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A thermal model for predicting time-dependent temperature distributions during ultrasound heating was tested quantitatively. The relevant thermal processes incorporated in the model are heat conduction and ultrasound power absorption, and the required input parameters include the absolute ultrasound power, the shape and frequency of the ultrasound transducer, and the thermal and acoustical properties of the medium. Testing was done by heating an ultrasonically tissue-mimicking phantom with a 525 kHz, single element, focused source. The phantom has muscle-like acoustical properties and contains an array of copper-constantan thermocouples. Time-dependent temperature changes predicted with the thermal model were in very good agreement with those measured in the phantom, verifying the validity of the model for use in optimizing an ultrasound applicator design for a specific treatment situation.

From December 1980 to January 1984, all patients with stage I nonseminomatous testicular cancer in Denmark entered a randomized trial comparing surveillance only with radiotherapy after orchiectomy. One hundred fifty patients were assessable for the final analysis. Relapse occurred in 23 patients in the surveillance group and in 11 patients in the radiotherapy group. Radiotherapy completely prevented retroperitoneal relapse; 14 retroperitoneal relapses occurred in the surveillance-only group. All relapsing patients in the surveillance-only group are without evidence of disease with a median observation time after chemotherapy of 67 months. Two of the patients with relapse in the radiotherapy group died with disease; the others are alive without evidence of disease, with a median observation time after relapse treatment of 72 months. In the surveillance group, four relapses occurred later than 2 years after orchiectomy; only one such late relapse occurred in the radiotherapy group. Four of the retroperitoneal relapses occurred without concomitant increase in the serum marker levels (alpha-fetoprotein [AFP] and human chorionic gonadotropin [HCG]). It is concluded that surveillance only should replace radiotherapy after orchiectomy as standard treatment for clinical stage I nonseminomatous testicular cancer. Improved methods for control of retroperitoneal relapses, especially of embryonal carcinomas, are needed.

A method of measuring ultrasonic propagation in the os calcis was devised for assessing bone properties in humans. Speed-of-sound (SOS) and broadband ultrasound attenuation (BUA) were measured using broadband acoustic pulses transmitted and received by a pair of focused transducers. The transducers are mounted coaxially in a water tank with the subject's heel in between. Reproducibility of results in an adult male was 10% for the BUA and 1.2% for the SOS. Both SOS and BUA changed when the transmission path through the os calcis was varied. For a population of normal male subjects, SOS and BUA were correlated with densitometry results on the os calcis, but less well correlated to area density at remote sites.

Conventional approaches for proving in situ biodegradation of organic pollutants in aquifers have severe limitations. In the approach described here, patterns in a comprehensive set of microbiological activity and distribution data were analyzed. Measurements were performed on sediment samples gathered at consistent depths in aquifer boreholes spanning a gradient of contaminant concentrations at a buried coal tar site. Microbial adaptation to polyaromatic hydrocarbons (PAHs) was demonstrated by mineralization of naphthalene and phenanthrene in samples from PAH-contaminated, but not adjacent pristine, zones. Furthermore, contaminant-stimulated in situ bacterial growth was indicated because enhanced numbers of protozoa and their bacterial prey were found exclusively in contaminated subsurface samples. The data suggest that many convergent lines of logically linked indirect evidence can effectively document in situ biodegradation of aquifer contaminants.

A phantom made from tissue-mimicking materials is reported for testing 1H MRI systems regarding their ability to detect small low-contrast focal lesions and to delineate the boundaries of larger lesions. Two sets of seven spherical simulated lesions with diameters of 2, 3, 4, 5, 6.3, 7.9, and 9.5 mm have T1 and T2 values somewhat higher than the corresponding values in the surrounding simulated normal tissue. Relaxometer determinations of T1 and T2 for the simulated normal tissue yielded 955 and 106 ms, respectively, at 22 degrees C and 1 T. The corresponding values in set #1 of the simulated lesions were 1017 and 175 ms and in set #2 were 1002 and 127 ms. These T1 and T2 values are similar to those for brain and brain lesions but are too high to represent soft tissue such as liver and muscle. The centers of the 14 lesions are coplanar, and eight alignment devices surround them facilitating superposition of the scan plane and the plane containing the centers of the lesions. Illustrative images made with a 1.5-T system are shown. All simulated lesions are detectable in T2-weighted head coil images. Corresponding T1-weighted images are also shown, the 2- and 3-mm lesions of set #2 and the 2-mm lesion of set #1 not being detectable. The phantoms could be useful for performance or acceptance testing and perhaps for quality assurance testing.

An anthropomorphic torso section phantom is described that is intended for use during initial stages of ultrasonographer training. The phantom represents a section of the upper abdomen, with simulated ribs, liver, kidney with fat pad, gallbladder, aorta, and bowel gas. Positioned in the liver are ten simulated soft tissue masses, which produce a variety of typical echographic patterns. All simulated soft tissue components are formed of tissue-mimicking materials that match their corresponding tissue counterparts in terms of speed of sound, ultrasonic attenuation, and density. Construction details are presented and examples of images are shown.

