WO1993010821A1

WO1993010821A1 - A method and formulations useful to improve the study of human body cavities

Info

Publication number: WO1993010821A1
Application number: PCT/EP1992/002712
Authority: WO
Inventors: Andrea Giovagnoni; Paola Ercolani; Christoph De Haen; Friedrick Cavagna
Original assignee: Bracco S.P.A.; Dibra S.P.A.
Priority date: 1991-11-29
Filing date: 1992-11-25
Publication date: 1993-06-10
Also published as: ITMI913218A0; EP0614376A1; IT1252145B; AU2945492A; ITMI913218A1

Abstract

Formulations useful for diagnostic imaging by nuclear magnetic resonance (NMR) of the gastrointestinal (GI) tract, the bladder and the cavities of the female reproductive apparatus with the use of T2-weighted sequences, characterized in that they contain water-soluble paramagnetic substances at concentrations ranging from 0.01 to 0.8 - preferably from 0.02 to 0.4 - times the concentration which gives the highest water signal when operating with T1-weighted sequences with the same compounds.

Description

A METHOD AND FORMULATIONS USEFUL TO IMPROVE THE STUDY OF HUMAN BODY CAVITIES

This invention relates to a method and formula¬ tions useful for obtaining the in-vivo visualization of body cavities using Nuclear Magnetic Resonance (NMR) . In particular, it relates to the use of solutions of positive paramagnetic contrast agents for NMR examina¬ tions of said cavities via proton-density and T_- weighted sequences, with the proviso that said parama¬ gnetic agents are kept in a well-defined concentration range. In this way it is possible to obtain clear images of organic alterations (whether neoplastic and not) of the GI (gastro-intestinal) tract, the bladder, and/or the cavities of the female reproductive apparatus in patients suffering from these pathologies. It is well known that NMR allows the imaging of internal organs of living .organisms. Often it can support or substitute the diagnostic techniques based on the use of ionizing radiations, for its positive impact on patients¹ and operators' health. Unfortuna¬ tely, the diagnostic advantages of this technique, when used for examinations involving the Gi tract, the bladder and/or the cavities of the female reproductive apparatus, are very limited due to a series of problems basically related to signal iεointensity of adjacent tissues which, when images are taken, usually occurs among the intestinal or the bladder wall, the lumen content, the contiguous organs, and neoplastic intra- and/or extra lumen lesions. Moreover, the interpreta¬ tion of GI images is complicated by the winding confi- guration and the unhomogenized filling of ^' the intestine. And it is well known in the present radiolo¬ gical practice that clear images for diagnostic use, are obtained only if the cavity walls under examination are properly relaxed.

Researchers have tried to overcome these problems, although in a partial way, by administering adequate contrast media. Up to now they have mainly proposed the so-called negative contrast media, which basically rely on the use of particles of ferromagnetic or superpara- magnetic material. These substances bring about a decrease of signal intensity of the lumen content when T_-weighted sequences are used [WO 8504330 (Nyegaard) , EP 186616 (Schering), WO 8800060 (Advanced Magnetics), EP 414287 (Nycomed)]. However, the use of said contrast media is limited by the presence in the images of so- called metal artefacts (distortions) , reducing their diagnostic value.

Other negative contrast media irely on a dispersion of diamagnetic substances such as: kaolin and bentonite

[Listinsky et al. , "Gastrointestinal contrast agent: A diamagnetic Approach", Magnetic Resonance in Medicine, , 285-292 (1989)]. These substances have an impact on transverse relaxivity ^' due to the imposition of a dynamic anisotropy on the water molecules movement near their surfaces.

Also the use of positive contrast agents has been proposed, that is to say, the use of solutions of para¬ magnetic ions and chelates, which, by decreasing the longitudinal relaxation time of the lumen content, produce an increase in the signal intensity in T-- weighted images [EP 124766 (Schering) EP 414288 (Nycomed)]. Unfortunately, only T_-weighted images enable the distinction of the various layers of cavity walls and hence, only these can be successfully used to determine the extent of infiltration by the neoplasia into the walls.

Finally, we should also mention the substances cancelling the NMR signal by lack of protons such as for instance the perfluoro derivatives [WO 893693 (Fluoro ed) ] .

