Biomedical subjects

C Bremer

Publications and source records attributed to C Bremer.

41 records · Page 3Linked to original sources

PubMedDate not supplied

Assessment of reperfusion injury by means of MR contrast agents in rat liver.

The purpose of this study was to investigate whether extracellular MR contrast agents or intracellular liver-specific MR contrast agents may enable the assessment of liver reperfusion injury. Ischemia-related reperfusion was induced in 32 rats using Pringle's maneuver. Pringle's maneuver consisted of cross-clamping of the complete hepatoduodenal ligament for 45 minutes followed by 90 minutes of reperfusion. Two extracellular (gadopentetate dimeglumine and gadobutrol) and two intracellular gadoxetic acid and SH U 555 A) MR contrast agents were evaluated as model agents. Control animals and animals with liver ischemia were used to calculate changes in liver signal enhancement after Pringle's maneuver. Significant changes in liver signal after reperfusion injury were observed only with reticuloendothelial system (RES)-specific SH U 555 A. Liver signal enhancement after Pringle's maneuver with RES-specific SH U 555 A was decreased by 25.4% as compared with the control group. RES-specific contrast agents such as SH U 555 A seem to be more sensitive to ischemia-related dysfunction of the liver than hepatobiliary contrast agents such as gadoxetic acid or extracellular gadolinium chelates at different concentrations because Kupffer cells are more sensitive to liver ischemia than hepatocytes.

Analysis of Variance↗

PubMedDate not supplied

Preliminary clinical experience with laser-induced interstitial thermotherapy in patients with hepatocellular carcinoma.

The purpose of this preliminary study was to evaluate whether laser-induced interstitial thermotherapy (LITT) may be used for palliative treatment of localized hepatocellular carcinomas (HCC). We applied LITT to two patients suffering from unresectable localized hepatocellular carcinomas of different sizes (2.5 and 4 cm). LITT was performed with an Nd:YAG laser (1,064 nm) at 5 W laser power (15-20 minutes). Thermometry during LITT was performed by MRI using a temperature-sensitive T1-weighted fast low-angle shot (FLASH) sequence. Follow-up for local tumor control was performed by MRI and ultrasound. LITT was well tolerated and no adverse events occurred during or after LITT; no secondary liver lesions were seen in the follow-up (11 or 12 months, respectively). Only minimal tumor growth was observed in the larger HCC (from 4 to 5 cm), whereas the smaller HCC remained unchanged in size during 11 months of follow-up. We conclude that LITT might be an effective minimally invasive palliative treatment option for patients with small unresectable HCC.

Aged↗

PubMedDate not supplied

MR-monitored LITT as a palliative concept in patients with high grade gliomas: preliminary clinical experience.

The purpose of this study was to evaluate the clinical utility of laser-induced thermotherapy (LITT) as a palliative treatment for patients with high-grade gliomas. Four consenting patients with recurrent high grade III/IV gliomas near the primary language or motor areas were palliatively treated with LITT (2-5 W, 3-13 minutes; Neodym YAG Laser, Dornier, Friedrichshafen, Germany). Temperature monitoring was performed by T1-weighted turbo-fast low-angle shot (FLASH) imaging at 1.5 T (Siemens Magnetom SP 4000, Siemens, Erlangen, Germany). MRI studies before LITT included contrast-enhanced conventional scans and functional activation studies to localize the primary motor cortex or language areas using an echo-planar imaging (EPI) spin-echo (SE) sequence. Follow-up studies consisted of contrast-enhanced conventional scans as well as diffusion studies (contrast-enhanced Fourier-acquired steady-state technique and EPI-SE) and perfusion studies (EPI-SE with .2 mmol of gadolinium (Gd)/kg body weight) to differentiate post-therapeutic effects from residual or recurrent tumor growth. Local tumor control was achieved in areas with laser energy deposition with clinically stable conditions > or = 6 months. Conventional contrast-enhanced scans demonstrated strong enhancement surrounding ablated tumor components, which showed a reduction in CBV/CBF. Perfusion studies were useful to discriminate granulomatous tissue enhancement from residual or recurrent tumor growth. Careful application of LITT may evolve as an alternative palliative concept for patients with end-stage high-grade cerebral gliomas reducing clinical symptoms from circumscribed areas of pathology.

Adult↗

PubMedDate not supplied

MR and optical approaches to molecular imaging.

With an increasing understanding of the molecular basis of disease, various new imaging targets have recently been defined that potentially allow for an early, sensitive, and specific diagnosis of disease or monitoring of treatment response. Different approaches to depict these molecular structures in vivo are currently being explored by the molecular imaging community. We briefly review methodologies for molecular imaging by magnetic resonance imaging and optical methods. Special emphasis is put on different contrast agent designs (e.g., targeted and smart probes). New technical developments in optical imaging are briefly discussed. In addition, current research results are put into a clinical perspective to elucidate the potential merits one might expect from this new research field.

Capillary Permeability↗

PubMedDate not supplied

Reduction of hepatic reperfusion injury by indomethacin-mediated vasoconstriction: a rat model with temporary splenocaval shunt.

For reduction of radical formation during reperfusion, a lower oxygen supply by limiting the reperfusion flow rate should be beneficial for the organ. Thus, indomethacin was given prior to reperfusion for induction of temporary postischemic vasoconstriction. In an in vivo model (female Wistar rats, 200-250 g, n = 16) with portal decompression by a splenocaval shunt, hepatic ischemia was induced for 30 min by cross-clamping of the hepatoduodenal ligament followed by portal intravenous injection of indomethacin (2 mg/kg body wt) at the end of ischemia. Liver injury was assessed by serum levels of Aspartat-aminotransferase (ASAT) and Alaninaminotransferase (ALAT) that were determined prior to ischemia, on days 2, 4, 6 and 21 postoperatively. The local tissue pO2 was measured preischemically, 1 h after reperfusion and on day 21. Application of indomethacin significantly reduced the local tissue-pO2 by about 50% after 1 h of reperfusion (p < .05). The increase in serum ASAT levels on day 2 was significantly diminished after indomethacin application (p < .05). ALAT values on day 2 showed a significant increase in the control group but did not differ from baseline in the indomethacin group. These data support the hypothesis that temporarily limited reperfusion results in an amelioration of reperfusion injury, although further studies with more selectively vasoactive agents must still be performed since indomethacin also has a major effect on the eicosanoid metabolism.

Animals↗