Water insoluble non-magnetic manganese particles as magnetic resonance contract enhancement agents

This invention is directed to a magnetic resonance imaging composition for imaging of an organ rich in mitochondria comprising particles of a substantially insoluble manganese compound. In a preferred embodiment, the organ rich in mitochondria is the liver. In a further preferred embodiment, the particles are substantially nonmagnetic. In another preferred embodiment, the particles have a particle size of less than about 10 microns. In a still further preferred embodiment, the insoluble manganese compound is a manganese salt. The manganese compound is preferably selected from the group consisting of manganese phosphate, manganese carbonate and manganese 8-hydroxy quinolate. In another preferred embodiment, the composition of the present invention further comprises a surfactant. The present invention is also directed to a method of diagnosis comprising administering to a mammal a contrast effective amount of particles of a substantially insoluble manganese compound suspended or dispersed in a physiologically tolerable carrier and generating an NMR image of said mammal.

FIELD OF THE INVENTION 
This invention relates to diagnostic compositions useful in magnetic 
resonance imaging. More particularly, this invention relates to water 
insoluble manganese particles that can be used in magnetic resonance 
imaging of organs. 
BACKGROUND OF THE INVENTION 
The enhancement of positive contrast in the magnetic resonance (MR) image 
of an organ rich in mitochondria, such as the liver, pancreas, or kidney, 
requires an agent that specifically locates in those organs and causes an 
increase in the longitudinal relaxation rate of water protons in those 
organs. The increase in the relaxation rate, which is responsible for 
enhancing positive contrast, is due to a dipolar interaction between the 
magnetic moments of the water protons and the magnetic moments of the 
paramagnetic contrast enhancement agent. The increase in the relaxation 
rate per unit concentration of paramagnetic contrast enhancement agent is 
called the relaxation efficiency, or relaxivity, of the agent. 
Runge et al., U.S. Pat. No. 4,615,879 discloses a contrast media 
composition for nuclear magnetic resonance (NMR) imaging of the 
gastrointestinal tract. The compositions prepared in that invention 
provided a decrease in both the spin lattice (T.sub.1) and the spin-spin 
(T.sub.2) relaxation time of protons, thereby increasing the imaging of 
the gastrointestinal tract. 
However, it would be desirable to have a composition for MR imaging which, 
in its native form, did not affect proton T.sub.1 and T2, that is, a 
composition which is substantially nonmagnetic, and which becomes a 
contrast agent upon in vivo administration. The present invention provides 
for a MR imaging composition for MR imaging of organs such as the liver. 
BRIEF DESCRIPTION OF THE INVENTION 
This invention is directed to a magnetic resonance imaging composition for 
imaging of an organ rich in mitochondria comprising particles of a 
substantially insoluble manganese compound. In a preferred embodiment, the 
organ rich in mitochondria is the liver. In a further preferred 
embodiment, the particles are substantially nonmagnetic. In another 
preferred embodiment, the particles have a particle size of less than 
about 10 microns. 
In a still further preferred embodiment, the insoluble manganese compound 
is a manganese salt. The manganese compound is preferably selected from 
the group consisting of manganese phosphate, manganese carbonate and 
manganese 8-hydroxy quinolate. 
In another preferred embodiment, the composition of the present invention 
further comprises a surfactant. 
The present invention is further directed to a method of preparing a 
magnetic resonance imaging composition useful for imaging an organ rich in 
mitochondria comprising particles of a substantially insoluble manganese 
compound comprised of contacting a manganese source, preferably a 
manganese (II) source, with a counter ion source for a time and under 
conditions sufficient for the formation of said insoluble manganese 
compound. In a preferred embodiment, the contacting is by simultaneous 
admixing in an aqueous solution. 
In a further preferred embodiment, the manganese source is an aqueous 
solution of a soluble manganese salt. The soluble manganese salt is 
preferably selected from the group consisting of manganese chloride, 
manganese nitrate and manganese sulfate. 
In a still further preferred embodiment, the counter ion source is an 
aqueous solution of a carbonate salt. The carbonate salt is preferably 
selected from the group consisting of sodium carbonate, potassium 
carbonate, and ammonium carbonate. 
In another preferred embodiment, the counter ion source is an aqueous 
solution of a phosphate salt. The phosphate salt is preferably selected 
from the group consisting of sodium phosphate, potassium phosphate, and 
ammonium phosphate. 
