Uniform Activity Distribution Research Articles

Nafion–Zirconium Phosphate Composite Membrane: A New Approach to Prepare 32P Patches for Superficial Brachytherapy Applications

This article describes a method for the preparation of (32)P patch for the treatment of skin cancer. It is based on the surface modification of a Nafion film by treatment with ZrOCl(2) solution, impregnation of a predicted quantity of (32)P into the film, and its subsequent immobilization into a nonleachable matrix by lamination. The effect of variations of critical parameters on the incorporation of (32)P into the membrane, such as solution pH, contact time, reaction volume, inactive carrier concentration of the feed, reaction temperature, and so on, was investigated to arrive at the conditions resulting in optimum retention of (32)P activity. The morphology of the membrane was evaluated by scanning electron microscope and energy dispersive spectral analyses. Quality control tests were carried out to ensure nonleachability, uniform distribution of activity, and stability of the patches.

Preparation of spherical 57Co source for the calibration of intra-operative gamma probe

This paper describes an electrochemical method for deposition of a thin layer of (57)Co on the outer surface of a copper sphere of 5mm diameter intended to be used as a point radioactive source. A description of the electrolytic cell, the process of deposition and the assay of the (57)Co activity are presented. About 1.48MBq (∼40μCi) of (57)Co could be deposited using the described method. The quality of the prepared source in terms of nonleachability, uniform distribution of activity and stability, which are necessary attributes to be ensured before application were evaluated and found to be satisfactory.

Effect of experimental jaw‐muscle pain on the spatial distribution of surface EMG activity of the human masseter muscle during tooth clenching

This study tested the hypothesis that painful injections of glutamate into the human masseter muscle differentially affect the distribution of the electromyographic (EMG) activity in the masseter muscle at rest and during tooth clenching. Surface EMG signals were recorded bilaterally from the superficial masseter of nine healthy men with a grid of 32 electrodes, before and after intramuscular injection of glutamate or isotonic saline, during rest and isometric contractions at 20%, 40%, 60% and 80% of the maximal voluntary bite force. Intramuscular injection of glutamate evoked moderate pain (0-10 visual analogue scale: 6·4 ± 1·4), with sensory-discriminative characteristics of the perceived pain, evaluated with the use of the McGill Pain Questionnaire (MPQ), similar to those previously reported for patients with temporomandibular disorders. There was no effect of the glutamate injection on EMG amplitude during rest, whereas during tooth clenching, the spatial distribution of the masseter EMG activity on both sides was more uniform in the painful condition compared to the control condition. Moreover, the overall EMG amplitude decreased on both sides during the more forceful tooth clenching following glutamate injection. In conclusion, a unilateral painful stimulation was associated with a bilateral inhibition of the masseter muscles during tooth clenching which resulted in a more uniform distribution of EMG activity.

EQPlanar: a maximum-likelihood method for accurate organ activity estimation from whole body planar projections

Optimizing targeted radionuclide therapy requires patient-specific estimation of organ doses. The organ doses are estimated from quantitative nuclear medicine imaging studies, many of which involve planar whole body scans. We have previously developed the quantitative planar (QPlanar) processing method and demonstrated its ability to provide more accurate activity estimates than conventional geometric-mean-based planar (CPlanar) processing methods using physical phantom and simulation studies. The QPlanar method uses the maximum likelihood-expectation maximization algorithm, 3D organ volume of interests (VOIs), and rigorous models of physical image degrading factors to estimate organ activities. However, the QPlanar method requires alignment between the 3D organ VOIs and the 2D planar projections and assumes uniform activity distribution in each VOI. This makes application to patients challenging. As a result, in this paper we propose an extended QPlanar (EQPlanar) method that provides independent-organ rigid registration and includes multiple background regions. We have validated this method using both Monte Carlo simulation and patient data. In the simulation study, we evaluated the precision and accuracy of the method in comparison to the original QPlanar method. For the patient studies, we compared organ activity estimates at 24 h after injection with those from conventional geometric mean-based planar quantification using a 24 h post-injection quantitative SPECT reconstruction as the gold standard. We also compared the goodness of fit of the measured and estimated projections obtained from the EQPlanar method to those from the original method at four other time points where gold standard data were not available. In the simulation study, more accurate activity estimates were provided by the EQPlanar method for all the organs at all the time points compared with the QPlanar method. Based on the patient data, we concluded that the EQPlanar method provided a substantial increase in accuracy of organ activity estimates from 24 h planar images compared to the CPlanar using 24 h SPECT as the golden standard. For other time points, where no golden standard is available, better agreement between estimated and measured projections was observed by using the EQPlanar method compared to the QPlanar method. This phenomenon is consistent with the improvement in goodness of fit seen in both simulation data and 24 h patient data. Therefore, this indicates the improved reliability of organ activity estimates obtained though the EQPlanar method.

