Computed Tomography Modalities Research Articles

Patient-Tailored Cerebral Arterial Model for Simulating Neurovascular Intervention (2nd Report, In Vitro Reproduction of Membranous Vascular Structure Accompanied with Elastic Deformation)

In this paper, we propose an in vitro patient-specific anatomical model of human cerebral artery, a hardware platform for simulating endovascular intervention for making diagnosis and surgical trainings. Proposed vessel model hollowly reproduces 3-dimensional configuration of vascular lumens with elastic membranous configuration as a transparent silicone structure, using fluoroscopic information, which is obtained with CT (Computed Tomography), MRI (Magnetic Resonance Imaging) and other imaging modalities. This vessel model also reproduces the physical characteristics of artery tissue, such as elastic modulus, Poisson's ratio and friction coefficient, within respectively 10% of errors. Consequently, it allows practically simulating procedures, which is accompanied by realistic vascular deformation, realistic feel of operating catheters and realistic behavior of surgical instruments (e.g. slip/stick motion and unwinding motion). Presented vasculature model should provide a helpful platform for interventionalists to make preliminary simulation, for young trainees to practice surgical procedures and for developers to evaluate surgical robots, device and other various medical instruments.

Clinical Validity of a Negative Computed Tomography Scan in Patients With Suspected Pulmonary Embolism

The clinical validity of using computed tomography (CT) to diagnose peripheral pulmonary embolism is uncertain. Insufficient sensitivity for peripheral pulmonary embolism is considered the principal limitation of CT. To review studies that used a CT-based approach to rule out a diagnosis of pulmonary embolism. The medical literature databases of PubMed, MEDLINE, EMBASE, CRISP, metaRegister of Controlled Trials, and Cochrane were searched for articles published in the English language from January 1990 to May 2004. We included studies that used contrast-enhanced chest CT to rule out the diagnosis of acute pulmonary embolism, had a minimum follow-up of 3 months, and had study populations of more than 30 patients. Two reviewers independently abstracted patient demographics, frequency of venous thromboembolic events (VTEs), CT modality (single-slice CT, multidetector-row CT, or electron-beam CT), false-negative results, and deaths attributable to pulmonary embolism. To calculate the overall negative likelihood ratio (NLR) of a VTE after a negative or inconclusive chest CT scan for pulmonary embolism, we included VTEs that were objectively confirmed by an additional imaging test despite a negative or inconclusive CT scan and objectively confirmed VTEs that occurred during clinical follow-up of at least 3 months. Fifteen studies met the inclusion criteria and contained a total of 3500 patients who were evaluated from October 1994 through April 2002. The overall NLR of a VTE after a negative chest CT scan for pulmonary embolism was 0.07 (95% confidence interval [CI], 0.05-0.11); and the negative predictive value (NPV) was 99.1% (95% CI, 98.7%-99.5%). The NLR of a VTE after a negative single-slice spiral CT scan for pulmonary embolism was 0.08 (95% CI, 0.05-0.13); and after a negative multidetector-row CT scan, 0.15 (95% CI, 0.05-0.43). There was no difference in risk of VTEs based on CT modality used (relative risk, 1.66; 95% CI, 0.47-5.94; P = .50). The overall NLR of mortality attributable to pulmonary embolism was 0.01 (95% CI, 0.01-0.02) and the overall NPV was 99.4% (95% CI, 98.7%-99.9%). The clinical validity of using a CT scan to rule out pulmonary embolism is similar to that reported for conventional pulmonary angiography.

Survey of computed tomography techniques and absorbed dose in Italian hospitals: a comparison between two methods to estimate the dose–length product and the effective dose and to verify fulfilment of the diagnostic reference levels

The aim of this study was the production of the first Italian survey of radiation dose in computed tomography (CT) prior to the widespread adoption of multislice CT, in order to have a reference point to facilitate later investigation of dose exposure changes brought by this new CT modality. The collected dose data were compared with diagnostic reference levels (DRLs). The agreement between experimental dose evaluation and Monte Carlo (MC) simulations was investigated. The survey was carried out in 29 Italian hospitals, covered 48 CT scanners and 232 examinations. The dose-length product (DLP) and effective dose (E) values were estimated based on MC simulations for seven clinical protocols using the CT-Dose program. Statistical analysis showed a significant difference (p<0.01) in the DLP between the two methods, with MC values being greater than the experimental ones. For E, the MC values were greater in routine head (8.2%), cervical spine (2.7%) and lumbar spine (2.9%) studies. The weighted CT dose index, the DLP and E were always below the DRLs set by the European Community. This dose survey gives a good but incomplete picture of the Italian CT dose situation and may be useful as a reference baseline for defining clinical multislice protocols in the near future.