In yet another preferred embodiment, the counter ion source is an aqueous 
solution of 8-quinolinol. 
The present invention is also directed to a method of diagnosis comprising 
administering to a mammal a contrast effective amount of particles of a 
substantially insoluble manganese compound suspended or dispersed in a 
physiologically tolerable carrier and generating an NMR image of said 
mammal.

DETAILED DESCRIPTION OF THE INVENTION 
This invention is described hereinafter in connection with a preferred 
embodiment featuring particles of a substantially insoluble manganese 
compound. In addition, it is believed that the invention can be practiced 
with particles of other substantially insoluble compounds. 
The relaxivity of the contrast enhancement agent in organs such as the 
liver is not necessarily the same as the relaxivity of the agent in a 
beaker of water. Although the relaxivities of various manganese-containing 
agents are different in water, these agents have the same relaxivity in 
liver homogenates. 
Although not wishing to be bound by theory, this similarity of relaxivities 
in liver homogenates suggests that manganese-containing agents are merely 
vehicles that deliver manganese to the liver, where the manganese is 
stripped from the agent and becomes bound to some macromolecule in the 
liver. It is the relaxivity of the manganese-liver macromolecule complex 
that is related to the enhancement of positive contrast in a liver MR 
image. 
Although manganese is a targeting vector to organs such as the liver, not 
all of the injected dosage of manganese localizes in the liver. Manganese 
has been found in other organs as well. 
One way of increasing liver specificity is to use water-insoluble manganese 
particles as contrast enhancement agents according to the composition of 
the present invention. Examples would include, but are not limited to, 
water-insoluble inorganic salts such as manganese phosphate or manganese 
carbonate, and manganese chelates. In general, water-insoluble particles 
with diameters ranging from about one hundred nanometers to a few 
micrometers are known to be taken up rapidly in the liver. Water-insoluble 
iron particles, which have a large T.sub.2 (transverse relaxation time) 
effect on water protons under imaging conditions are currently being 
investigated as negative contrast enhancement agents for liver MR imaging. 
Unlike their iron counterparts, manganese particles do not significantly 
affect T.sub.1 or T.sub.2 of water protons. Any possible affect on T.sub.1 
or T.sub.2 would be due to free manganese ions as a result of a solubility 
product. This effect can be removed by encapsulation of the 
manganeseparticles. 
However, once localized in the liver, the manganese particle dissolves and 
releases manganese to form a manganese -liver macromolecule complex with a 
high relaxivity as explained in the previous paragraph. In summary, 
water-insoluble manganese particles afford higher liver specificity than 
water-soluble manganese chelates. As a result, the dosage of manganese 
required to enhance positive contrast in a liver MR image to a given 
extent will be less for water-insoluble manganese particles than for 
water-soluble manganese chelates. 
The present invention is directed to a magnetic resonance imaging 
composition for imaging of organs rich in mitochondria comprising 
particles of a substantially insoluble manganese compound which, in its 
native form, is substantially nonmagnetic. 
The residue of the particles is visualized by imaging that tissue with a 
magnetic resonance imaging system. The visualization of the residue of the 
particles can be accomplished with commercially available magnetic imaging 
systems such as a General Electric 1.5 T Signa imaging system [.sup.1 H 
resonant frequency 63.9 megahertz (Mhz)]. Commercially available magnetic 
resonance imaging systems are typically characterized by the magnetic 
field strength used, with a field strength of 2.0 Tesla as the current 
maximum and 0.2 Tesla as the current minimum. 
For a given field strength, each detected nucleus has a characteristic 
frequency. For example, at a field strength of 1.0 Tesla, the resonance 
frequency for hydrogen is 42.57 Mhz; for phosphorus-31 it is 17.24 Mhz; 
and for sodium-23 it is 11.26 Mhz. 
As used herein, the phrase "organs rich in mitochondria" refers to organ 
systems in the body of a mammal which contain an abundance of the 
organelle called mitochondria. One measure of mitochondrial abundance is 
the level of mitochondrial enzymes present in a particular organ system. 
Organs rich in mitochondria include the liver, kidney, pancreas and 
biliary network. Preferred organs rich in mitochondria include the liver 
and kidney. A more preferred organ rich in mitochondria is the liver. 
