Effect of fat-contamination and fat-suppression on T2 quantitation of knee articular cartilage in vivo

This study aims to investigate the effect of fat contamination and fat suppression (FS) on in vivo T2 mapping of knee articular cartilage. T2 mapping is a technique used in magnetic resonance imaging (MRI) and it has advantages over radiography techniques, such as no ionizing radiation and T2 maps give information about cartilage content and structure. Knee articular cartilage has high water concentration and near the cartilage, there is fat tissue, i.e. bone marrow and subcutaneous fat. Fat causes chemical shift artifact and can contaminate T2 values of T2 maps. To minimize chemical shift artifacts, FS is needed to suppress the fat signal. Four volunteers were imaged on a 3 Tesla MRI clinical scanner and T2 values were calculated in several regions of tibiofemoral cartilage using a multi-echo spin-echo sequence (MSME) with and without FS (NoFS). Two frequency encoding directions, superior-inferior (SI) and inferior-superior (IS), were used to evaluate the effects of FS on chemical shift artifact. Sagittal slices of the knee were manually segmented to 18 region of interests (ROIs) and then T2 maps were calculated with MATLAB based scripts. The repeatability of segmentation was evaluated, which was achieved by segmenting same slices multiple times. Differences between NoFS T2-SI and NoFS T2-IS ranged widely and in 11 out of 18 ROIs the differences were high, suggesting that the chemical shift artifact affects most of the cartilage regions. Particularly affected were the superficial and deep femoral cartilage and deep tibia. Differences between FS T2-SI and FS T2-IS values were low to moderate in most of the ROIs, with the highest differences observed in deep parts of anterior and central femur. Comparing NoFS T2 and FS T2 values with the same frequency encoding direction, differences were on average higher using SI direction than IS direction, and the deep ROIs were the most affected. Repeatability of segmentation was great in eight ROIs without FS and six ROIs with FS and the average differences were low for both NoFS and FS T2 mapping. For NoFS T2 mapping, segmentation repeatability was high in deep tibial cartilage. On the contrary, FS T2 mapping showed that the repeatability of the segmentation was low to moderate in superficial parts of posterior femur and deep parts of posterior tibia. The use of FS improved slightly repeatability of the cartilage segmentation in several regions and reduced the chemical shift artifacts. However, the regional heterogeneity in FS sequence introduced further uncertainties in T2 measurements

Hengitystahdistuksen merkitys rintasyövän sädehoidossa ja sydämen säteilyannoksen vähentämisessä

Rintasyöpä on yleisin syöpä Suomessa ja sitä esiintyy lähinnä naisilla, mutta myös muutama tapaus vuodessa esiintyy miehillä. Rintasyöpää hoidetaan usein osaresektiolla, johon yhdistetään sädehoito, mutta myös mastektomiaan voidaan yhdistää sädehoitoa. Sädehoidossa pitää huomioida terve kudos ja huolehtia siitä, että sädetettävän kohdealueen vieressä oleva terve kudos saa mahdollisimman vähän säteilyä. Toisaalta samalla kohdealueelle pitää saada tarpeeksi suuri säteilyannos, jotta sädehoito on tehokasta ja toimivaa. Vasemman rinnan rintasyövän sädehoidossa täytyy ottaa huomioon sydämen sijainti. Vapaassa hengityksessä sydän sijaitsee hyvin lähellä vasenta rintaa eli lähellä sädetettävää aluetta. Sydän ja sen pinnalla kulkevat verisuonet voivat saada helposti suuren sädeannoksen, jollei tätä oteta huomioon sädehoidon annossuunnittelussa. Säderasitteesta voi seurata myöhemmin komplikaatioita ja siksi tähän ongelmaan on kehitetty hengitystahdistus tekniikoita, joista tässä tutkielmassa keskitytään DIBH -tekniikka (Deep Inspiration Breath-Hold). DIBH-tekniikassa potilas hengittää syvään sisään ja pidättää hengitystä hetken, jonka aikana vasenta rintaa säteilytetään. Syvällä sisäänhengityksellä sydämen ja vasemman rinnan väliin saadaan välimatkaa muutamia senttejä ja sydämeen kohdistuva sädeannos pienenee. Tässä tutkielmassa päätavoitteena oli selvittää DIBH -tekniikan hyötyjä ja haittoja sekä vertailla DIBH -tekniikkaa vapaaseen hengitykseen, painottaen sydämen ja sydämen pinnalla olevan vasemman sepelvaltimon, Left Anterior Descending arteryn eli LAD:n, saamaa sädeannosta vasemman rinnan sädehoidossa. Tutkimustuloksien perusteella DIBH-tekniikan käyttö vasemman rinnan rintasyövän sädehoidossa on suositeltavaa, mikäli potilas siihen kykenee. DIBH -tekniikan käyttö vaati potilailta hieman harjoittelua sekä siinä määrin hyvän perusterveydentilan, että noin 15–20 sekuntia pitkät syvät sisäänhengitykset onnistuvat ongelmitta. Lisäksi DIBH -tekniikan käyttö vaatii myös hoitohenkilökunnalta hieman enemmän aikaa ja vaivaa kuin vapaa hengitys, mutta hyödyt ovat huomattavat potilaan kannalta. Sydämen ja LAD:n keskiarvoiset sädeannokset laskevat DIBH-tekniikalla noin puoleen siitä, mitä ne olisivat vapaassa hengityksessä