Patient-Tailored Cerebral Arterial Model for Simulating Neurovascular Intervention (1st Report, In Vitro Reproduction of Vasculature Structure with Biomechanics)

In this paper, we propose an in vitro patient-tailored anatomical model of human cerebral artery, a hardware platform for simulating intravascular neurosurgery for making diagnosis and surgical trainings. Proposed vessel model hollowly reproduces 3-dimensional configuration of vessel lumens within an elastic transparent silicone cube, using fluoroscopic information which is obtained with CT (Computed Tomography), MRI (Magnetic Resonance Imaging) and other imaging modalities. It also reproduces the physical characteristics of artery tissue, such as elastic modulus, Poisson's ratio and friction coefficient, within respectively 10% of errors. Consequently, it allows simulating neurovascular procedures, which is accompanied by the realistic feel of operating catheters, and the realistic behavior of surgical instruments (e. g. slip/stick motion and unwinding motion). Presented vasculature model should provide an innovative platform for interventionalists to make preliminary surgical simulation, for young trainees to practice intervention procedures and for developers to evaluate surgical robots, device and other various medical instruments.

Minimum number of basis projections for caries detection with local CT

To investigate the relationship between the number of basis projections for local computed tomography (CT) and the detection of proximal caries and to find a minimum number of projections needed to maintain diagnostic accuracy. We presented observers (n = 12) with stacks of both axial and vertical CT slices of 23 extracted teeth placed in a dry human mandible. The slices were prepared with 14, 20, 33 and 100 basis projections. The observers scored the proximal surfaces for the presence of caries on a 1-5 confidence scale. The performance of the varying number of projections was compared with conventional digital radiographs. The performance of all four CT modalities was significantly better than conventional radiographs (P = 0.005 to P = 0.021) and showed a consistent increase with the number of projections. Diagnostic performance depended significantly on lesion depth (P = 0.00), but not on observer. We conclude that the number of CT projections used can be reduced at least to 20 with the diagnostic performance still markedly better than that of conventional film, provided that the observer can make use of both axial and vertical stacks of CT slices.

Multimodal imaging of the human temporal bone: A comparison of CT and optical scanning techniques

A collaborative effort between Washington University in St. Louis and Spencer Technologies in Seattle, WA has been undertaken to create a multimodal 3D reconstruction of the human cochlea and vestibular system. The goal of this project is to improve the accuracy of in vivo CT reconstructions of implanted cochleae, and to expand the knowledge of high-resolution anatomical detail provided by orthogonal-plane optical sectioning (OPFOS). At WUSL, computed tomography (CT) images of the cochlea are used to determine the position of cochlear implant electrodes relative to target auditory neurons. The cochlear implant position is determined using pre- and post-operative CT scans. The CT volumes are cross-registered to align the semicircular canals and internal auditory canal, which have a unique configuration in 3-D space. The head of a human body donor was scanned with a clinical CT device, after which the temporal bones were removed, fixed in formalin and trimmed prior to scanning with a laboratory Micro CT scanner. Following CT, the temporal bones were sent to the OPFOS Imaging Lab at Spencer Technologies for a further analysis. 3-D reconstructions of CT and OPFOS imaging modalities were compared, and results are presented. [Work supported by NIDCD Grants R44-03623-5 and R01-00581-13.]

The diagnosis of gastrointestinal tract injuries resulting from blunt trauma.

