Enhanced T1 differentiation between normal and dystrophic muscles.

Proton spin-lattice relaxation times (T1) of pectoralis major muscles from normal (Line 412) and homozygous dystrophic (Line 413) chicks was measured by FONAR QED 80 at 1.69 MHz. The T1 values of dystrophic muscles (216.8 +/- 17.3 ms) was two-fold higher than those of normal muscles (110.2 +/- 8.1 msec). When these values were compared with the T1 values obtained at high frequencies (20 MHz and 32 MHz), the T1 differentiation between normal and dystrophic muscles was considerably enhanced at 1.69 MHz. Based on these results, we suggest that the high resolution of T1 obtained at low frequency (1.69 MHz) could be effectively used to detect the degenerative processes in muscles by the NMR techniques.

The systemic effect of cancers on human sera proton NMR relaxation times.

In animal models of cancer, an elevation of T1 and T2 in uninvolved tissues and in the blood of tumor bearing animals has been termed "the systemic effect." This study reports T1 values in sera of human patients from Genoa, Italy, with several types of cancer and non-cancerous diseases. T1 values were significantly elevated over normal controls (1628 +/- 113 ms) in colorectal cancers (1725 +/- 149 ms) and stomach cancers (1817 +/- 219 ms). However a systemic effect was not demonstrated in acute myeloid leukemia, chronic lymphatic leukemia, chronic myeloid leukemia, or plasma cell myeloma, or in pancreatic and lung cancers. Noncancerous states of cirrhosis, chronic hepatitis, and monoclonal gammapathies did not show a T1 elevation. In general, T1 values of sera correlated with protein content of the sera; however, a disproportionate contribution of gamma-globulin protein on water proton relaxation times was observed in several cases.

Evaluation of muscle degeneration in inherited muscular dystrophy by nuclear magnetic resonance techniques.

Nuclear magnetic resonance (NMR) techniques were applied to study the muscular dystrophy in chicks. The water proton spin-lattice relaxation times (T1) of fast, slow, and mixed muscles and plasma were measured. The T1 values of dystrophic pectoralis major and posterior latissimus dorsi (PLD) were significantly higher than those of the normal pectoralis and PLD muscles. The present results establish a direct relationship between the differences in T1 values and the severity of muscle degeneration. Consistent with this conclusion, it was also found that the T1 values of muscles unaffected in muscular dystrophy, namely, the gastrocnemius, and anterior latissimus dorsi (ALD), were not different between the normal and dystrophic chicks. Although the affected muscles of dystrophic chicks contained higher percent water and fat than those of normal chicks, the results show that the higher T1 values in dystrophic muscles were not solely due to variations in their water content. The increase in the T1 values is principally a result of altered interaction between cellular water and macromolecules in the diseased muscles. These data also point out the potential use of NMR imaging in evaluating muscle degeneration.

Contrast-detail-dose and dose efficiency analysis of a scanning digital and a screen-film-grid radiographic system.

The purpose of this study is to examine the diagnostic potential of a scanning digital radiography (SDR) system currently used clinically as a CT localization device. The technique of contrast-detail-dose analysis is used to compare the low-contrast sensitivity and dose efficiency of an SDR unit with standard radiography (SR). The theory of threshold perceptibility in both digital radiography and SR is described, including the effects of scattered radiation and antiscatter devices, object attenuation, geometry, system image processing, and recorder quantum efficiency. The concept of dose efficiency is defined and derived from the contrast-detail-dose data. The SDR system is shown to operate with a threshold signal-to-noise ratio of 7.3 +/- 1.2 for large area detection (d greater than or equal to 2 mm); to be relatively scatter-free; and to be as much a 100x more dose efficient than SR for visualization of large low contrast objects (C less than or equal to 0.04, d greater than or equal to 2 mm).

Resolution in radiographic magnification.

Radiographic resolution and image sharpness are analyzed as a function of magnification for a few screen/film systems and a microfocal spot x-ray tube. Resolution and sharpness are described in terms of both MTF and effective aperture. The analysis demonstrates advantages of magnification for any combination of radiographic screen/film system and x-ray focal spot, and, in addition, allows one to compare different screen/film systems each used at different magnifications. Such an analysis is applicable to any radiographic system and may serve as a guide in selecting screen/film systems for use in magnification procedures.

