Synthesis and evaluation of [18F]1-amino-3-fluorocyclobutane-1-carboxylic acid to image brain tumors. (1/3048)

We have developed a new tumor-avid amino acid, 1-amino-3-fluorocyclobutane-1-carboxylic acid (FACBC), labeled with 18F for nuclear medicine imaging. METHODS: [18F]FACBC was prepared with high specific activity (no carrier added [NCA]) and was evaluated for its potential in tumor localization. A comparative study was performed for [18F]FACBC and [18F]2-fluorodeoxyglucose (FDG) in which the uptake of each agent in 9L gliosarcoma (implanted intracerebrally in Fisher 344 rats) was measured. In addition, the first human PET study of [18F]FACBC was performed on a patient with residual glioblastoma multiforme. Quantitative brain images of the patient were obtained by using a Siemens 921 47-slice PET imaging system. RESULTS: In the rat brain, the initial level of radioactivity accumulation after injection of [18F]FACBC was low (0.11 percentage injected dose per gram [%ID/g]) at 5 min and increased slightly to 0.26 %ID/g at 60 min. The tumor uptake exhibited a maximum at 60 min (1.72 %ID/g), resulting in a tumor-to-brain ratio increase of 5.58 at 5 min to 6.61 at 60 min. In the patient, the uptake of [18F]FACBC in the tumor exhibited a maximum concentration of 146 nCi/mL at 35 min after injection. The uptake of radioactivity in the normal brain tissue was low, 21 nCi/mL at 15 min after injection, and gradually increased to 29 nCi/mL at 60 min after injection. The ratio of tumor to normal tissue was 6 at 20 min after injection. The [18F]FACBC PET scan showed intense uptake in the left frontal region of the brain. CONCLUSION: The amino acid FACBC can be radiofluorinated for clinical use. [18F]FACBC is a potential PET tracer for tumor imaging.  (+info)

MIRD pamphlet no. 16: Techniques for quantitative radiopharmaceutical biodistribution data acquisition and analysis for use in human radiation dose estimates. (2/3048)

This report describes recommended techniques for radiopharmaceutical biodistribution data acquisition and analysis in human subjects to estimate radiation absorbed dose using the Medical Internal Radiation Dose (MIRD) schema. The document has been prepared in a format to address two audiences: individuals with a primary interest in designing clinical trials who are not experts in dosimetry and individuals with extensive experience with dosimetry-based protocols and calculational methodology. For the first group, the general concepts involved in biodistribution data acquisition are presented, with guidance provided for the number of measurements (data points) required. For those with expertise in dosimetry, highlighted sections, examples and appendices have been included to provide calculational details, as well as references, for the techniques involved. This document is intended also to serve as a guide for the investigator in choosing the appropriate methodologies when acquiring and preparing product data for review by national regulatory agencies. The emphasis is on planar imaging techniques commonly available in most nuclear medicine departments and laboratories. The measurement of the biodistribution of radiopharmaceuticals is an important aspect in calculating absorbed dose from internally deposited radionuclides. Three phases are presented: data collection, data analysis and data processing. In the first phase, data collection, the identification of source regions, the determination of their appropriate temporal sampling and the acquisition of data are discussed. In the second phase, quantitative measurement techniques involving imaging by planar scintillation camera, SPECT and PET for the calculation of activity in source regions as a function of time are discussed. In addition, nonimaging measurement techniques, including external radiation monitoring, tissue-sample counting (blood and biopsy) and excreta counting are also considered. The third phase, data processing, involves curve-fitting techniques to integrate the source time-activity curves (determining the area under these curves). For some applications, compartmental modeling procedures may be used. Last, appendices are included that provide a table of symbols and definitions, a checklist for study protocol design, example formats for quantitative imaging protocols, temporal sampling error analysis techniques and selected calculational examples. The utilization of the presented approach should aid in the standardization of protocol design for collecting kinetic data and in the calculation of absorbed dose estimates.  (+info)

The effect of the antiscatter grid on full-field digital mammography phantom images. (3/3048)