In a preferred embodiment, the particles of the present invention, in their 
native form, are substantially nonmagnetic. That is, the particles have no 
effect on T.sub.1 or T.sub.2 as composed ex vivo. Once the particles are 
used in the diagnosis of a mammal, according to the methods of the present 
invention, the Mn within the particles is liberated to form a Mn 
bioconjugate, as discussed elsewhere herein. 
In a further preferred embodiment, the particles of the present invention 
have a particle size of less than about 10 microns. As used herein, the 
phrase "particle size" refers to a number average particle size as 
measured by conventional particle size measuring techniques well known to 
those skilled in the art, such as sedimentation field flow fractionation, 
photon correlation spectroscopy, disk centrifugation, or scanning electron 
microscopy (SEM). The phrase "particle size of less than about 10 microns" 
as used herein means that at least 90 percent of the particles have a 
weight average particle size of less than about 10 microns when measured 
by the above-noted techniques. It is preferred that at least 95 percent, 
and, more preferably, at least 99 percent of the particles have a particle 
size of less than about 10 microns. A preferred particle size is less than 
about 5 microns. A more preferred particle size is less than about 2.5 
microns. 
In another preferred embodiment, the insoluble manganese compound of the 
present invention is a manganese salt. That is, the salt yields manganese 
ions when in solution. Preferred manganese salts include manganese oxide, 
manganese dioxide, manganese iodate, manganese oxalate, manganese 
hydroxide, manganese hydrogen phosphate, manganese sulfide, manganese 
phosphate, manganese carbonate, manganese bile salts such as manganese 
oleate, manganese stearate, manganese cholate, and manganese taurocholate, 
and manganese salts of various fatty acids, and the like. Particularly 
preferred manganese salts are manganese phosphate and manganese carbonate. 
The insoluble manganese compound can be a manganese chelate such as 
manganese 8-hydroxy quinolate and manganese 2-methyl-8-hydroxyquinolate. 
As used herein, the phrase "substantially insoluble manganese compound" 
refers to a manganese containing compound with a solubility product (Ksp) 
of less than about 1.times.10.sup.-6. Preferred substantially insoluble 
manganese compounds have a Ksp of less than about 5.times.10.sup.-7. 
Manganese compounds useful as a substantially insoluble manganese compound 
have Ksp values as follows: manganese iodate (4.4.times.10.sup.-7), 
manganese oxalate (1.7.times.10.sup.-7) , manganese hydroxide 
(2.1.times.10.sup.-13) , manganese hydrogen phosphate 
(1.4.times.10.sup.-13) , manganese sulfide (4.7.times.10.sup.-14) , 
manganese 2-methyl-8-hydroxyquinolate (4.5.times.10.sup.-19) , manganese 
carbonate (2.2.times.10.sup.-11) , and manganese 8-hydroxy quinolate 
(1.6.times.10.sup.-18). The solubility in plasma or in vivo may affect the 
preferred timing of imaging. 
In another preferred embodiment, the composition of the present invention 
may contain a surfactant. Preferred surfactants include Pluronic F68 NF, 
which is a block copolymer of ethylene oxide and propylene oxide, 
dimyristoylphosphatidylglycerol (DMPG), Tetronic 908, Tween 20, Tween 80, 
Pluronic F-108, Tyloxapol, Henkel APG 325cs, polyvinyl alcohol, or PVP 
k-15. Preferred surfactants include DMPG and Pluronic F68 NF. 
The present invention is further directed to a method of preparing a 
magnetic resonance imaging composition useful for imaging an organ rich in 
mitochondria comprising particles of a substantially insoluble manganese 
compound comprised of contacting a manganese source, preferably a 
manganese II source, with a counter ion source for a time and under 
conditions sufficient for the formation of said insoluble manganese 
compound. Such counter ions are typically anions which interact with the 
manganese cation to form an insoluble manganese compound. 
As used herein, the phrase "a manganese source" refers to an aqueous 
solution which contains free manganese ions, that is, manganese ions 
available for chemical reaction. For example, an aqueous solution of 
manganese chloride would contain free manganese ions available for 
chemical reaction. The manganese ion source need not contain the counter 
ion, in this case, chloride, to be useful in the processes of the present 
invention. 
A preferred manganese source is a soluble or insoluble manganese salt. 
Preferred soluble manganese salts include manganese chloride, manganese 
nitrate, manganese sulfate, manganese acetate, manganese fluoride, and the 
like. Other exemplary soluble manganese salts may be found in the Handbook 
of Chemistry and Physics, CRC Press, Cleveland, Ohio. 
