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H H Coenen

Publications and source records attributed to H H Coenen.

At least 19 recordsLinked to original sources
PubMed2007

Fluorine-18 labeling methods: Features and possibilities of basic reactions.

Many experimental and established tracers make fluorine- 18 the most widely used radionuclide in positron emission tomography with an increasing demand for new or simpler 18F-labeling procedures. After a brief summary of the advantages of the nuclide and its major production routes, the basic features of the principal radiofluorination methods are described. These comprise direct electrophilic and nucleophilic processes, or in case of more complex molecules, the labeling of synthons and prosthetic groups for indirect built-up syntheses. While addressing the progress of no-carrier-added 18F-labeling procedures, the following chapters on more specific topics in this book are introduced. Emphasis is given to radiofluorination of arenes--especially with iodonium leaving groups. Examples of radiopharmaceutical syntheses are mentioned in order to illustrate strategic concepts of labeling with fluorine-18.

Fluorine Radioisotopes↗
PubMed2006

Yield and purity of 82Sr produced via the natRb(p,xn) 82Sr process.

The recently reported cross-section data for the production of 82Sr via the natRb(p,xn) 82Sr process were evaluated. For the natRb(p,xn) 85Sr process, cross-sections were measured experimentally over the proton energy range of 25-45 MeV, a region where very few data existed. An evaluation of the recently published data on the formation of 85Sr was then also performed. From the recommended data curves, the integral yields of the desired radionuclide 82Sr and the impurity 85Sr were calculated. Yields were also determined experimentally over several energy ranges using thick natRbCl targets. The experimental and calculated yields were found to be in agreement within 15%. These integral tests add confidence to the evaluated cross-section data. For the production of 82Sr, an incident proton energy of 60 MeV or above is recommended; the 85Sr impurity then corresponds to <20%.

Journal Article↗
PubMed2006

Assessment of the short-lived non-pure positron-emitting nuclide (120)I for PET imaging.

PURPOSE: The non-pure positron-emitting iodine isotope (120)I (T(1/2)=81 min) is a short-lived alternative to (124)I. (120)I has a positron abundance more than twice that of (124)I and a maximum positron energy of 4 MeV. This study was undertaken to evaluate and characterise the qualitative and quantitative PET imaging of (120)I. METHODS: (120)I was produced via the (120)Te(p,n) reaction on highly enriched (120)Te. The measurements were done with the Siemens scanner HR+ and the 2D PET scanner GE PC4096+. A cylinder containing three cold inserts and a phantom resembling a human brain slice were used to evaluate half-life, positron abundance and background correction. To analyse the image resolution, a -mm tube placed in water was filled with (120)I and (18)F. Comparisons with (18)F, (124)I and (123)I (measured with SPECT) were made using the Hoffman 3D brain phantom. RESULTS: The half-life of 81.1 min was reproduced by the PET measurements. The PET-based positron abundance ranged from 47.9% to 55.0%. The reconstructed image resolution found with the HR+ was 5.4 mm FWHM (12.3 mm FWTM), in contrast to 4.6 mm (8.6 mm) when using (18)F. Erroneous positive and negative numbers of radioactivity found in the cold inserts became nearly zero when the background of gamma-coincidences was corrected for. Images of the Hoffman phantom were inferior to those obtained when (18)F or (124)I was applied but superior to the (123)I-SPECT images. CONCLUSION: Our data show that (120)I of high radionuclidic purity can be regarded as a suitable nuclide for the PET imaging of radioiodine-labelled pharmaceuticals.

Brain↗
PubMed2006

No-carrier-added nucleophilic 18F-labelling in an electrochemical cell exemplified by the routine production of [18F]altanserin.

