| 1. |
- Rösch, Frank, et al.
(författare)
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Radiolanthanides in nuclear medicine.
- 2004
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Ingår i: Metal ions in biological systems. - 0161-5149. ; 42, s. 77-108
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Forskningsöversikt (refereegranskat)
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| 2. |
- Töyräs, Juha, et al.
(författare)
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Speed of sound in normal and degenerated bovine articular cartilage.
- 2003
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Ingår i: Ultrasound in Medicine and Biology. - : Elsevier. - 0301-5629 .- 1879-291X. ; 29:3, s. 447-454
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Tidskriftsartikel (refereegranskat)abstract
- The unknown and variable speed of sound may impair accuracy of the acoustic measurement of cartilage properties. In this study, relationships between the speed of sound and cartilage composition, mechanical properties and degenerative state were studied in bovine knee and ankle cartilage (n = 62). Further, the effect of speed variation on the determination of cartilage thickness and stiffness with ultrasound (US) indentation was numerically simulated. The speed of sound was significantly (n = 32, p < 0.05) dependent on the cartilage water content (r = -0.800), uronic acid content (per wet weight, r = 0.886) and hydroxyproline content (per wet weight, r = 0.887, n = 28), Young's modulus at equilibrium (r = 0.740), dynamic modulus (r = 0.905), and degenerative state (i.e., Mankin score) (r = -0.727). In addition to cartilage composition, mechanical and acoustic properties varied significantly between different anatomical locations. In US indentation, cartilage is indented with a US transducer. Deformation and thickness of tissue are calculated using a predefined speed of sound and used in determination of dynamic modulus. Based on the simulations, use of the mean speed of sound of 1627 m/s (whole material) induced a maximum error of 7.8% on cartilage thickness and of 6.2% on cartilage dynamic modulus, as determined with the US indentation technique (indenter diameter 3 mm). We believe that these errors are acceptable in clinical US indentation measurements.
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| 3. |
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| 4. |
- Sahlman, Janne, et al.
(författare)
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A human COL2A1 gene with an Arg519Cys mutation causes osteochondrodysplasia in transgenic mice.
- 2004
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Ingår i: Arthritis and Rheumatism. - : John Wiley & Sons. - 0004-3591 .- 1529-0131. ; 50:10, s. 3153-3160
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Tidskriftsartikel (refereegranskat)abstract
- OBJECTIVE: An arginine-to-cysteine substitution at position 519 of the COL2A1 gene causes early generalized osteoarthritis with mild chondrodysplasia in humans. In this study, a human COL2A1 gene with the same mutation was introduced into a murine genome having 1 or no alleles of the murine Col2a1 gene, and the skeletal phenotypes of the transgenic mice were compared with those of control mice.METHODS: Mice with 1 allele of the normal murine Col2a1 gene and 1 allele of the mutated human COL2A1 gene (n = 10), those with no murine Col2a1 gene and 2 alleles of the mutated human COL2A1 gene (n = 13), those with no murine Col2a1 gene and only 1 allele of the mutated COL2A1 gene (n = 9), and normal control mice (n = 11) were studied for skeletal abnormalities, using radiographic imaging and light microscopic analyses of histologic sections. The collagen network of cartilage was also investigated with transmission electron microscopy.RESULTS: At 2 months of age, all transgenic mice had dysplastic changes in their long bones, flattened vertebral bodies, and osteoarthritic changes in their joints. The intervertebral discs of the transgenic animals were degenerated, and their histologic structure was disturbed. The changes were more severe in mice with no murine Col2a1 allele.CONCLUSION: The human COL2A1 gene with the Arg519Cys mutation causes osteochondrodysplasia in mice, as it does in humans.
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| 5. |
- Sundgren, Pia, et al.
(författare)
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Value of conventional, and diffusion- and perfusion weighted MRI in the management of patients with unclear cerebral pathology, admitted to the intensive care unit
- 2002
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Ingår i: Neuroradiology. - : Springer Science and Business Media LLC. - 1432-1920 .- 0028-3940. ; 44:8, s. 674-680
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Tidskriftsartikel (refereegranskat)abstract
- The aim of our retrospective study was to determine the extent to which diffusion- and perfusion- weighted MRI combined with conventional MRI could be helpful in the evaluation of intensive care unit (ICU) patients who have unknown or unclear cerebral pathology underlying a serious clinical condition. Twenty-one ICU patients with disparity between the findings on brain CT scan and their clinical status were studied. All patients underwent conventional MR and diffusion-weighted imaging and 14 also had MR perfusion studies. Abnormalities were present on diffusion-weighted imaging of 17 of the 21 patients and on perfusion-weighted studies of 7 of 14 patients. The MRI results changed the preliminary/working diagnosis in six patients. In eight other patients, MRI revealed additional pathology that had not been suspected clinically, and/or characterized more closely findings that had already been detected by CT or suspected clinically. MRI showed abnormalities in four of the five patients who had normal CT. MRI findings suggested a negative clinical outcome in all nine patients who subsequently died. MRI findings also suggested positive long-term outcome in five of nine patients who improved significantly as based on Glasgow and extended Glasgow outcome scales. In the three unconscious patients who had normal diffusion- and perfusion weighted imaging the clinical outcome was good. This study suggests that MRI in seriously ill ICU patients with unclear cerebral pathology can provide information that changes, characterizes, or supports diagnoses and/or prognoses and therefore facilitates further management.
