Drug – bio-affecting and body treating compositions – In vivo diagnosis or in vivo testing – Magnetic imaging agent
Patent
1992-11-06
1994-11-29
Hollinden, Gary E.
Drug, bio-affecting and body treating compositions
In vivo diagnosis or in vivo testing
Magnetic imaging agent
436173, 1286534, 424617, 514 54, 514 57, A61B 5055
Patent
active
053688392
DESCRIPTION:
BRIEF SUMMARY
The invention relates to suspensions of insoluble complexes or salts of lanthanide elements which are useful as contrast agents to produce NMR images of the gastrointestinal tract.
Currently, the techniques which are preferably employed for the diagnostic imaging of the abdomen include the use of X-rays, using suspensions of BaSO.sub.4 as contrast agents, computerised axial tomography and ecography. However, nuclear magnetic resonance, although already capable of competing with axial tomography, especially as regards the assessment of focal lesions of liver, of tumors of suprarenal glands, of kidneys and of pelvic organs, has not yet reached an adequate level of application in the gastrointestinal field. This is due to the fact that the visual display of the gastroenteric tract presents numerous problems which are associated, inter alia, with intestinal motility, with anatomical variations in different patients, and with the fact that the irregularities of the intestinal loops may be confused with anomalous structures associated with pathological feature. Further, the observation of the principal abdominal organs, for example pancreas, is made difficult by the superposition of images from stomach and/or duodenum.
Accordingly, it is necessary to obtain a contrast agent which permits the application of a safe diagnostic technique such as NMR for the examination of these organs as well. Till now, studies have been carried out on various classes of substances: and initial classification may subdivide them into positive contrast agents, i.e. those which are capable of simultaneously reducing both the longitudinal relaxation time T.sub.1 and the transverse relaxation time T.sub.2 of the protons of the surrounding water, and negative contrast agents which act selectively on T.sub.2 . Actually, while the positive contrast agents permit improved observations of the organs in which they accumulate, the negative contrast agents have the function of eliminating the signal from the regions which contain them, thus permitting the delimitation of the contours of said regions and the visual display of the adjacent organs. In order to find positive contrast agents useful for the gastrointestinal tract, studies have been carried out on substances such as iron salts [Young et al., Computerized Tomography 5 (1981) 543-547; Wesbey et al., Magnetic Resonance Imaging 3 (1985) 57-64 and Radiology 149 (1983) 175-180; Clanton et al., Radiology 153 (1984) 159] , gadolinium complexes [Weinmann et al., Radiology 153 ( 1984 ) 292 ]and chromium complexes [Kamisky et al., Magnetic Resonance in Medicine and Biology 1, (1988) 271]. On the other hand, with regard to negative contrast agents, consideration has been given to dispersions of diamagnetic substances such as kaolin or bentonite [Listinsky et al., Magnetic Resonance in Medicine 8 ( 1989 ) 285-92 ], while as far as their strong selective effect on T.sub.2 is concerned, suspensions of appropriately supported ferromagnetic or superparamagnetic substances have been tested [Edelman et al., Radiology 161 (P) (1986) 314; Hahn et al., Radiology 164 (1987) 37-41]. Moreover, it is then necessary to consider those substances which cancel the NMR signal due to lack of protons, such as perfluoro derivatives [Mattrey et al., American Journal Roentgenology 148 (1987) 1259-1263 and Radiology 161 (P) (1986) 314].
Possible contrast agents for NMR imaging of the gastroenteric tract are described in Patent documents U.S. Pat. No. 4,719,098 (Gries), EP-A-275,215 (Amersham), U.S. Pat. No. 4,615,879 (Runge), EP-A-299,910 (Schering), WO 85/04330 (Nyegaard), WO 88/00060 (Adv. Magnetics) . Such agents may be classified as positive contrast agents, in the light of what has been described in U.S. Pat. No. 4,719,098, EP-A-275, 215, U.S. Pat. No. 4,615,879 and EP-A-299,911. On the other hand WO 85/04330 WO 88/00060WO85/05554 describe particles which act on the relaxation time T2, and are therefore potential negative contrast agents. The contrast agents for gastrointestinal use which have been studied up to the
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Aime Silvio
Botta Mauro
Bracco S.p.A.
Hollinden Gary E.
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