Leonard Stanton

The Development of a Chest Phantom for Use in Radiologic Dosimetry

Our interest in the fabrication of a physically and anatomically realistic chest phantom was first stimulated by the work being done on supervoltage (2 mv) chest roentgenography by one of the authors (11, 12). In the course of investigations of the value of supervoltage technics in the detection of thoracic lesions, it became apparent that such a phantom was needed for two basic reasons: first, to permit the measurement of integral dose received by a patient at 2 mv compared to that absorbed during a similar examination at the usual diagnostic energy levels; second, for use in the comparative evaluation of diagnostic technics. Previous work by Weatherwax (14), Quimby (9), Granke (4), and Nahon (8) involving chest phantoms for dose measurements has contributed greatly to an understanding of intrathoracic dosage. None of the earlier phantoms, however, were suitable for use at energy levels below 200 kvp, and in none was there sufficient anatomic detail to permit the investigation of diagnostic technics. The...

A Penetrameter Method for Field kV Calibration of Diagnostic X-Ray Machines

Low-kilovoltage studies are useful for detection of objects which normally exhibit low radiographic contrast. For example, in mammography low kilovoltage and inherent filtration permit detection of punctate calcifications and fine soft-tissue structures in fat. Since diagnostic machines are designed primarily for use in the 50 to 150 kV range, their dial calibrations are usually in error at low settings. As an instance, dial settings of 27 pkV typically yield measured values of about 32, and occasionally up to 40 pkV. The problem is complicated by the fact that both contrast and film density depend critically on kilovoltage in this range. While knowledge of the calibration is most important in low-kilovoltage work, it is also useful in more conventional radiography, where it is often convenient to match technics in different x-ray rooms of the same or even different departments. For this reason, we have designed penetrameters for both low kilovoltage and conventional work. Table I summarizes five other fr...

A NEW AGENT FOR SPLENIC SCANNING: BMHP.

All Scintillation scanning technics depend upon a physiological concentrating mechanism of the administered radioisotope within the organ to be surveyed. It is only relatively recently that visualization of the spleen has been reported (5). This has been accomplished by various methods modifying red blood cells labeled with radioactive chromium 51 to promote their rapid selective sequestration from the circulation, primarily within the functioning spleen (2). Although at times successful, these methods have generally yielded scans of poor diagnostic quality, related to the radioisotope employed and to the erratic nature of sequestration of the altered red cells. The search for better agents for splenic scanning has continued. In 1957, Kessler, Lozano, and Pitts (1) found 1-iodo-mercuri-2-hydroxypropane concentrated in the spleen of dogs following intravenous injection. This discovery was not utilized until 1963 when Wagner (3) postulated that the splenic concentration might result from sequestration of re...

Evaluation of Calcium 47 in Normal Man and Its Use in the Evaluation of Bone Healing Following Radiation Therapy in Metastatic Disease

The use of external counting technics for the study of problems in bone metabolism has been hampered in the past by the lack of suitable isotopes. Many radioactive compounds have been utilized in the study of bone metabolism, but without great success. These have included gallium 72 (3, 4) sodium 22, sodium 24, barium 140, etc. Dudley et. al (5) are presently working with radioactive yttrium in this study. Bauer and his associates (1) introduced calcium 47 as an agent for the evaluation of bone metabolism. The radioactive calcium was found to be selectively localized in areas of osteoblastic activities such as the epiphyses in young persons, healing fractures, metastatic areas of carcinoma to bone, eosinophilic granulomas, osteomyelitis, chondromas, etc. Radioactive calcium 47 has a half-life of 4.7 days and emits a high-energy gamma ray of 1.3 Mev as well as a beta particle in its decay to scandium 47. Scandium 47 is also radioactive with a half-life of 3.8 days, and decays by the emission of a beta part...