Up to now none of the investigated contrast media have successfully overcome the problems connected to this type of diagnosis. As a consequence, there are no ideal contrast media, nor formulations of the same, useful for NMR examinations of the GI tract and/or the bladder [Tart et al. , Magn. Res. Imaging Vol. 9, pages 559-568 (1991)]. For this reason, physicians will posi¬ tively hail the introduction of a diagnostic product meeting the above mentioned needs, and in particular the following ones:

* the ability to identify the lumen as well as the organic alterations (whether neoplastic or not), by distinguishing them from the walls and by visualizing their impact on the wall layers, * the ability to provide good wall relaxation.

T.-relaxing media, if used with T.-weighted sequences, increase the lumen signal intensity of body cavities when compared to the nearby tissues. This causes a loss of differentiation capacity among the normal and the pathological (tumours or other) wall components, affecting and/or reducing the diagnostic efficacy of the method.

We have now surprisingly found, and this is the subject of this invention, that contrast media formula¬ tions containing paramagnetic substances, which are usually used as T,-relaxing agents, increase the intra- lu en signal, without affecting the differentiation of normal and pathological wall constituents, when proton- density and/or T_-weighted sequences are used and on the condition that the concentration of said paramagne- tic agent is kept within a precise interval, specific to said agent and lower than that recommended for imaging, with T,-weighted sequences.

As a result the maximum diagnostic potential of the NMR method is reached. After administering contrast media containing .- at least one paramagnetic species, selected from a series of conventional T,-relaxing contrast media, at a suitable concentration and using NMR proton-density and/or T--weighted sequences. It has been found that images of tumours have an intermediate intensity between that of the organ wall under examina¬ tion and the liquid contained in the lumen. In addition, thanks to the quality of the images obtained under the conditions of this invention, neoplastic lesions can be clearly identified and the extent of wall penetration may be determined. Furthermore, in images obtained by proton- ensity sequences, a good differential contrast among the lesion, the wall and the adjacent adipose tissue can be easily visualized.

This use of selected formulations of typical T,- relaxing agents, based on proton-density and/or T₂- weighted sequences, is particularly and surprisingly useful for obtaining NMR images of the GI tract, the bladder and/or the cavities of the female reproductive apparatus.

The amount of paramagnetic species used in the formulation of the contrast medium should be enough to create and keep inside the lumen liquid, after the administration, a concentration of contrast agent suf¬ ficient to obtain a contrast/noise ratio of at least 2 between the lumen content and the GI tract or the bladder walls for T_-weighted sequences. In addition, the contrast agent concentration in the lumen liquid should be kept preferably in a range in which the signal intensity .of the lumen content, in this case measured under proton-density-sequence conditions, does not exceed the signal intensity of fat by more than 20%. This second type of image, that is usually acquired with double echo sequences, can be obtained during the same diagnostic examination after a single administration of the contrast medium used for T_- weighted imaging.

As far as the state of the art related to this invention is concerned, Laniado et al. [Amer. J. Radiol. 150, 817 (1988); Gastrointestinal System in "Enhanced Magnetic Resonance Imaging", the C.V. Mosby Company (1989)] only mention that following an oral ad¬ ministration of 1.0-mM Gd-DTPA: "In 13 of 15 cases, T_- weighted images (SE 500/70 or SE 2000/70) also provided signal intensity of the opacified small bowel that was higher than that of the peritoneal fat" (Laniado, "Enhanced Magnetic Resonance Imaging", page 306). On the other hand, the same author further on remarks that "As a result, contrast enhancement was insufficient to identify the bowel loops when 0.5 mM Gd-DTPA was given" (page 307) and concludes by stating "Thus, for obtai¬ ning a consistent positive-contrast effect, 1.0-mM Gd- DTPA is not only appropriate but also required". (Laniado, "Enhanced Magnetic Resonance Imaging", page 307).

