Child Sexual Abuse-Challenging Conditions for Adult Oral Health: A Qualitative Study.

The aim was to analyze perceptions of oral health in adults who have been exposed to child sexual abuse. Eleven participants (10 women), 19 to 56 y of age, who had experienced sexual abuse as children were purposively selected and interviewed in-depth. The participants were encouraged to describe how they perceived the effect of the sexual abuse on their oral health as adults. The interviews were recorded digitally and transcribed verbatim. The collected material was analyzed according to qualitative content analysis. The theme "challenging conditions for maintaining oral health" was identified, comprising 2 categories: first, "the emotional significance," with the subcategories 1) emotional barriers and 2) powerful relief, and second, "the obstacles to oral health," with the subcategories 1) daily self-care with complications and 2) dental appointments with difficulties. The findings indicate that the experience of sexual abuse during childhood can have a negative impact on oral care in adulthood. The informants stated that oral health was of utmost importance but also associated with strong emotions. There were obstacles to maintenance of oral health that were difficult to surmount.Knowledge Transfer Statement:The study provides access to the attitudes of survivors of child sexual abuse regarding oral health and the needs and obstacles that they experience. This is important knowledge for dental professionals to optimize dental care.

Pancreas volume and fat fraction in children with Type 1 diabetes.

AIMS: People with Type 1 diabetes have smaller pancreases than healthy individuals. Several diseases causing pancreatic atrophy are associated with pancreatic steatosis, but pancreatic fat in Type 1 diabetes has not been measured. This cross-sectional study aimed to compare pancreas size and fat fraction in children with Type 1 diabetes and controls. METHODS: The volume and fat fraction of the pancreases of 22 children with Type 1 diabetes and 29 controls were determined using magnetic resonance imaging. RESULTS: Pancreas volume was 27% smaller in children with diabetes (median 34.9 cm(3) ) than in controls (47.8 cm(3) ; P < 0.001). Pancreas volume correlated positively with age in controls (P = 0.033), but not in children with diabetes (P = 0.649). Pancreas volume did not correlate with diabetes duration, but it did correlate positively with units of insulin/kg body weight/day (P = 0.048). A linear model of pancreas volume as influenced by age, body surface area and insulin units/kg body weight/day found that insulin dosage correlated with pancreas volume after controlling for both age and body surface area (P = 0.009). Pancreatic fat fraction was not significantly different between the two groups (1.34% vs. 1.57%; P = 0.891). CONCLUSIONS: Our findings do not indicate that pancreatic atrophy in Type 1 diabetes is associated with an increased pancreatic fat fraction, unlike some other diseases featuring reduced pancreatic volume. We speculate that our results may support the hypotheses that much of pancreatic atrophy in Type 1 diabetes occurs before the clinical onset of the disease and that exogenous insulin administration decelerates pancreatic atrophy after diabetes onset.

Reported sexually transmitted infections in Swedish Internet-using men and women.

Although the Internet has become a forum for making sexual contacts, and has been associated with increased sexually transmitted infection (STI) transmission, we have little information of history of STIs in Internet-based samples. The Internet behaviours that are associated with STI acquisition are poorly understood. We analysed STI histories reported by 904 Swedish men and 931 Swedish women who responded to an Internet-based survey on sexual behaviour in 2002: 16.6% of men and 22.5% of women reported a lifetime history of STIs, with Chlamydia being the most common for both genders. 3% of men and 5% of women who reported an STI, indicated that they had had more than one. Sources of the STI, where known, were Internet-acquired partners in only 3% of cases. There were no differences between men and women with or without an STI history regarding the kind of online sexual activities they engaged in, how they found sexual material online, and the reasons they engage in sexual activities. These rates are similar to those reported in a national random study of sexuality in Sweden. Contrary to prior research, these results suggest no relationship between STI and specific Internet characteristics usage patterns. These data suggest that the Internet is not yet a major source of STIs in Swedish men and women. Given these STI histories, the Internet may be a useful medium to include in STI prevention efforts.

Determining 'true' glomerular filtration rate in healthy adults using infusion of inulin and comparing it with values obtained using other clearance techniques or prediction equations.

