Technical Field This invention relates to novel 15O-labeledmonosaccharide usefulforpositronemissiontomography (PET) andproducingmethod thereof.

Background Art Positron emission tomography (PET) is a noninvasive bio-imaging technology which can be used to diagnose functions or disorders of a variety of organs such as brain and heart. In PET, a radioactive tracer is administrated to a subject to' determinethedistributionofthetracerinthebodyofthesubject. To date, [18F]2-fluoro-2-deoxyglucose (FDG) have been used as the most useful PET tracer. FDG can be used to determine sugar metabolism quantitatively and have lead to progressive improvement for brain study or cancer diagnosis. However, the number of times of PET measurement per one day is limited due to long half-life of 18F (110 min) . Moreover, since 18F-labeled compound is non-natural, the behavior of 18F-labeled compound in a body is different from that of the corresponding natural compound. Further, although synthesis of glucose labeled with 15O at Cl position has been tried, such 15O-labeled glucose has been failed to be synthesized. Moreover, OH group at the Cl

i-J. V position of glucose molecule is unstable and easily subjected to exchange reaction with H2O in blood. Therefore, such labeled glucose should not be suitable for PET measurement .

Summary of the invention The present inventors have established novel 15O-labeled monosaccharide and producing method thereof to overcome such shortcomings of conventional labeled compounds for PET. The method for producing 15O-labeled monosaccharide of the present invention is partially based on the alcohol production method described in WO98/34983. In one aspect, the present invention provides 15O-labeled monosaccharide which is labeled with 15O at hydroxymethyl group in the monosaccharide molecule. In another aspect, the present invention provides a method for producing 150-labeled monosaccharide, comprising reacting a monosaccharide, which is substituted with a halogen at hydroxyl of hydroxymethyl group in the monosaccharide molecule, with 15O oxygen in the presence of an organotin compound and a reducing agent, wherein said reacting occurs either in the absence of a radical initiatororinthepresenceofnotmorethan0.3 equivalent, based on the halogenated monosaccharide, of a radical initiator to provide 15O-labeled monosaccharide which is labeled with 15O at the hydroxymethyl group in the monosaccharide molecule. In another aspect, the present invention provides a method for diagnosing a whole body, organs or tissues of a subject, comprising administering the above 15O-labeled monosaccharide to the subject to measure metabolism of the 150-labeled monosaccharide in the subject. In another aspect, the present invention provides a kit for producing 15O-labeled monosaccharide, comprising a monosaccharide which is substituted with a halogen at hydroxyl of hydroxymethyl group in the monosaccharide molecule, an organotin compound and a reducing agent, wherein the kit is used to react the halogenated monosaccharide with 15O oxygen in the presence of the organotin compound and the reducing agent to produce a 15O-labeled monosaccharide which is labeled with 15O at the hydroxymethyl group in the monosaccharide molecule. Themethodof the inventioncanbeusedtoproduce15O-labeled monosaccharide rapidly with high yield. Since 15O has short half-life (2 min) , the 15O-labeled monosaccharide of the present invention can be used to practice more than once PET measurement per one day for a subject and with only little radioactive dose exposed to the subject. Moreover, thebehaviorof the 150-labeled monosaccharide of the present invention in a body is more similar to that of natural compound than that of 18F-labeled compound. Further, since the 150-labeled monosaccharide of the present invention is labeled with 15O at the hydroxymethyl group of the monosaccharide molecule (e.g., Cβ position of hexose or C5 position of pentose) , it is more stable in a body than monosaccharide labeled with 13O at Cl position. Therefore, the 15O-labeled monosaccharide of the present invention can be used in PET measurement to accomplish more successful imaging.