As used herein, the phrase "a counter ion source" refers to an aqueous 
solution which contains a free counter ion, that is, a counter ion which 
is available for chemical reaction. For example, an aqueous solution of 
sodium carbonate would contain free carbonate counter ions available for 
chemical reaction. The carbonate counter ion need not contain any other 
ions, in this case, sodium, to be useful in the processes of the present 
invention. 
A preferred counter ion source is a soluble carbonate or phosphate salt. 
Preferred soluble carbonate salts include sodium carbonate, potassium 
carbonate, and ammonium carbonate. Preferred soluble phosphate salts 
include sodium phosphate, potassium phosphate, and ammonium phosphate. 
Other exemplary soluble carbonate and phosphate salts may be found in the 
Handbook of Chemistry and Physics, CRC Press, Cleveland, Ohio. 
Another preferred counter ion source includes aqueous solutions of the 
salts of oleic and cholic acid. 
A further preferred counter ion source is an aqueous solution of 
8-quinolinol, which provides an 8-quinolinate counter ion in solution. 
In a preferred embodiment, contacting of the manganese ion source and the 
counter ion source is by simultaneous admixing in an aqueous solution. 
This aqueous solution is sometimes referred to herein as the "host 
solution", that is, the solution into which the manganese ion source and 
counter ion source are simultaneously admixed. 
The host solution may contain other buffers, salts, or surfactants useful 
in the processes of the present invention. For example, the host solution 
may contain citric acid, sodium citrate, ascorbic acid or other acids, 
bases or buffers to regulate the pH value of the host solution. 
Additionally, the host solution may contain a variety of surfactants and 
stabilizers, as is well known in the art. Several of theses surfactants 
and stabilizers have been discussed elsewhere herein. 
In brief, using the processes of the present invention, suspensions of 
manganese particulates, are prepared by a double-jet precipitation 
technique, i.e., by an addition of two reagents, each at a predetermined 
flow rate, into a vessel containing an aqueous host solution. The host 
solution may, in addition to water, contain additives (i.e., growth and 
crystal morphology modifiers), suspension stabilizing additives 
(stabilizers), and surfactants. The precipitation can take place at a 
temperature from 1 to about 95 degrees C, preferably 4 to 30 degrees C. In 
preferred embodiments, the temperature of the contents of the reaction 
vessel is controlled to within .+-.2.0 degrees C, more preferably .+-.0.5 
degrees C. 
In accordance with the present invention, the rate of reagents addition is 
determined from the stoichiometry of the underlying chemical reaction(s). 
As complete precipitation of Mn cation as determined by equilibria is 
desirable; therefore, the other reagent is added in a slight to moderate 
excess. 
In the present invention, the size, size distribution, morphology, and the 
degree of agglomeration of precipitated manganese particles is manipulated 
by the use of specific addition rates, initial volume of the host 
solution, and addition of certain additives, such as electrolytes, 
stabilizers, and surfactants to the host solution and/or to either or both 
reagents. 
Furthermore, the duration of the reagent addition is determined by the 
desired final solid content and the volume of the suspension, and the 
addition rate applied. The addition rate can be maintained by any means of 
volumetric or gravimetric flow rate control, such as a manual or automatic 
(including computer-driven) pump speed or displacement control or by 
control of the hydrostatic pressure of the reagents. 
The present invention is still further directed to a method of diagnosis 
comprising administering to a mammal a contrast effective amount of 
particles of a substantially insoluble manganese compound suspended or 
dispersed in a physiologically tolerable carrier and generating an NMR 
image of said mammal. 
A contrast effective amount of particles is that amount necessary to 
provide tissue visualization with magnetic resonance imaging. Means for 
determining a contrast effective amount in a particular subject will 
depend, as is well known in the art, on the nature of the magnetically 
active material used, the mass of the subject being imaged, the 
sensitivity of the magnetic resonance imaging system and the like. 
After administration of these particles, the subject mammal is maintained 
for a time period sufficient for the administered particles to be 
distributed throughout the subject and enter the tissues of the mammal. 
Typically, a sufficient time period is from about 5 minutes to about 8 
hours and, preferably from about 10 minutes to about 90 minutes. The 
residue of the particles is visualized by imaging that tissue with a 
magnetic resonance imaging system. 
