| 11. |
- Önsten, Ingemar, et al.
(författare)
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Migration and wear of a hydroxyapatite-coated hip prosthesis. A controlled roentgen stereophotogrammetric study
- 1996
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Ingår i: Journal of Bone and Joint Surgery: British Volume. - 2044-5377. ; 78:1, s. 85-91
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Tidskriftsartikel (refereegranskat)abstract
- A consecutive series of 30 total hip replacements using a hydroxyapatite (HA)-coated, modular implant (Omnifit) was followed clinically and by roentgen stereophotogrammetric analysis for two years and compared with two control groups, one of 27 cemented Charnley sockets and one of 40 cemented Charnley stems. Omnifit sockets with a central gap between the dome of the socket and the acetabular bone in the postoperative radiographs, migrated less than sockets without such gaps (p = 0.01). After adjustment for patient-related factors (age, gender and weight), no significant difference was found between the two prostheses with respect to micromotion and wear. We conclude that the early fixation of the HA-coated Omnifit prosthesis compares with that of the cemented Charnley prosthesis.
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| 12. |
- Spevack, Daniel M., et al.
(författare)
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Feasibility of quantification of unreconstructed SPECT projection views using the opposing view method
- 1996
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Ingår i: SPIE - The International Society for Optical Engineering. - : SPIE - International Society for Optical Engineering. ; , s. 734-741
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Konferensbidrag (refereegranskat)abstract
- When single photon emission computer aided tomography (SPECT) is performed, planar projection views are taken at a series of stepping angles covering the entire arc around the patient. These projection views are identical to planar gamma camera images, except that they are generally taken with a shorter acquisition time. The projection views are reconstructed to create transaxial SPECT images via backprojection techniques. We attempted the following studies to show that opposing SPECT projection views could yield the same correct quantitative information as the planar gamma camera images. Planar and SPECT images were used from patients who had received 0.135 MBq (5 mCi) of In-111-methyl benzyl DTPA BrE- 3 monoclonal antibodies. An In-111 filled flat flood source was utilized to acquire transmission images on the planar gamma camera in order to generate an attenuation map of the patient in the anterior/posterior plane. A camera calibration factor was obtained using a source of known activity. The activity of the liver was determined from abdominal planar images using regions of interest (ROIs) drawn around the liver on opposing anterior and posterior views. Similarly, the activity of the liver was determined from the opposing SPECT projection images which showed the anterior and posterior views. The same attenuation map was used for the correction of both the planar images and SPECT projection views. A cylindrical plastic phantom containing spherical plastic balls was used to validate that this technique accurately measured the activity contained in selected ROIs. Planar and SPECT images were taken of the phantom with each ball containing 6.8 kBq (250 (mu) Ci) of Tc- 99m. A Tc-99m filled flat flood source was utilized to acquire transmission images on the planar gamma camera, and a source of known activity was used to obtain a camera calibration. Using a similar method to that used on the liver images, the activity of the balls was determined from the planar images and the SPECT projection views. Liver activities calculated from SPECT projection views matched the activities calculated from the planar images within 20% error. The activities for each ball in the phantom, calculated from SPECT projection views, matched the activity calculated from the planar images within 5% error, and matched the known activity in each ball within 10% error. The data indicates that despite their short acquisition times, the SPECT projection views may be used to quantify the activity from ROIs, without a significant increase in error associated with activity measurement.
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| 13. |
- Akeson, P, et al.