OBJECTIVE: To determine 'true' glomerular filtration rate (GFR) in healthy adults as renal clearance following infusion of inulin, and compare that result with those obtained using other markers and clearance techniques and with estimations of GFR using creatinine-based prediction equations. MATERIAL AND METHODS: Twenty healthy volunteers (11 females) with a median age of 27 years (range 19-36 years) received bolus doses of inulin and iohexol i.v. and 16 blood samples were taken after injection. Then, inulin and iohexol were infused to give stable plasma concentrations and blood and urine samples were collected. Residual bladder volume was estimated using ultrasound scanning. Plasma and urine concentrations of inulin and iohexol were determined using chromatography and resorcinol methods, respectively. Different methods of GFR determination were compared as well as four formulae for GFR estimation based on serum creatinine. RESULTS: 'True' GFR, i.e. renal clearance of inulin during its infusion, was a median of 117 ml/min/1.73 m2 (inter-quartile range 106-129 ml/min/1.73 m2). Similar values of GFR were obtained with renal clearance of iohexol during its infusion and also with plasma (body) clearance of inulin or iohexol following bolus injections and using 16 or five plasma samples. Endogenous creatinine clearance was higher (p<0.001) than true GFR (median 23 ml/min/1.73 m2). Plasma clearance of iohexol and inulin based on their concentrations in four blood samples underestimated their renal clearance considerably. All four creatinine-based formulae markedly underestimated renal inulin clearance. CONCLUSIONS: Plasma and renal clearance of iohexol and inulin were similar in healthy adults. Underestimation of GFR was noted when plasma clearance of iohexol and inulin was based on four but not five or more blood samples. Some prediction equations underestimate true GFR to such an extent that caution must be taken when using them to evaluate normal or high GFR values.

Dose integration characteristics in normoxic polymer gel dosimetry investigated using sequential beam irradiation.

Dose integration properties were investigated for normoxic polymer gels based on methacrylic acid (nMAG) and acrylamide/N, N'-methylenebisacrylamide (nPAG). The effect of sequential irradiation was studied for different fractionation schemes and varying amounts of methacrylic acid for the nMAG gels. Magnetic resonance imaging (MRI) was used for read out of the absorbed dose response. The investigated gels exhibited a dependence on the fractionation scheme. The response when the total dose was divided into fractions of 0.5 Gy was compared with the response when the total dose was delivered in a single fraction. The slope of the R2 versus the absorbed dose response decreased when the absorbed dose per fraction was increased. Also, for higher amounts of methacrylic acid in the nMAG system the difference in the response increased. For gels containing 2, 4, 6 and 8% methacrylic acid, the R2 versus the absorbed dose response increased by 35, 37, 63 and 93%, respectively. Furthermore, the effect of the fractionation was larger when a higher total absorbed dose was given. The effect was less pronounced for the investigated nPAG, containing 3% acrylamide and 3% N, N'-methylenebisacrylamide, than for the nMAG systems. Consequently, this study indicates that the nPAG system has preferable beam integration characteristics compared with the nMAG system.

Self-reported oral problems, compared with clinical assessment in an epidemiological study.

OBJECTIVES: To study self-reported oral problems in relation to periodontal clinical findings in an epidemiological investigation. MATERIALS AND METHODS: 1676 individuals, 828 men and 848 women, participated. The clinical examination comprised the number of remaining teeth excluding third molars, plaque index (PLI), gingival index (GI), bleeding on probing (BOP%), calculus index (CI) and the number of teeth with pocket depth (PD) > or =5 mm. Participants answered a questionnaire concerning smoking and snuffing habits and described in their own words any oral problems present. Analysis of variance (anova), unpaired t-test and chi-squared test were the statistical methods used. RESULTS: The questionnaire was completed by 99.4% of participants. Problems of the teeth and mouth were reported by 28.9% of respondents comprising 31.8% females and 26.2% males. The difference between the sexes was statistically significant (P < 0.05). Of the reported oral problems, 57.4% was of periodontal origin. The differences between subjects with and without self-reported mobile teeth showed significant clinical outcome in PLI (P < 0.001), CI (P < 0.01), GI (P < 0.001), BOP% (P < 0.01), the number of teeth with PD > or = 5 mm (P < 0.001) and the number of remaining teeth (P < 0.001). The differences between subjects with and without self-reported periodontal disease and with and without bleeding gingiva also showed significant differences in CI (P < 0.05), GI (P < 0.05) and the number of teeth with PD > or = 5 mm (P < 0.05) and in PLI (0.001), CI (P < 0.01), GI (P < 0.001) and BOP% (P < 0.001) respectively. CONCLUSIONS: Present study clearly shows that self-reported periodontal problems were confirmed by clinical assessments.

