Presence Of Metallic Implants Research Articles

Dose perturbation in the presence of metallic implants: treatment planning system versus Monte Carlo simulations

An increasing number of patients receiving radiation therapy have metallic implants such as hip prostheses. Therefore, beams are normally set up to avoid irradiation through the implant; however, this cannot always be accomplished. In such situations, knowledge of the accuracy of the used treatment planning system (TPS) is required. Two algorithms, the pencil beam (PB) and the collapsed cone (CC), are implemented in the studied TPS. Comparisons are made with Monte Carlo simulations for 6 and 18 MV. The studied materials are steel, CoCrMo, Orthinox® (a stainless steel alloy and registered trademark of Stryker Corporation), TiAlV and Ti. Monte Carlo simulated depth dose curves and dose profiles are compared to CC and PB calculated data. The CC algorithm shows overall a better agreement with Monte Carlo than the PB algorithm. Thus, it is recommended to use the CC algorithm to get the most accurate dose calculation both for the planning target volume and for tissues adjacent to the implants when beams are set up to pass through implants.

Effect of Metallic Implant on the Risk of Bacterial Osteomyelitis in Small Animals

Soontornvipart K., A. Neaas, M. Dvofiak: Effects of Metallic Implant on the Risk of Bacterial Osteomyelitis in Small Animals . Acta Vet. Brno 2003, 72: 235-247. Metallic implants are frequently used for stabilization of fractures in dogs and cats. Postoperative bacterial osteomyelitis is a recognized complication following fracture repair and can be influenced by the presence of metallic implants. Metallic implants influence susceptibility to infection through several mechanisms, including corrosion, adherence of biofilm, isolation from the immune response, and compromise of blood supply. Factors that should be considered when using metallic implants include antibiotic prophylaxis, appropriate implant selection, meticulous surgical technique and proper aseptic technique.

Osteomyelitis: etiology, diagnosis, treatment and outcome in a public versus a private institution.

Although bone infections are difficult to diagnose and manage, primary health care providers often give comprehensive care to patients with few referrals. To evaluate how trends in care impact upon management of bone infections, we performed a retrospective review of medical records of 198 osteomyelitis patients. 130 patients were hospitalized at a private institution and 68 were hospitalized at a public (teaching) institution. Outcomes measured were bone salvage or loss in relation to predisposing co-morbidities and infectious disease (ID) physician involvement in the patient care. Co-morbidities predominating at the public and private hospitals, respectively, were presence of metal implants (20% and 37%) and diabetes (32% and 31%). The most common pathogens at the public and private hospitals, respectively, were methicillin-susceptible Staphylococcus aureus (MSSA, 16 and 32%) and methicillin-resistant S. aureus (MRSA, 3% and 31%). ID specialists treated longer with i.v. antibiotics (42 and 43.5 median treatment days) than non-ID specialists (14 and 7 median treatment days). When ID specialists were involved in case management, a trend to bone salvage was seen at the public hospital (p < 0.09). Osteomyelitis patient outcome varies less by hospital setting than by case management.

Use of Fluorine-18 Fluoro-2-deoxy-D-glucose Positron Emission Tomography in Assessing the Process of Tuberculous Spondylitis

Fluorine-18 fluoro-2-deoxy-D-glucose positron emission tomography can be used to quantify the pathologic increase in glucose metabolism of inflammatory processes. Preliminary studies indicate a high level of sensitivity and specificity in detecting and identifying chronic osteomyelitis. This case study shows that positron emission tomography can be used to assess the process of inflammatory activity in tuberculous spondylitis. This technology also has the advantage of higher spatial resolution compared with other nuclear medicine procedures. In addition, it can differentiate between bone and soft tissue infection and allows imaging in the presence of metal implants.

A quantitative study of the pixel-shifting, blurring and nonlinear distortions in MRI images caused by the presence of metal implants

Magnetic resonance imaging has found an increasing number of medical applications in recent years due to its technical merits as well as its non-invasive nature. However, its full potential has been severely limited by magnetic susceptibility difference artefacts caused by the presence of ferromagnetic sources such as orthopedic implants, dental work or metallic needles used in neurosurgery. In this study, we propose a method to numerically quantify the distortions resulting from the magnetic susceptibility differences by investigating the phenomena from three perspectives: (1) pixel displacement, (2) blurring and (3) nonlinearity. For this purpose, phantom images obtained from a magnetic resonance scanner were studied. Attempts made to reconstruct an ideal image from its distorted version by appropriately compensating for the three types of distortions yielded encouraging results.

Magnetic Resonance Imaging of Musculoskeletal Infections

In summary, MRI has a high sensitivity for the detection of inflammatory disease involving the musculoskeletal system. Because of the usual anatomic pattern of involvement in the vertebral column, there is also a high specificity. In the appendicular skeleton and pelvis, it is unclear whether MRI can add to the sensitivity and specificity of radionuclide studies in uncomplicated cases of acute infection. However, it can be performed more rapidly and provides greater anatomic detail and delineation of the extent of marrow involvement than radionuclide studies. MRI can be used in both acute and chronic osteomyelitis to guide a diagnostic interventional test to the appropriate site. It is capable of excluding involvement of the medullary canal, and it is better than radionuclide studies for differentiating soft tissue infection with periostitis from osteomyelitis. It has only a limited role in the immediate postoperative period, and in the presence of metallic implants, an indium-labeled leukocyte scan may be more appropriate. Finally, it must be remembered that the current data base of MRI is small and that further refinement of its role in the evaluation of inflammatory processes will be forthcoming.

The effect of an antimicrobial coating on metal implants. A pilot study in goats.

Reconstructive surgery in which implants are used is an ever widening sphere in which the techniques demand highly integrated team work with considerable emphasis on the prevention of wound infection. It is well recognised that factors influencing sepsis are increasing agc of the patient, the presence of a foreign body, the exposure of tissues for long periods of time, and the inability to use ‘no touch’ techniques. These factors operate when complicated procedures involving massive prosthetic replacements are undertaken. Implants separate the tissues and many of the prostheses used have cavities where bacteria can proliferate remote from attack via the blood stream. There is a divergence of opinion concerning the value of locally applied antibacterial agents, especially when uscd in the presence of metal implants. No assessment of the use of these agents could be found in the literature. This investigation was undertaken to try and establish the value of a known bactericidal agent when carried in a vehicle with which implants could be coated. To be effective the agent should be slowly released at the site. Infection was deliberately introduced at the time of operation in the goats, which were the animals used in this pilot study. Polyvinyl alcohol was chosen as the most suitable vehicle for the following reasons: