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The key to applying targeted imaging to personalized medicine is the choice of the right radiolabeled probe for the right target for the right disease following the lead of pharmaceutical development. The imaging approach differs depending on whether the target is a single disease control point (e.g. a specific receptor or transport protein linked to the mechanistic activity of a drug) or a general disease control point applicable to a number of treatment paradigms (e.g. proliferation, angiogenesis, inflammation). But in either case, the number of control points must be small given the time constraints on molecular imaging procedures in the clinic. Regardless of the choice, the radiotracer must be validated as binding to the target with the appropriate pharmacokinetics and pharmacodynamics for effective external imaging. Such an imaging agent developed in concert with drug development has a built in synergy that will accelerate the drug development process, targeted imaging and personalized medicine as well.

We describe a 58-year-old woman who presented with new onset of temporal headaches and a nondiagnostic temporal artery biopsy in whom positron emission tomography led to the diagnosis of giant cell arteritis. After treatment with corticosteroids the patient's symptoms resolved. A repeat (18)FDG PET-CT scan illustrated virtually complete resolution of the abnormal (18)FDG uptake in the arterial wall.

A new type of alpha-particle irradiator allows survival of each cell to be observed individually along with the size and shape of its nucleus and the positions of the hits it receives. This paper discusses methods of data analysis that can utilize these additional data. Using idealizations of the cell nucleus geometry (i.e., spheres, ellipsoids), the path length (l), energy deposited (e), and specific energy (z) has been determined on a cell-by-cell basis for 772 cells all subjected to the same fluence. Each cell is regarded as a Bernoulli trial with a different probability for success (colony formation). For the survival expectation, A exp(-z/z(o)), the values of A and z(o) are chosen to maximize the likelihood for the observed outcome. Similar results are presented using the alternate functional forms A exp(-e/e(o)) and A exp(-l/l(o)). With these parameter values, the goodness of fit is also evaluated using a chi-square method with variances given by the binary (Bernoulli) methods. A further purpose of the paper is to assess the validity of the microdosimetric computations that would have had to be made if these individual cell-by-cell experimental measurements were not available or were incomplete.

In cases where both the source and cell geometry are well known, track-etch dosimetry allows the potential for individual cell dosimetry. However, analysis of track-etch images is both tedious and time-consuming. We describe here several image processing tools that we are using in conjunction with a track-etch based irradiator. Briefly, cells grown on LR 115 (a track-etch material) are irradiated from below by a collimated, planar alpha-particle source. Prior to irradiation, images of the cells are obtained. A computer program reads each image and automatically determines the location of individual cells. Next, the algorithm automatically identifies the cellular and nuclear boundaries. Following irradiation, and after the cells have reached their biological endpoint (e.g., cell survival), the cell dish is etched and images are obtained of alpha-particle tracks. Using the characteristic background pattern in the LR 115, the etched images are spatially registered to the original images. These two sets of images are then superimposed to create a composite image of the cells and associated alpha-particle tracks. Incorporating this tool into our irradiation scheme will enable more efficient analysis of the large amounts of data that are essential in assessing biological endpoints.

Despite advances in the understanding and treatment of ischemic cardiomyopathy, characterized by extensive coronary artery disease and left ventricular (LV) dysfunction, the prognosis remains poor with only a 50-60% 5-year survival rate. The composition of atherosclerotic lesions is currently regarded as being more important than the degree of stenosis in determining acute events. If imaging techniques could distinguish vulnerable from stable plaques, then high-risk patient subgroups could be identified. Another important concept is that LV dysfunction may be the result of either scarring due to necrosis or to the presence of myocardial hibernation, in which there is sufficient blood flow to sustain viable myocytes, but insufficient to maintain systolic contraction. This concept of myocardial viability is critical for making optimal clinical management decisions. This review describes how noninvasive imaging methods can be used to distinguish regions of irreversibly injured myocardium from viable but hibernating segments. Technical advances in CT and MR have made imaging of the beating heart possible. Considerable clinical progress has already been made and further cardiac applications are expected. Radiologists therefore have new opportunities for involvement in cardiac imaging but must recognize the political implications as well as the diagnostic potential of these modalities not only for the heart, but also for the whole vascular system. This review focuses on imaging myocardial injury. It compares state-of-the-art CT and MR with more established yet contemporary echocardiography and nuclear scintigraphy.

Cancer comprises a group of diseases characterized by the uncontrolled growth of abnormal cells that spread from the anatomical site of origin. For many types of cancer, surgery alone has proven inadequate, necessitating a broader approach to treatment incorporating chemotherapy and radiotherapy. Of particular recent interest has been the use of α-emitters in the treatment of microscopic carcinoma. The effective application of these materials requires an understanding of the physical and biological bases of radiation therapy. In addition, both radiochemical and radionuclidic purity are essential in all clinical applications. Recent work with the α-emitting radionuclide bismuth-212 offers considerable promise in the treatment of microscopic ovarian carcinoma resistant to conventional treatment modalities. Ongoing improvements in methods for its preparation are expected to further improve its therapeutic utility.

We have built a model of the D-2 dopaminergic receptor protein and have docked the agonist dopamine and two dopamine D-2 receptor antagonists, (S)-N-[(1-allyl-2-pyrrolidinyl)- methyl]-5-(3-fluoropropyl)-2,3-dimethoxybenzamide (fallypride) and (S)-N-[(1-iso-butyl- 2-pyrrolidinyl)methyl]-5-(3-fluoropropyl)-2,3-dimethoxybenzamide (ZYY-106), to its putative active site. We have utilized the structures of bacteriorhodopsin and rhodopsin for modeling the D-2 receptor by homology. Mutation studies and structure-activity studies have been used to refine our model further. Docking exercises of the ligands to the computer-generated D-2 model are used to explain the observed in vitro and in vivo behavior of these compounds. Interactions with the aspartate residue (Asp67) in helix-3 and the serine residues (serine-117 and serine-120) in helix-5 were observed for both dopamine and fallypride. A significant interaction of the phenyl ring of fallypride was observed with Phe121 and Trp155, which was weaker in the case of dopamine. The N-allyl group of fallypride is flanked by Phe158 and His162, possibly enhancing π-π interaction and the fluoropropyl group in fallypride is flanked by helix5:Pro124, helix5:phe125 and helix3:Ile75, which seem to form a pocket. These interactions may account for the higher affinity of fallypride for the D-2 receptor compared to dopamine.

Some fluoro- and iodo-derivative of 5-[[4-[(4-diisobutylamino)butyl]-1-phenyl]acetyl]-10,11-dihydro-5H-dibenzo[b,e][1,4]diazepin-1l-one and 11-[[4-[(dialkylamino)butyl]-1-phenyl]acetyl]-5,11-dihydro-6H-pyrido[2,3-b][1,4]benzodiazepin-6-ones 6 (Scheme 1) and their analogues were synthesized. The synthesis of dibenzodiazepinones 1 (Scheme 1) is based on the reaction between 1,4-phenylenediamine and substituted benzoic acids. The intermediate pyridobenzodiazepinones 3 (Scheme 1) were prepared by condensation of 2-chloro-3-aminopyridine with methyl anthranilate and its chlorine derivative. The condensation of 4-[(halo)alkyl]phenylacetyl chloride with dibenzodiazepinones and pyridobenzodiazepinones followed by the reaction of mono- or dialkyl- or dialkenylamine provides 6 (Scheme 1).

Alzheimer’s disease (AD) involves selective loss of muscarinic m2, but not m1, subtype neuroreceptors in cortical and hippocampal regions of the human brain. Until recently, emission tomographic study of the loss of m2 receptors in AD has been limited by the absence of available m2-selective radioligands that can penetrate the blood-brain barrier. We now demonstrate the in vivo m2 selectivity of an analog of (R)-QNB, 3-quinuclidinyl 2-(5-bromothienyl)-2-thienylglycolate (BrQNT), by dissection and autoradiographic studies of the in vivo inhibition of radioiodinated Z-1-azabicyclo[2.2.2]oct-3-yl α-hydroxy-α-(1-iodo-1-propen-3-yl)-α-phenylacetate (Z-(-,-)-[125I]IQNP) binding by unlabeled BrQNT in rat brain. In the absence of BrQNT, Z-(-,-)-[125I]IQNP labels brain regions containing muscarinic receptors, with an enhanced selectivity for the m2 subtype. In the presence of 60–180 nmol of co-injected racemic BrQNT, Z-(-,-)-[125I]IQNP labeling in those brain regions containing predominantly m2 subtype is reduced to background levels, while levels of radioactivity in areas not enriched in the m2 subtype do not significantly decrease. We conclude that BrQNT is m2-selective in vivo, and that [76Br]BrQNT, or a radiofluorinated analog, may be of potential use in positron emission tomographic (PET) study of the loss of m2 receptors in AD. In addition, a radioiodinated analog may be of potential use in single photon emission tomographic (SPECT) studies.

Radioiodinated (R,S)-IQNB and (R,R)-IQNB are prepared either from a triazene precursor or using an exchange reaction. In both cases the radiochemical yield is low. The product of the exchange reaction also suffers from having a fairly low specific activity. A new method for preparing radioiodinated (R,S)-IQNB and (R,R)-IQNB from a tributylstannyl precursor has recently been developed. This method is more convenient and much faster than the triazene and exchange methods, and it reliably results in a high radiochemical yield of a high specific activity product. In rat brain, the in vivo properties of the radioiodinated products of the tributylstannyl method are identical to those of the corresponding radioiodinated (R,S)-IQNB and (R,R)-IQNB prepared using the triazene and exchange methods. Dissection studies of selected brain regions show that at 3 h post injection (R,S)-[125I]IQNB prepared by all three methods have indistinguishable %dose g−1 values in all brain regions studied. Autoradiographic comparison of coronal slices through the anteroventral nucleus of the thalamus, through the hippocampus and through the pons at 2 h post injection shows that (R,S)-[125I]IQNB prepared by the triazene and tributylstannyl methods have indistinguishable patterns of bindings

Both 1-azabicyclo[2.2.2]oct-3-yl α-(1-fluoroeth-2-yl)-α-hydroxy-α-phenylacetate (FQNE, 5) and 1-azabicyclo[2.2.2]oct-3-yl α-(1-fluoropent-5-yl)-α-hydroxy-α-phenylacetate (FQNPe, 6) were prepared and evaluated as potential candidates for the determination of muscarinic cholinergic receptor (mAChR) density by positron emission tomography (PET). The results of in vitro binding assays demonstrated that although both 5 and 6 had high binding affinities for m 1 and m 2 mAChR subtypes, 6 displayed a higher affinity (nM, m 1 ; K D , 0.45, m 2 ; K D , 3.53) as compared to 5 (nM, m 1 K D , 12.5, m 2 ; K D , 62.8). It was observed that pretreatment of female Fisher rats with either 5 or 6 prior to the i.v. administration of Z-(−)(−)-[ 131 I]-IQNP, a high-affinity muscarinic ligand, significantly blocked the uptake of radioactivity in the brain and heart measured 3 h postinjection of the radiolabeled ligand. These new fluoro QNB analogues represent important target ligands for evaluation as potential receptor imaging agents in conjunction with PET.

In vivo nonspecific binding can be estimated using the inactive stereoisomer of a receptor radioligand. However, the binding of the inactive stereoisomer may be partially specific. Specific binding of the inactive (S,S)-[125I]IQNB was estimated from the inhibition induced by a competing nonradioactive ligand. This technique differed from the usual approach, since it was used to study the inactive rather than the active stereoisomer. The results indicate that there is substantial specific binding for (S,S)-[125I]IQNB.

Alzheimer's disease (AD) involves selective loss of muscarinic m2, but not m1, subtype neuroreceptors in cortical and hippocampal regions of the human brain. Emission tomographic study of the loss of m2 receptors in AD is limited by the fact that there is currently no available m2-selective radioligand which can penetrate the blood-brain barrier. We now demonstrate the in vivo m2 selectivity of a fluorine derivative of QNB (FQNB), by studying autoradiographically the in vivo inhibition of radioiodinated (R)-3-quinuclidinyl (S)-4-iodobenzilate ((R,S)-[125I]IQNB) binding by unlabeled FQNB. In the absence of FQNB, (R,S)-[125I]IQNB labels brain regions in proportion to the total muscarinic receptor concentration; in the presence of 30.0 nmol of racemic FQNB, (R,S)-[125I]IQNB labeling in those brain regions containing predominantly the m2 subtype is reduced to background levels. We conclude that FQNB is m2-selective in vivo and that [18F]FQNB or a closely related analogue may be of potential use in positron emission tomographic study of the loss of m2 receptors in AD.

Alzheimer's disease (AD) involves selective loss of muscarinic m2, but not m1, subtype neuroreceptors in cortical and hippocampal regions of the human brain. Emission tomographic study of the loss of m2 receptors in AD is limited by the fact that there is currently no available m2-selective radioligand which can penetrate the blood-brain barrier. We now demonstrate the in vivo m2 selectivity of an analogue of QNB, 4-(bromophenyl)-2-thienylglycolate (QBPTG), by studying autoradiographically the in vivo inhibition of radioiodinated (R)-3-quinuclidinyl (S)-4-iodobenzilate ((R,S)-[125I]IQNB) binding by unlabeled QBPTG in rat brain. In the absence of QBPTG, (R,S)-[125I]IQNB labels brain regions in proportion to the total muscarinic receptor concentration; in the presence of 37.5 nmol of racemic QBPTG, (R,S)-[125I]IQNB labeling in those brain regions containing predominantly the m2 subtype is reduced to background levels. We conclude that QBPTG is m2-selective in vivo and that [76Br]QBPTG, or a radiofluorinated analogue, may be of potential use in positron emission tomographic study of the loss of m2 receptors in AD. In addition, a radioiodinated analogue may be of potential use in single photon emission tomographic studies.

Summary A series of 5-[[[(dialkylamino)alkyl]-1-phenyl]acetyl]-10,11-dihydro-5 H -dibenzo[ b,e ][1,4]diazepin-11-ones 1 were prepared as potential m 2 -selective ligands. The binding affinities and selectivities of these compounds for the muscarinic cholinergic receptor subtypes were determined. The best m 2 -selective antimuscarinic agent studied was 5-[[4-[4-(diisobutylamino)butyl]-1-phenyl] acetyl]-10,11-dihydro-5 H -dibenzo[ b,e ][1,4]diazepin-11-one 1h (DIBD), which caused a significant reduction in (R,R)-3-quinuclidinyl-[ 125 I]-4-iodobenzilate ((R,R)-[ 125 I]-4IQNB) binding in brain regions known to contain a high percentage of m 2 -receptors. Thus DIED penetrates the blood-brain barrier and exhibits in vivo selectivity for the m 2 subtype. In contrast, neither DIBA, AF-DX 116, nor AQ-RA 741 caused a significant m 2 -selective reduction in (R,R)-[ 125 I]-4IQNB binding in the brain regions studied.

Two series of 5-[[4-[4-dialkylamino)butyl]-1-cyclohexyl]acetyl], and 5- [(dialkylamino)acyl]-10,11-dihydro-5H-dibenzo[b,e][1,4]diazepin-11-ones were synthesized as potential m2-selective ligands (1),(2). Their affi- nity and selectivity for the muscarinic cholinergic receptor m-AChR su- btypes were determined. Replacing a nitrogen with CH in the piperidine ring of 5-[[4-[4-dialkylamino)butyl]-1-piperidinyl]acetyl]-10,11-dihy- dro-5H-dibenzo[b,e][1,4]diazepin-11-ones (3) significantly altered the affinity and selectivity to the muscarinic receptor subtypes

For the reconstruction of a series of computer simulations of statistically-independent noisy realizations of projection data, the total error of the ith reconstructed voxel in the rth realization, Er,i, is composed of the statistical error, Sr,i, and the (deterministic) inaccuracy in the presence of noise, Di+. Di+ is composed of the (deterministic) inaccuracy in the absence of noise, Di-, and the (deterministic) additional inaccuracy in the presence of noise, Di delta. E(Er,i), the theoretical expected value of Er,i, is given by E(Er,i) = E(Di+) + E(Sr,i). Similarly, E(Di+) = E(Di-) + E(Di delta). The corresponding theoretical variances are given by sigma 2(Er,i) = sigma 2(Di+)+2C(Di+, Sr,i)+ sigma 2(Sr,i) and sigma 2(Di+) = sigma 2(Di-)+2C(Di-, Di delta)+ sigma 2(Di delta), where C(.,.) is the covariance. We have utilized these relationships to evaluate three reconstruction algorithms: standard filtered back projection (FBP), an iterative reconstruction algorithm (IRA), and a version of the IRA which incorporates a linear transformation (TIRA). For simulated brain images in which the projection data (500,000 events detected) were degraded as the result of convolution of the true radioactivity distribution with a realistic distance-dependent detector response function, for FBP the major contribution to both E(Er,i) and sigma 2(Er,i) was Di-. For the IRA and TIRA, the major contributions to E(Er,i) were Di- and Di delta, and the major contribution to sigma 2(Er,i) was Sr,i, although in some cases Di delta was also a contributing factor. Furthermore, the errors due to sigma 2(Er,i) (that is, [sigma 2(Er,i)]0.5) were more severe than those due to E(Er,i). We conclude that, in contrast to FBP, the effects of statistical noise are an important limiting factor for the IRA and TIRA, and that the future development of tomographic devices with higher sensitivity would expand the quantitative potential of the IRA and TIRA.

Alzheimer's disease (AD) involves selective loss of muscarinic m2, but not m1, subtype neuroreceptors in the posterior parietal cortex of the human brain. Emission tomographic study of the loss of m2 receptors in AD is limited by the fact that there is currently no available m2-selective radioligand which can penetrate the blood-brain barrier. In our efforts to prepare such a radioligand, we have used competition studies against currently existing muscarinic receptor radioligands to infer the in vitro and in vivo properties of a novel muscarinic receptor ligand, 5-[[4-[4-(diisobutylamino)butyl]-1-phenyl]acetyl]-10,11-dihydro-5H - -dibenzo [b,e][1,4]diazepin-11-one (DIBD). In vitro competition studies against [3H](R)-3-quinuclidinylbenzilate ([3H]QNB) and [3H]N-methylscopolamine ([3H]NMS), using membranes derived from transfected cells expressing only m1, m2, m3, or m4 receptor subtypes, indicate that DIBD is selective for m2/m4 over m1/m3. In vivo competition studies against (R,R)-[125I]IQNB indicate that DIBD crosses the blood brain barrier (BBB). The relationship of the regional percentage decrease in (R,R)-[125I]IQNB versus the percentage of each of the receptor subtypes indicates that DIBD competes more effectively in those brain regions which are known to be enriched in the m2, relative to the m1, m3, and m4, receptor subtype; however, analysis of the data using a mathematical model shows that caution is required when interpreting the in vivo results. We conclude that a suitably radiolabeled derivative of DIBD may be of potential use in emission tomographic study of changes in m2 receptors in the central nervous system.

To improve the radiolabeling yield and the specific activity of [ 125 I] N -(2-diethylaminoethyl)-4-iodobenza-mide (DAB), the aryltributyltin precursor was synthesized from the N -(2-diethylaminoethyl)-4-bromobenzamide derivative by palladium catalyzed stannylation using bis(tributyltin). The radiolabeled product, [ 125 I]DAB, was obtained by an iododestannylation reaction in high radiochemical yields (85–94%, radiochemical purity, > 98%) using chloramine-T as an oxidizing agent. The specific activity was greater than 1600 Ci/mmol. The biodistribution studies in nude mice implanted with human malignant melanoma xenograft showed a good tumor uptake (6.14% ID/g at 1 h, 2.81% ID/g at 6 h and 0.42% ID/g at 24 h) of [ 125 I]DAB. Unfortunately, a high uptake in the non-target organs, such as liver and lung, was found. At 1 h post-injection the activity level in liver and lung was 11.76 and 7.58% ID/g, respectively. A slow clearance of activity from liver and lung was observed at 6 h (3.43 and 0.49% ID/g). These results demonstrate that iodinated IDAS is a potential radiopharmaceutical for the management of patients with malignant melanoma.

Reaction of (dialkylamino)alkyl chloride with picolyllithiums provides the corresponding pyridine derivatives from which the piperidines are obtained by catalytic hydrogenation.

Some fluoro- and iodo-derivative of 5-[[4-[(4-diisobutylamino)butyl]-1-phenyl]acetyl]-10,11-dihydro-5H-dibenzo[b,e][1,4]diazepin-1l-one and 11-[[4-[(dialkylamino)butyl]-1-phenyl]acetyl]-5,11-dihydro-6H-pyrido[2,3-b][1,4]benzodiazepin-6-ones 6 (Scheme 1) and their analogues were synthesized. The synthesis of dibenzodiazepinones 1 (Scheme 1) is based on the reaction between 1,4-phenylenediamine and substituted benzoic acids. The intermediate pyridobenzodiazepinones 3 (Scheme 1) were prepared by condensation of 2-chloro-3-aminopyridine with methyl anthranilate and its chlorine derivative. The condensation of 4-[(halo)alkyl]phenylacetyl chloride with dibenzodiazepinones and pyridobenzodiazepinones followed by the reaction of mono- or dialkyl- or dialkenylamine provides 6 (Scheme 1).

Seven human ocular melanoma cell lines were established in vitro and 3 of these, GU-4, LLN-40 and its subline C17-11, were characterized. Mice were immunized with these ocular melanoma cell lines, and 2 hybridomas producing monoclonal IgG1antibodies (MAb) were produced. MAb 2/10SN recognizes a 44-kDa monomeric protein, whereas MAb 10/12SN reacts with an 83/65-kDa heterodimeric protein. These melanoma-associated antigens (MAA) are detected at high concentrations in the cytoplasm of ocular melanoma cells. However, cell-surface labelling techniques suggest that these MAA are also associated with the cell-surface membrane. These 2 ocular MAA are also expressed by several skin melanoma cell lines. Immunohistochemical studies have localized these antigens to ocular and skin melanomas, to sweat ducts and basal squamous cells in normal skin, with limited expression in several other normal tissues and some carcinomas. Biodistribution studies in nude mice with human ocular melanomas have demonstrated good localization of 125I-labeled MAb 2/10SN at the tumor sites. Therefore, these 2 MAbs, 2/10SN and 10/12SN, recognize MAA which appear to be unique and may prove useful for imaging purposes. © 1992 Wifey-Liss, Inc.

Five analogues of 3-quinuclidinyl benzilate were prepared in which one phenyl ring was substituted by a heterocycle; a bromine was included on either the remaining phenyl or the heterocycle to provide information relating to the affinity of potential radiohalogenated derivatives. Their affinities for the muscarinic cholinergic receptor were determined. Replacing a phenyl ring with either the 2- or 3-furyl moiety or the 2- or 3-thienyl moiety did not significantly alter the affinity to the muscarinic receptor compared with 3-quinuclidinyl 4-bromobenzilate.

A new hexadentate aminethiol ligand (TACNS) derived from triazacyclononane was synthesized and characterized for the development of technetium radiopharmaceuticals. The ligand formed a neutral, lipophilic and stable complex with [99mTc]pertechnetate in the presence of tin(II)tartarate as a reducing agent. The biodistribution of [99mTc]TACNS indicates slight uptake in brain (0.23% ID/organ at 5 min) with a washout at 30 min to 0.14% ID/organ. A small uptake in heart (0.48% ID at 5 min) was also observed. The characterization of [99mTc]TACNS complex using single crystal x-ray analysis and mass spectroscopy has shown that an Sn-N3S3 complex was formed in which tin is oxidized from Sn(II) to Sn(IV). Pertechnetate was incorporated into the complex as counter anion. The nature of the species formed with Tc-99 and “no-carrier-added” [99mTc]pertechnetate is different as confirmed by ratio TLC. From these results, it is demonstrated that sometimes it may be difficult to predict the structure of new technetium radiopharmaceuticals, especially when stannous ion is used as a reducing agent. Moreover, the nature of the chemical species may not be the same at millimolar and at nanomolar levels.

Alzheimer's disease (AD) involves selective loss of muscarinic M2, but not M1, subtype neuroreceptors in the posterior parietal cortex of the human brain. Emission tomographic study of the loss of M2 receptors in AD is limited by the fact that there is currently no available M2-selective radioligand which can penetrate the blood-brain barrier. However, by taking advantage of the different pharmacokinetic properties of (R,R)-[123I]IQNB for the M1 and M2 subtypes, it may be possible to estimate losses in M2. It has previously been hypothesized that the difference between an early study and a late study should provide information on the M2 receptor population. In order to test this hypothesis, we present here the results of pharmacokinetic simulations of the in vivo localization of (R,R)-[123I]IQNB in brain regions containing various proportions of M1 and M2 subtypes. These results permit us to conclude that SPECT imaging of (R,R)-[123I]IQNB localization can potentially be used to quantitate changes in the M2 subtype in a disease state within a brain region for which the ratio M2/M1 is sufficiently high in normal individuals.

This pilot study assessed the urinary fibrinopeptide A (uFPA) levels and the combination of uFPA test plus ventilation/perfusion (V/Q) scan in the diagnostic evaluation of acute pulmonary embolism (PE). One hundred consecutive patients were studied prospectively. Twenty-nine patients fulfilled diagnostic criteria defined in this study (seven with and 22 without PE). The uFPA concentration was significantly higher in patients with than without PE (41.1 +/- 2.6 vs 4.8 +/- 2.5 ng/mg of creatinine, p less than 0.0001). In all patients with PE, the uFPA levels were higher than threshold value derived by adding 2 standard deviations to the mean uFPA concentration of patients without PE. In patients without PE, the V/Q scan was negative in 16, the uFPA test was negative in 18, and at least one of the tests was negative in 21. These preliminary data suggest that a negative uFPA test may be helpful in excluding PE and that uFPA in combination with V/Q lung scans may correctly exclude PE in more patients than either test alone. Further studies in a large unselected population are needed to confirm these results.

The in vivo washout kinetics of [3H]quinuclidinyl benzilate ([3H]QNB) varies significantly in various structures in the rat brain. The slowest washout rates are from the hippocampus, corpus striatum, and cortex, intermediate rates are exhibited from the thalamus and colliculi, while the fastest washout rate is from the cerebellum. We have also demonstrated a difference in the in vitro dissociation rates (k−1) of [3H]QNB from various structures. The k−1 for the hippocampus, corpus striatum and cortex, is two-fold slower than that observed in the thalamus, colliculi, and cerebellum. The differences in the in vitro dissociation kinetics are not, however, sufficient to explain the differences in the in vivo washout kinetics. We have developed a theoretical formulation which describes conditions under which the washout kinetics are a function of the concentration of receptor in a structure. Furthermore, we present a graphical method in which a plot of the reciprocal of the observed washout rate constant, 1/kobs, vs receptor concentration is linear. Analysis of the washout kinetics of [3H]QNB from various structures of the CNS of rat were well described by this theory when the differences in in vitro k−1 are included.