The present invention includes the particles described above formulated 
into compositions together with one or more non-toxic physiologically 
acceptable carriers, adjuvants or vehicles which are collectively referred 
to herein as carriers, for parenteral injection, for oral administration 
in solid or liquid form, for rectal or topical administration, or the 
like. 
The compositions can be administered to humans and animals either orally, 
rectally, parenterally (intravenous, intramuscular or subcutaneous), 
intracisternally, intravaginally, intraperitoneally, locally (powders, 
ointments or drops), or as a buccal or nasal spray. 
Compositions suitable for parenteral injection may comprise physiologically 
acceptable sterile aqueous or nonaqueous solutions, dispersions, 
suspensions or emulsions and sterile powders for reconstitution into 
sterile injectable solutions or dispersions. Examples of suitable aqueous 
and nonaqueous carriers, diluents, solvents or vehicles include water, 
ethanol, polyols (propyleneglycol, polyethyleneglycol, glycerol, and the 
like), suitable mixtures thereof, vegetable oils (such as olive oil) and 
injectable organic esters such as ethyl oleate. Proper fluidity can be 
maintained, for example, by the use of a coating such as lecithin, by the 
maintenance of the required particle size in the case of dispersions and 
by the use of surfactants. 
These compositions may also contain adjuvants such as preserving, wetting, 
emulsifying, and dispensing agents. Prevention of the action of 
microorganisms can be ensured by various antibacterial and antifungal 
agents, for example, parabens, chlorobutanol, phenol, sorbic acid, and the 
like. It may also be desirable to include physiological salts, dextran, 
and isotonic agents, for example sugars, sodium chloride and the like. 
Prolonged absorption of the injectable pharmaceutical form can be brought 
about by the use of agents delaying absorption, for example, aluminum 
monostearate and gelatin. 
Solid dosage forms for oral administration include capsules, tablets, 
pills, powders and granules. In such solid dosage forms, the active 
compound is admixed with at least one inert customary excipient (or 
carrier) such as sodium citrate or dicalcium phosphate or (a) fillers or 
extenders, as for example, starches, lactose, sucrose, glucose, mannitol 
and silicic acid, (b) binders, as for example, carboxymethylcellulose, 
alignates, gelatin, polyvinylpyrrolidone, sucrose and acacia, (c) 
humectants, as for example, glycerol, (d) disintegrating agents, as for 
example, agar-agar, calcium carbonate, potato or tapioca starch, alginic 
acid, certain complex silicates and sodium carbonate, (e) solution 
retarders, as for example paraffin, (f) absorption accelerators, as for 
example, quaternary ammonium compounds, (g) wetting agents, as for 
example, cetyl alcohol and glycerol monostearate, (h) adsorbents, as for 
example, kaolin and bentonite, and (i) lubricants, as for example, talc, 
calcium stearate, magnesium stearate, solid polyethylene glycols, sodium 
lauryl sulfate or mixtures thereof. In the case of capsules, tablets and 
pills, the dosage forms may also comprise buffering agents. 
Solid compositions of a similar type may also be employed as fillers in 
soft and hard-filled gelatin capsules using such excipients as lactose or 
milk sugar as well as high molecular weight polyethyleneglycols, and the 
like. 
Solid dosage forms such as tablets, dragees, capsules, pills and granules 
can be prepared with coatings and shells, such as enteric coatings and 
others well known in the art. They may contain opacifying agents, and can 
also be of such composition that they release the active compound or 
compounds in a certain part of the intestinal tract in a delayed manner. 
Examples of embedding compositions which can be used are polymeric 
substances and waxes. 
The active compounds can also be in micro-encapsulated form, if 
appropriate, with one or more of the above-mentioned excipients. 
Liquid dosage forms for oral administration include pharmaceutically 
acceptable emulsions, solutions, suspensions, syrups and elixirs. In 
addition to the active compounds, the liquid dosage forms may contain 
inert diluents commonly used in the art, such as water or other solvents, 
solubilizing agents and emulsifiers, as for example, ethyl alcohol, 
isopropyl alcohol, ethyl carbonate, ethyl acetate, benzyl alcohol, benzyl 
benzoate, propyleneglycol, 1,3-butyleneglycol, dimethylformamide, oils, in 
particular, cottonseed oil, groundnut oil, corn germ oil, olive oil, 
castor oil and sesame oil, glycerol, tetrahydrofurfuryl alcohol, 
polyethyleneglycols and fatty acid esters of sorbitan or mixtures of these 
substances, and the like. 