Brief description of the drawings Fig. 1 shows the glass filter reactor used for radical hydroxylation of halogenated glucose in the Example. Numbers in this figure are length in mm. Fig.2 shows the purification systemused for purification of 15[0]2-deoxy-D-glucose. Fig. 3 shows the cyclotron system used for generation of 15O oxygen and introduction of it into the reaction system. Fig. 4 shows the results of PET scans for rat performed by using several of labeled compounds. Fig. 4A and 4B show integrated PET image from 15 min to 30 min after administration of 15 [O] 2-deoxy-D-glucose and18 [F] FDG, respectively. Fig.4C and 4D show PET image of initial blood flow from 0 sec to 90 sec and from 15 min to 30 min after administration of [15O]H2O, respectively. Fig. 5 shows the results of PET scans for mouse performed by using several of labeled compounds. Fig. 5A and 5B show integrated PET image from 15 min to 30 min after administration of 15[0]2-deoxy-D-glucose and18 [F]FDG, respectively. Fig.5C and 5D show PET image of initial blood flow from 0 sec to 90 sec and from 15 min to 30 min after administration of [15O]H2O, respectively. Detailed description of the present invention The present invention is now described in detail. The "monosaccharide" useful for the present invention includes any monosaccharide and derivative thereof known in the art. Preferably, the "monosaccharide" useful for the present invention is hexose or pentose. Hexose useful for the present invention includes D-glucose, D-galactose, D-mannose, D-fructose and derivative thereof. Pentose useful for the present invention includes D-xylose, D-ribose, D-deoxyribose, D-arabinose and derivative • thereof. ■ Preferably, the "monosaccharide" useful for the present invention is D-glucose or derivative thereof, and most preferably, D-glucose or 2-deoxy-D-glucose. The term "labeled with 15O at hydroxymethyl group in the monosaccharidemolecule" means that hydroxymethyl (-CH2OH) group inthemonosaccharidemoleculeislabeledwith15Otoform-CH215 [O]H group. More specifically, the term means, for example, that if the monosaccharide is a hexose, the free hydroxyl on C6 carbon of the hexose is labeled with 15O, and that if the monosaccharide is a pentose, the free hydroxyl on C5 carbon of the pentose is labeled with 15O. The "amonosaccharide which is substitutedwith a halogen" or "a halogenated monosaccharide" in the present invention is used as a precursor in the method for producing 150-labeled monosaccharide of the present invention. Each of the terms is referred to a monosaccharide having a halogenated methyl group (-CH2X, X is a halogen atom) formed by substituting a halogen for hydroxyl of hydroxymethyl group in the monosaccharide molecule. The "halogen" in the halogenated monosaccharide to be used in the present invention includes chloro, iodo, bromo and so on, iodo is the most preferred halogen for purposes of the invention. The "organotin compound" useful for the present invention includes, but is not limited to, organotin hydrides (e.g., trialkyltin hydrides and triaryltin hydrides) and organotin halides (e.g., tributyltin chloride, dibutyl (t-butyl) tin chloride and triaryltin halides (e.g. triphenyltin chloride) ) . Preferably, organotin compound includes trialkyltin hydrides. Most preferable organotin compound is tributyltin hydrides. Theamountof theorganotincompoundtobeusedinthepresent invention may be a catalyst amount, is preferably 1.0-6.0 equivalents, and more preferably 2.0-5.0 equivalents, based on the substrate halogenated monosaccharide. The "reducing agent" useful for the present invention includes, but is not limited to, reducing agents known in the art such as phosphine, sulfide, selenide, telluride, arsine, stibane, bismuthane or derivative thereof, borohydrides. Preferred reducing agent for use in the present invention is triphenylphosphine. The amount of the reducing agent to be used in the present invention is sufficient for reducing peroxide produced in the reaction, and preferably at least 1 equivalent based on the substrate halogenated monosaccharide. The reaction according to the present invention can be carried out using various solvents which do not interfere with the' reaction. Such solvent includes fluorine-solvent (e.g., , benzofluoride, benzotrifluoride, perfluorodecalin, etc.) , alcohol (e.g. ethanol, isopropyl alcohol, butanol, t-butanol, etc.) , BTX, and ethers (e.g. tetrahydrofuran etc.) , inclusive of mixtures thereof, among others. Those skilled in the art can select suitable solvent for the reaction based on, for example, solubility of the halogenated monosaccharide or 15O oxygen in the reaction system. Preferred solvent is a mixture of fluorine-solvent and alcohol. The reaction temperature for use in the present invention is not particularlyrestrictedprovidedthat the radical reaction is enabled to proceed, although the reaction is preferably conducted at not less than 5O0C, and more preferably 75-85°C. 15O oxygen used in the present invention can be produced, for example, by generating the nuclear reaction 15N(p, n) 15O by proton bombardment from a cyclotron on target gas containing 16O2 and 15N2, or by generating the nuclear reaction 15N(d, n) 15O by deuteron bombardment from a cyclotron on target gas containing 16O2 and 15N2. Then the target gas containing 15O oxygen produced is mixed with cold carrier gas and introduced into the reaction system (Fig. 