The purpose of this article is to summarize the role of gamma probes in intraoperative tumor detection in patients with colorectal cancer (CRC), as well as provide basic information about the physical and practical characteristics of the gamma probes, and the radiopharmaceuticals used in gamma probe tumor detection. In a significant portion of these studies, radiolabeled monoclonal antibodies (Mabs), particularly 125I labeled B72.3 Mab that binds to the TAG-72 antigen, have been used to target tumor. Studies have reported that intraoperative gamma probe radioimmunodetection helps surgeons to localize primary tumor, clearly delineate its resection margins and provide immediate intraoperative staging. Studies also have emphasized the value of intraoperative gamma probe radioimmunodetection in defining the extent of tumor recurrence and finding sub-clinical occult tumors which would assure the surgeons that they have completely removed the tumor burden. However, intraoperative gamma probe radioimmunodetection has not been widely adapted among surgeons because of some constraints associated with this technique. The main difficulty with this technique is the long period of waiting time between Mab injection and surgery. The technique is also laborious and costly. In recent years, Fluorine-18-2-fluoro-2-deoxy-D-glucose (18F-FDG) use in gamma probe tumor detection surgery has renewed interest among surgeons. Preliminary studies during surgery have demonstrated that use of FDG in gamma probe tumor detection during surgery is feasible and useful.

We have developed an algorithm for simulating the 3D projection data for a SPECT imaging system with a spatially-invariant, distance-dependent 3D point spread function. We have simulated the projection data, in the absence of attenuation, scattering, or noise, of both a parallel hole (PH) and a multidetector SPECT system with point focusing (PF) collimators. The simulated projection data were then reconstructed using standard software. The projection data resulting from the distribution of grey matter in a realistic 3D Hoffman brain model was simulated. The results of these simulations indicate the existence of significant qualitative and quantitative artifacts in reconstructed human brain images. For example, the reconstructed values for grey matter along a cortical circumferential profile in a transverse slice through the basal ganglia varied by a factor of 2.40 (PH) and 2.99 (PF), although the original grey matter values were identical in all cortical regions in the model. This artifactual variation could cause inaccuracies in regional receptor quantification.

Background and purpose: To incorporate single-photon emission computed tomography (SPECT) bone marrow (BM) imaging into the treatment planning process to reduce the volume of BM irradiated in gynecologic patients receiving intensity-modulated whole-pelvic radiation therapy (IM-WPRT). Materials and methods: A planning CT scan was obtained of a patient with early stage endometrial cancer. The same patient also underwent a Tc-99m sulfur colloid SPECT scan of the pelvis. Tc-99m sulfur colloid is sequestered by the macrophages in the BM thereby identifying areas of active (red) BM. Using image fusion software, the SPECT scan was aligned with the planning CT scan and used to delineate regions of active BM. An IMRT plan was then generated to provide coverage of the planning target volume (PTV) while sparing areas of active BM and other normal pelvic structures. Results: The areas of high active BM density were observed predominantly in the lumbar vertebrae, sacrum and medial iliac crests. IMRT planning reduced the dose to these areas by 50% for doses greater than 30 Gy compared to conventional planning. Furthermore, the IMRT plan did not compromise coverage of the PTV or sparing of normal tissues. Conclusions: Our results suggest that SPECT-BM imaging is a useful adjunct to IMRT planning in gynecologic patients undergoing IM-WPRT. q 2005 Published by Elsevier Ireland Ltd. Radiotherapy and Oncology 77 (2005) 11–17.

A computer-controlled, alpha-particle irradiator is described that allows for the measurement of the number and location of alpha-particle hits to individual cell nuclei, and subsequent scoring of cell survival. Cells are grown on a track-etch material (LR 115) and images are obtained of the cells prior to irradiation. The cells are then irradiated from below by a planar, collimated Am-241 source. The exposure time is varied so that the average number of hits to cell nuclei ranges from 0 to 3. After cell survival has been scored, images of the etched material are obtained and spatially registered to the original cell images. The etched images and cellular images are superimposed allowing for the determination of the number and position of hits to individual cell nuclei. This paper characterizes the irradiator including the energy and fluence of the incident alpha particles. Additionally, we describe the sources of uncertainty associated with this experiment, including the cell dish repositioning and cell migration during scanning and irradiation.

Muscarinic M 2 receptors have been found to be severely depleted in post-mortem brains of Alzheimer's patients. This loss of receptor may represent a useful diagnostic marker, if it could be quantitatively imaged with single-photon emission computed tomography (SPECT) or positron emission tomography (PET) imaging. In order to develop a radioligand with selectivity for muscarinic M 2 receptors, we now report that 3-α-chlorimperialine is a potent M 2 receptor antagonist with a K i of 0.32 nM at M 2 receptors, a 12-fold selectivity for M 2 over M 1 receptors, and a 5-fold selectivity for M 2 over M 4 receptors. Furthermore, 2% of the injected dose of 3-α-chlorimperialine per gram tissue penetrates into brain within 30 min, then washes out gradually. Taken together, these studies demonstrate that 3-α-chlorimperialine is a potent M 2 -selective muscarinic antagonist that penetrates into brain and may be a useful substrate for radioiodination and subsequent imaging of brain muscarinic M 2 receptors.

The quantitative potential of PET or SPECT for imaging neuroreceptors is degraded by inaccuracies in kinetic modeling. The authors have simulated the pharmacokinetics for the in vivo binding of carfentanil to the mu opiate receptor in both normal and epileptic human brain. Brain regions within transverse slices through hippo/amyg/cereb and basal ganglia/occ ctx in the mathematical Hoffman 3D brain model were assigned realistic mu concentrations, with 20% elevation in left post temp ctx and hippo for the epileptic brain. Radioligand time-courses, simulated using published plasma curves and rate constants, were used to determine: (1) when equilibrium or state-state exist so that modeling and data analysis might be simplified; (2) when the radioactivity in a control region can be subtracted from the radioactivity in a region of interest as a measure of nonspecific binding; and (3) whether the receptor (delivery) sensitivity is too low (high) to permit accurate estimation of changes in pharmacokinetic parameters in a disease state. These results indicate the caution required for interpretation of clinical data. >

The synthesis of some substituted 1,5-benzodiazepines are described. The route is based on the reaction between 1,4-phenylenediamine and its derivative with crotonic acid or methacrilic acid.

