The use of intraoperative devices requires compact detectors and portable imaging systems.  In order to image the biodistribution of radiolabeled monoclonal antibodies at surgery, Radiation Monitoring Devices (RMD) developed a small (3" diameter) scintillation camera using a Hamamatsu position sensitive photomultiplier tube (psPMT) coupled to a collimated NaI(Tl) scintillator.  The portable data acquisition system we developed and used to collect and display images was coupled to a Macintosh IIfx computer via CAMAC-based nuclear electronics.  The system software has been written in LabView 2.2 (National Instruments Corp.).  The design of the system is presented along with an evaluation of its performance in planar and tomographic image reconstruction.  Software for data acquisition, planar and tomographic image analysis and display was written entirely in LabView 2.2.

An investigation was performed of the changes in image quality and patient dose as a result of increasing filtration for fluoroscopy performed under automatic brightness control.  Filtration was added either at the x-ray tube housing (i.e., scatter-free geometry) or adjacent to a tissue equivalent phantom simulating the patient (i.e., with-scatter geometry).  Patient doses were expressed in terms of the total energy imparted to patients simulated by either a 10 cm (i.e., pediatric) or 20 cm (i.e., adult) acrylic phantoms.  Changes in image quality were determined by measuring the relative visibility of circular disks in a Leeds Test Object 10 contrast-detail phantom.  In the scatter-free geometry, the addition of 4 mm Al filtration reduced the energy imparted by 27% (10 cm phantom) and 20% (20 cm phantom).   In the with-scatter geometry, the corresponding reductions in energy imparted were 17% and 9% for the 10 and 20 cm phantoms, respectively.  The visibility of low contrast disks generally decreased as the thickness of the added aluminum increased but the location of the added Al (i.e., with-scatter or scatter-free geometry) had no significant effect on the resultant image quality.  These results demonstrate that the use of patient support pads with a thickness of about 4 mm Al will generally have an adverse impact on fluoroscopic image quality and result in modest reductions (about 10%) of adult patient doses.

Energy imparted is a measure of the total ionizing energy deposited in the patient during a radiologic examination and may be used to quantify the patient dose in diagnostic radiology.  Values of the energy imparted per unit exposure-area product, w(z), absorbed by a semi-infinite water phantom with a thickness z, were computed for x-ray spectra with peak x-ray tube voltages ranging from 50-140 kV and with added filtration, ranging from 1- 6 mm aluminum.  For a given phantom thickness and peak x-ray tube voltage, the energy imparted was found to be directly proportional to the x-ray beam half-value layer (HVL) expressed in millimeters of aluminum.  Values of w(z) were generated for constant waveform x-ray tube voltages and an anode angle of 12°, and were fitted to the expression w(z)=a x HVL + b.   Fitted a and b parameters are provided which permit the energy imparted to be determined for any combination of tube voltage, half-value layer, and phantom thickness from the product of the entrance skin exposure (free-in-air) and the corresponding x-ray beam area.  The results obtained using our method for calculating energy imparted were compared with values of energy imparted determined using Monte Carlo techniques and anthropomorphic phantoms for a range of diagnostic examinations.  At 60, 80 and 120 kV, absolute values of energy imparted obtained using our method differed by 8%, 10% and 12% respectively, from the corresponding results of Monte Carlo computations obtained for an anthropomorphic phantom.  The method described in this paper permits a simple determination of energy imparted for any type of diagnostic x-ray examination which may be used to compare the radiologic risks from differing types of x-ray examinations, optimize imaging techniques with respect to the patient dose, or estimate the patient effective dose equivalent.

PURPOSE: To assess the clinical performance and usefulness of an on-line patient exposure meter installed on a neuroradiologic biplane imaging system.

MATERIALS AND METHODS: A commercial on-line patient exposure meter was installed on each plane of a biplane neuroradiologic imaging system.  The meter computed skin exposures on the basis of selected technique factors (tube potential and current) and information about patient location relative to the x-ray tube.   Simulations were performed to measure the system accuracy with an angiographic anthropomorphic head phantom with the skin exposures measured with an ionization chamber.   Skin doses were computed for 114 consecutive patients who underwent diagnostic and interventional neuroradiologic procedures.