Quantitative dual contrast photon-counting computed tomography for assessment of articular cartilage health

Photon-counting detector computed tomography (PCD-CT) is a modern spectral imaging technique utilizing photon-counting detectors (PCDs). PCDs detect individual photons and classify them into fixed energy bins, thus enabling energy selective imaging, contrary to energy integrating detectors that detects and sums the total energy from all photons during acquisition. The structure and composition of the articular cartilage cannot be detected with native CT imaging but can be assessed using contrast-enhancement. Spectral imaging allows simultaneous decomposition of multiple contrast agents, which can be used to target and highlight discrete cartilage properties. Here we report, for the first time, the use of PCD-CT to quantify a cationic iodinated CA4+(targeting proteoglycans) and a non-ionic gadolinium-based gadoteridol (reflecting water content) contrast agents inside human osteochondral tissue (n=53). We performed PCD-CT scanning at diffusion equilibrium and compared the results against reference data of biomechanical and optical density measurements, and Mankin scoring. PCD-CT enables simultaneous quantification of the two contrast agent concentrations inside cartilage and the results correlate with the structural and functional reference parameters. With improved soft tissue contrast and assessment of proteoglycan and water contents, PCD-CT with the dual contrast agent method is of potential use for the detection and monitoring of osteoarthritis.Peer reviewe

Acute Chlamydia pneumoniae infection causes coronary endothelial dysfunction in pigs.

Background: Coronary endothelial dysfunction contributes to the pathogenesis of acute coronary syndromes (ACSs). Acute Chlamydia pneumoniae infection has been epidemiologically associated with ACS. In this study, we investigated whether acute C. pneumoniae infection could alter the endothelial vasomotor function of porcine coronary vessels. Methods and results: Twenty pigs, 7–9 kg in weight, were inoculated intratracheally with C. pneumoniae (n=12) or saline (n=8), and investigated at 3 days (five infected/four non-infected) and 2 weeks (5+2 infected/four non-infected) after inoculation. The endothelium-dependent reactivity of coronary microcirculation was assessed at both time points by measuring peak coronary flow velocity (CFV) in response to bradykinin, before and after infusions with glutathione, an antioxidant, and Image-arginine, a substrate for nitric oxide synthase (NOS). CFV after bradykinin was significantly decreased in infected animals at both time points. At 2 weeks, both glutathione and Image-arginine significantly improved CFV after bradykinin. CFV after sodium nitroprusside (SNP) was similar in both groups. At 3 days, the relaxation responses of bradykinin-induced pre-contracted left anterior descending (LAD) coronary rings to bradykinin were significantly less in infected animals. NG-nitro-Image-arginine-methyl-ester, an NOS inhibitor, had significantly greater inhibitory effect on bradykinin-induced relaxation in infected animals. Plasma nitrate–nitrite and fibrinogen, and NOS activity from LAD coronary samples were significantly increased in infected animals. Conclusion: Acute C. pneumoniae infection causes endothelial dysfunction of both resistance and epicardial coronary vessels, and favours a pro-coagulant status. These effects could in part account for the epidemiologically suggested association between acute infection and ACS

Protective effects of simvastatin on coronary artery function in swine with acute infection