Laniado did not recognize at all the general effect exerted by any paramagnetic species on the signal intensity of T^-weighted sequences. In addition, the concentration he considered indispensable is far higher than the one useful for obtaining the contrast effects subject of this invention. Finally, he did not perceive, nor anticipate, the clinical usefulness stressed in the present invention for the diagnosis of abnormalities of the intestine, the bladder and/or the cavities of the female reproductive apparatus, nor suggest a possible retrograde administration. This technique is essential for obtaining valuable images of the bladder and is preferred for the terminal intestine tract in order to assure the volume and the ideal con¬ centration of the contrast medium for the method of this invention. Furthermore, a retrograde administra¬ tion requires an advantageously short preparation time. On the other hand, oral administration can be taken into consideration for the imaging of the early digestive regions and for the upper abdomen providing that the formulations are not diluted or concentrated excessively through physiological processes. Giovagnoni et al. [Congress of the European Society of Magnetic Resonance in Medicine and Biology, Strasbourg, 2-5 May, 1990, Abstr. N° 295] refer to "a ferrous contrastographic solution", named JKAl, useful for the imaging of wall lesions of the intestine and the bladder by using T_-weighted sequences. The product exact nature was not reported and furthermore the contrast effect of such a formulation was hypotheti- cally attributed to a T„ prolongation caused by an active ingredient in JKAl. This presentation in no way suggests the basic elements of the present invention. The same authors in a quite similar publication

(Radiol. Med. 80: 207-212, 1990) disclose the results of the staging of urinary bladder cancers by means of the same "contrastographic solution", i.e. JKAl, by using T^-weighted sequences. In this document they. define JKAl as a "home-made solution of Fe-gluconate" but no data at all are given about the preparation composition. In particular no teaching is provided at least on the main characteristics of said formulation, for instance, osmolality and preferred concentration of the active principle.

Tart et al. [Magn. Res. Imaging, Vol. 9, pages 559-568 (1991)] mention that, despite the fact that many agents have been proposed as GI NMR contrast media, the ideal agent has not yet been found. In their investigation they take into account different possible contrast agents both negative and positive and among them also a paramagnetic product (Geritol 0) , a dietary supplement product containing ferric ammonium citrate).

However, they conclude by stating that "none of the agents tested fulfil all the criteria of an ideal contrast agent". In addition, on a scale of efficacy and tolerability, the paramagnetic compound Geritor^ ranks second-last, indicating that the use of soluble paramagnetic species is not recommended for intestinal imaging. Tart in a previously published work , [(Magn. Res. Imaging, Vol. 8, pages 589-598 (1991)] reports the results of a study performed in order to obtain oil emulsions of paramagnetic agents as oral MRI contrast media. Different combinations of paramagnetic compounds with different types of oil were tested on volunteers either by using T.- or T~- weighted sequences, but in particular said emulsions were subjected to taste tests with the aim of obtaining oral compositions with the best patient acceptance. Ka insky, Laniado et al. (Radiol. Diagn. 30 (1988) H.5, 541-548) studying the efficacy of a paramagnetic oral formulation containing Gd-DTPA and mannitol (claimed in patent EP 124766) on 80 patients, found that, when administered in 1 mM concentration "high signal intensity of intraluminal Gd-DTPA solution was detectable also with T₂-weighted sequences". This finding is substantially the same disclosed in Laniado (Amer. J. Radiol. 150, 817 (1988) and therefore gives no teaching on the specific formulations and on the usefulness of the method of the present invention.

Now, it has been surprisingly found that any physiologically tolerable water-soluble substance containing at least one paramagnetic metal species is useful for the aim of the present invention, providing that it is used in a precise interval of concentra¬ tions, that is specific to it. Particularly preferred species are, for instance, chelates of linear or cyclic aminopolycarboxylic acids or their derivatives, such as, for instance, amides, hydroxyamides and esters, with paramagnetic metal ions. Preferred compounds are, for instance, the Gd complex of N,N-bis-(2-(bis (carboxymethyl)amino)ethyl)- glycine (Gd-DTPA), its corresponding amido or bisamido derivatives like Gd-DTPA-bismethylamide and Gd-DTPA- bismorpholide or its ethoxy-benzyl (EOB) derivatives like Gd-EOBDTPA, the Gd complex of 4-carboxy-5, 8 , 11- tris(carboxymethyl)-l-phenyl-2-oxa-5, 8, 11-triaazatride- can-13-oic acid (Gd-30PTA) and its salts and derivati¬ ves, the Gd complex of 1,4 , 7 , 10-tetraazacyclododecan- 1, 4 ,7 , 10-tetraacetic acid (Gd-DOTA) and its derivati- ves, the Gd complex of 1,4 , 7 , 10-tetraazacyclododecan- 1,4 ,7-triacetic acid (Gd~D03A) , the Gd complex of 1,4,7,10-tetraazacyclododecan-lO-(2-hydroxy-propyl)- 1,4,7-triacetic acid (Gd-HPD03A) , the Gd complex of 1,4 ,7,10-tetraazacyclododecan-10-[ (lRS,2SR)-2, 3-dihy- droxy-l-(hydroxymethyl)propyl]-l,4, 7-triacetic acid, as well as the same complex compounds in which any remai¬ ning free acid functions have been neutralized with physiologically tolerable inorganic and/or organic bases such as, for instance, NaOH or N-methyl-glucamine (meg) .