Transcriptional upregulation and unmethylation of the promoter region of p16 in invasive basal cell carcinoma cells and partial co-localization with the gamma 2 chain of laminin-332.

Basal cell carcinoma cells show low proliferation rates at the invasive front and a concordant upregulation of the cdk-inhibitor p16, limiting proliferative capacity. Little is known about the mechanisms of p16 regulation in normal and malignant cells apart from that many transcription factors such as Ets1, Ets2, SP1, SP3, JunB and the polycomb protein Bmi1 have the potential to induce or repress p16 expression. Therefore, the aim of this study was to determine how p16 is regulated in basal cell carcinoma with special focus on its upregulation in invasive cells. By analysing various microdissected areas of basal cell carcinoma using real-time quantitative PCR we observed upregulation of p16 mRNA in invasive tumour cells compared to centrally localized tumour cells. The methylation status of the p16 promoter, analysed by methylation-specific PCR, also showed diminished methylation in tumour cells at the invasive front, supporting the hypothesis that promoter methylation can affect the transcriptional activation of p16 in vivo. There was only sporadic co-localization of Ets, or ERK1/2 phosphorylation with p16 upregulation at the invasive front, suggesting that these factors were not directly involved in the regulation of p16. Furthermore, the gamma 2 chain of laminin-332 has been reported to be increased at the invasive front compared to the central areas of many tumours. Interestingly, in basal cell carcinoma we observed partial co-localization between p16 and the gamma 2 chain of laminin-332 in tumour cells towards areas of ulceration and in the majority of clearly infiltrative tumour cells but not in p16 positive tumour cells with a more pushing invasive growth pattern. These data suggest that concurrent p16 upregulation and decreased proliferation are more general phenomena in different types of invasive growth patterns in basal cell carcinomas and that these only partially overlap with the gamma 2 chain of laminin-332 associated invasion patterns.

Levels of matrix metalloproteinases-8 and -9 with simultaneous presence of periodontal pathogens in gingival crevicular fluid as well as matrix metalloproteinase-9 and cholesterol in blood.

BACKGROUND AND OBJECTIVES: To investigate the levels of matrix metalloproteinase (MMP) -8 and -9 with the simultaneous presence of periodontal pathogens in gingival crevicular fluid (GCF) as well as MMP-9 and cholesterol in blood. Although bacterial pathogens are required to initiate the periodontal disease process, in some individuals the reaction to bacteria may lead to an excessive host response, resulting in a general inflammatory response. METHODS: MMP-9 and lipids were analyzed from the blood samples of 33 subjects with a 16-year history and oral health records of periodontal disease as well as from 31 periodontally healthy controls. Information was obtained on education, body mass index, and family history of atherosclerosis. GCF was taken to determine MMP-8 and MMP-9 levels, and bacterial samples were simultaneously collected for polymerase chain reaction assessment of Actinobacillus actinomycetemcomitans, Porphyromonas gingivalis, Prevotella intermedia, Prevotella nigrescens, Tannerella forsythia, and Treponema denticola. Analysis of variance, chi-squared test, and multiple logistic regression analysis were used to analyze the results. RESULTS: Demographic data showed significant differences between patients and controls in smoking (P < 0.01), body mass index (P < 0.05), family history of atherosclerotic disease (P < 0.01), and education (P < 0.01). Significant differences were also observed in oral health data, in the detection of P. gingivalis (P < 0.001), P. intermedia (P < 0.01), P. nigrescens (P < 0.001), and T. forsythia (P < 0.001) and in the levels of MMP-8 and MMP-9 in GCF between patients and controls. T. forsythia[odds ratio(OR) 10.1; P = 0.001] and age (OR 5.54; P = 0.008) appeared to be the main independent predictors for high MMP-8 in GCF. Patients had significantly higher total cholesterol (P < 0.01), low-density lipoprotein cholesterol (P = 0.05), and triglycerides (P < = 0.01) than controls. Plasma levels of MMP-9 were significantly higher in patients than in controls (P = 0.001). CONCLUSIONS: Specific periodontal microorganisms appeared to induce host response, with increased release of MMP-8 and MMP-9 in gingival pockets as well as of MMP-9 in plasma, possibly triggering its up-regulation in blood.