RESULTS: Agreement between measured and computed skin exposures in fluoroscopy, plain radiography, and digital imaging was generally within 5% of the true skin dose.  For all fluoroscopic and radiographic procedures, total median skin doses were 1.20 and 0.64 Gy for the frontal and lateral planes, respectively.  in both planes, patient skin doses resulted primarily from digital subtraction angiographic acquisitions.  In 29 (25%) patients, the skin dose exceeded 2.00 Gy, but no radiation-induced deterministic effects were observed.

CONCLUSIONS: An on-line patient exposure meter can provide accurate radiation skin dose data in patients undergoing diagnostic and therapeutic neuroradiologic procedures

The patient effective dose, E, is an indicator of the stochastic radiation risk associated with radiographic or fluoroscopic x-ray examinations.   Determining effective doses for radiologic examinations by measurement or calculation is generally very difficult.  By contrast, the energy imparted, e, to the patient may be obtained from the x-ray exposure-area product incident on the patient.  As energy imparted is approximately proportional to the effective dose for any given x-ray radiographic view, the availability of E/e ratios for common radiographic projections provides a convenient way for estimating effective doses.   Ratios of E/e were obtained for 68 projections using E and e values obtained from published dosimetry data computed using Monte Carlo techniques on an adult anthropomorphic phantom.  The average E/e ratio for the 68 projections in adults was 17.8 ± 1.4 mSv/J whereas uniform whole body irradiation corresponds to 14.1 mSv/J.  The major determinant of E/e ratios was the projection employed (body region irradiated and x-ray beam orientation) whereas the tube potential and beam filtration were of secondary importance.  Adult E/e ratios may also be used to obtain effective doses to pediatric patients undergoing x-ray examinations by application of a correction factor based on the patient mass.

The energy imparted, e, to a patient undergoing an extremity x-ray examination may be obtained from the dose-area product incident on the patient.   Values of energy imparted can be subsequently converted into the corresponding effective dose, E, using an extremity specific E/e ratio.   In this study, an E/e ratio of 3.0 mSv/J was used to convert values of energy imparted into the corresponding upper limit of adult effective doses for all types of extremity examinations.  A modification factor, based on the patient mass, was employed to determine the corresponding extremity effective doses to pediatric patients undergoing extremity examinations.  Representative clinical technique factors for six common extremity examinations (hand, forearm, elbow, ankle, tibia/fibula, knee) were used to determine the dose-area product and the corresponding values of energy imparted.  For adult extremity x-ray examinations, values of energy imparted ranged from 55 µJ to 920 µJ, with the energy imparted to 1-year-old patients being a factor of about 20 lower.  Upper limits of effective doses for adult extremity x-ray examinations ranged from 0.17 to 2.7 µSv, whereas the corresponding doses to 1-year-old patients were about a factor of three lower.

PURPOSE: To measure viewbox luminance values in a teaching hospital, and to investigate the importance of viewbox luminance and viewing conditions on low contrast detection performance.

MATERIALS AND METHODS: The luminance values of 632 viewbox panels in a teaching hospital were obtained using a calibrated meter.  Radiographic images of a mammography contrast-detail phantom were viewed on viewboxes with luminance values ranging from 860 nit to 3300 nit.  Twelve radiologists reported the number of contrast detail disks for each size (0.3 mm to 7 mm diameter) that were deemed to be visible for films with optical densities ranging from 1.0 to 2.6.  Radiologist performance in reading low contrast phantom images was also studied as a function of room illuminance and image masking.

RESULTS: The median luminance value was 1700 nit with 25 and 75 percentile values of 1450 and 2150 nit, respectively.  In general, low contrast visibility was independent of viewbox luminance irrespective of film density or disk diameter.  Low contrast visibility deteriorated with removal of masking around the image as well as when images were read in normal room lighting.  The greatest deterioration in performance was observed at the highest film densities and the smallest size disks.

CONCLUSIONS: Detection of low contrast features in radiographs is relatively independent of viewbox luminance, but is significantly degraded by the presence of stray light and by increased room illuminance.