3) . Preferably, prior to introduction of 15O oxygen in the reactionsystem, carriergascontainingoxygen (16O2) is introduced into the reaction system to initiate radical reaction. Preferably, the initiation of the radical reaction is monitored, and the introduction of 15O oxygen into•the reaction system is startedsimultaneouslywiththeinitiationoftheradical reaction. The initiation of the radical reaction can be easily monitored by those skilled in the art using an analytical technique (e.g. , TLC) known in the art Concentration of 16O2 in the cold carrier gas introduced into the reaction system to initiate radical reaction is preferably at least 1.5% and more preferably 1.5%-5.0%, although the concentration is suitably adjusted by those skilled in the art based on, for example, reaction conditions such as induction time of the radical reaction. Concentration of 16O2 in the target gas is preferably equivalent to the concentration of 16O2 in the coldcarriergas, althoughit is suitablyadjustedbythose skilled in the art based on, for example, yield of 150-labeled monosaccharide produced. In the method for producing 150-labeled monosaccharide of the present invention, the radical reaction canbe causedwithout substantially using "radical initiator" . However, "radical initiator" may be introduced into the reaction system for promotingthereactionorforsuppressingproductionofreductants as byproduct. If "radical initiator" is used in the method of the present invention, the amount of the "radical initiator" is preferably no more than 0.3 equivalents and more preferably no more than 0.03 equivalents, based on the halogenated monosaccharide. The "radical initiator" for use in the present invention includes, but is not limited, to AIBN and dibenzoyl peroxide. The method for producing 15O-labeled monosaccharide of the present invention can be carried out by using any reaction vessel known in the art or an reaction vessel which those skilled in the art can easily make using any experimental appliance known intheart (e.g. , glass filter) . Forexample, apreferredreaction vessel useful forthemethodof thepresent invention is a reaction vessel comprising a glass filter at the bottom as shown in the following examples, wherein 15O oxygen in the mixed gas can bubble very finely in the reaction vessel . Such reaction vessel can ■ be made by those skilled in the art referring the teaching of the specification. Preferably, the reaction vessel has longitudinally long form for dissolving sufficient 15O oxygen in the reaction system. The kit for producing 150-labeled monosaccharide of the present invention comprises a halogenated monosaccharide, an organotin compound and a reducing agent, wherein the kit is used to react the halogenated monosaccharide with 15O oxygen in the presence of the organotin compound and the reducing agent to produce 15O-labeled monosaccharide of the present invention. The 15O oxygen can be supplied from, for example, a cyclotron equipped in an institution (e.g., a hospital) wherein a diagnosis of a subject is practiced. Preferably, the kit of the present invention further comprise no more than 0.3 equivalents, based on the halogenatedmonosaccharide, of radical initiator. In one embodiment, the kit of the present invention further comprises areactionvessel inwhichthereactioncanbepracticedtoproduce 15O-labeledmonosaccharide. Preferably, the reactionvessel may be a vessel in a disposable cassette format known in the art to be able toproduce 15O-labeledmonosaccharide easilyand rapidly. The 15O-labeled monosaccharide of the present invention canbeusedtodiagnoseawholebody, organsortissuesofasubject. The diagnosing method comprises administering the 15O-labeled monosaccharide of the present inventionto the subject tomeasure metabolismofthe15O-labeledmonosaccharideinthesubject. Such measurement canbe carriedout byusinganymedical imagingmethod known in the art such as positron emission tomography. The organ or tissue diagnosed by using the 15O-labeled monosaccharide of the present invention includes, but is not to be limited, brain, heart or tumor tissue which metabolizes glucose actively. Further, due to much shorter half-life of 15O than that of 18F, the 15O-labeled monosaccharide of the present invention can be used to measure diurnal variation of sugar metabolism in one subject over time. If the 150-labeled monosaccharide of the present invention is usedas a diagnostic agent, the reactionproduct is preferably purified to remove the organotin compound and the reducing agent in the reactionmixture. Suchpurificationmethod includes, but is not to be limited, solid-phase extraction using silica gel column (e.g., Sep-Pak C18) and HPLC. The reaction conditions of the present invention have been described above. In conducting a specific reaction, it is necessary to optimize the reaction conditions according to the structure of the halogenated monosaccharide and the species and amount of the organotin compound, among other variables, but such optimization is amatterwhichcanbemade easilybyanyone skilled in the art. Further, the method for producing 150-labeled monosaccharide of the present invention is applicable to disaccharide (e.g., maltose, sucrose, lactose) and oligosaccharideprovidedthatthesaccharideshaveafreehydroxy1 grouponCβ carbonofhexose residue orC5 carbonofpentose residue in the molecule. The following examples illustrate the present invention in further detail.

