Middle ear structure in relation to function : the rat in middle ear research

The present study was undertaken to evaluate the rat as a model for middle ear re­search. The rat was chosen primarily because the gross structure of its middle ear shows several similarities to that of man. It was considered of great importance to make a thorough structural study of the rat middle ear and to compare the results with those reported for the human middle ear. The thesis therefore includes indepen­dent studies on various aspects of rat middle ear structure and function as well as a review of the literature. The most pertinent findings in the experimental part of this study were the following. The rat Eustachian tube consists of a nasopharyngeal, and a cartilaginous and bony portion. The orifice of the nasopharyngeal portion is composed of two soft tissue lips, which appear to be opened mainly by the action of the salpingopharyngeal mus­cle, but also by the levator and tensor veli palatini muscles. The cartilaginous por­tion appears to be opened solely by the tensor veli palatini muscle. The tensor tympani muscle seems to have no effect on the tube. A ciliated and secretory epithelium lines the inferomedial walls of the tube throughout its length. In the tympanic cavity these thelial cell types extend as two tracts - one anterior and the other inferoposterior to  the promontory - which communicate with the epitympanic/attic compartments. The remaining parts of the tube and the tympanic cavity are covered by a squamous/cuboidal, non-ciliated epithelium. The subepithelial loose connective tissue contains vessels, nerves, and connective tissue cells, among these mast cells. The mast cells are confined to areas covered by the ciliated epithelium, and in the floor of the bulla, in the pars flaccida, and along the manubrial vessels. Glands are restricted to the Eustachian tube. In the clearance/transport of serum-like material, from the epitympanum towards the tube, hydrostatic forces appear to be important. The tympanic membrane is vascularized from meatal and tympanal vessels. Meatal ves­sels branch in the pars flaccida and along the handle of the malleus, where they are localized directly beneath the outer, keratinizing, stratified, squamous epithelium. Furthermore, meatal vessels form a vascular network at the junction between the fi­brocartilaginous annulus and the tympanic sulcus. Tympanal vessels send branches to the periphery of the pars tensa, where they run immediately beneath the tympanal, simple, squamous epithelium. In the major portion of the pars tensa, no blood vessels were found. The rat stapedial artery is a thin-walled vessel with a wide lumen. Without branch­ing, it runs through the tympanic cavity to the extratympanal regions it supplies. In contrast to the corresponding artery in man, the rat stapedial artery persists throughout life. The artery does not seem to be affected by the fluid produced during experimentally induced otitis media with effusion. The middle ear structure in the rat and in man show both similarities and differ­ences. If the differences are kept in mind and considered, it would seem that the rat is indeed a suitable model for experimental middle ear research.digitalisering@um

Decalcification by perfusion. A new method for rapid softening of temporal bones

We describe a new technique, decalcification by perfusion, for the softening of bony tissue. The blood circulatory system was perfused in 16 rats via a cannula through the left heart ventricle with a fixative followed by New DecalcR (an acidic demineralizer) for 30-240 minutes. Perfusion decalcification for 120 minutes softened al1 heads and middle ear specimens could be easily sampled and prepared for studies by both light and electron microscope. For comparison, a conventional immersion technique required 72 hours of decalcification to accomplish softening. The perfusion technique considerably reduced the time needed to decalcify the tissue and preserved the morphology better than did the immersion procedure

Contrast-enhanced magnetic resonance cholangiography with Gd-BOPTA and Gd-EOB-DTPA in healthy subjects

