Peter Bloch | University of Pennsylvania (original) (raw)
Papers by Peter Bloch
Journal of Nuclear Medicine, Apr 1, 1978
The early detection of lymph-node metastases in malignant disorders is of the utmost importance i... more The early detection of lymph-node metastases in malignant disorders is of the utmost importance in the management of the patients. Unfortunately there are certain shortcomings in current roentgenographic and radiotracer techniques available for this purpose (1â€"3). The gamma imaging of the lymph nodes has been restricted thus far by the size of the particles introduced and the radiation dose delivered to the site of injection.
The Use of Computers in Radiation Therapy, 2000
Medical Physics, 1981
Mercury exposure in dental offices may represent a health hazard. Previous studies evaluated merc... more Mercury exposure in dental offices may represent a health hazard. Previous studies evaluated mercury exposure through blood, urine or hair analysis. The mercury content of body fluids in hair depends on the time since mercury exposure, mode of intake and its excretion, and sequestration by different tissues. Utilizing an x-ray fluorescence technique, the mercury burden in bone, liver, lung, spleen, and kidney was measured in vitro. The x-ray fluorescence, XRF, and chemical assays of the mercury content of these samples correlated. The XRF technique was used to assay the mercury content of tissues irradiated in vivo. It was found that the mercury signal arising at a depth in tissue was reduced as the thickness of overlying material increased. Thus, the XRF assay for tissues in vivo is confined to organs near the surface. The mercury content of the superficial layers of the head and wrist were determined in situ for a dental population. Concentrations as low as 20 micrograms/g could be detected with an exposure of 60 mR. Of the 298 dentists evaluated, 28% had greater than 20 micrograms/g of mercury in the head.
Phys Med Biol, 1974
ABSTRACT
The Compendium of continuing education in dentistry
The American journal of roentgenology, radium therapy, and nuclear medicine
Several approaches for impraving the detection of small tumors m the breast9 were explored. These... more Several approaches for impraving the detection of small tumors m the breast9 were explored. These included; (1) Perceptual feedback to decrease errors in missing tumors that are actually visible on the initial screening mammogram. The observers head-eye-position was recorded while viewing mammograms. It was found that false negative decisions in identifying a lesion was associated with prolonged dwell time. Visual feedback, obtained by placing a small circle on the image surrounding the suspicious region (as predicted by the gaze duration), enhanced the detectability or masses. (2) Computer processing of screening mammograms for detection of clusters of microcalcifications and parenchyma patterns associated with developing lesions. Preserving the high spatial resolution and wide latitude in the digitized mammogram was found important for computer aided detection of subtle microcalcifications. Elevated mammography density has been associated with an increased risk of developing breas...
Advances in X-Ray Analysis
The occupational exposure to uranium associated with milling and fabrication of depleted uranium ... more The occupational exposure to uranium associated with milling and fabrication of depleted uranium is presently assessed from bioassay of urine samples. The evaluation of the body-burden of uranium from urine analysis has many difficulties and uncertainties associated with accounting for the bio-transport of inhaled uranium particles from the lungs, to absorption in the blood and excretion through the kidneys. The chemical toxicity of uranium and other transuranic elements is not fully understood, partially because of the difficulty of assessing the body burden of these metals in-situ. The transuranic elements are known to be deposited and retained in bone. A non-invasive X-ray fluorescence technique has been developed to assay the depleted uranium in bones in-situ. The K-shell electrons in uranium, which have a binding energy of 115.6 keV, are excited by the 122 and 136 keV gamma rays from a Co-57 source. A liquid N{sub 2} cooled intrinsic Ge-detector is employed to measure the chara...
The Journal of the American Dental Association, 1982
Strahlentherapie. Sonderbände, 1981
Computerized radiology : official journal of the Computerized Tomography Society
The appropriate therapeutic modality for a patient with a malignancy depends on knowledge of the ... more The appropriate therapeutic modality for a patient with a malignancy depends on knowledge of the extent of the disease. If the disease is localized and suited for a course of conventional radiotherapy, delineation of the borders of the gross tumor is necessary for treatment planning. The proton nuclear magnetic resonance scan may be useful in precisely delineating the extent of the tumor due to large differences in the spin-lattice relaxation times between normal and malignant tissues. Proton NMR scanning can also be used to provide information on the relative hydrogen concentration of various tissues in situ. Knowledge of the hydrogen concentration is required to calculate the dose to an organ irradiated with a fast neutron beam.
Radiology, 1988
The quality of low-contrast portal radiographs for radiation therapy can be improved with electro... more The quality of low-contrast portal radiographs for radiation therapy can be improved with electronic contrast enhancement. After the image is copied digitally with a laser scanner microdensitometer into 4,096 gray-scale levels (12 bits) and 1,686 X 2,048 pixels, a special software package permits linear, logarithmic, exponential, or sigmoid transformations of the optical density. The precise representation of the portal image can then be interactively adjusted to emphasize the desired anatomy. Clinical examples demonstrate the value of the digital enhancement approach.
Three-Dimensional Machine Perception, 1981
ABSTRACT Three-dimensional surface contour information is important for selective patients requir... more ABSTRACT Three-dimensional surface contour information is important for selective patients requiring radiation therapy. The patient contour is used to calculate the radiation dose distribution within the irradiated volume. A Moire photographic contouring device has been constructed to obtain these surface contours. The device consists of two light sources to project a grid pattern on the skin of the patient, and a camera with Polaroid back to photograph the image of the interference pattern on the skin. The interference fringes, as well as the patient's surface, is recorded on the photograph. Tissue thickness can be determined within 2.5 mm. It takes only a few minutes to get the contouring photograph. In addition to using the surface contour data for calculations of dose distributions, it can also facilitate construction of tissue compensators.