Development of a micro electrochemical cell forin-situdeposition of63Ni for use in electron capture detector (ECD) in gas chromatography

AbstractIn this work, we describe a novel electrochemical approach to deposit63Ni coatings on the inner surface of a copper annular ring for its application as an ionization source in electron capture detector of gas chromatograph. A description of the electrolytic cell, the process of deposition and the experimental set up used, analysis of the nickel deposit and results are presented in this article. Sources containing ∼370 MBq (∼10 mCi)63Ni could be prepared. The quality of the prepared source in terms of nonleachability, uniform distribution of activity and stability that are necessary before application were evaluated and found to be highly satisfactory.

SU-E-I-174: Monte-Carlo-Based Scatter Analysis for Improving Image Reconstruction of PET/CT Systems

Purpose: Scatter analysis plays an important role in image reconstruction system. In Philips GEMINI TF system, the image reconstruction system is idle, waiting for scatter information from all five bed positions. To reduce the time used for image reconstruction, this study was to investigate whether three bed positions might be enough for image reconstruction by exploring the distribution of scatters using Monte Carlo simulations. Methods: A Geant4-based Monte Carlo tool—GATE is used to generate detected event lists and spectra, and to simulate the Philips Allegro PET/GEMINI systems. To mimic clinically realistic conditions, two 70-cm-long phantoms with a uniform activity in the FOV and different activity distributions outside the FOV are required to perform scatter proportion and scatter distribution measurements. The outside of the FOV (OFOV) is divided into two components: the proximal OFOV (POFOV), describing the two bed positions on either side of the FOV under consideration, and the distal OFOV (DOFOV), describing the two bed positions on either side of the POFOV. Including the FOV, all five bed positions are currently required for single scatter simulation (SSS). It is possible to use what we learn from an analysis based on uniform activity to apply scaling factors when we analyze POFOV data corresponding to real patient activity. To test this hypothesis, we compare two (uniform and non-uniform) activity distributions outside the FOV in our Monte Carlo simulations. Results: Most (at the 80± 5% level, depending on the scanner) of the scattered coincidences are from the activity in the FOV, POFOV contributes at the 20± 5% level), and the activity in the DOFOV makes a negligible contribution (1%) to scatter events. Conclusions: Based on our preliminary results, we showed that only three bed positions are necessary for image reconstructions, thereby speeding up the image reconstruction systems, while the image quality remains unchanged.

Studies on the adsorption of 125I on bromide coated silver rods for the preparation of 125I-seeds for brachytherapy applications

This paper describes a method for the preparation of 125I brachytherapy sources. The process consist of surface oxidation of a silver rods [0.5 mm (ϕ) × 3 mm (1)], formation of a thin silver bromide over layer and finally replacement of bromide ions by 125I− ions. The effect of various parameters such as 125I feed activity, iodide carrier concentration and reaction time were examined and optimized for maximum impregnation of 125I activity on the substrate. Sources containing 74–111 MBq (2–3 mCi) 125I on a silver matrix could be prepared and encapsulated in titanium capsules [0.8 mm (ϕ) × 4.75 mm (1)] using Nd: YAG laser. Quality assurance tests to ensure nonleachability, uniform distribution of activity and leak tightness that are necessary before application were evaluated.

A facile and novel process for the preparation of 147Pm source

This paper describes a novel method for the preparation of 147Pm sources for beta backscatter coating thickness gauge. The process relied on the creation of a porous reactive surface in a precisely selected region of a long cylindrical aluminum substrate by anodization at a current density of 15 mA/cm2 at 15 °C in 3 M H2SO4 for 2 h. The anodized region was impregnated with 37 MBq (1 mCi) of 147Pm activity by keeping in contact with the radioactive solution at pH 6.0 for 24 h. The active region was subsequently coated with a thin layer of polymer to prevent the dispersion of activity in use. The sources were submitted to quality control tests such as non-leachability, uniform distribution of activity and surface contamination.

