe location after axial CT-guided needle placement should be obtained before RF ablation of liver lesions.

Spiral computed tomography assessment of resectability of pancreatic ductal adenocarcinoma: analysis of results

Background. Despite more recent technical advances, single detector spiral computed tomography is still the most widely used imaging technique for the detection and staging of pancreatic adenocarcinoma. Many reports have recently focused on single detector spiral computed tomography imaging findings indicative of unresectability. Aim. To evaluate the ability of single detector spiral computed tomography in the pre-operative staging of ductal adenocarcinoma of the pancreas in selecting surgically resectable versus unresectable cases, considering different parameters (vascular and local infiltration, liver metastases, lymphadenopathy, and peritoneal carcinomatosis). Patients and methods. A total of 1 DD patients diagnosed with ductal adenocarcinoma of the pancreas, pathologically verified, and examined with single detector spiral computed tomography were considered. Of these, 63 underwent surgery; 37 were excluded (imaging evidence of unresectability in biopsy-proven adenocarcinomas). Single detector spiral computed tomography studies, performed at the time of surgery, were retrospectively reviewed by two radiologists. The final results were reached by consensus, without being aware of the operation. All prospective clinical readings were also considered, and tabulated. Results. In the patients undergoing surgery, 44 proved to be unresectable and 19 resectable. Considering the above-mentioned parameters, the prospective assessment of resectability demonstrated a rather low sensitivity (68%), with high specificity (95%). Accordingly, a high positive predictive value (97%) was achieved, while the negative predictive value was 56%. After the retrospective evaluation, the value of sensitivity increased (84%) to the expense of the specificity (84%). Moreover, a positive predictive value of 92.5%, and a negative predictive value of 69.5% were obtained. Conclusions. The demonstration of many signs of unresectability of pancreatic ductal adenocarcinoma reported in the literature yields a better sensitivity in the diagnosis, but unfortunately, is associated with an inevitable reduction in specificity.

Efficacy of the Iodine-Free Computed Tomography Liver Contrast Agent, Dy-EOB-DTPA, in Comparison With a Conventional Iodinated Agent in Normal and in Tumor-Bearing Rabbits

To investigate the efficacy of the new liver-specific x-ray contrast agent, Dy-EOB-DTPA, in rabbits with VX2 liver tumors by spiral computed tomography (CT) in comparison to iopromide. The time course of liver enhancement was determined in five groups of two normal anesthetized rabbits, which received intravenous injections of Dy-EOB-DTPA before anesthesia at a dose of 0.5 mmol/kg. Fifteen, 30, 45, 60, and 90 minutes after administration spiral CT images were obtained and the attenuation in the livers were determined. A second group of ten rabbits with implanted VX2 tumors received in a random crossover design either Dy-EOB-DTPA at a dose of 0.5 mmol/kg or, 1 day later, iopromide at a dose of 600 mg iodine/kg. CT images were obtained 60 minutes after Dy-EOB-DTPA administration and both in the arterial and portal-venous phases after iopromide injection. Three radiologists evaluated the images. The rabbits were killed, and their livers were investigated histologically for liver tumors. In normal animals, 0.5 mmol/kg Dy-EOB-DTPA resulted in a liver enhancement of 30 HU during the whole observation period of 90 minutes. In tumor-bearing animals, histology revealed 14 implanted tumors of 3-20 mm diameter. Sixty-five percent of the tumors were below 10 mm. Dy-EOB-DTPA was able to detect 13 tumors (93%), iopromide 11 (79%) both in the arterial and in the portal-venous phase. The difference was statistically not significant. In plain CT, seven tumors (50%) were found (P < 0.01 vs iopromide and Dy-EOB-DTPA). One scar and two sites of necrosis were detected by each of the methods. Dy-EOB-DTPA injection at a dose of 0.5 mmol/kg resulted in a long-lasting detectability of 93% of all implanted tumors versus 79% found with iopromide.