Background: The risk for coronary events may rise during acute infection. Perturbation in coronary endothelial function emerges as one important link. We investigated whether simvastatin could protect the coronary arterial function from the adverse effects of acute infection in swine. Methods: Coronary endothelium-dependent and -independent vasomotor responses were assessed by Doppler velocimetry in 12 Chlamydia pneunioniae-infected and 6 sham-infected swine 2 weeks after intratracheal inoculation. Half of animals from the infection group were pretreated with simvastatin (80 mg daily), while the remaining animals received placebo. The treatment was started 2 weeks prior to inoculation and Continued until the end of the Study. ANOVA was used for statistical calculations. Data are mean +/- S.D. Results: All animals inoculated with C. pneumoniae developed IgM antibodies against this organism. As compared to noninfected animals, peak-to-baseline coronary flow velocity (CFV) ratio after bradykinin was significantly decreased in infected animals regardless of statin treatment (1,p=0.01). Intracoronary 10(-6) M acetylcholine caused slight dilatory responses in both noninfected and infected-treated animals (CFV ratio: 1.6 +/- 0.2and 1.4 +/- 0.2, respectively: p > 0.1),while a velocity drop (CFV ratio: 0.7 +/- 0.1; p 0.5). There were no differences in markers of systemic inflammation (fibrinogen, amyloid, and CRP) and lipid profile (HDL, LDL and total cholesterol) between the groups (p > 0.2). Conclusion: Acute infection is associated with impairment of the muscarinic and kinin-related reactivity of coronary circulation. These functional abnormalities are in part prevented by simvastatin through mechanisms unrelated to lipid lowering. (c) 2005 Elsevier Ireland Ltd. All rights reserved

Warfarin Treatment Is Associated to Increased Internal Carotid Artery Calcification

Background: Long-term treatment with the vitamin K antagonist warfarin is widely used for the prevention of venous thrombosis and thromboembolism. However, vitamin K antagonists may promote arterial calcification, a phenomenon that has been previously studied in coronary and peripheral arteries, but not in extracranial carotid arteries. In this observational cohort study, we investigated whether warfarin treatment is associated with calcification of atherosclerotic carotid arteries. Methods: Overall, 500 consecutive patients underwent carotid endarterectomy, 82 of whom had received long-term warfarin therapy. The extent of calcification was assessed with preoperative computed tomography angiography, and both macroscopic morphological grading and microscopic histological examination of each excised carotid plaque were performed after carotid endarterectomy. Results: Compared with non-users, warfarin users had significantly more computed tomography angiography-detectable vascular calcification in the common carotid arteries (odds ratio 2.64, 95% confidence interval 1.51-4.63, P < 0.001) and even more calcification in the internal carotid arteries near the bifurcation (odds ratio 18.27, 95% confidence interval 2.53-2323, P < 0.001). Histological analysis revealed that the intramural calcified area in plaques from warfarin users was significantly larger than in plaques from non-users (95% confidence interval 3.36-13.56, P = 0.0018). Conclusions: Long-lasting warfarin anticoagulation associated with increased calcification of carotid atherosclerotic plaques, particularly in locations known to be the predilection sites of stroke-causing plaques. The clinical significance of this novel finding warrants further investigations.Peer reviewe

Quantitative dual contrast photon-counting computed tomography for assessment of articular cartilage health

Abstract Photon-counting detector computed tomography (PCD-CT) is a modern spectral imaging technique utilizing photon-counting detectors (PCDs). PCDs detect individual photons and classify them into fixed energy bins, thus enabling energy selective imaging, contrary to energy integrating detectors that detects and sums the total energy from all photons during acquisition. The structure and composition of the articular cartilage cannot be detected with native CT imaging but can be assessed using contrast-enhancement. Spectral imaging allows simultaneous decomposition of multiple contrast agents, which can be used to target and highlight discrete cartilage properties. Here we report, for the first time, the use of PCD-CT to quantify a cationic iodinated CA4+ (targeting proteoglycans) and a non-ionic gadolinium-based gadoteridol (reflecting water content) contrast agents inside human osteochondral tissue (n = 53). We performed PCD-CT scanning at diffusion equilibrium and compared the results against reference data of biomechanical and optical density measurements, and Mankin scoring. PCD-CT enables simultaneous quantification of the two contrast agent concentrations inside cartilage and the results correlate with the structural and functional reference parameters. With improved soft tissue contrast and assessment of proteoglycan and water contents, PCD-CT with the dual contrast agent method is of potential use for the detection and monitoring of osteoarthritis