Example Materials Unless otherwise noted, chemicals were used as they are. 2-Butanol (Kanto Chemical) was distilled from CaH2 prior to use. Benzotrifluoride, perfluorodecalin and AIBN were purchased from Acros, Fluorochem Ltd. and Wako Pure Chemicals, respectively. n-Bu3SnHwas obtained fromAldrich andusedwithout further purification. N2/02 gas (98.5/1.5) was obtained from Nippon Sanso Co., Ltd. Equipments Hydroxylation of 2,6-dideoxy-6-iodo-D-glucose and 6-iodo-6-deoxy-D-glucose was performed in the glass filter reactor as shown in Fig. 1. Sep-Pak cartridges were purchased from Waters. The cyclotron is OSCAR-12 (NKK/Oxford) . The target gas consisted of 1.5% O2 in 15N2. PET scans were obtained on Planar Positron Imaging System (Hamamatsu Photonics K.K.) .

Example 1: Synthesis of 2,6-dideoxy-6-iodo-D-glucose )

2-deoxy-D-glucose (1) (Aldrich) (5.Og, 30mmol) wasplaced in a flask, and HCl solution in methanol (10%, 60 ml) was added. Theresultingmixturewasheatedat 50°Covernight. Aftercooling to room temperature, silver carbonate was added, and the mixture wasvigorouslystirredbywhengenerationof CO2gashavefinished. The reaction mixture was filtrated through Celite, and the resultant solution was evaporated. Toluene (20 ml) was added tothesolution, andtheresultantmixturewasevaporatedtoremove the residual methanol. Toluene (250 ml) was added and dissolved in the concentrated residue, and imidazole (6.12 g, 90.0 mmol) , triphenylphosphine (11.8 g, 45.0 mmol) and iodine (11.5g, 42.0 mmol) were added. Again, toluene (200 ml) was added, and the resultant mixture was vigorously stirred under N2 flow at 70°C for 2.5 h. After the reaction completed, the supernatant in the reactionvessel was transferredtoanothervessel andevaporated. Ontheotherhand, chloroformwasaddedtothegummysolidcomponent in the reaction vessel to give a suspension, and the suspension was filtrated through Celite. The filtrate was evaporated and combined to the concentrated supernatant solution obtained previously. The combined solution was subjected to column chromatography (chloroform:methanol = 20 :1, twice) toafford5.9 g of compound 3. The yield is 68% based on compound 1. Compound 3 (5.9 g) was placed in a flask, and sulfuric acid (0.5 M aqueous solution, 200 ml) was added. The solution was stirred at 80°C for 1.5 h. After cooling to room temperature, sodium hydrogencarbonate was carefully added portionwise to the acidic solution to neutralize it. The resultant mixture was then directly evaporated (bath temp, no more than 40°C) . The evaporation was stopped when the volume of the solution reduced to about 10-20 ml. Methanol (100 ml) was added to the resultant concentrated solution, which led to growth white solid of sodium sulfate. The solution was filtrate through Celite, and the filtrate was evaporated at no more than 30°C. The concentrated residue was subjected to column chromatography (chloroform:methanol = 8:1) repeatedly to afford 4.2 g of 2, 6-dideoxy-6-iodo-D-glucose (compound4) . Theyieldis 51%based on compound 1.