Besides such inert diluents, the composition can also include adjuvants, 
such as wetting agents, emulsifying and suspending agents, sweetening, 
flavoring and perfuming agents. 
Suspensions, in addition to the active compounds, may contain suspending 
agents, as for example, ethoxylated isostearyl alcohols, polyoxyethylene 
sorbitol and sorbitan esters, microcrystalline cellulose, aluminum 
metahydroxide, bentonite, agar-agar and tragacanth, or mixtures of these 
substances, and the like. 
Compositions for rectal administrations are preferably suppositories which 
can be prepared by mixing the compounds of the present invention with 
suitable non-irritating excipients or carriers such as cocoa butter, 
polyethyleneglycol or a suppository wax, which are solid at ordinary 
temperatures but liquid at body temperature and therefore, melt in the 
rectum or vaginal cavity and release the active component. 
Dosage forms for topical administration of a compound of this invention 
include ointments, powders, sprays and inhalants. The active component is 
admixed under sterile conditions with a physiologically acceptable carrier 
and any preservatives, buffers or propellants as may be required. 
Ophthalmic formulations, eye ointments, powders and solutions are also 
contemplated as being within the scope of this invention. 
Actual dosage levels of active ingredients in the compositions of the 
present invention may be varied so as to obtain an amount of active 
ingredient that is effective to obtain a desired diagnostic response for a 
particular composition and method of administration. The selected dosage 
level therefore depends upon the desired diagnostic effect, on the route 
of administration, on the desired duration of contrast and other factors. 
Dosages up to about 5 millimoles per kilogram of body weight are believed 
to be useful. 
The following examples further illustrate the invention and are not to be 
construed as limiting of the specification and claims in any way. 
Example 1 
Manganese Carbonate 
50 g of water, 100 mg of anhydrous citric acid, and 400 mg of Pluronic F-68 
NF surfactant (altogether=host solution) were added to a 100 ml beaker, 
mixed with a magnetic bar, placed in a 40.degree. C. water bath to 
facilitate dissolution, and subsequently cooled to the room temperature. 
To the host solution was added a 1.0-M solution of MnCl.sub.2 (=manganese 
source) at a controlled rate of 4.0 mL/min. Simultaneously, a 1.02-M 
solution of Na.sub.2 CO.sub.3 (=carbonate source) was added thereto at a 
controlled rate of 4.8 mL/min. Each addition was maintained for 1.0 
minute. The final pH was adjusted to pH=7.2-7.7. The resultant suspension 
contained a uniform, spherilitic crystalline precipitate of the mean grain 
diameter being 400 nm, as measured by a scanning electron microscopy 
(=SEM). The free manganese concentration of this suspension, measured by 
an inductively coupled plasma atomic emission spectroscopy (=ICP-AES), was 
less than 90 .mu.g/mL. Variations of the above formula, each resulting in 
similar or different: suspension density, morphology of precipitate, mean 
size, size distribution, the concentration of free manganese, and the 
degree of particle agglomeration: 
The manganese source could be any other water-soluble salt of manganese, 
such as Mn (NO.sub.3).sub.2, MnSO.sub.4, etc, and may contain a nontoxic 
ionic additive, e.g. 0.5 g of NH.sub.4 Cl and/or 0.68 g of Al.sub.2 
(SO.sub.4).sub.3.18H.sub.2 O, to prevent agglomeration. 
The carbonate source may be any other water-soluble carbonate, such as 
ammonium carbonate, potassium carbonate, etc. 
The host solution may be: (a) water, (b) water and citric acid, (c) water 
and sodium citrate, (d) as in Example 1, except that the concentration of 
Pluronic surfactant may vary from 0-5 wt.%, (e) as in Example 1, except 
that Pluronic surfactant is replaced by any or a mixture of nontoxic 
surfactant or stabilizer, such as: DMPG, Tetronic 908, Tween 20, Tween 80, 
Pluronic F-108, Tyloxapol, Henkel APG 325cs, polyvinyl alcohol, PVP k-15, 
ascorbic acid, etc., whose concentration may vary from 0-5 wt %, (f) any 
variation given above and an ionic additive, such as NH.sub.4 Cl Al.sub.2 
(SO.sub.4).sub.3.18H.sub.2 O, in the amount of 0-1 wt %. 