Perfusion assessment with bolus differentiation: a technique applicable to hyperpolarized tracers.

A new technique for assessing tissue blood flow using hyperpolarized tracers, based on the fact that the magnetization of a hyperpolarized substance can be destroyed permanently, is described. Assessments of blood flow with this technique are inherently insensitive to arterial delay and dispersion, and allow for quantification of the transit time and dispersion in the arteries that supply the investigated tissue. Renal cortical blood flow was studied in six rabbits using a 13C-labeled compound (2-hydroxyethylacrylate) that was polarized by the parahydrogen-induced polarization (PHIP) technique. The renal cortical blood flow was estimated to be 5.7/5.4 +/- 1.6/1.3 ml/min per milliliter of tissue (mean +/- SD, right/left kidney), and the mean transit time and dispersion in the renal arteries were determined to be 1.47/1.42 +/- 0.07/0.07 s and 1.78/1.93 +/- 0.40/0.42 s2, respectively.

Cerebral perfusion assessment by bolus tracking using hyperpolarized 13C.

Cerebral perfusion was assessed with 13C MRI in a rat model after intravenous injections of the 13C-labeled compound bis-1,1-(hydroxymethyl)-1-13C-cyclopropane-D8 in aqueous solutions hyperpolarized by dynamic nuclear polarization (DNP). Since the tracer acted as a direct signal source, several of the problems associated with techniques based on traditional dynamic susceptibility contrast (DSC) MRI contrast agents were avoided. Maps of cerebral blood flow (CBF), cerebral blood volume (CBV), and mean transit time (MTT) were calculated. The MTT was determined to be 2.8 +/- 0.8 sec. However, arterial partial-volume effects in the animal model prevented accurate absolute quantification of CBF and CBV. It was demonstrated that depolarization of the hyperpolarized 13C tracer via relaxation and the imaging sequence had little influence on CBF assessment when the time resolution of the imaging sequence was short compared to the MTT. However, CBV and MTT were increasingly underestimated as MTT or the depolarization rate increased if depolarization was not taken into account. With a modified bolus-tracking theory depolarization could be compensated for, assuming that the depolarization rate was known. Three separate compensation methods were investigated experimentally and by numerical simulations.

Molecular imaging using hyperpolarized 13C.

MRI provides unsurpassed soft tissue contrast, but the inherent low sensitivity of this modality has limited the clinical use to imaging of water protons. With hyperpolarization techniques, the signal from a given number of nuclear spins can be raised more than 100 000 times. The strong signal enhancement enables imaging of nuclei other than protons, e.g. (13)C and (15)N, and their molecular distribution in vivo can be visualized in a clinically relevant time window. This article reviews different hyperpolarization techniques and some of the many application areas. As an example, experiments are presented where hyperpolarized (13)C nuclei have been injected into rabbits, followed by rapid (13)C MRI with high spatial resolution (scan time <1 s and 1.0 mm in-plane resolution). The high degree of polarization thus enabled mapping of the molecular distribution within various organs, a few seconds after injection. The hyperpolarized (13)C MRI technique allows a selective identification of the molecules that give rise to the MR signal, offering direct molecular imaging.

Gradient echo imaging of flowing hyperpolarized nuclei: theory and phantom studies on 129Xe dissolved in ethanol.

