| 1. |
- Geijer, Håkan, et al.
(författare)
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Optimizing the tube potential for lumbar spine radiography with a flat-pane digital detector
- 2009
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Ingår i: British Journal of Radiology. - : British Institute of Radiology. - 0007-1285 .- 1748-880X. ; 82:973, s. 62-68
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Tidskriftsartikel (refereegranskat)abstract
- The purpose of this study was to find the optimal settings for lumbar spine radiography with a flat-panel detector. A CDRAD contrast-detail phantom was imaged at various tube potentials, system speeds and filtration settings. Factorial experiments yielded a range of optimized exposure settings, which were submitted to visual grading analysis with images of an Alderson phantom. The first optimized settings involved a system speed increase from 400 to 800. For anteroposterior projection, the optimal tube potential was reduced from the default of 77 kV to 60 kV to give the best image quality without increasing the effective dose, or to 66 kV to give the lowest dose without reducing image quality. For lateral projection, the tube potential was similarly reduced from the default of 90 kV to 70 kV or 77 W. Visual grading analysis confirmed the results, with significantly better image quality when optimizing for image quality. The study thus shows that the tube potential can be reduced as long as the system speed is increased simultaneously. This leads to a lower effective dose and/or increased image quality depending on the settings chosen. The factorial experiments provided a powerful way to evaluate several parameters concomitantly.
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| 2. |
- Jansson, Margareta, et al.
(författare)
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Reducing dose in urography while maintaining image quality - a comparison of storage phosphor plates and a flat-panel detector
- 2006
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Ingår i: European Radiology. - Berlin / Heidelberg : Springer. - 0938-7994 .- 1432-1084. ; 16:1, s. 221-226
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Tidskriftsartikel (refereegranskat)abstract
- The introduction of new flat-panel detector technology often forces us to accept too high dose levels as proposed by the manufacturers. We need a tool to compare the image quality of a new system with the accepted standard. The aim of this study was to obtain a comparable image quality for two systems-storage phosphor plates and a flat-panel system using intravenous urography (IVU) as a clinical model. The image quality figure was calculated using a contrast-detail phantom (CDRAD) for the two evaluated systems. This allowed us to set a dose for the flat-panel system that gave equivalent image quality to the storage phosphor plates. This reduced detector dose was used in an evaluation of clinical images to find out if the dose reduction from the phantom study indeed resulted in images of equal clinical image quality. The image quality was assessed using image criteria of the European guidelines for IVU with visual grading analysis. Equivalent image quality in image pairs was achieved at 30% of the dose. The CDRAD contrast-detail phantom makes it possible to find dose levels that give equal image quality using different imaging systems.
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| 3. |
- Larzon, Thomas, et al.
(författare)
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Fascia suturing of large access sites after endovascular treatment of aortic aneurysms and dissections
- 2006
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Ingår i: Journal of Endovascular Therapy. - 1526-6028 .- 1545-1550. ; 13:2, s. 152-157
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Tidskriftsartikel (refereegranskat)abstract
- PURPOSE: To evaluate a technique for closure of a femoral artery access in which the cribriform fascia covering the common femoral artery is sutured.METHODS: A consecutive series of 127 patients (103 men; median age 74 years, range 45- 89) underwent endovascular aortic aneurysm repair between August 2001 and September 2004. Twelve patients underwent a secondary intervention for a total of 139 procedures in the group. Sixty-one (43.9%) of the 139 operations were acute. Among the 257 femoral arteries used for access, a fascia suturing technique was performed in 131 (51.0%). Data were collected for analysis of access site complications, bleeding, thrombosis, pseudoaneurysm, and stenosis. A subgroup of 72 patients had ankle-brachial indexes (ABI) recorded; another subgroup of 50 patients were also investigated by duplex ultrasonography.RESULTS: Complications occurred in 18 (13.7%) of the 131 sutured cases. The majority (n = 16) arose within 24 hours: 8 cases of perioperative bleeding or thrombosis required open surgery and 8 cases were reoperated within 24 hours for bleeding (n = 4), thrombosis (n = 3), and 1 intimal dissection. The acute failure rate was 12.2%. Two patients had late complications: 1 case of neuralgia and 1 pseudoaneurysm that required acute surgery 28 months postoperatively. The ABI did not change significantly from pre- to postoperatively in the 72 patients examined. Five patients with stenoses did not have a reduction in ABI. In the 66 sites examined with ultrasound in 50 patients, 3 minor pseudoaneurysms were detected.CONCLUSION: The fascia suturing technique for closure of a femoral artery access during endovascular repair of aortic diseases is feasible, even in acute situations. Failures can be managed easily. Late complications requiring additional procedures are rare.