Prevalence of Emphysema in Individuals Who Underwent Screening CT for Lung Cancer in Nagano Prefecture of Japan

Background: Screening for lung cancer with low-dose spiral computed tomography (CT) was carried out in Nagano prefecture in Japan. Objective: To study the prevalence of emphysema in 7,847 individuals based on the Nagano spiral CT screening and to correlate the prevalence and severity of emphysema with various factors. Methods: Spiral CT images with scan parameters of 120 kV, 50 mA, 10-mm collimation and a pitch of 2 obtained at full inspiration were retrospectively evaluated in 7,847 individuals. Emphysema was defined as the presence of low-attenuation areas in the lung parenchyma. Extent of emphysema was graded on a four-level scale and correlated with gender, age and smoking habits. Results: There were 4,288 males and 3,559 females. Mean age of the subjects was 61 years; 45.8% of the participants were smokers. Overall prevalence of emphysema was 2.9%; the prevalence was significantly higher in males (5.0%) than in females (0.5%); it was also significantly higher in smokers, and increased with age. Emphysema was positively correlated with age, but there was no correlation with smoking indices. Emphysema was mostly mild and localized in the upper lung. The logistic model revealed that gender, age and smoking indices were significant factors for developing emphysema. Conclusions: Overall prevalence of emphysema was 2.9%. The prevalence was higher in males and in older people. Smoking was also related to a higher prevalence of emphysema but not to its severity.

The validation of 3D spiral CT based measurements of simulated maxillofacial neoplasms

The purpose of this study was to determine the precision and accuracy of 3-dimensional spiral computed tomography-based linear measurements of neoplasms associated with the mandible. Four cadaver heads, each with 2 simulated tumors made of clay, containing contrast medium, and positioned medial to the mandible, were examined by means of a subsecond spiral computed tomography unit. The computed tomography data were transferred to a computer workstation and analyzed through use of 3-dimensional reconstructed images. Linear measurements of the length, width, and depth of the simulated tumors were made by 2 observers, twice each. The soft tissues were then removed and the same measurements made by means of calipers. There were no statistically significant differences between the 3-dimensional computed tomography and physical measurements (P >.05). The mean difference was found to be less than 0.4 mm. Spiral computed tomography imaging allows for precise and accurate 3-dimensional computed tomography-based measurements for neoplastic lesions in the mandible.

Can Preoperative Spiral CT Scans Alone Determine the Feasibility of Endovascular AAA Repair? A Comparison to Angiographic Measurements

Purpose:To determine whether computed tomography (CT) alone can be used for excluding patients from endovascular repair for abdominal aortic aneurysms (AAA).Methods:Among 71 patients evaluated for endovascular AAA repair using spiral CT imaging and angiography, 31 were selected who had both studies performed within 6 months of each other using a graduated measuring catheter or guidewire. Measurements of aneurysm neck diameter, neck length, and infrarenal aortic length were made from the CT and angiographic images using handheld calipers with calibration markers as guides. Infrarenal aortic length and neck length were determined from CT images by multiplying the width of the cuts by the number of slices between the lowest renal artery and the aortic bifurcation or the top of the aneurysm, respectively.Results:CT neck diameter measurements differed significantly from the angiographic dimensions (6.3 ± 5.1-mm mean difference, p < 0.001). In the majority of patients (25, 81%), CT neck diameters were larger (m...

Can Preoperative Spiral CT Scans Alone Determine the Feasibility of Endovascular AAA Repair? A Comparison to Angiographic Measurements