Example 2: Synthesis of 6-iodo-β-dideoxγ-D-glucose

D-Glucose

D-Glucose (20.0 g, 0.111 mol) was placed in a 1000-mL

round-bottomed flask, and pyridine (300 ml) was added. Some of

glucose remainedundissolved. p-Toluensulfonyl chloride (22.Og,

0.115 mol) was added at ambient temperature. After stirring for

11 h, acetic anhydride (80 ml, 0.83 mol) was added in one portion.

Gentle exothermic reaction took place. After being stirred for

1.5 h, the mixture was evaporated. Ethanol (200 ml) was added

to a residual oil . The oil was dissolved and soon a white crystal

appeared. After the mixture stood undisturbed at -10°C for 27

h, the crystal was collected on a glass filter, washed with cold

ethanol (25 ml, twice) , and dried under reduced pressure;

6-O- (p-Toluenesulfonyl) -1,2,3,4-tetra-O-acetyl-β-D-glucose

(compound 5) was obtained in 33% yield (18.5g, 36.8 mmol) .

6-0- (p-Toluenesulfonyl) -1,2,3, 4-tetra-O-acetyl-β-D-glu

cose (5, 18.5 g, 36.8 mmol) was place in a 500-mL round-bottomed

flask. Acetone (200 ml) and sodium iodide (18.5g, 123 mmol) were added. The resulting mixture was heated at reflux for 2Oh. The reaction proceeded gradually. The mixture was poured into 1000 ml of water, and the resulting solid was filtered with a glass filter. Recrystalization from ethanol afforded 6-deoxy-6-iodo -1, 2, 3, 4-tetra-O-acetyl-β-D-glucose (compound 6) in 65% yield (11.0 g, 24.0 mmol) . ■ 6-Deoxy-6-iodo-l, 2, 3, 4-tetra-O-acetyl-β-D-glucose (6, 6.87 g, 15.0 mmol) was placed in a 500-mL round-bottomed flask. Sulfuric acid (0.5 M aqueous solution, 150 ml) and acetonitrile (30 ml) were added to 6, and the mixture was heated at 80°C for 6.5 h. Aftercooling to roomtemperature, sodiumhydrogecarbonate was carefully added portionwise to the acidic solution. Neutralization was checked with indicator paper, and the mixture was then directly evaporated (bath temp.40°C) . Before complete removal of solvent (ca. 10-20 ml) , methanol (100 ml) was added totheflask, whichledtogrowthofwhiteprecipitate. Filtration through Celite, concentration of the filtrate (bath temp. 30°C) , and silica gel column purification (chloroform:methanol = 3:1) afforded 6-deoxy-6-iodo-D-glucose (compound 7) (2.16g g, 7.44 mmol, 50%) .

Example 3: Radical hydroxylation of 2, 6-dideoxy-6-iodo~D- glucose in the glass filter reactor (1)