Equally preferred metal chelates are also those with phosphonates, phosphinates, sulphonates or analo¬ gous compounds: non-limiting examples are the Gd complex of diethyl-triamino-pentakis(methylenephospho- nate) (Gd-PMP) and the Mn complexes of ethylene- diamino-tetrakis(methylenephosphonate) (Mn-TP) or of ,N'-1,2-ethanediyl-bis-(N-( (3-hydroxy-2-methyl-5-

((phosphonoxy)methyl)-4-pyridinyl)methyl)-glycine) (Mn-

DPDP) .

Equally preferred are also iron salts such as 5 Fe^ -citrate or Fe -gluconate, or Fe^{l +} ' chelates with aminopolycarboxylic acids containing at least one aryl ring, preferably two, such as the Fe¹ complex of N,N'-1,2-ethanediyl-bis-(2-(2-hydroxy-4-methylphe- nyl))-glycine [FE^II:[-EHPG]. 10 Equally preferred are ferrioxamine paramagnetic compounds like for .example ferrioxamine mesylate or manganese desferrioxamine mesylate.

Paramagnetic metal ions may be conveniently selec¬ ted from those of the metal elements having atomic 15 numbers of from 21 to 29, 42, and 44 and from 57 to 83, preferably from among iron, manganese, copper, chromium, nickel, gadolinium, holmium, europium, dy¬ sprosium, lanthanum, ytterbium, terbium, erbium and sa¬ marium. 20. Preferred concentration ranges for paramagnetic contrast media in the formulations of this invention have been individually determined and they have shown to be far lower than the ranges preferred when these agents are used to obtain T,-weighted images (see 25 Laniado, and experimental examples from 1 to 6). In particular, concentration ranges of the above-mentioned agents in the formulations object of the invention are between 0.01 and 0.8 - preferably between 0.02 and 0.4 - times the concentration which gives the highest water 0 signal with T.-weighted sequences with , the same compounds. Examples 1 to 6 do not limit the invention and only •report concentration intervals obtained for some preferred contrast agents which were used to produce the formulations of the present invention. Applying the procedure disclosed in the given examples to any para¬ magnetic agent with the intention of determining the potentially useful ranges of concentration, should not present any major difficulty for skilled technicians.

By way of example, concentration intervals useful for obtaining images using T₂-weighted sequences for some of the preferred paramagnetic agents of this invention are herein reported:

Preferred formulations of this invention may also contain suitable additives, for instance, excipients which are useful for controlling the transit speed of the administered bolus, or for keeping the dilution of the formulation in the lumen fluid within the desired operation limits. Particularly desired are also additives useful for maintaining the homogeneity and the initial concentra¬ tion of the formulations after patient administration.

Agents which influence viscosity may be equally useful because the formulation viscosity level affects magnetic relaxivity. Xanthan gum may be, for instance, a useful agent influencing viscosity. Other possible excipients useful for meeting the above mentioned criteria may be selected from among those usually used in pharmaceutical techniques. Non-limiting examples include: carrageenines, alginates, pectins, carboxy - methylcellulose, hydroxyethylcellulόse, polyvi¬ nylpyrrolidone, polyethylene glycol, barium sulphate, kaolin and bentonite, For these additives, the preferred concentration varies according to the type of excipient used and according to the administration route. In any case, the viscosity of formulations should be kept between 0 and 700 mPa " s.