Computer Analysis of Mammography Phantom Images (CAMPI) is a method for making quantitative measurements of image quality. This article reports on a recent application of this method to a prototype full-field digital mammography (FFDM) machine. Images of a modified ACR phantom were acquired on the General Electric Diagnostic Molybdenum Rhodium (GE-DMR) FFDM machine at a number of x-ray techniques, both with and without the scatter reduction grid. The techniques were chosen so that one had sets of grid and non-grid images with matched doses (200 mrads) and matched gray-scale values (1500). A third set was acquired at constant 26 kVp and varying mAs for both grid conditions. Analyses of the images yielded signal-to-noise-ratio (SNR), contrast and noise corresponding to each target object, and a non-uniformity measure. The results showed that under conditions of equal gray-scale value the grid images were markedly superior, albeit at higher doses than the non-grid images. Under constant dose conditions, the non-grid images were slightly superior in SNR (7%) but markedly less uniform (60%). Overall, the grid images had substantially greater contrast and superior image uniformity. These conclusions applied to the whole kVp range studied for the Mo-Mo target filter combination and 4 cm of breast equivalent material of average composition. These results suggest that use of the non-grid technique in digital mammography with the GE-DMR-FFDM unit, is presently not warranted. With improved uniformity correction procedure, this conclusion would change and one should be able to realize a 14% reduction in patient dose at the same SNR by using a non-grid technique.  (+info)

Computed radiography dual energy subtraction: performance evaluation when detecting low-contrast lung nodules in an anthropomorphic phantom. (4/3048)

A dedicated chest computed radiography (CR) system has an option of energy subtraction (ES) acquisition. Two imaging plates, rather than one, are separated by a copper filter to give a high-energy and low-energy image. This study compares the diagnostic accuracy of conventional computed radiography to that of ES obtained with two radiographic techniques. One soft tissue only image was obtained at the conventional CR technique (s = 254) and the second was obtained at twice the radiation exposure (s = 131) to reduce noise. An anthropomorphic phantom with superimposed low-contrast lung nodules was imaged 53 times for each radiographic technique. Fifteen images had no nodules; 38 images had a total of 90 nodules placed on the phantom. Three chest radiologists read the three sets of images in a receiver operating characteristic (ROC) study. Significant differences in Az were only found between (1) the higher exposure energy subtracted images and the conventional dose energy subtracted images (P = .095, 90% confidence), and (2) the conventional CR and the energy subtracted image obtained at the same technique (P = .024, 98% confidence). As a result of this study, energy subtracted images cannot be substituted for conventional CR images when detecting low-contrast nodules, even when twice the exposure is used to obtain them.  (+info)

3D angiography. Clinical interest. First applications in interventional neuroradiology. (5/3048)

3D angiography is a true technical revolution that allows improvement in the quality and safety of diagnostic and endovascular treatment procedures. 3D angiography images are obtained by reconstruction of a rotational angiography acquisition done on a C-arm (GE Medical Systems) spinning at 40 degrees per second. The carotid or vertebral selective injection of a total of 15 ml of non-ionic contrast media at 3 ml/sec over 5 seconds allows the selection of the "arterial phase". Four hundred sixty 3D angiographic studies were performed from December 1996 to September 1998 on 260 patients and have been analyzed in MIP (Maximum Intensity Projection) and SSD (Shaded Surface Display) views. The exploration of intracranial aneurysms is simplified and only requires, for each vascular axis, a biplane PA and Lateral run followed by a single rotational angiography run. The 3D angiography image is available on the workstation's screen (Advantage Workstation 3.1, GE Medical Systems) in less than 10 minutes after the acquisition of the rotational run. It therefore allows one to analyze, during the intervention, the aneurysm's angioarchitecture, in particular the neck, and select the best therapeutic technique. When endovascular treatment is the best indication, 3D angiography allows one to define the optimal angle of view and accurately select the microcoils dimensions. 3D angiography replaces the multiple oblique views that used to be required to analyze the complex aneurysms and therefore allows a reduction of the total contrast medium quantity, the patient X-ray dose and the length of the intervention time which is a safety factor. Also, in particular for complex cases, it brings additional elements complementing the results of standard 2D DSA and rotational angiograms. In the cervical vascular pathology, 3D angiography allows for a better assessment of the stenosis level and of dissection lesions. Our current research activities focus on the matching without stereotactic frame between 3D X-ray angiography and volumetric MR acquisition, which should allow us to improve the treatment of intracerebral arterio-venous malformations (AVMs).  (+info)

Biodistribution, radiation dosimetry and pharmacokinetics of 111In-antimyosin in idiopathic inflammatory myopathies. (6/3048)