2, 6-dideoxy-6-iodo-D-glucose (4) (162 mg, 0.600 mmol) as obtained in Example 1 and AIBN (2.4 mg, 0.015 mmol) were placed in a 20-mLvial.2-Butanol (1.8ml) was added, and4 was dissolved. Benzotrifluoride (12.0 ml) and perfluorodecalin (2.7 ml) were then added. Tributyltin hydride (485 μl, 1.80 mmol) was introduced by a microsyringe. Note that addition by a normal syringe may cause initiation of the reaction before bubbling, givingonlycompound 8. Thehomogeneous solutionwas transferred witha Pasteurpipette into the glass filter reactor. The reactor was then immersed in an oil bath (80°C) with bubbling of mixed gas (N2/O2 = 98.5/1.5, 200 ml/min) . The glass filter made very fine bubbles. TLC analyses were done every 30 sec, which indicated that the reaction actually started at 1.5 min and completed at 4.0 min after the heating started. After 7.0 min, the reaction mixture was transferred to a solution of triphenylphosphine (157 mg, 0.600 mmol) in toluene (1.5ml) . The reactor was rinsed with 10 ml of methanol once. Concentration under reduced pressure afforded a mixture of oil and viscous residue. Toluene (10 ml) was added, and the resulting supernatant was passed through a Sep-Pak Cartridge silica (long body, conditioned with 10 ml of toluene prior to use) . Here the gummy residue, which consisted of glycosides, was not soluble in toluene. The eluent containing tin and phosphine compounds was thrown away. Again, toluene was addedtothegummyresidue, andthetoluenelayerwaspassedthrough the same cartridge. The cartridge was then washed with methanol (5 ml + 5 ml) by using the same syringe that was employed to take up the toluene solutions. The methanolic eluent was added the gummy glycosides . Evaporation. and 1H NMR measurement (1, 1,2, 2-tetrachloromethane as an internal Standard) revealed that the mixture consisted of 0.182 mmol (31% based on 4, 54% based on O2 that passed through the solution during the radical chain) of 2-deoxy-D-glucose (2-DG) and 0.402 mmol (67%) of 8, in addition to a trace of tin and phosphine impurities.

Example 4: Radical hydroxylation of 2, 6-dideoxy-6-iodo~D- glucose in the glass filter reactor (2) The method used in this example was substantially same as the method shown in the above Example 3. A mixture of 4 (270 mg, 1.0 mmol), tributyltin hydride (3.0 mmol) and AIBN (0.025 mmol) in α,α,α, -trifluorotoluene (20.0 ml) /perfluorodecalin (4.5 ml) /2-butanol (3.0ml) washeatedat 800Cwithconcomitantbubbling of N2/O2 (98.5/1.5, 180 ml/min for 0 to 2 min 40 sec, 200 ml/min for 2 min 40 sec to 6 min 20 sec) . TLC analyses were done every 30 sec, which indicated that the reaction actually started at 3 min 20 sec and completed at 6.5 min after the heating started. After 7.0 min, workup with triphenylphosphine (1.0 mmol) reduced hydroperoxide into 2-DG. 1H NMR measurement revealed that the mixture consisted of 0.280 mmol (28% based on 4, 70% based on O2 that passed through the solution during the radical chain) of 2-DG and 0.72 mmol (72%) of 8, in addition to a trace of tin and phosphine impurities. Example 5: Radical hydroxylation of 6-iodo-6-dideoxy-D-glucose in the glass filter reactor

7 Glucose 9 6-iodo-6-dideoxy-D-glucose (7) (261 mg, 0.900 mmol) as obtained in Example 2 and AIBN (3.6 mg, 0.015 mmol) were placed in a 20-mLvial .2-Butanol (3.5ml) was added, and 7 was dissolved. Benzotrifluoride (15.0 ml) and perfluorodecalin (2.0 ml) were then added. Tributyltin hydride (484 μl, 1.80 mmol) was introduced by a microsyringe. The homogeneous solution was transferredwith a Pasteurpipette into the glass filter reactor. The reactor was then immersed in an oil bath (80°C) with bubbling of mixed gas (N2/O2 = 98.5/1.5, 200 ml/min) . TLC analyses were done every 30 sec, which indicated that the reaction actually started at 2.0 min and completed at 5.0 min after the heating started. After 7.0 min, the reaction' mixture was transferred to a solution of triphenylphosphine (236 mg, 0.900 mmol) in toluene (2.0 ml) . The reactor was rinsed with 10 ml of methanol twice. Workup, purification, and NMR analysis as shown in Example 3 revealed that the mixture consisted of 0.198 mmol (22% based on 7, 50% based on O2 that passed through the solution during the radical chain) of glucose, 0.569 mmol (63%) of 9 and 0.137 mmol (15%) of 7 in addition to a trace of tin andphosphine impurities .