Alzheimer's disease (AD) involves selective loss of muscarinic m2, but not m1, subtype receptors in cortical and hippocampal regions of the human brain. Emission tomographic study of the loss of m2 receptors in AD has been limited by the absence of available m2-selective radioligands, which can penetrate the blood-brain barrier. We now report on the in vitro and in vivo m2 muscarinic subtype selectivity of a series of dibenzodiazepinones and pyridobenzodiazepinones determined by competition studies against (R)-3-quinuclidinyl (S)-4-iodobenzilate ((R,S)-[125I]IQNB) or [3H]QNB. Of the compounds examined, three of the 5-[[4-[(4-dialkylamino)butyl]-1-piperidinyl]acetyl]-10, 11-dihydro-5-H-dibenzo[b,e][1,4]diazepin-11-ones (including DIBA) and three of the 11-[[4-[4-(dialkylamino)butyl]-1-phenyl]acetyl]-5, 11-dihydro-6H-pyrido [2,3-b][1,4]benzodiazepin-6-ones (including PBID) exhibited both high binding affinity for the m2 subtype (/=5 nM) and high m2/m1 selectivity (/=10). In vivo rat brain dissection studies of the competition of PBID or DIBD against (R,S)[125I]IQNB or [3H]QNB exhibited a dose-dependent preferential decrease in the binding of the radiotracer in brain regions that are enriched in the m2 muscarinic subtype. In vivo rat brain autoradiographic studies of the competition of PBID, BIBN 99, or DIBD against (R,S)[125I]IQNB exhibited an insignificant effect of BIBN 99 and confirmed the effect of PBID and DIBD in decreasing the binding of (R,S)[125I]IQNB in brain regions that are enriched in the m2 muscarinic subtype. We conclude that PBID and DIBD are potentially useful parent compounds from which in vivo m2 selective derivatives may be prepared for potential use in positron emission tomographic (PET) study of the loss of m2 receptors in AD.

Radioiodinated (R)-quinuclidinyl-4-iodobenzilate (4IQNB) is a high affinity muscarinic antagonist which has been utilized for in vitro and in vivo assays, and for SPECT imaging in humans. 4IQNB exists in four different diastereomeric forms, since there are two asymmetric centers at the quinuclidinyl and benzilic acid centers. Based upon our in vivo studies, we have determined that the absolute stereochemistry previously assigned to the benzilic center was incorrect for the diastereomer that had been previously referred to as ‘(R)-quinuclidinyl-(R)-4-iodobenzilate’ [(R,R)-4IQNB]. The correct designation for this diastereomer is ‘(R)-quinuclidinyl-(S)-4-iodobenzilate’ [(R,S)-4IQNB].

OBJECTIVE: Our objective was to develop the α-emitting radionuclide bismuth 212 for possible intraperitoneal use against microscopic ovarian cancer. STUDY DESIGN: The radiobiologic effectiveness of bismuth 212 was compared in vitro to x rays and chromic phosphate phosphorus 32). The distribution, toxicity, and maximum tolerated dose of bismuth 212 were determined after intraperitoneal administration in animal models. Dose estimates in animals and humans were made. RESULTS: In in vitro studies bismuth 212 was three times more effective in eradicating tumor cells grown in monolayers and in 800 μm spheroids. In in vivo studies bismuth 212 was distributed uniformly after intraperitoneal administration. The maximum tolerated dose in rabbits was 60 mCi. There was reversible hematologic toxicity with minimal organ damage. Bismuth 212 prolonged survival and cured up to 40% of animals inoculated with Ehrlich carcinoma cells. Dose estimates made from these studies indicated that dosages administered were effective in eradicating tumor cells and were within the radiotolerance of normal human tissue. CONCLUSION: Bismuth 212 appears to be a suitable candidate for intraperitoneal use against microscopic ovarian cancer. (Am J Obstet Gynecol 1997;176:833-41.)

Left ventricular (LV) mass estimates obtained from post-stress gated single-photon emission computed tomographic (SPECT) perfusion images were compared with 2-dimensionally targeted M-mode echocardiograms and with resting electrocardiographic voltage in 32 patients with stress perfusion scans that were either normal or only mildly abnormal. Myocardial pixel volumes were obtained from SPECT transaxial slices at end-diastole, end-systole, and summed (“ungated”) static reformatted SPECT images at 2 levels of background subtraction, 37.5% and 35% of peak myocardial activity. The S-wave amplitude in lead V1 and the R-wave amplitude in V5 were summed for an electrocardiographic index of voltage. Echocardiographic LV mass was calculated using the modified Penn convention formula. SPECT myocardial mass estimates were significantly greater at diastole when compared with systolic or summed images. There was a moderate, although highly significant, correlation between echocardiographic and SPECT indexes of LV mass with the lower (35%) background threshold (r = 0.59, 0.60, and 0.53 for diastole, summed, and systole, each p < 0.001). The diastolic SPECT estimate of LV mass correlation with electrocardiographic voltage (r = 0.56) was superior to the correlation between echocardiography and electrocardiography (r = 0.30). With use of published criteria for the presence of LV hypertrophy on echocardiography, diastolic and systolic gated SPECT predicted echocardiographic results with 78% accuracy.