(författare)
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MR imaging in recurrent pain after back surgery. A comparative study using standard and high doses of gadolinium contrast agents
- 1996
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Ingår i: Acta Radiologica. - 1600-0455. ; 37:6, s. 858-858
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Tidskriftsartikel (refereegranskat)abstract
- PURPOSE: To compare the diagnostic results following injection of (a) a high dose (0.3 mmol/kg b.w.) of gadodiamide injection and (b) the standard dose (0.1 mmol/kg b.w.) of Gd-DTPA, in patients with recurrent symptoms after surgery for lumbar disc herniation. MATERIAL AND METHODS: Twenty patients with recurrent or sustained symptoms after surgery for lumbar disc herniations were examined. MR imaging (0.3 T) was first performed before and after Gd-DTPA at 0.1 mmol/kg b.w., and then within one month (17 patients) or within 3 months (3 patients) before and after gadodiamide injection at 0.3 mmol/kg b.w. The examinations were first evaluated by 2 neuroradiologists blinded to dose but not to patient as the images were presented in pairs. Six months later the same investigators evaluated the examinations again, this time blinded to both dose and patient. RESULTS: At the evaluation in pairs (with the investigators blinded to dose only) the high-dose examinations were considered the most informative (p=0.05). However, at the later evaluation (with the investigators blinded both to dose and patient) no significant difference between high and standard dose was found regarding diagnosis or diagnostic certainty. CONCLUSION: In this study the high-dose contrast enhancement of MR imaging at 0.3 T did not increase the diagnostic information for differentiating between scar and recurrent hernia. The high-dose images were considered more informative when evaluated in pairs, but gave no additional or different information when evaluated separately. The study also indicated that comparisons in pairs should be interpreted with caution.
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| 14. |
- Albeck, M J, et al.
(författare)
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Billeddiagnostik ved mistanke om lumbal diskusprolaps. En kontrolleret sammenligning af myelografi, CT og magnetisk resonans-billeddannelse
- 1996
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Ingår i: Ugeskrift for Læger. - 0041-5782. ; 158:10, s. 1362-1362
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Tidskriftsartikel (refereegranskat)abstract
- Eighty patients with monoradicular sciatica were examined by myelography, computed tomography (CT) and magnetic resonance imaging (MRI) and all had subsequent surgery. The images were evaluated by a decision-analytic regret function. The largest amount of diagnostic information was gained from CT followed by MRI and myelography. Myelography was not significantly informative. The results suggest that CT or MRI should be the first choice examination in patients with suspected lumbar disc herniation.
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| 15. |
- Annertz, Mårten, et al.
(författare)
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MR imaging as the primary modality for neuroradiologic evaluation of the lumbar spine. Effects on cost and number of examinations
- 1996
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Ingår i: Acta Radiologica. - 1600-0455. ; 37:3 Pt 1, s. 373-380
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Tidskriftsartikel (refereegranskat)abstract
- PURPOSE: To evaluate the effects on cost, and number of primary and supplementary neuroradiologic examinations, after introducing MR imaging as the primary modality in the evaluation of the lumbar spine. MATERIAL AND METHODS: Two 5-month periods were compared: period 1--before MR; and period 2--after introduction of a 2nd MR device. In period 1, patients were examined with myelography and/or CT after referral from specialists only, whereas in period 2 both specialists and general practitioners could refer patients for MR imaging. The direct cost (neuroradiologic methods and hospitalization) and indirect cost (sick-leave and estimated loss of production caused by the diagnostic procedure) were estimated. RESULTS AND CONCLUSION: In period 1, investigations were started in 75 patients (62 myelographies and 13 CT examinations); in period 2, in 227 patients (198 MR, 21 CT, and 8 myelographies). The estimated total cost increased from SEK 825,000 to 1,265,000 (53%), the cost per investigated patient decreasing from 11,000 to 5565 (50%), and the cost of preoperative investigation per operated patient decreasing from 8616 to 5563 (35%). The number of supplementary examinations was unchanged.
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| 16. |
- Belletti, S., et al.
(författare)
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Quality assurance in radiotherapy: the importance of medical physics staffing levels. Recommendations from an ESTRO/EFOMP joint task group
- 1996
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Ingår i: Radiotherapy and Oncology. - 1879-0887. ; 41:9, s. 89-94
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Tidskriftsartikel (refereegranskat)abstract
- The safe application of ionising radiation for diagnosis and therapy requires a high level of knowledge of the underlying processes and of quality assurance. Sophisticated modern equipment can be used effectively for complicated diagnostic and therapeutic techniques only with adequate physics support. In the light of recent analyses and recommendations by national and international societies a joint working group of representatives from ESTRO (European Society for Therapeutic Radiology and Oncology) and from EFOMP (European Federation of Organisations for Medical Physics) was set up to assess the necessary staffing levels for physics support to radiotherapy. The method used to assess the staffing levels, the resulting recommendations and examples of their practical application are described.