To determine whether computed tomography (CT) alone can be used for excluding patients from endovascular repair for abdominal aortic aneurysms (AAA). Among 71 patients evaluated for endovascular AAA repair using spiral CT imaging and angiography, 31 were selected who had both studies performed within 6 months of each other using a graduated measuring catheter or guidewire. Measurements of aneurysm neck diameter, neck length, and infrarenal aortic length were made from the CT and angiographic images using handheld calipers with calibration markers as guides. Infrarenal aortic length and neck length were determined from CT images by multiplying the width of the cuts by the number of slices between the lowest renal artery and the aortic bifurcation or the top of the aneurysm, respectively. CT neck diameter measurements differed significantly from the angiographic dimensions (6.3 +/- 5.1-mm mean difference, p < 0.001). In the majority of patients (25, 81%), CT neck diameters were larger (mean 7.3 +/- 3.8 mm). The mean difference in neck length measurements was 0.5 +/- 15.9 mm (p = NS). Twenty-two (71%) patients had aortic length measurements that were longer on the angiogram (mean 15.4 +/- 17.2 mm, p = NS). Five patients who would have been excluded as candidates based on overestimated CT neck diameter measurements subsequently underwent successful endovascular aneurysm repair. Considerable discrepancies exist between preoperative neck diameter and infrarenal aortic length measurements obtained from CT scans and angiograms used to evaluate candidates for endovascular aortic aneurysm repair. CT alone may not be adequate for predicting the feasibility of endovascular AAA repair.

Use of three-dimensional spiral computed tomography imaging for staging and surgical planning of head and neck cancer.

We compare four different three-dimensional (3D) reconstruction methods of spiral computed tomography (CT) data for head and neck cancer to establish the method best suited for specific uses, eg, staging of lymph nodes and viewing of spatial relationships between the tumor, fascial spaces, adjacent soft tissues, and others structures. We evaluated a series of 10 patients (six men and four women), aged 32 to 60 years. Of these, five were histologically diagnosed with squamous cell carcinoma, two with lymphoma, one with thyroid cancer, one with Kikuchi's disease or necrotizing lymphadenitis, and one with esthesioneuroblastoma. All scans were obtained using high-resolution spiral CT (General Electric Medical Systems, Milwaukee, WI). The collimations used were 3 mm and 5 mm, matrix 512 x 512, and reconstruction interval not more than 3 mm. Scanning was performed from the skull base to the aortic arch. Iodinated contrast medium was injected so that the blood vessels were clearly differentiated from nodes. Different techniques of three-dimensional reconstruction were employed, including shaded surface display (SSD), multiplanar reconstructions (MPR), maximum intensity projection (MIP), 3D volume rendering (VR), and combined techniques. The reconstructions were performed in a variety of planes, including sagittal, coronal, and oblique views. In our series of selected patients, the technique of 3D VR showed potential advantages over other techniques. The MIP technique was useful in analyzing the patency of vessels and to exclude thrombus, compression, or displacement by tumor. The use of combined techniques such as SSD and MPR, accurately demonstrated the levels of lymph nodes and the relationship between the tumor projection of interest and various anatomic structures. In conclusion, 3D reconstruction of CT data is useful in the localization and staging of neck tumors and assists in surgical planning and radiation treatment.

The effect of pitch in multislice spiral/helical CT.

The purpose of this study is to understand the effect of pitch on raw data interpolation in multislice spiral/helical computed tomography (CT) and provide guidelines for scanner design and protocol optimization. Multislice spiral CT is mainly characterized by the three parameters: the number of detector arrays, the detector collimation, and the table increment per x-ray source rotation. The pitch in multislice spiral CT is defined as the ratio of the table increment over the detector collimation in this study. In parallel to the current framework for studying longitudinal image resolution, the central fan-beam rays of direct and opposite directions are considered, assuming a narrow cone-beam angle. Generally speaking, sampling in the Radon domain by the direct and opposite central rays is nonuniform along the longitudinal axis. Using a recently developed methodology for quantifying the sensitivity of signal reconstruction from nonuniformly sampled finite points, the effect of pitch on raw data interpolation is analyzed in multislice spiral CT. Unlike single-slice spiral CT, in which image quality decreases monotonically as the pitch increases, the sensitivity of raw data interpolation in multislice spiral CT increases in an alternating way as the pitch increases, suggesting that image quality does not decrease monotonically in this case. The most favorable pitch can be found from the sensitivity-pitch plot for any given set of multislice spiral CT parameters. An example for four-slice spiral CT is provided. The study on the effect of pitch using the sensitivity analysis approach reveals the fundamental characteristics of raw data interpolation in multislice spiral CT, and gives insights into interaction between pitch and image quality. These results may be valuable for design of multislice spiral CT scanners and imaging protocol optimization in clinical applications.