The surfactants, stabilizers, and/or ionic additives listed above, and/or 
citric acid, and/or sodium citrate, may be added to one, two or all three 
of the following: the manganese source, the carbonate source and the host 
solution. 
The concentration of reagents, and/or the flow rates, and/or the time of 
addition may be different than given in Example 1. 
Example 2 
Manganese (II) Phosphate 
50 g of water, 100 mg of anhydrous citric acid, and 400 mg of Pluronic F68 
NF surfactant were added to a 100-mL beaker, mixed with a magnetic bar, 
placed in a 40.degree. C. water bath to facilitate dissolution, and 
subsequently cooled to the room temperature. To this host solution was 
added a 1.0-M solution of MnCl.sub.2 at a controlled rate of 4.0 mL/min. 
Simultaneously, a 0.68-M solution of Na.sub.3 PO.sub.4 was added thereto 
at a controlled rate of 6.0 mL/min. Each addition was maintained for 1.0 
minute. The final pH was adjusted to pH=7.2-7.7. The resultant suspension 
contained a crystalline precipitate of the mean grain size being 150 nm, 
as measured by SEM. The suspension's free manganese concentration measured 
by ICP-AES, was less than 10 .mu.g/mL. Variations of the above formula, 
each resulting in similar or different: suspension density, morphology of 
precipitate, mean size, size distribution, the concentration of free 
manganese, and the degree of particle agglomeration: 
The manganese source could be any other water-soluble salt of manganese, 
such as Mn(NO.sub.3).sub.2, MnSO.sub.4, MnF.sub.2, manganese acetate, 
etc., and may contain a nontoxic ionic additive, e.g. 0.5 g of NH.sub.4 Cl 
and/or 0.68 g of Al.sub.2 (SO.sub.4).sub.3.18H.sub.2 O, to prevent 
agglomeration. 
The phosphate source may be any other water-soluble phosphate such as 
sodium phosphate, dibasic; sodium phosphate, monobasic; potassium 
phosphate, dibasic; potassium phosphate, monobasic; ammonium phosphate, 
dibasic; ammonium phosphate, monobasic; etc. 
The host solution may be: (a) water, (b) water and citric acid, (c) water 
and sodium citrate, (d) as in Example 2, except that the concentration of 
Pluronic surfactant may vary from 0-5 wt %; (e) as in Example 2, except 
that Pluronic surfactant is replaced by any or a mixture of other nontoxic 
surfactants or stabilizers, such as: DMPG, Tetronic 908, Tween 20, Tween 
80, Pluronic F-108, Tyloxapol, Henkel APG 325cs, polyvinyl alcohol, PVP 
k-15, etc., whose concentration may vary from 0-5 wt %, (f) any variation 
given above and an ionic additive, such as NH.sub.4 Cl, Al.sub.2 
(SO.sub.4).sub.3.18H.sub.2 O, in the amount of 0-1 wt %. 
The surfactants, stabilizers, and/or ionic additives listed above, and/or 
citric acid, and/or sodium citrate, may be added to one, two or all three 
of the following: the manganese source, the phosphate source and the host 
solution. 
The concentration of reagents, and/or the flow rates, and/or the time of 
addition may be different than given in Example 2. 
Example 3. 
Manganese (II) 8-hydroxy quinolinate 
77.50 g of 1.0-M HCl was mixed with 8.00 g of 8-quinolinol at the room 
temperature until dissolved. 13.40 g of a such prepared solution, 36.00 g 
of water, 500 mg of Tween 20, and 500 mg of Tween 80 were added to a 
100-mL beaker, and mixed with a magnetic bar. To this host solution was 
added a 1.0-M solution of MNCl.sub.2 at a controlled rate of 4.0 mL/min. 
Simultaneously, a 2.0-M solution of NaOH (=base source) was added thereto 
at a controlled rate of 8.5 mL/min. Each addition was maintained for 1.0 
minute. The resultant suspension, whose final pH was adjusted to 
pH=7.2-7.7 using a diluted aqueous solution of NaOH, contained a 
crystalline precipitate of the mean grain size being 1,500 nm, as measured 
by SEM. The suspension's free manganese concentration, measured by 
ICP-AES, was less than 2 .mu.g/ML. Variations of the above formula, each 
resulting in similar or different: suspension density, morphology of 
precipitate, mean size, size distribution, the concentration of free 
manganese, and the degree of particle agglomeration: 
The manganese source could be any other water-soluble salt of manganese, 
such as Mn(No.sub.3).sub.2, MnSO.sub.4, manganese acetate, manganese 
fluoride, etc., and may contain a nontoxic ionic additive, e.g. 0.5 g of 
NH.sub.4 Cl and/or 0.68 g of Al2(SO.sub.4).sub.3.18H.sub.2 O, to prevent 
agglomeration. 