A new type of electrochemical cell with anodic deposition of no-carrier-added [(18)F]fluoride and variable reaction volume has been developed. The reactor is designed for small reaction volumes and non-thermal drying of [(18)F]fluoride. The implementation of this reactor into a complete remotely controlled synthesis device is described for the routine production of [(18)F]altanserin. A radiochemical yield of 23+/-5% was obtained via cryptate-mediated nucleophilic (18)F-fluorination. Batches of up to 6 GBq [(18)F]altanserin, suitable for human application, with a molar activity of >500 GBq/micromol were obtained within 75 min.

Chromatography, High Pressure Liquid↗
PubMed2006

Nuclear data for production of the therapeutic radionuclides 32P, 64Cu, 67Cu, 89Sr, 90Y and 153Sm via the (n,p) reaction: evaluation of excitation function and its validation via integral cross-section measurement using a 14 MeV d(Be) neutron source.

Nuclear data for production of the therapeutic radionuclides 32P, 64Cu, 67Cu, 89Sr, 90Y and 153Sm via (n,p) reactions on the target nuclei 32S, 64Zn, 67Zn, 89Y, (90)Zr and 153Eu, respectively, are discussed. The available information on each excitation function was analysed. From the recommended data set for each reaction the average integrated cross section for a standard 14 MeV d(Be) neutron field was deduced. The spectrum-averaged cross section was also measured experimentally. A comparison of the integrated value with the integral measurement served to validate the excitation function within about 15%. A fast neutron source appears to be much more effective than a fission reactor for production of the above-mentioned radionuclides in a no-carrier-added form via the (n,p) process. In particular, the possibility of production of high specific activity 153Sm is discussed.

Neutrons↗
PubMed2005

(3)He-particle-induced reactions on (nat)Sb for production of (124)I.

Excitation functions of the reactions (nat)Sb((3)He,xn)(124,123,121)I were measured from their respective thresholds up to 35 MeV, with particular emphasis on data for the production of the medically important radionuclide (124)I. The conventional stacked-foil technique was used. From the experimental data the theoretical yields of the three investigated radionuclides were calculated. The yield of (124)I over the energy range E9(30He) = 35 --> 13 MeV amounts to 0.95 MBq/microA h. The radionuclidic impurities are discussed. A comparison of (3)He- and alpha-particle-induced reactions on antimony for production of (124)I is given. The alpha-particle-induced reaction on enriched (121)Sb and the (3)He-particle-induced reaction on enriched (123)Sb would lead to comparable (124)I yields, but the level of impurities in the latter case would be somewhat higher.

Journal Article↗
PubMed2005

Alpha-particle induced reactions on natSb and 121Sb with particular reference to the production of the medically interesting radionuclide 124I.

Excitation functions of the reactions (nat)Sb(alpha,xn)(123,124,125,126)I and (121)Sb(alpha,xn)(123,124)I were measured from their respective thresholds up to 26 MeV, with particular emphasis on data for the production of the medically important radionuclide (124)I. The conventional stacked-foil technique was used, and the samples for irradiation were prepared by a sedimentation process. The measured excitation curves were compared with the data available in the literature. From the experimental data the theoretical yields of the investigated radionuclides were calculated as a function of the alpha-particle energy. The calculated yield of (124)I from the (nat)Sb(alpha,xn)(124)I process over the energy range E(alpha) = 22-->13 MeV amounts to 1.02 MBq/microA x h and from the (121)Sb(alpha,n)(124)I reaction over the same energy range to 2.11 MBq/microA x h. The radionuclidic impurity levels are discussed. Use of (nat)Sb as target material would not lead to high-purity (124)I. Using highly enriched (121)Sb as target, production of (124)I of high radionuclidic purity is possible; the batch yield, however, is low.

Alpha Particles↗
PubMed2005

O-(2-[18F]fluorethyl)-L-tyrosine PET in the clinical evaluation of primary brain tumours.