The formulations of this invention may also contain other physiologically tolerable additives, which make them isotonic. For example salts such as sodium chloride (NaCl),. potassium chloride (KC1) , sodium hydrogen carbonate (NaHCO-), sodium sulphate (Na₂SO.) , alcoholic sugars such as glucose or mannitol and/or ionic or neutral iodinated organic compounds, usually known or used as X-ray contrast media, are useful for this purpose.

This invention is also aimed at obtaining a method for producing images of wall organic alterations (whether neoplastic or not) of the GI tract, the bladder and/or the cavities of the female reproductive apparatus. This method foresees the oral or retrograde administration to patients of a suitable dose of a paramagnetic formulation according to the invention. Patients are submitted to NMR tomography following the most appropriate operating conditions, that is to say, for instance, double echo sequences, proton-density (SE

200/22) and T--weighted sequences (SE 2000/90 or SE 2000/100).

The high diagnostic improvement to the state of the art, deriving from this invention, is widely reported in the clinical cases of Example 11 and the enclosed images. The differences between the images obtained before and after the retrograde administration of suitable paramagnetic formulations, in diagnostic investigations of colorectal and bladder tumours, are extremely significant.

By exposing patients to T--weighted sequences, according to the above-mentioned operating instruc¬ tions, after administering the contrast medium, the organ wall under examination is visualized as a very dark structure, while the tumours show a higher signal intensity, by generating a clearer image. Hence, the resulting contrast between the tumour, the wall and the lumen liquid, which has a still higher signal intensity, is very clear. In this way the outline of neoplasia contours, is surprisingly sharp when compared to the wall, making the identification and the wall infiltration extent of the neoplastic shape easier to ascertain. EXAMPLE 1 In-vitro experimental determination of the concentra- tion interval useful for obtaining NMR images, using

T₂-weighted sequences and the di-meglumine salt of the Gd-BOPTA complex (Gd-BOPTA/dimeg) .

Ten Gd-BOPTA/dimeg aqueous solutions with concen¬ trations ranging from 2.5 " 10^" mM to 29 mM were prepared and submitted to imaging by ^' using both T-.- weighted sequences ( SE 2000/10), and T, -weighted sequences (SE 500/16). All measurements were performed by using an ESAOTE Esatom 5000 (Ansaldo) imager set at 0.5 T. As a reference for the detection of the appropriate concentration interval, the water signal intensity in T₂-weighted sequences was selected. Higher signal intensities in comparison to that of water correspond to concentration values which may be used to obtain desired images.

The maximum enhancement of signal intensity for T_-weighted sequences corresponded to a concentration equal to 0.125 mM, while for T,-weighted sequences the maximum value was reached at a far higher concentration

(1.25 mM).

The concentration interval which may be used to obtain useful images using T₂-weighted sequences ranges from about 0.01 mM to about 0.9 mM. EXAMPLE 2

In-vitro experimental determination of the concentra¬ tion interval useful for obtaining NMR images, using T₂-weighted sequences and the di-meglumine salt of the Gd-DTPA complex (Gd-DTPA/dimeg).

Ten Gd-DTPA/dimeg aqueous solutions with concentrations ranging from 0.1 mM to 100 mM were prepared and submitted^' to NMR imaging according to the procedure explained in Example 1.

The maximum enhancement of signal intensity for

T₂-weighted sequences corresponded to a concentration equal to 0.4 mM, while for T.-weighted sequences the maximum value was reached at a concentration of about 2 mM.

The concentration interval which may be used in T₂-weighted sequences ranges from about 0.05 mM to about 0.8 mM. EXAMPLE 3

In-vitro experimental determination of the concentra- tion interval useful for obtaining NMR images, using T₂-weighted sequences and the meglumine salt of the Gd- DOTA complex (Gd-DOTA/meg) .

Thirteen Gd-DOTA/meg aqueous solutions with concentrations ranging from 1.25 " 10 -3 mM to 20 mM were prepared and submitted to NMR imaging according to the procedure explained in Example 1.

