PubMed · 15496790
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Rosemary E Leitch, Michaelene Ouwendyk, Robert M Lindsay. 2004. Vascular access.. https://doi.org/10.1159/000081665
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PURPOSE: To investigate motion and shape change when using an endorectal balloon (ERB) in patients receiving radiotherapy for prostate cancer. METHODS: In nine patients treated for prostate cancer using an ERB, the anterior wall of the ERB was contoured on right lateral images taken immediately before irradiation, and on left lateral images taken immediately after irradiation. Changes in the contours were used to calculate inter-fraction shape change and inter-imaging motion and shape change. Inter-imaging motion describes changes that occur after the right lateral image is taken that are seen in the left lateral image. RESULTS: Eighty-six percent of all inter-imaging shifts of the anterior wall of the ERB were in the posterior direction (mean: 1.8 mm, 1 SD: 1.8 mm, maximum posterior shift: 2.8-7.2 mm). The inter-fraction shape change (1 SD) of the anterior wall was equivalent to a change in the angle of the balloon of 2.5-5.7 degrees, with a range of 8-20 degrees, depending on the patient. Inter-imaging shape changes were similar in size. CONCLUSIONS: The inter-imaging motion and shape changes may be explained by the patient relaxing some time after insertion of the ERB, indicating that it could be reduced by a waiting period after insertion before irradiation. Development of image-guided localization strategies should consider intra-fraction motion and also inter- and intra-fraction shape change.
The placement of guide-wires and catheters to gain access to the upper urinary tract can induce undesirable stresses on tissues. Previous studies have characterized the performance of wires and catheters by evaluating their physical properties such as stiffness and friction coefficient. However, the results of these studies do not directly quantify the wire's effects on tissues. Furthermore, the individual physical properties of wires and catheters investigated in previous studies cannot be simply summed up to characterize the behavior of an entire wire/catheter ensemble. This paper presents an objective method for testing guide-wires and catheters that estimates the forces applied by these instruments to anatomical structures during urological procedures. Our model utilizes a computer-controlled test stand that simulates a urological environment by including a tortuous path and a stone obstruction. Experimental results using this model show significant promise in reflecting the performance of guide-wires and catheters measuring the stress exerted upon relevant anatomical structures. Furthermore, due to the modularity of the approach, the model can be easily reconfigured to simulate environments relevant to other medical fields.