Example 6: Hydroxylation of 2, 6-dideoxy-6-iodo-D-glucose in the glass filter reactor followed by rapid purification For administration to an animal, the produced 2-DG is necessary to be separated from tin-compound and phosphine-compound. Therefore,, the present inventors constructed a purification system as shown in Fig. 2 andpurified the produced 2-DG by using the system. Afterthereactionwasperformedfor4minas showninExample 3, triphenylphosphine (157 mg, 0.600 mmol in 2 mL of PhCF3) was added to the reaction mixture, and bubbling continued for 10 sec. Water (3 ml) was added, and bubbling continued"for 20 sec. The whole mixture was transferred to a reservoir and then stood undisturbed for 20 sec to float an aqueous layer (ca. 2.3 ml) on a fluorous organic layer. The lower layer was eluted away through a Sep-Pak C18 cartridge (conditioned with 10 ml of PhCF3) by using a reduced pressure. The elution stopped at the boundary of the two layers . The aqueous layer on the top of the cartridge wasthenpassedthroughanotherSep-PakC18 cartridge (conditioned with 10 ml of methanol and then with 10 ml of water) . The eluate was a tin- andphosphine-free aqueous solutionof 2-DG (17%, 0.103 mmol), 4 (trace) and 8 (47%, 0.280 mmol) .

Example 7 : PET imaging using 15 [O] 2 -deoxy-D-glucose

4 2-deoxy-D-glucose (2-DG) A solution of 2 , 6 -dideoxy- 6 - iodo-D-glucose ( 274 mg , 1 . 0 tnmol) , tributyltin hydride (807 μl, 3.0 mmol) and AIBN (4.0 mg, 0.025 mmol) in PhCF3 (20.0 ml) /C10Fi8 (4.5 ml) /2-BuOH (3.0 ml) was placed in the reactor, which was on the automated synthetic apparatus (Fig. 3) . Proton bombardment (beam current 50 μA) on target gas started (N2/θ2 = 98.5/1.5, target gas pressure = 6 kg/cm2) . The beginning of the bombardment was defined as 0 sec for convenience. Coldgas (N2/O2 = 1773/3, 180ml/min) was provided and heating with temperature-controlled air (800C) started simultaneously at 2 min 40 sec. At 4.0 min, the target gas was evacuated from the targeting area in the cyclotron system (20 ml/min) . The target gas was mixed with cold N2/O2 gas (target gas/N2/O2 = 20/177/3, 200 ml/min) , and the resulting gas was then supplied to the reaction vessel. At 4 min 40 sec, the RI counter at the detector indicated arrival of hot gas. At 5 min 20 sec, the bombardment stopped. However, evacuation of the target gas continued. Triphenylphosphine (262 mg, 1.0 mmol in 1.5 ml of PhCF3) was added at 6.0 min. At 6 min 10 sec, all the mixture was transferredfromthe reactor to a Sep-PakVac Silica cartridge (conditioned with 10 ml of. PhCF3) (A in Fig. 3) and the eluent was removed. Saline (3.0 ml) was consequently passed through the Sep-Pak Vac Silica cartridge. The eluted aqueous solution was passed through Sep-Pak C18 cartridge (conditioned with 10 ml of acetonitrile and then with 10 ml of saline) (B in Fig. 3) and afforded to a tin- and phosphine-free aqueous solution of 15[0] 2-deoxy-D-glucose ( [15O] 2-DG) (ca. 3 ml, 15-20 mCi) . For rat imaging, 1 mL of the [15O] 2-DG solution was injected from his tail vein. [15O] 2-DG-PET scans could be performed over 30 min after the administration. Integrated PET image from 15 min to 30 min appeared accumulation of [15O] 2-DG in heart, kidney andbladder (Fig.4A) . Forcomparisonwith [15O] 2-DG, [18F]FDG-PET scanswerealsoperformed, andintegratedPETimage for sameperiod appeared accumulation of [18F] FDG-PET like that of [15O] 2-DG (Fig. 4B) . Theseimageswereclearlydifferent fromthe imageof initial blood flow from 0 sec to 90 sec (Fig. 4C) and from 15 min to 30 min (Fig. 4D) of [15O]H2O. Similar results were also obtained for mouse imaging (Fig. 5) . These results proves that [15O] 2-DG can be used as a PET tracer like [18F]FDG.