8-quinolinol may be dissolved in a base rather than in an acid. The 
examples of such a base include NaOH or KOH. Then, an addition of an acid 
rather than of a base accompanies the addition of the manganese source. 
Examples of such an acid include HCl, HNO.sub.3, H.sub.2 SO.sub.4, etc. 
The mixture of the Tween surfactants in Example 3, may be replaced by any 
or a mixture of the following nontoxic surfactants or stabilizers: DMPG, 
Tetronic 908, Tween 20, Tween 80, Pluronic F-108, Tyloxapol , Henkel APG 
325cs, polyvinyl alcohol, PVP k-15, etc., whose concentration may vary 
from 0-5%. The host solution may contain an ionic additive, such as 
NH.sub.4 Cl Al.sub.2 (SO.sub.4).sub.3.18H.sub.2 O, in the amount of 0-1 wt 
%. 
The host solution may contain citric acid and/or sodium citrate. 
The surfactants, stabilizers, and/or ionic additives listed above, and/or 
citric acid, and/or sodium citrate, may be added to one, two or all three 
of the following: the manganese source, the base/acid source and the host 
solution. 
The concentration of reagents, and/or the flow rates, and/or the time of 
addition may be different than given in Example 3. 
Example 4 
Several of the formulations from the above examples 1-3 were examined for 
their size, zeta potential (ZP), plasma stability, and whether the 
particular compositions could be autoclaved. The results of these studies 
are shown in Table 1. 
TABLE 1 
______________________________________ 
Size Plasma 
Surfactant 
(PCS)* ZP (mV) Stability 
Autoclavable 
______________________________________ 
F68 1.8 .mu.m 
-16.2 Fine Yes 
DS20HDA 822 nm -16.4 Fine 
T1508 1.6 .mu.m 
-15.7 
TWEEN20 2.2 .mu.m 
-13.9 
OMLF108 1.4 .mu.m 
-14.4 
DOSS 639 nm -15.8 Fine Yes 
SA90HAQ 829 nm -17.4 
DMPG 613 nm -24.3 Fine 
______________________________________ 
*Photon correlation spectroscopy 
Example 5 
The hepatic clearing of manganese particles made in accordance to the 
processes of the present invention was tested. Animals were injected via 
the tail vein with 50 .mu.moles per kilogram of body weight with manganese 
particles. At various times thereafter, the animals were euthanized and 
the livers of the animals were excised. Livers were frozen until assay, 
and then homogenized prior to the assay. The results of these experiments 
are shown in FIGS. 1 and 2. In FIG. 1, the time course of hepatic 
clearance was studied from 0 to 500 minutes after administration of the 
manganese particles. In FIG. 2, the time course of hepatic clearance was 
studied from 0 to 9000 minutes after administration. 
Example 6 
The effects of surfactant coatings on the relaxation rate of the liver was 
studied using manganese particles prepared in accordance with the 
processes of the present invention. Animals were injected via the tail 
vein with the particles at various doses ranging from 5.mu. moles per 
kilogram of body weight to 200.mu. moles per kilogram of body weight. 
After 30 minutes, the animals were euthanized, and the livers were 
excised. Livers were homogenized 1:1 (w/v) with saline, and then the 
relaxation rate of the homogenate was determined. The results are shown in 
FIG. 3. 
Example 7 
The compositions of the invention produced impressive images of the liver. 
A formulation of manganese carbonate particles stabilized with DMPG 
provided optimal imaging 5 to 30 minutes post injection. A formulation of 
manganese carbonate particles stabilized with F68 provided optimal imaging 
30 minutes to 2 hours post injection. 
The foregoing specification, including the specific embodiments and 
examples is intended to be illustrative of the present invention and is 
not to be taken as limiting. Numerous other variations and modifications 
can be effected without departing from the true spirit and scope of the 
present invention.