On the application of electrochemical techniques for the preparation of 57Co source core, encapsulation and quality evaluation for radiometric assay of nuclear fuel rods

Abstract This paper describes an electrochemical method for the preparation of 57Co source to be used in quality evaluation of nuclear fuel rods. The electrolytic cell, the experimental set up used and the process of deposition are described. The effect of various parameters such as pH of the electrolyte, bath temperature, current density, content of cobalt in the bath, electrolyte volume in the cell and deposition time were investigated and optimized for maximum deposition. The texture and morphology of the electrodeposited samples were examined by X-ray diffraction (XRD), SEM and EDS analyses. Sources containing ∼370 MBq (10 mCi) 57Co on a circular copper foil of 4 mm diameter could be prepared and encapsulated in an aluminum capsule. Quality assurance tests performed to ensure non-leachability, uniform distribution of activity and stability of the sources gave satisfactory results.

Development of a 147Pm source for beta-backscatter thickness gauge applications

This paper describes a method for the preparation of (147)Pm sources, utilized in the determination of graphite coating thickness on the inner surface of the zircaloy cladding tube of nuclear fuels. (147)Pm was adsorbed on a limited surface area [1.5mm (ϕ)×2mm (l)] of a cylindrical aluminum rod [1.5mm (ϕ)×10mm (l)]. In brief, the selected tip area [1.5mm (ϕ)×2mm (l)] was anodized at a current density of 15mA/cm(2) at 15°C in 3M·H(2)SO(4) for 2h followed by immersion of this area in 10μL of (147)Pm solution containing 37MBq (1mCi) of activity at pH 6.0 for 24h. The radioactive area was subsequently covered with a thin layer of Polymethyl Methacrylate (PMMA) to prevent leaching of (147)Pm from the source. The quantity of incorporated (147)Pm activity was assayed in a calibrated ion chamber. Quality control tests were carried out to ensure nonleachability, uniform distribution of activity and stability of the sources.

A generic biokinetic model for Carbon-14

The generic biokinetic model currently recommended by the International Commission on Radiological Protection (ICRP) for the treatment of systemic radiocarbon assumes uniform distribution of activity in tissues and a biological half-time of 40 d. This model is intended to generate cautiously high estimates of dose per unit intake of C-14 and, in fact, generally predicts a much higher effective dose than systemic models that have been developed on the basis of biokinetic studies of specific carbon compounds. The simplistic model formulation precludes its application as a bioassay model or adjustment to fit case-specific bioassay data. This paper proposes a new generic biokinetic model for systemic radiocarbon that is less conservative than the current ICRP model but maintains sufficient conservatism to overestimate the effective dose coefficients generated by most radiocarbon-compound-specific models. The proposed model includes two systemic pools with different biological half-times representing an initial systemic form of absorbed radiocarbon, a submodel describing the behaviour of labelled carbon dioxide produced in vivo, and three excretion pathways: breath, urine and faeces. Generic excretion rates along each path are based on multi-phase excretion curves observed in experimental studies of radiocarbons. The generic model structure is designed so that the user may adjust the level of dosimetric conservatism to fit the information at hand and may adjust parameter values for consistency with subject-specific or site-specific bioassay data.

Regularized reconstruction in quantitative SPECT using CT side information from hybrid imaging

A penalized-likelihood (PL) SPECT reconstruction method using a modified regularizer that accounts for anatomical boundary side information was implemented to achieve accurate estimates of both the total target activity and the activity distribution within targets. In both simulations and experimental I-131 phantom studies, reconstructions from (1) penalized likelihood employing CT-side information-based regularization (PL-CT), (2) penalized likelihood with edge preserving regularization (no CT) and (3) penalized likelihood with conventional spatially invariant quadratic regularization (no CT) were compared with (4) ordered subset expectation maximization (OSEM), which is the iterative algorithm conventionally used in clinics for quantitative SPECT. Evaluations included phantom studies with perfect and imperfect side information and studies with uniform and non-uniform activity distributions in the target. For targets with uniform activity, the PL-CT images and profiles were closest to the ‘truth’, avoided the edge offshoots evident with OSEM and minimized the blurring across boundaries evident with regularization without CT information. Apart from visual comparison, reconstruction accuracy was evaluated using the bias and standard deviation (STD) of the total target activity estimate and the root mean square error (RMSE) of the activity distribution within the target. PL-CT reconstruction reduced both bias and RMSE compared with regularization without side information. When compared with unregularized OSEM, PL-CT reduced RMSE and STD while bias was comparable. For targets with non-uniform activity, these improvements with PL-CT were observed only when the change in activity was matched by a change in the anatomical image and the corresponding inner boundary was also used to control the regularization. In summary, the present work demonstrates the potential of using CT side information to obtain improved estimates of the activity distribution in targets without sacrificing the accuracy of total target activity estimation. The method is best suited for data acquired on hybrid systems where SPECT-CT misregistration is minimized. To demonstrate clinical application, the PL reconstruction with CT-based regularization was applied to data from a patient who underwent SPECT/CT imaging for tumor dosimetry following I-131 radioimmunotherapy.

