Determination of Radiation Doses to Patients Undergoing Fluoroscopically Guided Orthopaedic Procedures at Muhimbili Orthopaedic Institute in Tanzania

The aim of the present study was to determine the magnitude of radiation doses delivered to patients undergoing Fluoroscopically Guided Orthopaedic Procedures (FGOP’s) in Tanzania. The air Kerma Area Product (KAP), fluoroscopy time, organ dose and effective dose to patients undergoing FGOP’s were obtained from Muhimbili Orthopaedic Institute. A total of 72 adult patients from selected three FGOPs namely Lumbar Spine (LS), Dynamic Hip Screw (DHS) and Thoracic Spine (TS) procedures were investigated using C-arm fluoroscopy machine. The knowledge of patient demographic data, radiographic data, KAP and Monte Carlo-based PCXMC software were used to obtain the magnitude of organ doses (OD) and effective doses (ED) of the patients. The median values of KAP for the LS, DHS and TS were 2.569, 2.410 and 0.770 Gy cm2, respectively. The mean values of ED for the LS, DHS, and TS procedures were 0.27, 0.47 and 2.70 mSv, respectively. The observed wide variations of KAP, organ dose, effective and exposure protocols within the hospital under study and relative high dose in this study compared to reported values from the literature call for standardization of procedural protocols and optimize fluoroscopically guided orthopaedic procedures. Keywords: Kerma-area-product; organ dose; effective dose; C-arm fluoroscopy machine; orthopaedic proceduresDetermination of Radiation Doses to Patients Undergoing Fluoroscopically Guided Orthopaedic Procedures at Muhimbili Orthopaedic Institute in Tanzani

Evaluation of the Influence of Additional Beam Filtration on Image Quality and Patient Dose in X-ray Fluoroscopy Procedures

The aim of the study was to evaluate the influence of additional filtration on radiation dose and image quality for patients during hysterosalpingography (HSG) and retrograde urethrography (RUG) procedures. The influence of filtering on image quality for each phantom thickness was made using a combination of different filter thicknesses. Entrance surface air kerma (ESAK) rates to Perspex phantom were measured using a solid state detector for various added combination of filter materials. Fluoroscopic image contrast was assessed using a Leeds TOR-18FG test object with a range of filter materials and phantom thicknesses. Phantom studies demonstrated that the use of additional filter materials of up to 0.35 mm thickness of copper could be used without significant effect on the image quality. ESAK values were determined for 16, 20, 24 and 28 cm phantom. Phantom ESAK reduced by 63%, 63%, 64% and 65% for 16, 20, 24 and 28 cm, respectively, when using 0.35 mm Cu + 1 mmAl, without degrading image contrast. Three independent radiologists perceived no change in clinical image quality with added filtration. On adding 0.35 mm Cu and 1 mm Al, the KAP per examination for the HSG was reduced by 71%, while for the RUG was reduced by 75%.Key words: Additional filtration; image quality; patient dose; X-ray fluoroscopy procedure

Preliminary Investigation of the Process Capabilities of Hydroforging

Hydroforging is a hybrid forming operation whereby a thick tube is formed to a desired geometry by combining forging and hydroforming principles. Through this process hollow structures with high strength-to-weight ratio can be produced for applications in power transmission systems and other structural components that demands high strength-to-weight ratio. In this process, a thick tube is deformed by pressurized fluid contained within the tube using a multi-purpose punch assembly, which is also used to feed tube material into the die cavity. Fluid pressure inside the thick tube is developed by volume change governed by the movement of the punch assembly. In contrast to the conventional tube hydroforming (THF), the hydroforging process presented in this study does not require external supply of pressurized fluid to the deforming tube. To investigate the capability of hydroforging process, an experimental setup was developed and used to hydroforge various geometries. These geometries included hollow flanged vessels, hexagonal flanged parts, and hollow bevel and spur gears

Utilization of Secondary Jet in Cavitation Peening and Cavitation Abrasive Jet Polishing

The cavitation peening (CP) and cavitation abrasive jet polishing (CAJP) processes employ a cavitating jet to harden the surface or remove surface irregularities. However, a zero incidence angle between the jet and the surface limits the efficiency of these two processes. This limitation can be improved by introducing a secondary jet. The secondary jet interacts with the main jet, carrying bubbles to the proximity of the workpiece surface and aligning the disordered bubble collapse events. Through characterizing the treated surface of AL6061 in terms of the hardness distribution and surface roughness, it was found out that the secondary jet can increase the hardening intensity by 10%, whereas the material removal rate within a localized region increased by 66%. In addition, employing multiple secondary jets can create a patched pattern of hardness distribution. Another finding is that the hardening effect of the cavitation increases with the processing time at first and is then saturated