The influence of flip angle and flow velocity on the signal intensity achieved when imaging a hyperpolarized substance with a spoiled gradient echo sequence was investigated. The study was performed both theoretically and experimentally using hyperpolarized xenon dissolved in ethanol. Analytical expressions regarding the optimal flip angle with respect to signal and the corresponding signal level are presented and comparisons with thermally polarized substances are made. Both experimentally and theoretically, the optimal flip angle was found to increase with increasing flow velocity. Numerical calculations showed that the velocity dependence of the signal differs between the cases of hyperpolarized and thermally polarized substances.

Echo-planar MR imaging of dissolved hyperpolarized 129Xe.

PURPOSE: The feasibility of hyperpolarized 129Xe for fast MR angiography (MRA) was evaluated using the echo-planar imaging (EPI) technique. MATERIAL AND METHODS: Hyperpolarized Xe gas was dissolved in ethanol, a carrier agent with high solubility for Xe (Ostwald solubility coefficient 2.5) and long relaxation times. The dissolved Xe was injected as a bolus into a flow phantom where the mean flow velocity was 15 cm/s. Ultrafast EPI images with 44 ms scan time were acquired of the flowing bolus and the signal-to-noise ratios (SNR) were measured. RESULTS: The relaxation times of hyperpolarized Xe in ethanol were measured to T1=160+/-11 s and T2 approximately 20 s. The resulting images of the flowing liquid were of reasonable quality and had an SNR of about 70. CONCLUSION: Based on the SNR of the obtained Xe EPI images, it was estimated that rapid in vivo MRA with 129Xe may be feasible, provided that an efficient, biologically acceptable carrier for Xe can be found and polarization levels of more than 25% can be achieved in isotopically enriched 129Xe.

Biliary and total extrarenal clearance of inulin and iohexol in pigs. A source of error when determining gfr as body clearance.

Biliary clearance, total extrarenal clearance, body and renal clearance of inulin and iohexol were determined in 11 normal and 11 nephrectomized pigs. The biliary clearance of inulin, calculated as biliary excretion divided by the plasma concentration, was 0.04 and 0.01 ml min(-1) 10 kg(-1) and of iohexol 0.21 and 0.1 ml min(-1) 10 kg(-1), in normal, respectively, nephrectomized pigs (p < 0.05). The extrarenal clearance of inulin, calculated as body minus renal clearance, was 2.7 and 0.7 ml min(-1) 10 kg(-1) and of iohexol 3.7 and 0.7 ml min(-1) 10 kg(-1) in normal, respectively, nephrectomized pigs (p < 0.05). Some hours after injection of the markers their plasma concentrations were much higher in the nephrectomized pigs. This higher plasma concentration was not matched by an equally higher biliary excretion and therefore biliary clearance decreased. The smaller total extrarenal clearance in nephrectomized pigs, i.e. the overestimation of GFR when calculated as body clearance, indicates that this source of error decreases with decreasing renal function.

Parahydrogen-induced polarization in imaging: subsecond (13)C angiography.

High nuclear spin polarization of (13)C was reached in organic molecules. Enhancements of up to 10(4), compared to thermal polarization at 1.5 T, were achieved using the parahydrogen-induced polarization technique in combination with a field cycling method. While parahydrogen has no net polarization, it has a high spin order, which is retained when hydrogen is incorporated into another molecule by a chemical reaction. By subjecting this molecule to a sudden change of the external magnetic field, the spin order is transferred into net polarization. A (13)C angiogram of an animal was generated in less than a second. Magn Reson Med 46:1-5, 2001.

Differences between Internet samples and conventional samples of men who have sex with men: implications for research and HIV interventions.