1-Azabicyclo[2.2.2]oct-3-yl alpha-hydroxy-alpha-(1-iodo-1-propen-3-yl)- alpha-phenylacetate (IQNP, 1), is a highly selective ligand for the muscarinic acetylcholinergic receptor (mAChR). There are eight stereoisomers in the racemic mixture. The optical isomers of alpha-hydroxy-alpha-phenyl-alpha-(1-propyn-3-yl)acetic acid were resolved as the alpha-methylbenzylamine salts, and the optical isomers of 3-quinuclidinol were resolved as the tartrate salts. The E and Z isomers were prepared by varying the reaction conditions for the stannylation of the triple bond followed by purification utilizing flash column chromatography. In vitro binding assay of the four stereoisomers containing the (R)-(-)-3-quinuclidinyl ester demonstrated that each isomer of 1 bound to mAChR with high affinity. In addition, (E)-(-)-(-)-IQNP demonstrated the highest receptor subtype specificity between the m1 molecular subtype (KD, nM, 0.383 +/- 0.102) and the m2 molecular subtype (29.6 +/- 9.70). In vivo biodistribution studies demonstrated that iodine-125-labeled (E)-(-)-(+)-1 cleared rapidly from the brain and heart. In contrast, iodine-125-labeled (E)-(-)-(-)-, (Z)-(-)-(-)-, and (Z)-(-)-(+)-1 have high uptake and retention in mAChR rich areas of the brain. It was also observed that (E)-(-)-(-)-IQNP demonstrated an apparent subtype selectivity in vivo with retention in M1 (m1, m4) mAChR areas of the rain. In addition, (Z)-(-)-(-)-IQNP also demonstrated significant uptake in tissues containing the M2 (m2) mAChR subtype. These results demonstrate that the iodine-123-labeled analogues of the (E)-(-)-(-)- and (Z)-(-)-(-)-IQNP isomers are attractive candidates for single-photon emission-computed tomographic imaging of cerebral and cardiac mAChR receptor densities.

We have studied the in vivo rat brain muscarinic acetylcholine receptor (mAChR) m2 subtype selectivities of three quinuclidine derivatives: (R)-3-quinuclidinyl benzilate (QNB), E-(+,+)-1-azabicyclo[2.2.2]oct-3-yl alpha-hydroxy-alpha-(1-iodo-1-propen-3-yl)-alpha-phenylacetate (E-(+,+)-IQNP), and E-(+,-)-1-azabicyclo[2.2.2]oct-3-yl alpha-hydroxy-alpha-(1-iodo-1-propen-3-yl)-alpha-phenylacetate (E-(+,-)-IQNP), and two tricyclic ring compounds: 5-[[4-[4-(diisobutylamino)butyl]-1-phenyl]-10,11-dihydro-5H-dibenz o [b,e][1,4]diazepin-11-one [sequence: see text] (DIBD) and 11-[[4-[4-(diisobutylamino)butyl-1-phenyl]acetyl]-5,11-dihydro-6H- pyrido [2,3-b][1,4]benzodiazepin-6-one [sequence: see text] (PBID), by correlating the regional inhibition of (R,S)-[125I]IQNB with the regional composition of the m1-m4 subtypes. Subtle effects are demonstrated after reduction of the between-animal variability by normalization to corpus striatum. Substantial in vivo m2-selectivity is exhibited by QNB and DIBD, modest in vivo m2-selectivity is exhibited by E-(+,+)-IQNP, and little or no in vivo m2-selectivity is exhibited by PBID and E-(+,-)-IQNP. Surprisingly, the in vivo m2-selectivity is not correlated with the in vitro m2-selectivity. For example, QNB, which appears to be the most strongly in vivo m2-selective compound, exhibits negligible in vitro m2-selectivity. These examples indicate that a strategy which includes only preliminary in vitro screening may very well preclude the discovery of a novel compound which would prove useful in vivo.

Alzheimer's disease (AD) involves selective loss of muscarinic m2, but not m1, subtype neuroreceptors in cortical and hippocampal regions of the human brain. Emission tomographic study of the loss of m2 receptors in AD is limited by the fact that there is currently no available m2-selective radioligand which can penetrate the blood-brain barrier. We have previously reported the results of in vivo dissection studies, using both carrier-free and low specific activity [3H]QNB, which show that [3H]QNB exhibits a substantial in vivo m2 selectivity. Because of the expense of the radioligand and the long exposure time required for the X-ray film, performing a large number of direct in vivo autoradiographic studies using [3H]QNB is precluded. Therefore, we now confirm these results autoradiographically by studying the in vivo inhibition of radio-iodinated (R)-3-quinuclidinyl (S)-4-iodobenzilate ((R,S)-[125I]IQNB) binding by unlabeled QNB. In the absence of QNB, (R,S)-[125I]IQNB labels brain regions in proportion to the total muscarinic receptor concentration; in the presence of 15 nmol QNB, (R,S,)-[125I]IQNB labeling in those brain regions containing predominantly m2 subtype is reduced to background levels. We conclude that QNB is m2-selective in vivo and that a suitably radiolabeled derivative of QNB, possibly labeled with 18F, may be of potential use in positron emission tomographic study of the loss of m2 receptors in AD.

We have determined the binding of (R)-3-Quinuclidinyl 8-xanthenecarboxylate to muscarinic acetylcholine receptor preparations from rat cortex, hippocampus, caudate/putamen, thalamus, pons and colliculate bodies. The competition curves determined with [3H]quinuclidinyl benzilate as the radioligand are well described by a two site model with a difference in affinity between the two sites of 12-fold. The proportions of high affinity site vary from 100% in the caudate/putamen to 0% in the pons/medulla. The selectivities are different from those measured by pirenzepine and are consistent with QNX exhibiting similar affinity for the M1, M3, and M4 receptors with lower affinity for the M2 receptor. This assignment was confirmed by determining the affinities of QNX for the cloned receptor subtypes.