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| 17. |
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| 18. |
- Blad, Börje, et al.
(författare)
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The influence of air humidity on an unsealed ionization chamber in a linear accelerator
- 1996
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Ingår i: Physics in Medicine and Biology. - : IOP Publishing. - 1361-6560 .- 0031-9155. ; 41:11, s. 2541-2548
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Tidskriftsartikel (refereegranskat)abstract
- The safe and accurate delivery of the prescribed absorbed dose is the central function of the dose monitoring and beam stabilization system in a medical linear accelerator. The absorbed dose delivered to the patient during radiotherapy is often monitored by a transmission ionization chamber. Therefore it is of utmost importance that the chamber behaves correctly. We have noticed that the sensitivity of an unsealed chamber in a Philips SL linear accelerator changes significantly, especially during and after the summer season. The reason for this is probably a corrosion effect of the conductive plates in the chamber due to the increased relative humidity during hot periods. We have found that the responses of the different ion chamber plates change with variations in air humidity and that they do not return to their original values when the air humidity is returned to ambient conditions.
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| 19. |
- Cronqvist, Mats, et al.
(författare)
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Evaluation of time-of-flight and phase-contrast MRA sequences at 1.0 T for diagnosis of carotid artery disease. I. A phantom and volunteer study
- 1996
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Ingår i: Acta Radiologica. - 1600-0455. ; 37:3 Pt 1, s. 267-277
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Tidskriftsartikel (refereegranskat)abstract
- PURPOSE AND MATERIAL: The aim of this work was, firstly, to compare different manufacturer-provided MRA sequences in a 1.0 T MR unit, with respect to the visibility of an artificial stenosis in a flow phantom and, secondly, to evaluate the same sequences in healthy volunteers with respect to S/N ratio levels and practical in vivo implementation routines. METHODS: The studied sequences were 2D and 3D TOF and sequences with an acquisition time of approximately 10 min. Quantitative signal evaluation was made using single transverse partitions in all phantom experiments. MIP angiograms and MPR reconstructions were made for visual inspection of image quality. In vivo, the images were individually evaluated by visual inspection by experienced neuroradiologists. RESULTS: In the evaluation of the grade and length of a stenosis, a combination of MIP and MPR was seen to be the optimal and necessary procedure. A shortening of TE played an important and significant role in the visualization of the poststenotic flow in the phantom using TOF MRA. However, the shortest TE values gave poor S/N ratio in vivo. The good results achieved in the phantom studies for 3D phase-contrast were somewhat reversed in the volunteer studies, whereas 3D TOF sequences showed good results in both the phantom and the volunteer studies.
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| 20. |
- Ekberg, Olle, et al.
(författare)
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Sports-related groin pain: evaluation with MR imaging
- 1996
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Ingår i: European Radiology. - 0938-7994. ; 6:1, s. 52-55
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Tidskriftsartikel (refereegranskat)abstract
- Our purpose was to assess the role of MRI in evaluating the musculoskeletal system in athletes with chronic pain laterally in the groin of unknown etiology. Magnetic resonance imaging (MRI) of the pubic ring was performed in 11 young athletes (soccer players) with long-standing groin pain. MR findings were compared with plain films and isotope examination (bone scan Tc 99M). Abnormal MRI findings included a broadened and irregular symphysis with a characteristic pattern of low signal intensity on T1W and high signal intensity on T2W images localized in the superior pubic ramus at a distance from the symphysis. Positive findings were also observed on plain films and on nuclear medicine studies. However, the imaging findings in the superior public ramus of the symphysis was located considerably more laterally on MRI. MRI is a valuable method for evaluating discrete and ambiguous pelvic pain in athletes, particularly for identifying concomitant changes in the superior ramus, which may give rise to long-standing pain localized laterally in the groin.
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