The maximum enhancement of signal intensity for T₂-weighted sequences corresponded to a concentration equal to 0.3 mM, while for T, -weighted sequences the maximum value was reached at a concentration of 1.3 mM. The concentration interval which may be used in T₂-weighted sequences ranges from about 0.04 mM to about 1 mM. EXAMPLE 4 In-vitro experimental determination of the concentra¬ tion interval useful for obtaining NMR images, using T₂-weighted sequences and Gd-HPD03A complex.

Twelve Gd-HPD03A aqueous solutions with concentrations ranging from 2.3 ^* 10^" mM .to 20 mM were prepared and submitted to NMR imaging according to the procedure explained in Example 1.

The maximum enhancement of signal intensity for T₂-weighted sequences corresponded to a concentration equal to 0.3 mM, while for T..-weighted sequences the maximum value was reached at a concentration of 1.25 mM. The concentration interval which may be used in T₂-weighted sequences ranges from about 0.04 mM to about 0.9 mM. EXAMPLE 5 In-vitro experimental determination of the concentration interval useful for obtaining NMR images, using T₂-weighted sequences and the Fe -gluconate complex.

Thirteen Fe -gluconate aqueous solutions with concentrations ranging from 1.125 mM to 224 mM were prepared and submitted to NMR imaging according to the procedure explained in Example 1.

The maximum enhancement of signal intensity for T_-weighted sequences corresponded to a concentration equal to 11.2 mM, -•while for T.-weighted sequences the maximum value was reached at a concentration of 112 mM.

The concentration interval which may be used in T₂-weighted sequences ranges from about 1 mM to about 70 mM. " - EXAMPLE 6

In-vitro experimental determination of the concentration interval useful for obtaining NMR images, using T₂-weighted sequences and the Fe ⁺ -citrate complex. Eleven Fe -citrate aqueous solutions with con- centrations ranging from 5 ^* 10 -2 mM and 50 mM were prepared and submitted to NMR imaging according to the procedure explained in Example 1.

The maximum increase in signal intensity for T₂- weighted sequences corresponded to a concentration equal to 0.4 mM, while for T.-weighted sequences the maximum value was reached at a concentration of 3.1 mM.

The concentration interval which may be used in T₂-weighted sequences ranges from about 0.05 mM to about 2.5 mM. EXAMPLE 7

Formulations of Gd-BOPTA/dimeg, Gd-DTPA/dimeg, and Fe -gluconate with agents influencing viscosity.

The following 0.5% methylcellulose solutions (viscosity - 21 mPa ^* s at 22 °C) were prepared: 1. 0.125-mM Gd-BOPTA/dimeg solution.

2. 0.4-mM Gd-DTPA/dimeg solution.

3. 11.2-mM Fe -gluconate solution.

These solutions were submitted to T_-weighted sequence imaging as described in Example 1. The recorded signal intensity of the three solutions was equal to that found for the corresponding aqueous solutions. EXAMPLE 8 Isotonic formulation of Gd-BOPTA/dimeg 0.125 mM useful for maintaining the original concentration after administration.

Gd-BOPTA/dimeg 0.13 g polyethylene glycol 4000 65.55 g sodium sulphate 6.32 g sodium hydrogen carbonate 1.87 g sodium chloride 1.63 g potassium chloride 0.82 g

Distiled water is added until the total volume of the solution is 1000 ml. The formulation is isotomic, i.e. 296 m"osmol/kg H_0. EXAMPLE 9

Preparation of Gd-BOPTA/dimeg, Gd-DTPA/dimeg, and Fe^ -gluconate formulations to carry out "in-vivo" experiments on animals. The following formulations were prepared and kept in sealed containers.

1. A 0.25-M Gd-BOPTA/dimeg aqueous solution was diluted with a saline solution in order to obtain a 0.125-mM solution (at which concentration the detected "in-vitro" signal intensity for T₂~ weighted sequences is at a maximum) .

2. A 0.5-M GD-DTPA/dimeg aqueous solution was diluted with a saline solution in order to obtain a 0.4-mM solution. 3. A 11.2-mM solution of Fe -gluconate in physiological solution was prepared. EXAMPLE 10 "In-vivo" experiments on healthy animals.

15 ml of each solution described in Example 9 were rectally administered to healthy rats through pediatric catheter.

For each contrast medium, two male Sprague-Dawley rats, weighing 200 to 300 g, and fasted for 24 h, were used. Before administering the contrast medium, the animals were anaesthetized with 30 ml/kg of i.p. sodium pentobarbital.