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| 6. |
- Sjögreen Gleisner, Katarina
(författare)
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Image Processing for Quantitative Scintillation-Camera Imaging. Application to Radionuclide Therapy.
- 2001
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Individual-based determinations of the absorbed dose in radionuclide therapy largely rely on absolute measurement of the activity distribution and its redistribution over time. Scintillation-camera imaging is the most commonly employed measuring technique, applied in planar or SPECT mode, sometimes in combination with structural images from CT. In this thesis, methods for processing and analysis of scintillation-camera images have been studied, with the intent to compensate for the physical limitations involved in the imaging process and thereby improve the quantification accuracy. In particular, methods for image registration and segmentation have been developed. Evaluation of the earlier SPECT based quantification program revealed limitations for the measurement of small volumes, their activity and contrast, in situations where the object contrast deviated from 100%. A 3D deformable segmentation method was developed and applied for SPECT images. In preliminary evaluations, this method gave an adequate boundary, also in situations with low contrast and high levels of noise. For registration of SPECT and CT images, a method was developed where the possibility to use images acquired in the Compton scatter region was explored. The registration accuracy was obtained to about 10 mm, where the largest deviations occurred for slices with heterogeneous activity distributions. To achieve automation, this method was further developed by applying mutual information as similarity measure and spatial transformations in 3D. This registration method was applied for activity quantification and absorbed dose calculations in 3D, using the combined information from CT and SPECT. For planar image activity quantification, a 2D method for registration of whole-body emission and transmission images was developed, including a tailored spatial transformation. The accuracy was obtained to below pixel level (< 3.6 mm) for simulated images, to 9 mm in comparison to point markers for patients. A quantification method based on conjugate scintillation-camera images was also developed, in which a registered CT image was used for attenuation correction, background compensation and segmentation of organs. Evaluation using Monte Carlo simulated images showed an accuracy of within 10% for organ activity quantification. Throughout this thesis, the major application has been images acquired in association with radionuclide therapy using an 131I labeled monoclonal antibody.
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| 7. |
- Wikman, Per
(författare)
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On effects of low doses : Reply
- 2004
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Ingår i: Journal of Radiological Protection. - 0952-4746 .- 1361-6498. ; 24:4, s. 428-429
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Tidskriftsartikel (refereegranskat)
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| 8. |
- Engellau, Lena
(författare)
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MRI with MR Angiography in Endovascular Repair of Abdominal Aortic Aneurysms
- 2002
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The aim of this study was to evaluate MRI with contrast enhanced MR angiography (MRI/CE MRA) as imaging method before and after endovascular repair of abdominal aortic aneurysms (AAA). A 1.5 T scanner was used for all examinations. In this prospective study 26 consecutive patients were included. Follow-up was performed between February 1995 and May 2002 (median follow-up; 36 months, range 8-84 months). In Paper I, we assessed the value of MRI/CE MRA as follow-up method. MRI/CE MRA provided the relevant information. MRI was the sole method demonstrating intramural thrombus organization and vertebral body infarction. In Paper II, we evaluated MR safety; ferromagnetism and heating of a nitinol stent-graft. Image artefacts were also evaluated on MRI/CE MRA and CT. In addition, an extended MR protocol including velocity mapping was assessed. MRI in a 1.5 T system may be performed safely in patients with the nitinol stent-graft (Vanguard). MRI/CE MRA provided diagnostic image information with only minor metal artefacts. Image evaluation on CT can be disturbed at the graft limb junction and graft bifurcation by the beam hardening artefacts. MR velocity mapping did not provide additional information. In Paper III, we compared measurements for stent-graft planning. MRI/CE MRA was compared with DSA and CT. The MRA post processing techniques MIP and VRT were also compared. The length measurements obtained with MRA-MIP were significantly shorter, but probably more correct, than those obtained with DSA. The diameter measurements obtained with MRI/CE MRA were more variable. Improvements of the MRA technique and a standardized determination of the vessel boundaries are needed for more reliable diameter measurements. In Paper IV, we compared costs of follow-up with MRI/CE MRA with costs of follow-up with CT with DSA, or CTA. The cost analysis included a risk analysis of contrast media induced nephropathy. MRI/CE MRA can be cost-effective for follow-up depending on the risk of contrast media induced nephropathy for CT with DSA, or CTA. In Paper V, we presented mid-term results with the Stentor and Vanguard stent-grafts assessed with MRI/CE MRA. Complications and secondary interventions were common. Long-term follow-up is mandatory. This study has shown that for MR-compatible stent-grafts, MRI/CE MRA could be the method of choice for follow-up of endovascularly repaired AAA. For patients with pre-existing renal insufficiency MRI/CE MRA should be the method of choice.
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| 9. |
- Ståhl, H., et al.