Solutions to the TG-43 Geometry Function for Ring, Disk, Sphere, and Dome Sources

Purpose: A simple inverse square-law, IVS, calculation is sufficient for most brachytherapy calculations, particularly for distances far from the source. Closer to the source it becomes important to more accurately model the source geometry. The line source approximation is commonly used. This work provides solutions for the geometry function for several other interesting source geometries, including a ring, a disk, a sphere and a dome. Analytical solutions are presented, along with calculations for relevant clinical scenarios. Materials and Methods: TG-43 formalism incorporates a geometry function to isolate the inverse square-law component in dose calculations. The inverse-square law applies for radiation emitted outward radially from a point, where emitted radiation spreads out over the surface area of a sphere (4πr2) as distance from the source, r, increases. The amount of radiation passing through a given solid angle is inversely proportional to the square of the distance from the source. Hence the geometry function for a point source is simply 1/r2. The geometry function for more complicated source distributions may be calculated by integrating the contributions of many infinitesimal “point” sources. Traditional integration techniques are used to solve the geometry function for ring, disk, sphere, and dome source distributions. Sources are modeled as having uniform distribution of activity over the surface or volume. Coordinate system definitions are provided in Figure C. Results: Computation of the geometry function for ring, disk, and dome solutions provides an intuition for expected dose distributions. Figure A presents the geometry function along the transverse axis as a function of distance from the source: “Depth Dose” along transverse axis. For ring, disk, and sphere sources, distance = 0 corresponds to the center of the circle or sphere. For the dome source, distance = 0 corresponds to the apex of the dome. All distances in the plot are normalized by R (Figure C.). Dose falls off less rapidly for ring, disk, sphere, and dome sources than IVS. The dome result depends upon the ratio of the base of the dome and the radius of the sphere upon which the dome lies. Figure B presents the geometry function angular dependence for a 16-mm diameter eye plaque (dome) resting on a 24-mm diameter eye. Clinically relevant distances from the plaque are included. The geometry function decreases significantly as the measurement point rotates away from the transverse axis. The greatest change is observed for tissues nearest the plaque surface. Clinically this implies that, considering only geometric effects, the dose difference between the center of the plaque and the edge of the plaque, at fixed tissue depth, i.e. the penumbra, is sharpest near the plaque. Conclusions: We have obtained analytical solutions for several interesting source geometries. The solution for a dome of activity is particularly relevant for treatments using eye plaques, which ideally place a dome of activity distributed over a portion of the eye modeled as a sphere. These factors can be useful in simplified calculations using a spreadsheet, particularly for situations where IVS is an insufficient approximation.

Differences among Monte Carlo codes in the calculations of voxel values for radionuclide targeted therapy and analysis of their impact on absorbed dose evaluations

