Titanium clips in neurosurgery for elimination of artefacts in computer tomography (ct) a technical note

Quantitative Analysis of Factors Affecting Cobalt Alloy Clip Artifacts in Computed Tomography

Objective

Clip artifacts limit the visualization of intracranial structures in CT scans from patients after aneurysmal clipping with cobalt alloy clips. This study is to analyze the parameters influencing the degree of clip artifacts.

Methods

Postoperative CT scans of 60 patients with straight cobalt alloy-clipped aneurysms were analyzed for the maximal diameter of white artifacts and the angle and number of streak artifacts in axial images, and the maximal diameter of artifacts in three-dimensional (3-D) volume-rendered images. The correlation coefficient (CC) was determined between each clip artifact type and the clip blade length and clip orientation to the CT scan (angle a, lateral clip inclination in axial images; angle b, clip gradient to scan plane in lateral scout images).

Results

Angle b correlated negatively with white artifacts (r=-0.589, p<0.001) and positively with the angle (r=0.636, p<0.001) and number (r=0.505, p<0.001) of streak artifacts. Artifacts in 3-D images correlated with clip blade length (r=0.454, p=0.004). Multiple linear regression analysis revealed that angle b was the major parameter influencing white artifacts and the angle and number of streak artifacts in axial images (p<0.001), whereas clip blade length was a major factor in 3-D images (p=0.034).

Conclusion

Use of a clip orientation perpendicular to the scan gantry angle decreased the amount of white artifacts and allowed better visualization of the clip site.

Magnetic resonance imaging and aneurysm clips

The problem of implanted metals causing tissue damage by movement in patients exposed to MRI fields has produced a confusing welter of erroneous, pseudoscientific publications about magnetics, metals, medical equipment, and tissue compatibility. Quite simply, among the devices made for implantation, only those fabricated of stainless steel have the ferromagnetic properties capable of causing such accidents. The author, who introduced the basic design of the modern aneurysm clip in the late 1960s and then a cobalt nickel alloy as an improvement over steel, while chairing the neurosurgical committee assigned to the task of establishing neurosurgical standards at American Society for Testing and Materials, exposes this flawed information and offers clear guidelines for avoiding trouble.

Influence of metal artifacts on in vivo micro-CT for orthodontic mini-implants

This study aimed to show the effects of metal artifacts on the in vivo micro-CT of mini-implants by measuring bone volume. We drilled a hole in the cortical bone of a rat tibia and embedded a titanium orthodontic mini-implant (diameter, 1.5 mm) in the hole. Twelve individually weighed hydroxyapatite grains (HA grains) were placed around the implant either by one dentist (method 1) or separately by 12 dentists (method 2). In vivo micro-CT was used to scan the model after placement of each grain to measure increases and decreases in bone volume voxel number. The subtracted bone voxel volume increased with HA weight in both methods. Simple linear regression analysis showed a significant correlation between weight and volume in both methods (method 1: regression coefficient: 516.502, P < 0.05; method 2: regression coefficient: 4837.432, P < 0.05). Metal artifacts did not appear to influence measurements of bone volume, although further studies are required to determine the effect of thicker implants.

An anthropomorphic phantom study of visualisation of surgical clips for partial breast irradiation (PBI) setup verification

Surgical clips were investigated for partial breast image-guided radiotherapy (IGRT). Small titanium clips were insufficiently well visualised. Medium tantalum clips were best for megavoltage IGRT and small tantalum clips were best for floor mounted kilovoltage IGRT (ExacTrac). Both small tantalum and medium titanium clips were suitable for isocentric kilovoltage IGRT.

Dose distribution close to metal implants in Gamma Knife Radiosurgery: a Monte Carlo study

Materials with high atomic numbers favor the occurrence of the photoelectric effect when they are irradiated with gamma rays. Therefore, the photoelectric effects of metal implants within the target regions in Gamma Knife Radiosurgery are worth studying. In the present work, Monte Carlo simulations using EGS4 were employed to investigate the resulting dose enhancements. A dose enhancement as high as 10% was observed close to a platinum implant along the x and y axes, while no significant dose enhancements were observed for silver, stainless steel 301, and titanium ones. A dose enhancement as high as 20% was observed close to the platinum implant along the z axis at the superior position of the metal-phantom interface and was 10% higher for other metal implants.

Aneurysm clips

This communication outlines the development of aneurysm clips, from those originally used by Walter Dandy to those in use today. The history is rich, with many contributions from neurosurgical pioneers and innovators. As a result, the modern neurosurgeon has a wide selection of biocompatible aneurysm clips from which to choose, clips that have known closing pressures and various sizes and shapes, as well as a selection of clip applicators that do not obstruct the surgical field.

A brief history of aneurysm clips

In this communication the authors outline the development of aneurysm clips from those originally used by Walter Dandy to those currently in use. The history is rich in contributions from neurosurgical pioneers and innovators. As a result, the modern neurosurgeon has a wide selection of biocompatible aneurysm clips with known closing pressure, of variable sizes and shapes, and a selection of clip applicators that do not obstruct the surgical field.