(författare)
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Factors influencing organic carbon recycling and burial in Skagerrak sediments
- 2004
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Ingår i: Journal of Marine Research. - : Journal of Marine Research/Yale. - 0022-2402 .- 1543-9542. ; 62:6, s. 867-907
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Tidskriftsartikel (refereegranskat)abstract
- Different factors influencing recycling and burial rates of organic carbon (OC) were investigated in the continental margin sediments of the Skagerrak (NE North Sea). Two different areas, one in the southern and one in the northeastern part of the Skagerrak were visited shortly after a spring bloom (March 1999) and in late summer (August 2000). Results suggested that: (1) Organic carbon oxidation rates (C-ox) (2.2-18 mmol Cm-2 d(-1)) were generally larger than the O-2 uptake rates (1.9-25 mmol m(-2) d(-1)). Both rates were measured in situ using a benthic lander. A mean apparent respiration ratio (C-ox:O-2corr) of 1.3 +/- 0.5 was found, indicating some long-term burial of reduced inorganic substances in these sediments. Measured O-2, fluxes increased linearly with increasing C-ox rates during the late summer cruise but not on the, early spring cruise, indicating a temporal uncoupling of anaerobic mineralization and reoxidation of reduced substances. (2) Dissolved organic carbon (DOC) fluxes (0.2-1.0 mmol Cm-2 d(-1)) constituted 3-10% of the C-ox rates and were positively correlated with the latter, implying that net DOC production rates were proportional to the overall sediment OC remineralization rates. (3) Chlorophyll a (Chl-a) concentrations in the sediment were significantly higher in early spring compared to late summer. The measured C-ox rates, but not O-2 fluxes, showed a strong positive correlation with the Chl-a inventories in the top 3 cm of the sediment. (4) Although no relationship was found between the benthic fluxes and the macrofaunal biomass in the chambers, total in situ measured dissolved inorganic carbon (C-T) fluxes were 1-5.4 times higher than diffusive mediated C-T fluxes, indicating that macrofauna have a significant impact on benthic exchange rates of OC remineralization products in Skagerrak sediments. (5) OC burial fluxes were generally higher in northeastern Skagerrak than in the southern part. The same pattern was observed for burial efficiencies, with annual means of similar to62% and similar to43% for the two areas respectively. (6) On a basin-wide scale, there was a significant positive linear correlation between the burial efficiencies and sediment accumulation rates. (7) The calculated particulate organic carbon (POC) deposition, from benthic flux and burial measurements, was only 24-78% of the sediment trap measured POC deposition, indicating a strong near-bottom lateral transport and resuspension of POC. (8) A larger fraction of the laterally advected material of lower quality seemed to settle in the northeastern Skagerrak rather than in the southern Skagerrak. (9) Skagerrak sediments, especially in the northeastern part, act as an efficient net sink for organic carbon, even in a global continental margin context.
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| 10. |
- Christensson, Anders, et al.
(författare)
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Serum cystatin C advantageous compared with serum creatinine in the detection of mild but not severe diabetic nephropathy.
- 2004
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Ingår i: Journal of Internal Medicine. - : Wiley. - 1365-2796 .- 0954-6820. ; 256:6, s. 510-518
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Tidskriftsartikel (refereegranskat)abstract
- OBJECTIVE: To determine whether serum cystatin C is more accurate than serum creatinine in the detection of diabetic nephropathy, also after adjustment for age.METHODS: Forty-one patients with type 1 and 82 patients with type 2 diabetes were evaluated with serum creatinine, serum cystatin C, and (51)Cr-EDTA clearance (reference method). Cystatin C was measured by a particle-enhanced turbidimetric method and creatinine by an enzymatic method. Statistical estimations were performed both without and with age adjustment created by z-scores for (51)Cr-EDTA clearance, creatinine, and cystatin C. The cut-off levels for glomerular filtration rate (GFR) ((51)Cr-EDTA clearance) were 60 and 80 mL min(-1) 1.73 m(-2), respectively, in absolute values and 80, 90 and 95% CIs, respectively, in age-adjusted values (z-scores).RESULTS: Estimations without age adjustment showed significantly (P = 0.0132) closer correlation for cystatin C (r = 0.817) versus (51)Cr-EDTA clearance as compared with creatinine (r = 0.678). However, when using age-adjusted values, the correlation for cystatin C and creatinine, respectively, versus (51)Cr-EDTA clearance did not differ. When comparing the diagnostic utilities for serum cystatin C versus serum creatinine in manifest renal impairment (GFR < 60 mL min(-1) 1.73 m(-2) or z-scores <-1.28 SD), there were no significant differences between the two markers whether age adjusted or not. However, for diagnosing mild nephropathy (GFR < 80 mL min(-1) 1.73 m(-2) or z-score -0.84 SD), serum cystatin C is significantly more useful.CONCLUSIONS: Serum cystatin C performed better compared with serum creatinine even when measured enzymatically, to detect mild diabetic nephropathy. However, serum creatinine was as efficient as serum cystatin C to detect advanced diabetic nephropathy.
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