PURPOSE: The aim of this study was to evaluate the differential uptake of O-(2-[18F]fluorethyl)-L-tyrosine (FET) in suspected primary brain tumours. METHODS: Positron emission tomography (PET) was performed in 44 patients referred for the evaluation of a suspected brain tumour. Acquisition consisted of four 10-min frames starting upon i.v. injection of FET. Tumour uptake was calculated as the ratio of maximal tumour intensity to mean activity within a reference region (FETmax). RESULTS: FET uptake above the cortical level was observed in 35/44 lesions. All histologically confirmed gliomas and many other lesions showed FET uptake to a variable extent. No uptake was observed in nine lesions (one inflammatory lesion, one dysembryoplastic neuroepithelial tumour, one mature teratoma, six lesions without histological confirmation). An analysis of uptake dynamics was done in the patients with increased FET uptake (22 gliomas, three lymphomas, three non-neoplastic lesions, three lesions with unknown histology and four other primaries). Upon classification of tumours into low (i.e. WHO I and II) and high grade (i.e. WHO III and IV), a significant difference in FETmax between the two categories was observed only in the first image frame (0-10 min p.i.), with FETmax=2.0 in low-grade and 3.2 in high-grade tumours (p<0.05); no significant differences were found in frame 4 (30-40 min p.i.), with FETmax=2.4 vs 2.7. Similar results were obtained when the analysis was applied only to astrocytic tumours (2.0 vs 3.1 in the first frame; 2.4 vs 2.6 in the fourth frame). CONCLUSION: These initial results indicate that FET PET is a useful method to identify malignant brain lesions. It appears that high- and low-grade brain tumours exhibit a different uptake kinetics of FET. A kinetic analysis of FET PET may provide additional information in the differentiation of suspected brain lesions.

Adolescent↗
PubMed2005

Labelling of manganese-based magnetic resonance imaging (MRI) contrast agents with the positron emitter 51Mn, as exemplified by manganese-tetraphenyl-porphin-sulfonate (MnTPPS4).

The potential tumor seeking MRI contrast agent MnTPPS(4) was labelled with the positron emitting nuclide (51)Mn in no-carrier-added (n.c.a.) form. The complex formation kinetics were investigated and the apparent rate constants were determined under pseudo-first-order conditions. The derived bimolecular rate constants gave the Arrhenius parameters E(A)=84 kJ mol(-1) and A=2 x 10(12)s(-1)M(-1). Optimum labelling conditions were derived (radiochemical yields >99% possible, effective yields about 32%). Separation and purification of n.c.a. (51)MnTPPS(4) were performed for potential human use. All impurities were <1%.

Contrast Media↗
PubMed2005

Cross-section measurement of the 169 Tm p,n reaction for the production of the therapeutic radionuclide 169 Yb and comparison with its reactor-based generation.

The radionuclide (169)Yb (T(1/2)=32.0 d) is potentially important for internal radiotherapy. It is generally produced using a nuclear reactor. In this work the possibility of its production at a cyclotron was investigated. A detailed determination of the excitation function of the (169)Tm(p,n)(169)Yb reaction was done over the proton energy range up to 45 MeV using the stacked-foil technique and high-resolution gamma-ray spectrometry. The integral yield of (169)Yb was calculated. Over the optimum energy range E(P)=16-->7 MeV the yield amounts to 1.5 MBq/micro Ah and is thus rather low. A comparison of this production route with the established (168)Yb(n,gamma)(169)Yb reaction at a nuclear reactor is given. The (169)Yb yield via the reactor route is by several orders of magnitude higher than by the cyclotron method. The latter procedure, however, leads to "no-carrier-added" product.

Isotope Labeling↗
PubMed2005

Bilateral subdural haematomata and lumbar pseudomeningocele due to a chronic leakage of liquor cerebrospinalis after a lumbar discectomy with the application of ADCON-L gel.