The purpose of the study is to compare computed tomography optical imaging with traditional breast imaging techniques.  Images produced by a computed tomography laser mammography (CTLM™) scanner are compared with images obtained from mammography, and in some cases ultrasound and/or magnetic resonance imaging (MRI). During the CTLM procedure, a near infrared laser irradiates the breast and an array of photodiodes detectors records light scattered through the breast tissue. The laser and detectors rotate synchronously around the breast to acquire a series of slice data along the coronal plane.  The procedure is performed without any breast compression or optical matching fluid. Cross-sectional slices of the breast are produced using a reconstruction algorithm. Reconstruction based on the diffusion theory is used to produce cross-sectional slices of the breast. Multiple slice images are combined to produce a three-dimensional volumetric array of the imaged breast.  This array is used to derive axial and sagittal images of the breast corresponding to cranio-caudal and medio-lateral images used in mammography. Over 200 women and 3 men have been scanned in clinical trials. The most obvious features seen in images produced by the optical tomography scanner are vascularization and significant lesions. Breast features caused by fibrocystic changes and cysts are less obvious. Breast density does not appear to be a significant factor in the quality of the image. We see correlation of the optical image structure with that seen with traditional breast imaging techniques.  Further testing is being conducted to explore the sensitivity and specificity of optical tomography of the breast.

Digital subtraction angiography (DSA) images were obtained of a phantom containing 1 mm diameter vessels.  The iodine concentrations ranged from 5 to 50 mg/cc, which permitted the determination of the detection threshold concentration of iodine.  The source to image receptor distance was 105 cm, and image magnification was varied between 1.15 and 2.0.  One experiment was performed at an input exposure of 1 mGy per frame, and a second experiment was performed at 4 mGy per frame.  Surface (skin) doses were measured using an ionization chamber, and the corresponding values of energy imparted were determined from the exposure-area product.  Increasing the radiation exposure by a factor of four reduced the threshold iodine concentration by ~30%.  The average detection threshold iodine concentration for a magnification of 1.15 was 13.6 mg/cc.  Detection performance improved linearly with magnification, with an average value of 7.4 mg/cc at a magnification of 2.0.  Values of energy imparted were essentially independent of geometric magnification, whereas surface doses increased by a factor of four when geometric magnification was increased from 1.15 to 2.0.  Magnification offers improved image performance at no additional patient risk provided that surface doses do not exceed the dose threshold for deterministic effects such as skin burns and epilation.

We investigated the radiation doses to 149 adult patients who underwent interventional neuroradiologic procedures, including 132 patients who had diagnostic imaging examinations and the remaining 17 patients who had therapeutic procedures.  All procedures were performed on a biplane imaging system capable of performing fluoroscopy and digital subtraction angiography (DSA) imaging.  The x-ray imaging system has a commercial patient dosimetry system which computes surface (skin) doses based on the selected radiographic technique factors in both radiographic and fluoroscopic imaging modes.  For each patient, an assessment was made of the maximum surface dose received during the procedure, which is a predictor of the possibility of inducing deterministic effects.  Knowledge of the surface doses, beam quality and x-ray cross sectional area permitted the total energy imparted to the patients to be determined.  We computed the corresponding effective dose to each patient, which is an estimate of their stochastic radiation risk, using projection specific effective dose to energy imparted ratios. In general, doses for the lateral plane were much lower than those observed for the frontal plane.  For diagnostic imaging examinations, the median surface dose for the frontal plane was 1.3 Gy, with a maximum surface dose of 5.1 Gy.  For therapeutic procedures, the median surface dose for the frontal plane was 2.8 Gy with a maximum surface dose of 5.0 Gy.  In interventional neuroradiology, surface doses could result in the induction of deterministic effects.  The median energy absorbed was 1.77 J during fluoroscopy, and 4.30 J for radiographic imaging, showing that most of the patient exposure to radiation results from DSA imaging.  For diagnostic imaging examinations, the median patient effective dose was 22 mSv, with a maximum of 102 mSv.  For therapeutic procedures, the median patient effective dose was 51 mSv, with a maximum of 97 mSv.  Patient effective doses in interventional neuroradiology are much higher than those of other common types of diagnostic procedures, which employ ionizing radiation.