PURPOSE: To evaluate the biliary enhancement dynamics of the two gadolinium chelates Gd-BOPTA (MultiHance) and Gd-EOB-DTPA (Primovist) in normal healthy subjects. MATERIAL AND METHODS: Ten healthy volunteers were evaluated with both agents by magnetic resonance (MR) imaging at 1.5T using a breath-hold gradient-echo T1-weighted VIBE sequence. The relative signal intensity (SI) differences between the common hepatic duct (CHD) and liver parenchyma were measured before and 10, 20, 30, 40, 130, 240, and 300 min after contrast medium injection. RESULTS: Biliary enhancement was obvious 10 min post-injection for Gd-EOB-DTPA and was noted at 20 min for Gd-BOPTA. At 40 min delay, Gd-BOPTA reached its peak biliary enhancement, but at neither 30 nor 40 min delay was there any significant difference compared with that of Gd-EOB-DTPA. At later delays, the contrast between CHD and liver continued to increase for Gd-EOB-DTPA, whereas it decreased for Gd-BOPTA. CONCLUSION: The earlier onset and longer duration of a high contrast between CHD and liver for Gd-EOB-DTPA facilitates examination of hepatobiliary excretion. Therefore, Gd-EOB-DTPA may provide adequate hepatobiliary imaging within a shorter time span than Gd-BOPTA and facilitate scheduling at the MR unit. Further studies in patients are required to compare the imaging advantages of Gd-EOB-DTPA and Gd-BOPTA in clinical practice.This is an electronic version of an article published in: Nils Dahlström, Anders Persson, Nils Albiin, Örjan Smedby and Torkel Brismar, Contrast-enhanced magnetic resonance cholangiography with Gd-BOPTA and Gd-EOB-DTPA in healthy subjects, 2007, Acta Radiologica, (48), 4, 362-368. Acta Radiologica is available online at informaworldTM: http://dx.doi.org/10.1080/02841850701196922 Copyright: Taylor &amp; Francis http://www.tandf.co.uk/journals/default.asp</p

Gallbladder emptying in patients with primary sclerosing cholangitis

AIM: To assess gallbladder emptying and its association with cholecystitis and abdominal pain in patients with primary sclerosing cholangitis (PSC). METHODS: Twenty patients with PSC and ten healthy subjects were investigated. Gallbladder fasting volume, ejection fraction and residual volume after ingestion of a test meal were compared in patients with PSC and healthy controls using magnetic resonance imaging. Symptoms, thickness and contrast enhancement of the gallbladder wall and the presence of cystic duct strictures were also assessed. RESULTS: Median fasting gallbladder volume in patients with PSC [67 (19-348) mL] was twice that in healthy controls [32 (16-55) mL] (P < 0.05). The median postprandial gallbladder volume in patients with PSC was significantly larger than that in healthy controls (P < 0.05). There was no difference in ejection fraction, gallbladder emptying volume or mean thickness of the gallbladder wall between PSC patients and controls. Contrast enhancement of the gallbladder wall in PSC patients was higher than that in controls; (69% ± 32%) and (42% ± 21%) (P < 0.05). No significant association was found between the gallbladder volumes and occurrence of abdominal pain in patients and controls. CONCLUSION: Patients with PSC have increased fasting gallbladder volume. Gallbladder Mucosal dysfunction secondary to chronic cholecystitis, may be a possible mechanism for increased gallbladder

Low tube voltage CT for improved detection of pancreatic cancer: detection threshold for small, simulated lesions

Abstract Background Pancreatic ductal adenocarcinoma is associated with dismal prognosis. The detection of small pancreatic tumors which are still resectable is still a challenging problem. The aim of this study was to investigate the effect of decreasing the tube voltage from 120 to 80 kV on the detection of pancreatic tumors. Methods Three scanning protocols was used; one using the standard tube voltage (120 kV) and current (160 mA) and two using 80 kV but with different tube currents (500 and 675 mA) to achieve equivalent dose (15 mGy) and noise (15 HU) as that of the standard protocol. Tumors were simulated into collected CT phantom images. The attenuation in normal parenchyma at 120 kV was set at 130 HU, as measured previously in clinical examinations, and the tumor attenuation was assumed to differ 20 HU and was set at 110HU. By scanning and measuring of iodine solution with different concentrations the corresponding tumor and parenchyma attenuation at 80 kV was found to be 185 and 219 HU, respectively. To objectively evaluate the differences between the three protocols, a multi-reader multi-case receiver operating characteristic study was conducted, using three readers and 100 cases, each containing 0–3 lesions. Results The highest reader averaged figure-of-merit (FOM) was achieved for 80 kV and 675 mA (FOM = 0,850), and the lowest for 120 kV (FOM = 0,709). There was a significant difference between the three protocols (p t-test) shows that there was a significant difference between 120 and 80 kV, but not between the two levels of tube currents at 80 kV. Conclusion We conclude that when decreasing the tube voltage there is a significant improvement in tumor conspicuity.</p

Magnetic resonance spectroscopy of bile in the detection of cholangiocarcinoma

Peer reviewed: YesNRC publication: Ye