Neurosurgery at the University of Virginia

Before 1937, members of the Department of Surgery and Gynecology practiced emergency neurosurgery at the University of Virginia in the same fashion as in other hospitals in the United States. In 1937, Claude C. Coleman, Chairman of the Department of Neurosurgery at the Medical College of Virginia in Richmond, organized a Division of Neurosurgery as part of the Department of Surgery and Gynecology at the University of Virginia. He designated one of his staff members, John M. Meredith, as Neurosurgeon-in-charge. Dr. Coleman served as Clinical Professor of Neurological Surgery at the University of Virginia from 1937 to 1941, while also working in Richmond. This arrangement attracted increasing numbers of patients, leading to the formation of a separate department, under the direction of William Gayle Crutchfield, in 1941. In conjunction with Juan de Dios Martinez-Galindo, who joined the faculty in 1943, Dr. Crutchfield built and directed the neurosurgical training program until his retirement. In 1969, John A. Jane, Sr., became Professor and Chairman of the Department of Neurosurgery. Pursuing the Jeffersonian intent of attracting "... those of due degree of science and of talents for instruction," the Department has been enhanced by the arrival of Neal F. Kassell in 1984, Ladislau Steiner in 1987, Edward R. Laws, Jr., in 1992, Dheerendra Prasad in 1995, Gregory Helm in 1996, and Mark Shaffrey in 1997. Resident training has been a priority of the Department of Neurosurgery; many academic neurosurgeons were trained and practiced their specialty in the Department early in their careers. Sixty years after its foundation, the Department of Neurosurgery continues its commitment to patient care, research, and the "... instruction of those who come after us."

Cost analysis of stapling versus suturing for skin closure

A randomized, prospective study was performed to test the null hypothesis that there is no difference between the cost of stapling and suturing for skin closure of selected linear lacerations. Appropriate wounds were randomly assigned to be closed by staples or sutures. Wound lengths, skin closure times, and the number of staples or the number and types of sutures used were recorded. Costs for materials and labor were calculated. The average total cost per case was $17.69 (with suture kit) and $7.84 (without suture kit) for the staple Group compared with $21.58 for the suture Group (P = .0001 for each). It is concluded that stapling is less costly than suturing and that the advantage appears to increase as laceration length increases.

The blood tumour barrier in intracranial tumours studied with X-ray computed tomography and positron emission tomography using 68-Ga-EDTA

Disruption of the blood brain barrier or rather blood tumour barrier in cerebral tumours was studied with CT after intravenous injection of contrast medium and with PET after intravenous administration of 68-Ga-EDTA. Histology from stereotactic biopsies or open surgery is compared with the radiologic findings and advantages of the respective methods are discussed. The material consisted of 47 patients mainly with supratentorial gliomas and a few miscellaneous tumours. Astrocytomas (Kernohan grade II) were found to have no disruption of blood tumour barrier while anaplastic astrocytomas and glioblastomas (Kernohan grade III and IV) had. PET is somewhat superior to CT in detection of disruption of the blood tumour barrier. It is concluded that the combination of CT and PET is of value in the assessment of intracranial tumours.

Computed tomographic evaluation of surgical clip artifact: tissue phantom and experimental animal assessment

Surgical clips in postoperative patients create streak artifact on computed tomographic (CT) studies which often significantly degrade image quality. We have evaluated three types of surgical clips: tantalum, stainless steel, and titanium in a phantom and animal model to assess their relative CT artifact. Tantalum clips showed the greatest artifact, stainless steel intermediate, and titanium the least artifact. Artifact could be reduced with the use of faster scan times. The type of clip used may enter into surgical decision making depending upon the need for high resolution scanning to detect small pathological processes in the area of surgical clips.

Histological change in permanently clipped or ligated cerebral arterial wall. Part II: Autopsy cases of aneurysmal neck clipping

An investigation was carried out on clinical autopsy cases into histological changes in the vessel wall and into the surrounding tissue reaction after permanent clipping. 1. There were 17 autopsy cases of cerebral aneurysm, which included seven cases treated with the Yaşargil clip, five with the Heifetz clip, and five control cases. 2. Clipping period ranged from 6 days to 11 months. Both the Yaşargil and the Heifetz clips, even with long duration of clipping, caused no changes, and inflammatory reaction was slight. 3. As for the necrosis of the vessel wall beneath the blade, the Yaşargil clip produced marked necrosis at the blade edge in 4 of 7 cases (57%), while the Heifetz clip caused necrosis under the midconvexity of the blades in all 5 cases (100%). 4. The granulation tissue reaction round the clip began to occur after one month, and was enough to embed the blade of the clip after three months. We considered it very unlikely for a slip-out accident to occur after this stage. 5. Formation of mural red thrombus and deposition of fibrin with irregular intimal thickening were noted in the aneurysmal lumen in cases clipped for less than 13 days. After one month the intimal thickening was diffuse, and organized thrombus was noted. After three months or more, the aneurysmal lumen was found to have been filled almost completely by intimal thickening. Based on the above finding, the optimum condition for temporary and permanent clips was also considered.

Titanium, silver, and tantalum clips in brain tissue

The brain tissue reaction to a recently devised titanium haemoclip and to the conventional silver and tantalum clips were investigated in rabbit brain. Titanium, silver, and tantalum wires 5 X 0.5 X 0.5 mm in size were implanted into the white matter of the brain. After one and six months the brain specimens were sectioned, stained with haematoxylin eosin and with phosphotungstic acid Haematoxylin, and were studied by light microscopy. The examination revealed neither tissue reaction nor pigmentation in the case of titanium implant, while there was pigmentation surrounding the tantalum, and there was pigmentation as well as reactive gliosis around the silver wires.

Diagnosis of acoustic neuroma with computed tomography

Sixty-one acoustic neuromas were examined with computed tomography (CT). For differential diagnosis the tumors were thoroughly analyzed for manner of growth, shape, volume, calcification, attenuation pattern, constrast enhancement, presence of peripheral edema, and cisternal deformation.