The Internet is becoming a new erotic oasis for obtaining sex online or in person. We reviewed the literature on cybersex and compared differences in data from samples of homosexually active men obtained on identical questionnaires from a conventional written questionnaire, distributed through the mailing and contact lists of a large national gay organization in Sweden, and through the same organization's website and chat room. A total of 716 written questionnaires and 678 Internet questionnaires were obtained. The Internet sample was younger, more likely to live in small towns or cities, live with parents or a girlfriend, and have lower formal education. They are less likely to have previous sexual experience solely with other men (one in three of the Internet sample vs. 1 in 14 of the written sample defined themselves as bisexual) and more likely to visit erotic oases such as bathhouses, video clubs and erotic movie houses. They also visited Internet chat rooms more frequently (86% of the Internet sample vs. 50% of the written sample). One third of the Internet sample wanted the opportunity to talk with an expert about HIV compared with a quarter of the written sample. Sexual practices between the two samples were generally similar, although the Internet sample reported significantly less body contact, kissing, hugging, mutual masturbation, and more condom use for anal intercourse with steady partners. Over four times as many of the Internet samples reported sex with women in the past year as the written sample. These data indicate that Internet data collection is feasible and that this mode of data collection, despite the nonrandom and self-selected nature of both types of samples, is likely to be more significantly oriented toward the young, geographically more isolated, and more behaviorally and self-identified bisexual respondent than conventionally distributed written questionnaires.

Assessing residual renal function and efficiency of hemodialysis--an application for urographic contrast media.

BACKGROUND: In patients on hemodialysis with end-stage renal disease there is an increasing interest in measuring both residual renal function (RRF) and quantity and quality of dialysis because insufficient dialysis gives higher mortality. For that purpose we have measured clearances of two urographic iodine (I) contrast media (CM) with different molecular masses (iohexol 821 u and iodixanol 1, 550 u). These CM are filtered through glomeruli and dialysis membranes and have higher molecular masses than urea and creatinine and might represent the dialyzability of the hypothetic uremic toxins with a molecular mass of 300-5,000 u. METHODS: Thirteen patients (8 of them were anuric) immediately after hemodialysis received 15 ml iohexol (300 mg I/ml i.v.) and 2 weeks later in the same way 15 ml iodixanol (320 mg I/ml). Nine other patients (2 anuric) received CM after only one dialysis; 8 got iohexol and 1 got iodixanol. After the CM injections the iodine concentrations were measured with X-ray fluorescence in blood and, when available, urine during the following 2 days including both the start and end of the next dialysis. Eighteen patients after two dialysis sessions, 2 weeks apart, received 10 ml iohexol i.v., and a single blood sample was taken at the start of the next dialysis 2 days later to determine RRF alone. RESULTS: In the 10 anuric patients the extrarenal clearances (mean +/- SD) were 2.5 +/- 1.1 and 2.7 +/- 1.1 ml/min/1.73 m(2) for iohexol and iodixanol, respectively. In patients with RRF good correlations were demonstrated between body clearance, based on two blood samples, and renal clearance of CM. Good correlations (r(2) = 0.853 for iohexol, r(2) = 0.933 for iodixanol) were noted between two-sample and single-sample body clearances. Repeated single sample iohexol clearances gave a coefficient of variation of 15%. During dialysis the clearances of iohexol and iodixanol were, respectively, 69 +/- 16 and 58 +/- 11 ml/min/1.73 m(2) when calculated from a single-pool model (hemodialysis clearance of CM from plasma). A median increase (rebound) of CM concentrations in plasma 45 min dialysis was 8% for iodixanol and 18% for iohexol. When the CM concentration 45 min after dialysis was used, the clearance values were by 8-10% lower and represented the hemodialysis clearance of CM from the extracellular compartments. The dialysis eliminations of iohexol and iodixanol were similar to that of urea, measured as percentage reduction of serum levels during dialysis. CONCLUSIONS: A single injection of CM at the end of dialysis followed by a single blood sample at the start of the next dialysis gives total body clearance, i.e., an estimation of the RRF. An additional blood sample at the end of the next dialysis gives dialysis efficiency.

Glycogen content in rat liver. Importance for CT and MR imaging.