We investigated how varying the x-ray tube voltage and image receptor input exposure affected image quality and radiation doses in interventional neuroradiologic imaging.  Digital subtraction angiography (DSA) images were obtained of a phantom with 1 mm diameter vessels containing iodine at concentrations between 4.5 and 50 mg/cc.  The detection threshold concentration of iodine was determined by inspecting DSA images obtained at a range of x-ray tube voltages and input exposure levels.  Surface doses were generated using measured x-ray tube output data, and the corresponding values of energy imparted were determined using the exposure-area product incident on the phantom.  In one series of experiments, the air-kerma at the image intensifier (X) was varied between 0.44 mGy per frame and 8.8 mGy per frame at a constant x-ray tube voltage of 70 kVp.  In a second series of experiments, the kVp was varied between 50 and 100 kVp, and the mAs adjusted to maintain a constant exposure level at the image intensifier input surface.  At a constant x-ray tube voltage, the surface dose and energy imparted were directly proportional to the input exposure per frame used to acquire the DSA images.  Below 2.2 mGy per frame, the threshold iodine concentration was found to be proportional to X^-0.59, in reasonable agreement with the theoretical prediction for a quantum noise limited imaging system.  Above 2.2 mGy per frame, however, the threshold iodine concentration was proportional to X^-0.27, indicating that increasing the input exposure above this value will only achieve modest improvements in image quality.  At a constant image intensifier input exposure level, increasing the x-ray tube voltage from 50 kVp to 100 kVp reduced the surface dose by a factor of 6.1, and energy imparted by a factor of 3.5.  The detection threshold iodine concentration was found to be proportional to kVpⁿ, where n was 2.1 at 1.1 mGy per frame, and 1.6 at 3.9 mGy per frame.  Improvements in DSA imaging performance are best achieved by reducing the x-ray tube voltage rather than increasing the exposure level, since this will generally minimize patient doses.

The Department of Defense (DOD) spends approximately $170 billion on 15,000,000 contracts each year. In these contracts, the DOD uses military specifications (milspecs) to describe the products being purchased.  Milspecs have recently come under fire from Congress for being inefficient, costly, and wasteful.  The DOD was chastised by Congress for using milspecs that contained incorrect data, which led to exorbitant expenditures on such items as a $640 toilet seat and $7400 coffeepot.

The Manufacturing Studies Board has commissioned this report to study the use of milspecs and some of the problems associated with milspecs in order to help them develop a defense manufacturing strategy for the Under Secretary of Defense (Acquisition), John A. Betti.   To begin the study, an investigation into the use of milspecs within the Defense Acquisition Process was necessary.  This background information was crucial in evaluating the problems associated with the DOD's use of military and commercial specifications.

Upon investigating how milspecs are used within the Defense Acquisition Process, it was found that milspecs are blamed for being too long and complicated, and for containing obsolete technology.  In reference to their complexity, milspecs, by their nature, are technical documents which describe the products the DOD procures.  Contractors and DOD engineers who actually use milspecs usually have no problem understanding the technical language used.  There are, however, instances where milspecs can be overly complicated due to the inexperience of new writers.

In addition to being too complicated, milspecs in rapidly changing fields such as semiconductors and computer software have been criticized for containing obsolete technology.  Even though milspecs are reviewed every five years, they can be updated with Engineering Change Proposals.

Another problem occurs when writers do not examine all the specifications they reference to ensure that they are updated and relevant to the product.  Due to time constrains, the writers often cannot examine all the references.  Therefore, there may be some outdated or unnecessary references included in the final specification.

Many people say the DOD can avoid the problems with milspecs, as in the case of products such as the toilet seat, by buying directly from the commercial market (Defense Science Board, 1986).  The DOD's present policy is to buy commercial products as often as possible. However, there are several limiting factors to this policy.  Commercial products are often less expensive and work well in a commercial environment, but become unreliable in a military environment.  The commercial products also are not standardized with existing military equipment.