CT appearance of midgut volvulus with malrotation in a young infant

Computed tomography (CT) appearances of small bowel malrotation and midgut volvulus (MGV) have rarely been described in paediatric patients. We present spiral CT images of a surgically proven case in a young infant. The literature on imaging techniques to diagnose these conditions is reviewed. Radiation doses of upper gastrointestinal series (UGI) and spiral CT are estimated and compared.

Accurate linear measurements in the anterior maxilla using orthoradially reformatted spiral computed tomography.

To validate measurement accuracy in proximity to the incisive canal from two-dimensional (2D) reformatted spiral computed tomography (CT). Eight cadaver heads were examined with spiral CT with 1 mm thick axial slices and 1 mm.s-1 table feed. The data was transferred to a networked computer workstation to generate 2D orthoradially reformatted images. The length of the incisive canal and width of the alveolar crest were measured independently by two oral and maxillofacial radiologists. The soft tissues in the region of the incisive foramen were removed and physical measurements made using an electromagnetic digitizer. There was no statistically significant difference between measurements on orthoradial 2DCT images and physical measurements (P > 0.05). Accurate measurements for dental implant placement in proximity to the incisive canal can be made from reformatted spiral CT images.

Validation of spiral computed tomography for dental implants.

To investigate the accuracy of 2DCT orthoradial reformatted images from spiral computed tomography (CT) for pre-surgical planning of dental implants in proximity to the mental foramen. Eight cadaver heads were imaged by spiral CT (S/Xpress, Toshiba-America, Tustin, CA) with 1 mm thick axial slices by 1 mm/sec of table feed. The image data set was transferred to a networked computer workstation. Using computer graphics the data was analysed with 2D orthoradial reformatting using the ToothPix (Cemax, Fremont, CA, USA) protocol. Linear measurements were made by two oral radiologists independently from the superior border of the mental foramen to the crest of the alveolar process and from the inferior border of the mental foramen to the mandibular inferior border. The soft tissues were removed and physical measurements made using a 3 Space (Polhemus, Colchester, VT) electromagnetic digitizer with a personal computer running Windows 95. The differences between the measurements on orthoradial 2DCT images and the physical measurements were not statistically significant (P > 0.05). Two-dimensional spiral CT imaging allows highly accurate measurements for dental implant placement in proximity to the mental foramen. Computer graphics software, using reformatted reconstruction, is suitable for implant planning.

Spiral CT image deblurring for cochlear implantation.

Cochlear implantation is the standard treatment for profound hearing loss. Preimplantation and postimplantation spiral computed tomography (CT) is essential in several key clinical and research aspects. The maximum image resolution with commercial spiral CT scanners is insufficient to define clearly anatomical features and implant electrode positions in the inner ear. In this paper, we develop an expectation-maximization (EM)-like iterative deblurring algorithm to achieve spiral CT image super-resolution for cochlear implantation, assuming a spatially invariant linear spiral CT system with a three-dimensional (3-D) separable Gaussian point spread function (PSF). We experimentally validate the 3-D Gaussian blurring model via phantom measurement and profile fitting. The imaging process is further expressed as convolution of an isotropic 3-D Gaussian PSF and a blurred underlying volumetric image. Under practical conditions, an oblique reconstructed section is approximated as convolution of an isotropic two-dimensional (2-D) Gaussian PSF and the corresponding actual cross section. The spiral CT image deblurring algorithm is formulated with sieve and resolution kernels for suppressing noise and edge artifacts. A typical cochlear cross section is used for evaluation, demonstrating a resolution gain up to 30%40% according to the correlation criterion. Physical phantoms, preimplantation and postimplantation patients are reconstructed into volumes of 0.1-mm cubic voxels. The patient images are digitally unwrapped along the central axis of the cochlea and the implanted electrode array respectively, then oblique sections orthogonal to the central axis formed. After deblurring, representation of structural features is substantially improved in all the cases.