PURPOSE: CT and MR imaging are appropriate modalities for imaging of the liver. Contrast media are used to obtain a greater difference in attenuation and signal intensity, respectively, between normal liver tissue and focal lesions. However, no studies have attempted to determine whether physiological nutritional status of the liver during fasting is of importance for the native signal of normal liver tissue. MATERIAL AND METHODS: Using normal and fasting rats, we performed hepatic CT and MR imaging and glycogen analyses from excised tissue. RESULTS: A significantly higher liver attenuation in normal rats compared to fasting rats was found in CT. In MR images, there was a small but significantly lower liver signal-to-noise ratio in normal rats compared to fasting rats in T1-weighted and proton density-weighted images. Glycogen analyses showed depleted glycogen deposits in fasting rats and a mean glycogen content of 50.1 mg glucose equivalent/g liver tissue in normal rats. CONCLUSION: In CT, a normal nutritional status increases the native attenuation in normal liver tissue. The changes in attenuation in normal liver tissue correlate well with the additional attenuation of glycogen storage in the hepatocyte. The results indicate that the nutritional status is of less importance in MR imaging.

Investigation of lanthanide-based starch particles as a model system for liver contrast agents.

Gadolinium and dysprosium diethylenetriamine pentaacetic acid-labeled starch microparticles (Gd-DTPA-SP and Dy-DTPA-SP) were investigated as model liver contrast agents. The liver contrast efficacy of particles with low and high metal contents was compared in two imaging models: in vivo rat liver and ex vivo perfused rat liver. The biodistribution of intravenously injected particles was also assessed by ex vivo relaxometry and inductively coupled plasma atomic emission spectrophotometry of tissues. All particles reduced the liver signal intensity on T2-weighted spin-echo and gradient-recalled echo images as a result of susceptibility effects. Because of their higher magnetic susceptibility, the Dy-DTPA-SP were more effective negative contrast enhancers than the Gd-DTPA-SP. On T1-weighted spin-echo images, only the Gd-DTPA-SP with low metal content significantly increased the liver signal intensity. In addition, these low-loading Gd-DTPA-SP markedly reduced the blood T1. The two latter observations were not consistent with the anticipated blood circulation time of microparticles, but were a result of the lower stability of these particles in blood compared with Gd-DTPA-SP, which has a high metal content. Regardless of stability or imaging conditions, the paramagnetic starch particles investigated showed potential as negative liver contrast enhancers. However, the observed accumulation of particles in the lungs represented a biological limitation for their use as contrast agents.

Paramagnetic liposomes as magnetic resonance imaging contrast agents. Assessment of contrast efficacy in various liver models.

RATIONALE AND OBJECTIVES: Liposomal gadolinium (Gd)-HP-DO3A has been evaluated as a contrast agent for liver magnetic resonance imaging. The influence of various liposomal physicochemical properties on the liver uptake and contrast efficacy was investigated in various ex vivo and in vivo liver models. METHODS: Liposomes of different size and membrane properties were prepared. The liposome size ranged from 74 to 304 nm. Two types of phospholipid compositions were studied; a mixture of hydrogenated phosphatidylcholine (HPC) and hydrogenated phosphatidylserine (HPS) with a phase transition temperature (Tm) of 51 degrees C and, a blend composed of dipalmitoylphosphatidylcholine (DPPC) and dipalmitoylphosphatidylglycerol (DPPG) displaying a Tm of 41 degrees C. Ex vivo tissue relaxometry and in vivo liver imaging were used to study the influence of liposome composition on the liver uptake and contrast efficacy of intravenously injected liposomes. The influence of liposome size and composition on the kinetics of liver uptake and imaging effect was assessed ex vivo in the perfused rat liver. RESULTS: The HPC/HPS preparations showed generally a higher and faster liver uptake than the DPPC/DPPG preparations due to a higher stability in blood/perfusate (high Tm) and to the HPS component. The liposome size modulated the extent and kinetics of liver uptake; the larger the size, the faster and more extensive was the liver uptake. Both types of liposome preparations were shown to be efficient liver susceptibility agents both ex vivo and in vivo due to their uptake by the Kupffer cells of liver. The lack of full correlation between the extent of liver uptake and degree of contrast enhancement might be attributed to different regimes of susceptibility-based relaxation. CONCLUSIONS: The present study has demonstrated the influence of key liposomal physicochemical properties on the liver uptake and contrast efficacy of liposome-encapsulated Gd chelates, exemplified by Gd-HP-DO3A.