In view of the established role of 111In-antimyosin in the detection of heart muscle pathology, radiation dose estimates were made for this substance. Biodistribution and biokinetic data were obtained from our studies, which failed to show abnormal uptake of 111In-antimyosin in localized sites of skeletal muscle involvement in patients with idiopathic inflammatory myopathies. METHODS: After intravenous administration of 74 MBq (2 mCi) 111In-antimyosin, gamma camera scintigraphy was performed in 12 adult patients with inflammatory muscle disease and in 2 control patients. Six whole-body scans were performed over 72 h, and uptake of 111In-antimyosin in organs was quantified using an attenuation-corrected conjugate counting method. Residence times in source organs were used with MIRDOSE software to obtain radiation dose estimates. Pharmacokinetic parameters were derived from serial whole-blood and plasma 111In concentrations. RESULTS: The tracer cleared slowly from the circulation, and highest organ uptakes were found in the marrow and liver; kidneys showed the highest concentrations. Uptake was also evident in spleen, the facial image and male genitalia. CONCLUSION: For a typical administered activity of 74 MBq 111In-antimyosin, the kidneys receive the highest dose (58 mSv), and the effective dose is 11 mSv. Radioactivity was cleared from plasma at an average rate of 136 mL/h, and the mean steady-state distribution was approximately 5 L plasma.  (+info)

MIRD Pamphlet No. 15: Radionuclide S values in a revised dosimetric model of the adult head and brain. Medical Internal Radiation Dose. (7/3048)

Current dosimetric models of the brain and head lack the anatomic detail needed to provide the physical data necessary for suborgan brain dosimetry. During the last decade, several new radiopharmaceuticals have been introduced for brain imaging. The marked differences of these tracers in tissue specificity within the brain and their increasing use for diagnostic studies support the need for a more anthropomorphic model of the human brain and head for use in estimating regional absorbed dose within the brain and its adjacent structures. METHODS: A new brain model has been developed that includes eight subregions: the caudate nuclei, the cerebellum, the cerebral cortex, the lateral ventricles, the lentiform nuclei, the thalami, the third ventricle and the white matter. This brain model is incorporated within a total revision of the head model presented in MIRD Pamphlet No. 5 Revised. Modifications include the addition of the eyes, the teeth, the mandible, an upper facial region, a neck region and the cerebrospinal fluid within both the cranial and spinal regions. RESULTS: Absorbed fractions of energy for photon and electron sources located in 14 source regions within the new model were calculated using the EGS4 Monte Carlo radiation transport code for particles in the energy range 10 keV-4 MeV. These absorbed fractions were then used along with radionuclide decay data to generate S values for 24 radionuclides that are used in clinical or investigational studies of the brain, 12 radionuclides that localize within the cranium and spinal skeleton and 12 radionuclides that selectively localize in the thyroid gland. CONCLUSION: A substantial revision to the dosimetric model of the adult head and brain originally published in MIRD Pamphlet No. 5 Revised is presented. This revision supports suborgan brain dosimetry for a variety of radiopharmaceuticals used in neuroimaging. Dose calculations for the neuroimaging agent 1231-tropane provide an example of the new model and yield mean brain doses that are consistent with published values. However, the absorbed dose to subregions within the brain such as the caudate and lentiform nuclei may exceed the average brain dose by a factor of up to 5.  (+info)

Dose-related effects of single focal irradiation in the medial temporal lobe structures in rats--magnetic resonance imaging and histological study. (8/3048)

The dose-related effects of single focal irradiation on the medial temporal lobe in rats were investigated by sequential magnetic resonance imaging and histological examination. Irradiation of 200 Gy as a maximum dose using 4 mm collimators with a gamma unit created an area of necrosis consistently at the target site within 2 weeks after irradiation. Irradiation of 100 Gy caused necrosis within 10 weeks, and 75 Gy caused necrosis within one year. Irradiation of less than 50 Gy did not induce necrosis consistently, although a restricted area of necrosis was created in the medial temporal structures including the intraparenchymal portion of the optic tract. 75 Gy may be the optimum dose for creating necrosis consistently in the medial temporal lobe structures. However, careful dose planning considering both dose-time and dose-volume relationships in necrosis development is necessary to avoid injury to vulnerable neural structures such as the optic tract when applying radiosurgical techniques to treat functional brain disorders in medial temporal lobe structures such as temporal lobe epilepsy.  (+info)