The anti-adhesion gel ADCON-L has been available since the end of the 1990s. During disc surgery it can be applied to the spinal nerve roots and the dura mater spinalis in order to inhibit fibroblast migration and thus avoid postoperative adhesions or excessive keloids, respectively. Due to the way ADCON-L works, inadvertent, intraoperational dural lesions may stay open much longer than usual because ADCON-L inhibits the natural healing process. Possible consequences are a chronic leakage of cerebrospinal fluid in combination with intracranial hypotension syndrome. We report on a patient who underwent lumbar disc surgery with application of ADCON-L gel. Postoperatively he suffered from acute headache, nausea, and vomiting. A lumbar pseudomeningocele was demonstrated on magnetic resonance imaging (MRI). Furthermore, cranial MRI revealed bilateral, chronic subdural haematomata which indicated intracranial hypotension syndrome or continuous leakage of cerebrospinal fluid at the lumbar site. With conservative treatment the problems were gradually reduced and eventually the subdural haematomata were no longer detected. The pseudomeningocele persisted over a 4 month period of observation. Because of the complications we found, the local application of ADCON-L during lumbar disc surgery should be critically evaluated.

Brain↗
PubMed2004

Experimental studies and nuclear model calculations on proton-induced reactions on (nat)Se, (76)Se and (77)Se with particular reference to the production of the medically interesting radionuclides (76)Br and (77)Br.

Excitation functions of the reactions (nat)Se(p,x)(75,76,77,82)Br, (76)Se(p,xn)(75,76)Br, (76)Se(p,x)(75)Se and (77)Se(p,xn)(76,77)Br were measured from their respective thresholds up to 40 MeV, with particular emphasis on data for the production of the medically important radionuclides (76)Br and (77)Br. The conventional stacked-foil technique was used. The samples were prepared by a sedimentation process. Irradiations were performed using the compact cyclotron CV 28 and the injector of COSY, both at the Research Centre Jülich. In order to validate the data, nuclear model calculations were performed using the code ALICE-IPPE which is based on the preequilibrium-evaporation model. Good agreement was found between the experimental and theoretical data, except in the high-energy region where the calculated data were somewhat higher. All the measured excitation curves were compared with the data available in the literature. From the experimental data the theoretical yields of all the investigated radionuclides were calculated and plotted as a function of proton energy. The calculated yield of (77)Br from the (nat)Se(p,x)(77)Br process over the energy range E(p)=25-->15 is 72.7 MBq/microAh and from the (77)Se(p,n)(77)Br reaction over E(p)=15-->6 MeV it is 86.2 MBq/microAh. The yield of (76)Br from the (76)Se(p,n)(76)Br reaction for E(p)=15-->8 is 360.1 MBq/microAh and from the (77)Se(p,2n)(76)Br reaction for E(p)=28-->18 MeV it is 879.2 MBq/microAh. The radionuclidic impurity levels are discussed.

Bromine Radioisotopes↗
PubMed2004

Formation of short-lived positron emitters in reactions of protons of energies up to 200 MeV with the target elements carbon, nitrogen and oxygen.

Excitation functions were measured by the stacked-foil technique for proton induced reactions on carbon, nitrogen and oxygen leading to the formation of the short-lived positron emitters (11)C (T(1/2) = 20.38 min) and (13)N (T(1/2) = 9.96 min). The energy region covered extended up to 200 MeV. The product activity was measured non-destructively via gamma-ray spectrometry. A careful decay curve analysis of the positron annihilation radiation was invariably performed. The experimental results were compared with theoretical data obtained using the modified hybrid nuclear model code ALICE-IPPE for intermediate energies. The agreement was found to be generally satisfactory. The data are of importance in proton therapy.

Carbon Radioisotopes↗
PubMed2004

Binding of tritiated and radioiodinated ZM241,385 to brain A2A adenosine receptors.

Autoradiography on rat brain using tritiated (1*), mono- (2*) and di-radioiodinated (3*) derivatives of the A(2A) adenosine receptor antagonist ZM241,385 showed high receptor density in striatum. K(D)s of 1*, 2* and 3* were 0.4, 2.2 and 15 nM and nonspecific binding was 5, 40 and 50% of total binding. Striatal uptake of 2* in mice was approximately 0.2% ID/g 60 min post-injection; blocking by 2 was insignificant. Poor penetration of the blood brain barrier and high nonspecific binding make 2* unsuitable for imaging striatal receptors.