Several updated Monte Carlo (MC) codes are available to perform calculations of voxel S values for radionuclide targeted therapy. The aim of this work is to analyze the differences in the calculations obtained by different MC codes and their impact on absorbed dose evaluations performed by voxel dosimetry. Voxel S values for monoenergetic sources (electrons and photons) and different radionuclides (90Y, 131I, and 188Re) were calculated. Simulations were performed in soft tissue. Three general-purpose MC codes were employed for simulating radiation transport: MCNP4C, EGSnrc, and GEANT4. The data published by the MIRD Committee in Pamphlet No. 17, obtained with the EGS4 MC code, were also included in the comparisons. The impact of the differences (in terms of voxel S values) among the MC codes was also studied by convolution calculations of the absorbed dose in a volume of interest. For uniform activity distribution of a given radionuclide, dose calculations were performed on spherical and elliptical volumes, varying the mass from 1 to 500 g. For simulations with monochromatic sources, differences for self-irradiation voxel S values were mostly confined within 10% for both photons and electrons, but with electron energy less than 500 keV, the voxel S values referred to the first neighbor voxels showed large differences (up to 130%, with respect to EGSnrc) among the updated MC codes. For radionuclide simulations, noticeable differences arose in voxel S values, especially in the bremsstrahlung tails, or when a high contribution from electrons with energy of less than 500 keV is involved. In particular, for 90Y the updated codes showed a remarkable divergence in the bremsstrahlung region (up to about 90% in terms of voxel S values) with respect to the EGS4 code. Further, variations were observed up to about 30%, for small source-target voxel distances, when low-energy electrons cover an important part of the emission spectrum of the radionuclide (in our case, for 131I). For 90Y and 188Re, the differences among the various codes have a negligible impact (within few percents) on convolution calculations of the absorbed dose; thus either one of the MC programs is suitable to produce voxel S values for radionuclide targeted therapy dosimetry. However, if a low-energy beta-emitting radionuclide is considered, these differences can affect also dose depositions at small source-target voxel distances, leading to more conspicuous variations (about 9% for 1311) when calculating the absorbed dose in the volume of interest.

An electrochemical method for the preparation of 63Ni source for the calibration of thermoluminescence dosimeter (TLD)

A novel electrochemical approach for preparation of 63Ni sources for their application as check-light source for the calibration of thermo luminescence dosimeters (TLD) is described here. Required amount of 63Ni on a copper substrate could be deposited by optimizing the experimental parameters such as current density, time of deposition, pH of the electrolyte and nickel ion concentration in the bath. 63Ni sources of strength ∼3.7 MBq could be prepared by electrodeposition at constant current on the copper matrix. Quality assurance tests to ensure nonleachability, uniform distribution of activity and stability of the sources that are necessary before application were performed.

Bioevaluation studies of 32P incorporated mould brachytherapy sources for potential application in treatment of superficial tumors

To prepare 32P-based user-friendly mould brachytherpy sources for the treatment of superficial tumors. 32P as orthophosphoric acid was adsorbed on 15-25 mm (diameter) circular sheets of cellulose-based adsorbent paper to prepare sources containing approximately 37-74 MBq of 32P per cm of strip. The sources were immobilized between plastic sheets of 40 microm thickness. Autoradiography studies were carried out to determine the uniformity of 32P deposition in the source. Dosimetric evaluation of the sources was also carried out. Bioevaluation studies were carried out in C57BL6 mice bearing melanoma using 37-74 MBq sources. Cellulose-based sources containing 37-74 MBq of 32P per cm2 could be prepared from which no radioactivity leakage could be detected in water or saline. Autoradiography studies revealed 32P to be uniformly distributed in these sources. Dosimetric evaluation showed that the contact dose imparted was 10 Gy/h, sufficient for treatment of superficial tumors. In mice bearing melanoma, complete tumor regression could be achieved with two applications of 37-74 MBq sources, at an interval of 3 days. Histopathological examination of the skin tissue from the treated area proved the absence of tumor as compared with the controls. Preparation of P sources of various shapes and sizes (based on the tumor size) having uniform 32P activity distribution could be achieved. Efficacy of these sources in treating melanoma tumors could be established in the animal model.

Influence of Nonuniform Activity Distribution on Cellular Dosimetry

Dosimetry of nonuniformly distributed 210Po,67Cu, and 123I was evaluated for a single cell, modeled as a homogeneous unity-density sphere with a radius of 7.7 mum, which is typical of a B-cell lymphoma cell. A Visual Basic program was used to calculate S factors and radial absorbed dose-rate profiles for these radionuclides, taking into account their individual radiation energy spectra. The resulting absorbed doses were compared with those for uniform activity distributions of the respective radionuclides. It was shown that detailed radiation energy spectra are required for accurate cell-level dosimetry, especially for Auger-electron emitters. Nonuniform intracellular activity distributions do not affect the cell-to-cell S factor (i.e., S(C <-- C)) dramatically but greatly influence the cell-to-nucleus S factor (i.e., S(C <-- N)).