After analyzing these issues, this report states one major recommendation: the military and commercial industrial bases should begin to integrate into one base.  The integration of the two industrial bases is a long term recommendation.  To support the integration in the near future, some short term recommendations that can be applied presently are:

The Committee on Defense Manufacturing Strategy should be cautious about accepting myths about milspecs as fact.

All new milspec writers should be required to take a specification writing class which also explains how the documents are used in the Defense Acquisition Process.

The Committee on Defense Manufacturing Strategy should investigate the communication over specification changes within a contract between the DOD and contractors.

Writers should be required to submit an Engineering Change Proposal as soon as they see that a milspec is outdated.

This report, prepared at the Nuclear Medicine Department of the University of Massachusetts Medical Center, focuses on the synthesis of a working nuclear imaging system.  A 3" diameter Hammamatsu position sensitive PMT/3 mm NaI(Tl) scintillator is interfaced to a Macintosh IIfx computer via a CAMAC acquisition system.   An analog interface pulse height board selects wanted events and computes their location.  Square analog pulses representing the coordinates of each nuclear event are sent to two ADCs, which pass digitized addresses to a special built module used to strip the lower order bits from incoming information to 5, 6, 7, or 8 bits.  The same module also binds the two lateral addresses together into the low order 10, 12, 14, or 16 bits, respectively.  Two inputs are also available for setting the 15th and 16th bits high (e.g., for physiological triggers, or timing information).  These data are then passed to a data router, which controls the characteristics of the image.  The data router directs the information to two parallel histogramming memories, each of which can buffer one 128x128, or four 64x64 histogramming images.  A GPIB controller module in CAMAC passes the data to a Macintosh IIfx computer (System 7.0).  LabView 2 is used as the programming environment for acquiring and archiving 128x128 static images, or sequential four 64x64 frames without interframe dead time.  List mode studies can also be supported via two dual port memories.  Software support for image analysis and display in provided in LabView, along with C, FORTRAN, and Pascal support.  The system is designed for use as an intraoperative camera, and for small organ imaging.   The possibility of using the system in Tomography for three dimensional reconstruction was also evaluated. Intrinsic resolution of the system is 300 micrometers, and 2 mm resolution has been achieved with a high resolution parallel hole collimator.

Integral energy imparted to a patient is a better indicator of radiological risk than the entrance skin exposure, since the former takes into account both the area of exposure and x-ray beam penetration.  However, data on energy imparted are not readily available.  The objective of this study was to generate values of energy imparted per unit exposure per unit area of exposure as a function of patient thickness and x-ray beam qualities (kVp, HVL).  A semi-empirical model developed by Tucker et al. was used to generate the x-ray spectra.  X-ray spectra were obtained for a range of kV, tube anode angles and x-ray beam filtration for a tungsten-rhenium target.  A sine function was used to model the x-ray tube kilovolt waveform with a ripple factor ranging from 0% (i.e., constant potential) to 100% (i.e., single phase).  X-ray spectra were filtered by varying the thickness of aluminum to simulate x-ray beams encountered in clinical practice.  For each x-ray spectrum the free-in-air exposure was computed.  Energy imparted to a semi-infinite, water equivalent phantom from polychromatic x-rays was computed according to Boone’s parameterization of energy imparted.  Values of energy imparted per unit exposure per unit area of exposure were computed for constant potential and a 12° anode angle as a function of patient thickness and x-ray beam qualities.  Differences of less than 3% were found to be introduced by varying the kilovolt waveform ripple or the tube anode angle.  Values of energy imparted to a water phantom were compared to those obtained for an anthropomorphic phantom as determined by Jones and Wall.  Absolute values agreed to within 10% for typical x-ray examinations.  The agreement among relative values as a function of kV and filtration was better than 5% between the two phantoms.   Specification of the x-ray beam kVp and half value layer are generally sufficient to yield energy imparted per unit exposure data that have accuracy of better than a few percent.  Data are presented in tabular form which permits the estimation of the energy imparted to patients, for the range of kVp and HVL normally encountered in diagnostic radiology, by specifying patient thickness and x-ray beam qualities.