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| 4. |
- Norrman, Eva, et al.
(författare)
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A clinical evaluation of the image quality computer program, CoCIQ
- 2005
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Ingår i: Journal of digital imaging. - : Springer Science and Business Media LLC. - 0897-1889 .- 1618-727X. ; 18:2, s. 138-144
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Tidskriftsartikel (refereegranskat)abstract
- To provide an objective way of measuring image quality, a computer program was designed that automatically analyzes the test images of a contrast-detail (CD) phantom. The program gives a quantified measurement of image quality by calculating an Image Quality Figure (IQF). The aim of this work was to evaluate the program and adjust it to clinical situations in order to find the detectable level where the program gives a reliable figure of the contrast resolution. The program was applied on a large variety of images with lumbar spine and urographic parameters, from very low to very high image qualities. It was shown that the computer program produces IQFs with small variations and there were a strong linear statistical relation between the computerized evaluation and the evaluation performed by human observers (R2 = 0.98). This method offers a fast and easy way of conducting image quality evaluations.
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| 5. |
- Norrman, Eva, et al.
(författare)
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Optimization of image process parameters through factorial experiments using a flat panel detector
- 2007
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Ingår i: Physics in Medicine and Biology. - Bristol : IOP publishing. - 0031-9155 .- 1361-6560. ; 52:17, s. 5263-5276
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Tidskriftsartikel (refereegranskat)abstract
- In the optimization process of lumbar spine examinations, factorial experiments were performed addressing the question of whether the effective dose can be reduced and the image quality maintained by adjusting the image processing parameters. A 2(k)-factorial design was used which is a systematic and effective method of investigating the influence of many parameters on a result variable. Radiographic images of a Contrast Detail phantom were exposed using the default settings of the process parameters for lumbar spine examinations. The image was processed using different settings of the process parameters. The parameters studied were ROI density, gamma, detail contrast enhancement (DCE), noise compensation, unsharp masking and unsharp masking kernel (UMK). The images were computer analysed and an image quality figure (IQF) was calculated and used as a measurement of the image quality. The parameters with the largest influence on image quality were noise compensation, unsharp masking, unsharp masking kernel and detail contrast enhancement. There was an interaction between unsharp masking and kernel indicating that increasing the unsharp masking improved the image quality when combined with a large kernel size. Combined with a small kernel size however the unsharp masking had a deteriorating effect. Performing a factorial experiment gave an overview of how the image quality was influenced by image processing. By adjusting the level of noise compensation, unsharp masking and kernel, the IQF was improved to a 30% lower effective dose.
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| 6. |
- Souza, Domingos S. R., et al.
(författare)
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Harvesting the saphenous vein with surrounding tissue for CABG provides long-term graft patency comparable to the left internal thoracic artery : results of a randomized longitudinal trial
- 2006
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Ingår i: Journal of Thoracic and Cardiovascular Surgery. - : Elsevier BV. - 0022-5223 .- 1097-685X. ; 132:2, s. 373-U75
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Tidskriftsartikel (refereegranskat)abstract
- Objective: Conventional harvesting of the saphenous vein in coronary artery bypass surgery produces vessel damage that contributes to graft failure. A novel "no touch" technique provides high short- and long-term patency rates.Method: This randomized longitudinal trial compares graft patency of two patient groups undergoing coronary artery bypass surgery. Conventional: 52 patients had their veins stripped, distended, and stored in saline solution. No-touch: 52 patients had veins removed with surrounding tissue, not distended, and stored in heparinized blood. Angiographic assessment was performed at mean time 18 months after the operation in 46 patients in the conventional group and 45 patients in the no-touch group and repeated at mean time 8.5 years in 37 patients from both groups.Results: The distribution of the grafts to the recipient coronary arteries regarding their size and quality was similar in both groups. The angiographic assessment at 18 months postoperatively showed 89% conventional versus 95% no-touch grafts were patent. Repeated angiography at 8.5 years showed a patency rate for the conventional group of 76% and 90% for the no- touch group ( P =.01). The multivariate analysis showed that the most important surgical factors for graft patency were the technique of harvesting ( odds ratio = 3.7, P =.007) for the no- touch versus the conventional technique and the vein quality before implantation ( odds ratio = 3.2, P =.007) for veins that were of good quality. By comparison the patency of the thoracic artery grafts was 90%.Conclusion: Harvesting the saphenous vein with surrounding tissue provides high short- and long-term patency rates comparable to the left internal thoracic artery.
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