Active root distribution pattern of Hevea brasiliensis determined by radioassay of latex serum

The active root distribution pattern of mature rubber (Hevea brasiliensis Muell. Arg.) up to a lateral distance of 250 cm from the tree and to a soil depth of 90 cm was studied in an oxisol by employing 32P soil injection technique in Kerala, the state which accounts for 83% of rubber cultivation in India. The trees were aged 18 years and grown at a spacing of 4.9 × 4.9 m. The extent of absorption of applied 32P by the tree from various placements was assessed by radio assay of leaf and latex serum. Latex serum registered higher counts and variability was less compared to leaf indicating the suitability of latex serum as a potential source for radio assay for 32P studies in rubber. The results revealed that rubber is a surface feeder with 55% of the root activity confining to the top 10 cm of soil layer. Root activity declined with increasing depths and the concentration of physiologically active roots at 90 cm depth was only 6%. A more or less uniform distribution of root activity was noticed with respect to lateral distance indicating more extensive spread of lateral roots. Concentration of physiologically active roots in the surface layer suggests the possibility for competition under intercropped situation in mature plantations.

Geometric models in dosimetry of thyroid remnant mass

Absorbed dose to thyroid remnant tissue after 131I ablation becomes mass/size-dependent. This is a direct consequence of the small remnant size and radiation escape starts to be relevant. The self-absorbed fraction becomes mass/size-dependent. We have used Monte Carlo simulations to investigate the influence of the thyroid remnant shape upon the absorbed fraction calculation. Thyroid residue was modeled using spherical, cylindrical and elliptical shapes. Uniform beta activity distribution and unit density medium (water) within a remnant was assumed. For each of the geometrical models beta self-absorbed fraction (varphi(beta)) was calculated using Monte Carlo codes, while the mean absorbed dose per unit cumulated activity (S(beta)) was calculated using MIRD formalism. For spherical objects varphi(mono) for mean beta energy (E = 0.182 MeV) of 131I is always greater than varphi(beta) calculated for the complete beta spectrum. For spheres having diameters 2-6 mm and assumption varphi(beta) = 1, S(beta) is over-estimated by 11-37%. For cylinder and prolate spheroid of the same length and thickness, S(beta) for cylinder is 30% smaller because of the greater mass. Similarly, elliptical cylinder and general ellipsoid of the same length and the same perpendicular dimensions (width and breadth), have similar varphi(beta), while S(beta) for elliptical cylinder is correspondingly smaller. For accurate dosimetry of thyroid remnants having masses <1 g and chordal lengths <1 cm it is necessary to calculate varphi(beta) for the full beta spectrum, or S(beta) will be overestimated. The shape of the remnant may also be important since elongated non-spherical objects may also have varphi(beta) < 1.

Biodistribution and Radiation Dosimetry of the Synthetic Nonmetabolized Amino Acid Analogue Anti-18F-FACBC in Humans

The synthetic leucine amino acid analog anti-1-amino-3-(18)F-fluorocyclobutane-1-carboxylic acid (anti-(18)F-FACBC) is a recently developed ligand that permits the evaluation of the L-amino acid transport system. This study evaluated the whole-body radiation burden of anti-(18)F-FACBC in humans. Serial whole-body PET/CT scans of 6 healthy volunteers (3 male and 3 female) were acquired for 2 h after a bolus injection of anti-(18)F-FACBC (366 +/- 51 MBq). Organ-specific time-activity curves were extracted from the reconstructed data and integrated to evaluate the individual organ residence times. A uniform activity distribution was assumed in the body organs with urine collection after the study. Estimates of radiation burden to the human body were calculated on the basis of the recommendations of the MIRD committee. The updated dynamic bladder model was used to calculate dose to the bladder wall. All volunteers showed initially high uptake in the pancreas and liver, followed by rapid clearance. Skeletal muscle and bone marrow showed lower and prolonged uptake, with clearance dominated by the tracer half-life. The liver was the critical organ, with a mean absorbed dose of 52.2 microGy/MBq. The estimated effective dose was 14.1 microSv/MBq, representing less than 20% of the dose limit recommended by the Radioactive Drug Research Committee for a 370-MBq injection. Bladder excretion was low and initially observed 6 min after injection, well after peak tracer uptake in the body organs. The PET whole-body dosimetry estimates indicate that an approximately 370-MBq injection of anti-(18)F-FACBC yields good imaging and acceptable dosimetry. The nonmetabolized nature of this tracer is favorable for extraction of relevant physiologic parameters from kinetic models.