All measurements were performed by using an ESAOTE Esatom 5000 (Ansaldo) imager at 0.5 T, with a 8-cm i.d. crossed-elipse-shaped coil.

Transverse images (T₂-weighted) were taken before and 5, 15 and 30 min after the administration of contrast medium using a 2000/100/2 (TR/TE/NEX) spin echo sequence, a 2-mm slice, a 15.91-cm FOV, and a 128 x 256 matrix. After administering the contrast medium, a clear remarkable hyperintensity of the intestinal lumen when compared to the wall, was recorded in all cases.

In some animals, the presence of solid material

(feces) inside the loops was clearly visible. Images obtained 15 min after the administration of various contrast agents are reported in Figure 1.

EXAMPLE 11

"In-vivo" studies on patients suffering from rectal and/or bladder neoplasias. Hereinafter, a non-limiting case study is reported concerning the production of clear and diagnostically useful images of rectal and/or bladder neoplasias in patients affected by them.

All the patients were rectally or urethrally admi- nistered with a 13-mM Fe -gluconate aqueous solution , obtained by appropriately di luting Ferlixit^ speciality ( Nattermann ) which is available on the market .

All measurement s were performed by using a Magnetom Superconductive Tomographer ( Siemens ) at 1.0

T.

T₂-weighted images were taken before and after administering the contras t medium using 2000 / 90 ( TE/TE ) spin echo sequences , 40-cm FOV, 256 x 256 matrix. Case A: patient suffering from rectal adenocarcinoma

( Fig . 2 ) : The images obtained after rectal repletion with contrast medium (Fig. 2-b) clearly outline the tumoral mass area enabling the visualization of the interested wall infiltration. 5 Case B: patient suffering from rectal adenocarcinoma (Fig. 3):

The images obtained without contrast medium (Fig. 3-a) does not highlight the neoplastic lesion.

10 While in the images obtained after administra¬ tion of the contrast agent (Fig. 3-b) the lumen, which is rendered hyperintense by the presence of Fe( ⁺ -gluconate, allows a good wall relaxation, together with a clear defini-

15 tion of neoplasia limits.

Case C: patient suffering from rectal adenocarcinoma (Fig. 4):

Only the images obtained with contrast medium (Fig. 4-b) allow a correct:

20 * rectal lumen identification

* definition of neoplasia contours

* wall infiltration extent.

Case D: patient affected by bladder papilloma (Fig. 5): Fig. 5-a shows the relaxed bladder containing 25 the urine only. The lesion contours are very blurred . On the contrary, Fig. 5-b shows the bladder filled by the contrast medium. The hyperintensity generated by this agent enables an excellent identification of papilloma 30. contours .

Case E: patient suffering from rectal carcinoma (Fig. 6 ) :

In the image, the arrows define the neoplasia limits and its wall penetration. A small, otherwise hardly detectable polypous-shaped lesion (X) is also identified.

Case F: patient suffering from rectal carcinoma (Fig. 7):

The arrows define the neoplasia contours that, in this case, stenotize the rectal lumen (R). In addition there is a clear difference in the signal intensity between the lumen, which is rendered hyperintense by the contrast medium and the bladder (V) , which contains the urine only, and therefore has a lower signal. Case G: patient suffering from rectal polypus (Fig. 8):

The image clearly visualizes a bulky rectal polypus, which caused a wall thickening at the base level of its implant.

In all the above mentioned cases the subsequent surgical operation confirmed what was shown in the images obtained according to the above cited procedure.

Claims

1. ^'Formulations useful for diagnostic imaging by nuclear magnetic resonance (NMR) of the gastrointesti- 5 nal (GI) tract, the bladder and the cavities of the female reproductive apparatus with the use of T₂- weighted sequences, characterized in that they contain water-soluble paramagnetic substances at concentrations ranging from 0.01 to 0.8 - preferably from 0.02 to 0.4 10 - times the concentration which gives the highest water signal when operating with T, -weighted sequences with the s ame co po un ds .

2. Pharmaceutical formulations according to claim 1, characterized in that said paramagnetic species

15 comprise paramagnetic metal ions, which are salified, complexed or chelated with physiologically tolerable organic and/or inorganic counter-ions, ligands or chelants.