The Selection of Optimum Mammography Technic

To be of utmost value to the radiologist, a roentgenogram of the breast should clearly demonstrate both tiny calcific deposits and fine soft-tissue structures in fat. This requires far greater resolution than most other x-ray examinations, because calcific specks 0.5 mm. and smaller are common, as are soft-tissue fibrils 2 mm. and less in diameter. Roentgenographic images must hence be extremely sharp. In addition, high-contrast technic is required, especially to highlight images of fine soft-tissue structures which are otherwise only marginally detectable. The two technics in widespread use were developed empirically (1, 2). More recently, our previous paper attempted to provide a basis of greater precision for designing and evaluating technics (3). Further investigation, however, has been required to accomplish this goal, along the following lines: (a)More extensive studies below 30 kvp (b)Tests with a beryllium-window tube (c)The effect of patient motion; estimate of permissible amplitude (d)Film devel...

Determination of isodose curves for supervoltage and cobalt-60 teletherapy machines with x-ray film.

Treatment planning with supervoltage and cobalt-60 machines is often hampered by a surprisingly limited supply of suitable published information. Table I summarizes dosage references from four major radiologic journals. Supervoltage data are represented by only one treatment distance (100 cm.) and three square fields. Although there are more curves between actual and nominal field size is accurately known for the particular machine and treatment distance used, considerable errors are possible. A further difficulty is introduced in teletherapy machines by lack of standardization of penumbra factors, such as source sizes and collimator design (17). The effect of penumbra size on dosage for cobalt-60, they must be employed with care because of the variability of field-defining systems in such machines.3 Even the term “field size” is quite ambiguous. Table II shows actual measured separations in air of 50 per cent of maximum dose locations, for nominal 10 × 10-cm. fields, on several machines in the Philadelph...

A Breast Phantom Method for Evaluating Mammography Technique

A new breast phantom has been designed for use in evaluating mammographic system performance. This phantom incorporates simulated calcifications and fibrillar objects in fat, of graded size, to permit measurements of detail visibility. A special methodology has been developed for measuring visible object size to achieve reproducible and clinically relevant results. Materials and construction of the phantom also permit carrying out dosimetry with an appropriate ionization chamber. Dosage and detail visibility measurements are reported for the Xerox 125, Min-R and Xonics systems. In addition to providing information regarding technique and image receptors, these results demonstrate the usefulness of the basic phantom design, and suggest possible improvements.

Mammography With Magnification And Grids Detail Visibility And Dose Measurements

The possibility has been demonstrated of significant image improvement in screen-film mammography without increase in relevant patient dose, when a fast screen-film combination is used with magnification or grid, when compared with a slower screen-film combination using conventional technique (no grid use or magnification). An ideal dedi-cated mammography x-ray unit, containing a small (± 300 micron) tungsten focal spot, and a grid should result in optimal imaging of all breast sizes and tissue consistencies.

Some Physical Measurements of the “Electron Radiography” System

Studies are in progress on imaging characteristics of “electron radiography” (ERG), a new electrostatic system. Wide exposure latitude images have been obtained with patient exposures comparable to those of conventional radiography. This paper reports comparison measurements on an experimental ERG unit and Par Speed screens used with Eastman RP film, density vs. exposure response, edge-imaging characteristics, and image noise.

Obtaining proper contrast in mammography.

Mammography requires extremely fine technical quality for both contrast and detail. This stems directly from the objective of the examination: to identify suspicious small soft-tissue masses and fibrillar structures in fat, as well as punctate calcifications. Such objects are of inherently low contrast, and both clinical experience (1) and physical measurements (2, 3) have shown the importance of low kilovoltage and filtration to enhance contrast. Preferred factors are 24 to 40 pkV with inherent filtration only. These factors require operating x-ray tubes and machines at kilovolt values well below those of ordinary radiography (50 to 150 pkV), and many serious practical problems have been reported (4). For example, measurements on ten machines used for mammography in Philadelphia showed actual values were typically 5 kV greater than dial settings, with one 17 kV greater. In addition, inherent filtration of some tubes was so high they were unsuitable for mammography! This was because of both poor initial c...