This review studies the efficacy of the methods of assessment of the abdomen in blunt trauma for the detection of gastrointestinal tract injuries (GITI). MEDLINE searches of English language publications on the subjects of diagnostic peritoneal lavage, abdominal computed tomography (CT) in blunt trauma and gastrointestinal tract injuries between 1980 and 1998 were used to identify relevant material. Earlier publications were identified from reference lists. The methodology, data and conclusions of all studies were examined in detail. The contemporary roles of clinical assessment, diagnostic peritoneal lavage, CT and other diagnostic modalities in detection of significant GITI were determined based on the best available evidence. The most accurate and safest methods of assessment of the abdomen in haemodynamically unstable patients with suspected abdominal injuries following blunt trauma are immediate laparotomy or diagnostic peritoneal lavage (DPL). The goal of assessment of the abdomen in stable patients is to accurately define the site and extent of intra-abdominal injury, in order that further management may be tailored to the specific injuries. The most recent evidence suggests that CT of the abdomen fulfils these criteria better than the other modalities of assessment available. The risk of overlooking a significant GITI on CT scan is minimal provided that unexplained free fluid, bowel wall thickening or enhancement, mesenteric fat streaking and bowel dilatation are taken as evidence of GITI. When scan quality is suboptimal or expert interpretation is unavailable, DPL is recommended. Fully cooperative patients with negligible abdominal signs can be safely observed clinically.

Superior orbital fissure syndrome caused by intraorbital spread of a cutaneous squamous cell carcinoma and not detected on computed tomography and magnetic resonance imaging

Intraneural and perineural spread of a squamous cell carcinoma of the frontal region via the orbit to the cranial cavity is a rare cause of a superior orbital fissure syndrome. This mode of tumor spread, for which a previously excised invasive malignant tumor is responsible, is rarely reported. The absence of an intraorbital mass and the fact that computed tomography (CT) and magnetic resonance imaging (MRI) are normal make the diagnosis extremely difficult. We describe a 76-year-old patient in whom both intrane ural and perineural tumor growth deep into the orbit caused acute ocular motility disturbances, visual impairment, and ocular dysfunction with subsequent cerebral and vascular dysfunction. Surgery, radiotherapy, and orbital exenteration did not prevent spread of the tumor toward vital intracranial and intracerebral structures. Even the advanced diagnostic modalities of CT and MRI failed to reveal the cause of the pathologic process in our patient. In such a case, one should look carefully for both intraneural and perineural tumor invasion on previous histologic material and, if positive, treat the patient with radical surgery on purely clinical grounds as early as possible.

Mesenteric vascular occlusion: a new diagnostic method using a radiolabeled monoclonal antibody reactive with platelets.

A new method for diagnosing mesenteric vaso-occlusive bowel disease with the use of radioimmunoscintigraphy was developed and tested in experimental models of arterial and venous disease, as well as in a model simulating bowel strangulation. The method involves the use of a monoclonal antibody fragment mixture that binds to platelets. The antibody was labeled with technetium-99m, and imaging was performed with a gamma camera in the planar and single photon emission computed tomography modes. This method allowed visualization of areas of ischemia of 1-6 hours duration in bowel loops in 19 dogs 90-180 minutes after injection of the radiolabeled antibody. No bowel radioactivity accumulation occurred in dogs that underwent the same surgical procedure but were given a nonspecific Tc-99m-labeled antibody or in normal dogs given the specific antibody. It appears that the radiolabeled antibody used, which has higher reactivity with human platelets than with dog platelets, will be a good agent for noninvasive diagnosis of mesenteric vaso-occlusive disease in humans. It may also play a role in the intraoperative determination of the extent and location of ischemic bowel segments.

Stereotactic surgical planning with magnetic resonance imaging, digital subtraction angiography and computed tomography.

Over the past 2 years at the Montreal Neurological Institute and Hospital, we have evolved an integrated environment for the planning of stereotactic procedures, based on images from magnetic resonance imaging, digital subtraction angiography and computed tomography modalities. These procedures rely on fiducial marker sets which are attached to our 'OBT' stereotactic frame, and which may be recognized in the images. The software package is modular and operates in both minicomputer (PDP-11 and VAX) and IBM personal computer environments. In addition to routine tasks for stereotactic planning, the package also supports dosimetry planning for stereotactic radiosurgery.

Preoperative Localization of a Parathyroid Adenoma Using Computed Tomography and Thyroid Scanning

We report a case of parathyroid adenoma correctly localized prior to operation by computed tomography (CT) and thyroid scanning. The use of CT and other noninvasive diagnostic modalities to aid the surgeon prior to initial operation for parathyroid adenoma is discussed.