3. Formulations according to claim 2, characterized 20. in that said paramagnetic metal ions are chelated with aminopolycarboxylic acids, or derivatives thereof, in which the free ionic functions, which may be still present after the chelation, are optionally neutralized by physiologically tolerable organic and/or inorganic 5 bases or acids.

4. Formulations according to claim 3, characterized in that said chelants are selected from the group com¬ prising: N , -bis- ( 2- (bis ( carboxy ethy 1 ) amino ) ethyl ) - glycine (DTPA), 4-carboxy-5, 8,11- tris(carboxyme thyl) -1- 0 phenyl-2-oxa-5,8,ll-triaazatridecan-13-oic acid

(BOPTA) , 1,4,7, 10-te traazacyclododecan-1, 4 , 7 , 10-tetraa- cetic acid (DOTA) , 1, 4 , 7 , 10-tetraazacyclododecan-lO- ( 2- hydrox -propyl )-l, 4, 7-triacetic acid (HPD03A), and de¬ rivatives thereof.

5. Formulations according to claim 2, in which said paramagnetic metal ions are chelated with physiologi¬ cally tolerable phosphates or phosphonate derivatives.

6. Formulations according to claim 5 , ^' in which the chelant is preferably N,N ^■ -1, 2-ethanediyl-bis (N-( ( 3- hydroxy-2-methyl-5-( (phosphonoxy) methyl )-4-pyridi- nyDmethyl) glycine) (DPDP).

7. Formulations according to claim 2, in which said physiologically tolerable counter-ions of said paramagnetic free,_, complexed or chelated metal ions are preferably selected from acetate, citrate, glutamate, gluconate, phosphate, polyphosphate, Na , K^⁺ ,

Mg^ , Ca ⁺' and/or protonated species of N- methylglucamine, lysine, ornitine, polylysine, polyornitine.

8. Formulations according to claim 2, in which said paramagnetic metal ions are selected from those metal elements having atomic numbers of from 21 to 29, 42, and 44, and from 57 to 83.

9. Formulations according to claim 8, in which said paramagnetic metal ions are selected from the group comprising: Fe⁽²⁺⁾; Fe⁽³⁺⁾; Mn⁽²⁺⁾; Cu⁽²⁺⁾; Cr⁽³⁺⁾;

Dy(³⁺>; Gd<³⁺>; Ho<³⁺⁾; Yb^{3+>; La⁽³⁺⁾; Eu⁽³⁺>; Tb⁽³⁺>; Er⁽³⁺⁾; Sm⁽³⁺⁾.

10. Formulations according to claim 1, also comprising physiologically tolerable additives, which affect the viscosity and/or transit time and/or homogeneity of the same and/or maintain the original concentration of said formulations after the administration, these additives being preferably selected from xanthan gum, carrageeni- nes, alginates, pectins, carboxymethylcellulose, hy¬ droxyethylcellulose, polyvinylpyrrolidone, polyethylene 5 glycol, barium sulphate, kaolin, and bentonite.

11. Formulations according to claim 1, also comprising physiologically tolerable additives, which make them isotonic and/or maintain the original concentration of said formulations after the administration, these

1_.0 additives being preferably selected from among sodium chloride, potassium chloride, sodium hydrogen- carbonate, sodium sulphate, polyethylene glycol, and/or alcoholic sugars, such as glucose or mannitol.

12. Formulations according to claim 4, comprising one 5 of the following paramagnetic species at a concentration ranging within the values indicated for each species:

0

13. Method to obtain clear MR images of (whether 5 neoplastic or not) organic alterations of the GI tract, the bladder and/or the cavities of the female reproduc¬ tive apparatus in patients suffering from such pathologies in which, patients are administered with formulations containing paramagnetic species, according 0 to claims 1 to 12, then they are submitted to NMR imaging through T₂-weighted sequences, with the proviso that said paramagnetic species are present in the body cavities under examination at concentrations which generate images which clearly distinguish organic alte¬ rations from both the liquid content of said cavities and the organ walls.

14. Use of water-soluble paramagnetic substances in order to prepare contrast media for NMR imaging of body cavities using T₂-weighted sequences.