Spiral CT of pulmonary embolism: technical considerations and interpretive pitfalls.

The diagnostic work-up of pulmonary embolism has been recently modified by the introduction of spiral computed tomography (CT), which enables noninvasive depiction of endoluminal clots in second-to fourth-division pulmonary arteries. If this technique is currently considered a powerful imaging alternative for the detection of acute central emboli, it is mainly related to the possibility to obtain a uniform and high degree of arterial enhancement of pulmonary arteries down to 2-3 mm in diameter. Minimal experience in spiral CT angiography is necessary to achieve this goal and requires familiarity with both data acquisition and contrast medium injection. A number of interpretive pitfalls exist in assessing spiral CT images, and certain caveats have to be heeded. However, it is important to keep in mind that their recognition becomes less and less problematic as the radiologist gains experience with spiral CT of the pulmonary vasculature. Therefore, the purpose of this article is to review the diagnostic approach to pulmonary embolism with spiral CT, with special emphasis on protocol parameters and scan interpretation.

A semiautomatic three-dimensional segmentation method for disarticulation of bone structures on spiral computed tomography images.

The use of binary thresholding for segmenting bone structures on spiral computed tomography images is negatively influenced by partial volume effects (PVEs) induced by the image acquisition. PVE leads to mixed voxels, making the binary decision "bone" or "nonbone" a difficult one to take. As a result, two distinct bone structures that are close to each other will often appear to be connected by this method. A typical example consists of "acetabulum/femural head" pairs in the pelvic region. To separate them, a clinical user must interactively draw a disarticulation line. This procedure is time consuming (often interaction in 50 slices is needed) and leads to unsmooth visualization of the disarticulated areas (by three-dimensional [3D] rendering techniques). We developed a semiautomatic cutting algorithm that leads to smooth disarticulated surfaces and considerably decreases the amount of user interaction. A sheet detection operator is applied to automatically separate bone structures. Detected sheets are used as disarticulation lines. Postprocessing ensures that sheets not relevant for the application do not influence the resulting image. Our approach is encapsulated in an interactive segmentation environment based on thresholding and 3D connected-component labeling. Results are shown for pelvic region, wrist, and foot bone disarticulations.

Temporal bone volumetric image deblurring in spiral computed tomography scanning

We developed a method for volumetric image deblurring in spiral (helical) computed tomography (CT) scanning with a three-dimensional (3D) Gaussian point spread function (PSF) to improve the quality of temporal bone spiral CT images for assessing the position of cochlear implants electrodes. A patient was scanned after cochlear implantation, and the temporal bone was reconstructed into a volume with 128 voxels per dimension, 0.1 mm per voxel side, and x 10 gray-scale expansion. The 3D PSF in spiral CT imaging was assumed to be Gaussian separable transversely and longitudinally. Standard deviations of the PSF were derived and subjectively adjusted. The image was then deconvolved using Wiener filtering and maximum-likelihood deconvolution methods. Image quality was assessed both visually and quantitatively using cross-sectional area at half of the maximum (CAHM) of the implanted array as the figure of merit. Substantial image deblurring was achieved via deconvolution. Subjectively, anatomic structures were more clearly shown. Deconvolution reduced the CAHM by approximately one third, on average. Three-dimensional deconvolution had better image quality than two-dimensional deconvolution. The maximum-likelihood method produced superior image quality but took longer to process relative to Wiener filtering. Volumetric image deblurring is practical with a Gaussian PSF. The maximum-likelihood method is preferred if time permits. Deconvolution facilitates the study of fine details of the temporal bone and cochlear implant.