Animals↗
PubMed2003

Some optimisation studies relevant to the production of high-purity 124I and 120gI at a small-sized cyclotron.

Optimisation experiments on the production of the positron emitting radionuclides 124I(T(1/2) = 4.18d) and (120g)I (T(1/2) = 1.35 h) were carried out. The TeO(2)-target technology and dry distillation method of radioiodine separation were used. The removal of radioiodine was studied as a function of time and the loss of TeO(2) from the target as a function of oven temperature and time of distillation. A distillation time of 15 min at 750 degrees C was found to be ideal. Using a very pure source and comparing the intensities of the annihilation and X-ray radiation, a value of 22.0 +/- 0.5% for the beta(+) branching in 124I was obtained. Production of 124I was done using 200 mg/cm(2) targets of 99.8% enriched 124TeO(2) on Pt-backing, 16 MeV proton beam intensities of 10 microA, and irradiation times of about 8 h. The average yield of 124I at EOB was 470 MBq(12.7 mCi). At the time of application (about 70 h after EOB) the radionuclidic impurity 123I (T(1/2) = 13.2 h) was <1%. The levels of other impurities were negligible (126I < 0.0001%;125I = 0.01%). Special care was taken to determine the 125I impurity. For the production of (120g)I only a thin 30 mg target (on 0.5 cm(2) area) of 99.9% enriched 120TeO(2) was available. Irradiations were done with 16 MeV protons for 80 min at beam currents of 7 microA. The 120gI yield achieved at EOB was 700 MBq(19 mCi), and the only impurity detected was the isomeric state 120 mI(T(1/2) = 53 min) at a level of 4.0%. The radiochemical purity of both 124I and 120gI was checked via HPLC and TLC. The radioiodine collected in 0.02 M NaOH solution existed >98% as iodide. The amount of inactive Te found in radioiodine was <1 microg. High purity 124I and 120gI can thus be advantageously produced on a medium scale using the low-energy (p,n) reaction at a small-sized cyclotron.

Cyclotrons↗
PubMed2003

Radiosynthesis and in vitro stability evaluation of various radioiodine-labelled beta-iodoalkylether prosthetic groups linked to model compounds.

A systematic comparative investigation into the in vitro radiochemical stabilities of model compounds containing radioiodinated beta-iodoethoxyl units and derivatives thereof, as well as those of similar compounds lacking a beta-oxygen to serve as control references, was undertaken. The radioiodinations were carried out in fair to modest yields by means of substitution of a tosyl group by iodide. Stability evaluations were carried out by incubating the labeled compounds in human blood serum at 37 degrees C and measuring free radioiodide by means of radio-HPLC and radio-TLC. The compounds containing beta-iodoethoxyl units displayed much superior stabilities than those without, while the presence of small alkyl or aryl groups in such a unit rendered an additional degree of stability to the carbon-iodine bond, especially over a long period.

Chromatography, High Pressure Liquid↗
PubMed2003

Evaluation of radioiodinated 8-Cyclopentyl-3-[(E)-3-iodoprop-2-en-1-yl]-1-propylxanthine ([*I]CPIPX) as a new potential A1 adenosine receptor antagonist for SPECT.

8-Cyclopentyl-3-[(E)-3-[(131)I]iodoprop-2-en-1-yl]-1-propylxanthine (2*) was generated by iododestannylation of the tributyl-stannyl-precursor with [(131)I]NaI and chloramine T. The radiochemical yield of 2* was 82 +/- 4%, and the purity exceeded 98%. The specific activity was 33 +/- 19 GBq/micromol. Affinities for rat, pig and human A(1) adenosine receptors (A(1)ARs) were in the low nanomolar range, but poor selectivity for the human A(1)AR over the A(2A)AR was found. Additionally, in vitro and ex vivo autoradiographic studies revealed high unspecific binding which makes this ligand unsuitable for SPECT imaging.

Animals↗