Journal of Nuclear Medicine, Apr 1, 1978
The early detection of lymph-node metastases in malignant disorders is of the utmost importance i... more The early detection of lymph-node metastases in malignant disorders is of the utmost importance in the management of the patients. Unfortunately there are certain shortcomings in current roentgenographic and radiotracer techniques available for this purpose (1â€"3). The gamma imaging of the lymph nodes has been restricted thus far by the size of the particles introduced and the radiation dose delivered to the site of injection.
The Use of Computers in Radiation Therapy, 2000
Medical Physics, 1981
Mercury exposure in dental offices may represent a health hazard. Previous studies evaluated merc... more Mercury exposure in dental offices may represent a health hazard. Previous studies evaluated mercury exposure through blood, urine or hair analysis. The mercury content of body fluids in hair depends on the time since mercury exposure, mode of intake and its excretion, and sequestration by different tissues. Utilizing an x-ray fluorescence technique, the mercury burden in bone, liver, lung, spleen, and kidney was measured in vitro. The x-ray fluorescence, XRF, and chemical assays of the mercury content of these samples correlated. The XRF technique was used to assay the mercury content of tissues irradiated in vivo. It was found that the mercury signal arising at a depth in tissue was reduced as the thickness of overlying material increased. Thus, the XRF assay for tissues in vivo is confined to organs near the surface. The mercury content of the superficial layers of the head and wrist were determined in situ for a dental population. Concentrations as low as 20 micrograms/g could be detected with an exposure of 60 mR. Of the 298 dentists evaluated, 28% had greater than 20 micrograms/g of mercury in the head.
Phys Med Biol, 1974
ABSTRACT
The Compendium of continuing education in dentistry
The American journal of roentgenology, radium therapy, and nuclear medicine
Several approaches for impraving the detection of small tumors m the breast9 were explored. These... more Several approaches for impraving the detection of small tumors m the breast9 were explored. These included; (1) Perceptual feedback to decrease errors in missing tumors that are actually visible on the initial screening mammogram. The observers head-eye-position was recorded while viewing mammograms. It was found that false negative decisions in identifying a lesion was associated with prolonged dwell time. Visual feedback, obtained by placing a small circle on the image surrounding the suspicious region (as predicted by the gaze duration), enhanced the detectability or masses. (2) Computer processing of screening mammograms for detection of clusters of microcalcifications and parenchyma patterns associated with developing lesions. Preserving the high spatial resolution and wide latitude in the digitized mammogram was found important for computer aided detection of subtle microcalcifications. Elevated mammography density has been associated with an increased risk of developing breas...
Advances in X-Ray Analysis
The occupational exposure to uranium associated with milling and fabrication of depleted uranium ... more The occupational exposure to uranium associated with milling and fabrication of depleted uranium is presently assessed from bioassay of urine samples. The evaluation of the body-burden of uranium from urine analysis has many difficulties and uncertainties associated with accounting for the bio-transport of inhaled uranium particles from the lungs, to absorption in the blood and excretion through the kidneys. The chemical toxicity of uranium and other transuranic elements is not fully understood, partially because of the difficulty of assessing the body burden of these metals in-situ. The transuranic elements are known to be deposited and retained in bone. A non-invasive X-ray fluorescence technique has been developed to assay the depleted uranium in bones in-situ. The K-shell electrons in uranium, which have a binding energy of 115.6 keV, are excited by the 122 and 136 keV gamma rays from a Co-57 source. A liquid N{sub 2} cooled intrinsic Ge-detector is employed to measure the chara...
The Journal of the American Dental Association, 1982
Strahlentherapie. Sonderbände, 1981
Computerized radiology : official journal of the Computerized Tomography Society
The appropriate therapeutic modality for a patient with a malignancy depends on knowledge of the ... more The appropriate therapeutic modality for a patient with a malignancy depends on knowledge of the extent of the disease. If the disease is localized and suited for a course of conventional radiotherapy, delineation of the borders of the gross tumor is necessary for treatment planning. The proton nuclear magnetic resonance scan may be useful in precisely delineating the extent of the tumor due to large differences in the spin-lattice relaxation times between normal and malignant tissues. Proton NMR scanning can also be used to provide information on the relative hydrogen concentration of various tissues in situ. Knowledge of the hydrogen concentration is required to calculate the dose to an organ irradiated with a fast neutron beam.
Radiology, 1988
The quality of low-contrast portal radiographs for radiation therapy can be improved with electro... more The quality of low-contrast portal radiographs for radiation therapy can be improved with electronic contrast enhancement. After the image is copied digitally with a laser scanner microdensitometer into 4,096 gray-scale levels (12 bits) and 1,686 X 2,048 pixels, a special software package permits linear, logarithmic, exponential, or sigmoid transformations of the optical density. The precise representation of the portal image can then be interactively adjusted to emphasize the desired anatomy. Clinical examples demonstrate the value of the digital enhancement approach.
Three-Dimensional Machine Perception, 1981
ABSTRACT Three-dimensional surface contour information is important for selective patients requir... more ABSTRACT Three-dimensional surface contour information is important for selective patients requiring radiation therapy. The patient contour is used to calculate the radiation dose distribution within the irradiated volume. A Moire photographic contouring device has been constructed to obtain these surface contours. The device consists of two light sources to project a grid pattern on the skin of the patient, and a camera with Polaroid back to photograph the image of the interference pattern on the skin. The interference fringes, as well as the patient's surface, is recorded on the photograph. Tissue thickness can be determined within 2.5 mm. It takes only a few minutes to get the contouring photograph. In addition to using the surface contour data for calculations of dose distributions, it can also facilitate construction of tissue compensators.