Dose efficiency and the effects of resolution and noise on detail perceptibility in radiographic magnification.

The detail signal-to-noise ratio model of radiographic imaging is quantitatively analyzed in terms of its accuracy in describing observer threshold perceptibility of radiographic detail. The model is found to adequately describe the effects of magnification, scatter radiation, and system resolution on observer threshold perceptibility. However, it is shown that the model does not apply in screen/film radiography for very low contrasts and high scatter conditions due to insufficient optical density contrast. The dose-to-information conversion efficiency of a radiographic imaging system is defined and the effects of magnification, scatter, resolution, image processing, detector efficiency, grids, patient table support, field size, and geometry on the dose efficiency of the imaging system are investigated.

The degradation function in conventional tomography.

A method is developed by which the imaging characteristics of a tomographic x-ray unit may be determined directly from a study of the mechanical motion of the unit. In this method we first describe the mechanical motions in terms of a vector equation. From this vector equation, a "degradation function" is derived which acts as a multiplicative factor, directly relating the optical transfer function of the system in a tomographic mode to the optimal transfer function of the system in a stationary mode. Therefore, if the imaging properties of the system in the stationary mode are known (or, as is often the case, can be neglected), it is a simple matter to determine the imaging properties in the tomographic mode. The star pattern is used to verify the validity of this method.

Digital radiography using a computed tomographic instrument.

A prototype computed radiography (CR) system was evaluated for its efficacy as an independent diagnostic modality. Preliminary measurements of high contrast resolution, low contrast perceptibility, and dose were obtained. Clinical examinations including skull, abdomen, liver, gallbladder, biliary system, spine, and extremities were performed as an adjunct to either computed tomography or CR. The data suggest that CR can be an effective diagnostic imaging modality by itself. Advantages over conventional radiography include high scatter rejection, low patient dose, wide dynamic range, and good low contrast sensitivity for large objects; disadvantages, its long exposure time and relatively poor high contrast spatial resolution.

Practical considerations in gamma camera line spread function measurement.

In recent years the modulation transfer function (MTF) has played an important role in the quantitation of imaging performance of gamma cameras. The most common method of MTF determination requires line spread function (LSF) measurement. This paper reviews methods used for LSF measurements with special consideration given to the practical aspects of LSF measurement and MTF calculation. An analysis of errors in LSF measurements is made and means to reduce or to avoid these errors are discussed. Recommendations regarding practical considerations for LSF measurement and MTF calculation are presented in tabular form for convenience.

The use of photogrammetry in tissue compensator design. Part I: photogrammetric determination of patient topography.

The surface topography of a patient can be determined by photogrammetry before beginning radiotherapy. The source light of the therapy unit or simulator is used to project a grid pattern onto the patient, and this is then photographed together with control points consisting of miniature light bulbs mounted on a frame suspended from the wedge slot of the therapy machine. When the photograph is projected onto a graphics terminal for data entry into a computer, the three-dimensional topography of the patient's surface can be reconstructed as a two-dimensional matrix of discrete points. A computer algorithm can then design a tissue compensator to fit the individual patient.

The use of photogrammetry in tissue compensator design. Part II: experimental verification of compensator design.

A computer algorithm for designing sheet lead tissue compensators is described. Corrections are made for scatter within the radiation field as well as the shape of the patient for the mantle fields used in treating Hodgkin's disease. The method was tested experimentally with a phantom and found to be clinically acceptable. The advantages of employing this technique with parallel opposed fields are emphasized.

Computer simulation study of Siemens star x-ray image artifacts.

In the Siemens star image, exact determination of the first disappearance frequency, which is used to measure the focal spot size, is difficult since the disappearance band has a finite width and the image also has other artifacts. The origin of these artifacts and their appearance was studied by Siemens star image simulation on a digital computer. The simulated images were manipulated by using many different modulation and phase transfer functions. It is shown that the bending of spokes is not related to zero contrast; exact triplet splitting can occur only at the disappearance frequency, and therefore splitting is a valuable indicator of that frequency.