The effective dose is the best parameter for describing the amount of radiation received by a patient undergoing any diagnostic x-ray examination.   Benefits of the effective dose include the ease of intercomparing doses associated with diverse types of radiologic examination and the ability to compare patient doses with natural background or regulatory dose limits.  The major limitation of the effective dose is the requirement of obtaining mean organ doses of the irradiated tissues in the patient.  A method is proposed which can be used to generate patient effective doses using the selected radiographic technique factors (i.e., kVp/mAs), patient source to skin distance and x-ray beam cross-sectional area.  An algorithm based on computed x-ray spectra is used to generate the beam output (mR/mAs) and half-value layer at the selected tube voltage for a given tube anode angle and waveform ripple.  The energy imparted e to the patient is then obtained from the exposure area product, x-ray beam voltage, half-value layer and patient thickness.  Energy imparted is finally converted to an effective dose E using published body/projection specific E/e ratios.  Examples are provided of how the effective doses may be generated for representative radiographic examinations of the head, chest, abdomen and for the extremities.

Pediatric effective doses can be obtained for any radiologic examination using the selected radiographic technique factors (kV/mAs), the exposure geometry and the patient mass. The energy imparted e to the patient may be computed from the exposure area product, x-ray tube voltage, half-value layer and patient thickness. Values of energy imparted may be subsequently converted to an effective dose E using published radiographic projection specific E/e ratios determined using Monte Carlo techniques applied to anthropomorphic phantoms, with a correction applied for the patient mass. Pediatric effective doses (head, chest, abdomen and extremity) were computed for representative adult patients, as well as for pediatric patients ranging from new born to 15 year old youths. Values of patient effective dose were dependent on body size, selected technique factors as well as the type of radiographic imaging equipment used, with no clear trends for effective dose with patient age.

Diagnostic and therapeutic interventional neuroradiologic procedures involve imaging of catheter manipulation and vascular anomalies of the brain and generally require extensive use of x-ray radiation.  Knowledge of the surface dose allows one to estimate the probability of inducing deterministic effects, whereas the corresponding value of effective dose is related to the patient stochastic risk.  Modification of key imaging parameters (i.e., tube voltage, input exposure to the image receptor and geometric magnification) impact on patient doses and image quality, with the latter being defined as the lowest concentration of iodine in a vessel that may be visually detected in the radiographic image.  A dosimetry system was installed on a biplane neuroradiologic imaging system to determine the doses to patients undergoing interventional neuroradiologic procedures.  The dosimetry system computed surface doses on the basis of selected technique factors and information about patient location relative to the x-ray tube.  The energy imparted to the patient, e, was determined using the surface dose, x-ray beam quality (i.e., kVp and HVL), exposure area and thickness of the patient and was converted into the corresponding value of effective dose, E. Values of surface dose and E were obtained for 175 patients, consisting of 149 adults and 26 pediatrics.  Median values of surface doses to the head region were 1.2 Gy in the frontal plane and 0.62 Gy in the lateral plane.  Median values of the effective doses were 36 mSv for adult patients and 44 mSv for pediatric patients.  An acrylic phantom with 1-mm diameter vessels filled with iodine contrast was used to evaluate the effects of varying imaging parameters on signal detection and patient doses during digital subtraction angiography.  Reducing the x-ray tube voltage offered the largest improvement in image quality for a given increase in patient dose.  Increasing the image intensifier input exposure beyond 250 mR/frame provided very little improvement in image quality, and this II exposure level should not be exceeded in interventional neuroradiologic imaging.  A linear relationship was observed between magnification and threshold concentration, which offers significant patient benefits when surface doses are not expected to exceed the threshold doses for the induction of deterministic effects.

The field of biomedical optics, the use of light in medicine, has seen rapid growth over the last decade.  The development of non-invasive medical optical imaging (MOI) modalities using harmless near infrared (NIR) light is a major goal of biomedical optics research.  Arguably, the most interesting application of MOI is breast imaging, with the potential to provide a safer, and possibly more effective alternative to traditional x-ray mammography.