Uncertainties in measured attenuation and backscatter coefficients due to statistical fluctuations in echo signal data from a randomly scattering medium are estimated. The uncertainties are computed for the special case in which a reference phantom is employed to account for transducer and instrumentation factors when measuring attenuation and backscatter coefficients. The resultant uncertainty in the attenuation is inversely proportional to the 3/2 power of the depth range. The error in the backscatter coefficient arises both from the local fluctuation in the data and from the uncertainty in the attenuation estimate. The first of these is inversely proportional to the square root of the number of independent data points, while the second results in a contribution that is depth dependent. Predicted errors were tested by scanning tissue mimicking phantoms and estimating attenuation and backscatter coefficients for subsets of the digitized echo data. Standard deviations of the experimental results were in agreement with those predicted.

A method has been developed for mapping density and ultrasonic speed in 1 mm thick slices of soft tissue with a resolution of about 1 mm. Tests using phantom sections have verified the accuracy and resolution of the ultrasonic speed maps. The method has been applied to breast tissues of three patients including tumors and surrounding tissue. Fixing a specimen in 5% formaldehyde did not change the degree of local variation in ultrasonic speeds, and raised mean speeds by less than 0.8%. The densities with fixing remained almost unchanged at low tissue densities (0.93 g/cm3), but rose 1.5% for higher tissue density (greater than 1.00 g/cm3).

A new ultrasonically and thermodynamically tissue-mimicking material is reported. The material is well suited for use in phantoms for testing ultrasound hyperthermia systems or related predictive models. Controlled convective heat transfer effects, mimicking to some extent perfusive heat transfer in tissues, can be instituted in the material with appropriate fluid sources and sinks. The material consists of closely packed agar spheres varying in diameters from 0.3-3.6 mm. The interstitial space between spheres is filled with 10% n-propanol solution. The material has two practical advantages over the solid-gel-type tissue-mimicking materials. The first advantage is that it allows rapid return of a hyperthermia phantom to thermal equilibrium following a heating test by rapid circulation of the perfusion fluid. The second advantage is that the material is in a "liquid" form. It can be easily siphoned in and out of phantom containers of any geometric shape for different purposes without change in its physical properties. Methods for measuring ultrasonic and thermodynamic properties of the material and the results of the measurements are reported. The physical parameters measured are the intensity attenuation and absorption coefficients, the ultrasonic speed, the thermal conductivity, specific-heat capacity and the mass density. Temperature measurements in a hyperthermia phantom made of the material are also reported.

156 patients with stage I non-seminomatous testicular germ cell tumour entered a countrywide randomized study comparing the effect of postoperative irradiation of retroperitoneal lymph nodes with surveillance only. A total of 150 patients were included in this investigation of factors associated with increased risk of relapse. Thirty-four patients (23 per cent) had a relapse, i.e. 11/67 (16 per cent) in the former and 23/83 (28 per cent) in the latter group. Histopathological studies of the orchidectomy specimens were performed in order to identify features associated with relapse. Pure embryonal carcinoma and vascular involvement were significantly associated with increased risk of relapse. Thus, the relapse rate in the observation group in patients with pure embryonal carcinomas was 50 per cent (5/10) and 36 per cent (19/53) in all patients with tumours with vascular involvement.

In previous work, we demonstrated that accurate backscatter coefficient measurements are obtained with a data reduction method that explicitly accounts for experimental factors involved in recording echo data. An alternative, relative processing method for determining the backscatter coefficient and the attenuation coefficient is presented here. This method involves comparison of echo data from a sample with data recorded from a reference phantom whose backscatter and attenuation coefficients are known. A time domain processing technique is used to extract depth and frequency dependent signal ratios for the sample and the reference phantom. The attenuation coefficient and backscatter coefficient of the sample are found from these ratios. The method is tested using tissue-mimicking phantoms with known scattering and attenuation properties.

We have studied whether mouth-swishing with sucralfate, a well-known gastric mucosal protective agent, may be used as prophylaxis against chemotherapy-induced stomatitis. Using radioactively labelled sucralfate we found that 20-30% was still bound to the oral mucosal lining 2 1/2 h after mouth-swishing. Forty patients receiving cisplatin and continuous infusion with 5-fluorouracil (5-FU) for 5 days entered a double-blind placebo-controlled cross-over study. Among 23 evaluable patients a significant reduction (p = 0.04) in an objective score of edema, erythema, erosion and ulcerations was seen during treatment with sucralfate. Patient preference favored sucralfate, but this preference failed to reach statistical significance (p = 0.06). Seven patients were inevaluable for reasons not associated with the study treatment. However, ten patients did not complete the study since the swishing procedure aggravated chemotherapy-induced nausea. An equal rate of non-compliance was seen with sucralfate and placebo. To overcome this problem, the oral medication should have a neutral taste, the solution should not be swallowed after the swishing, which should not be started until the nausea had ceased.

An anthropomorphic breast phantom, built from materials which mimic tissue parenchymae with respect to attenuation coefficients, speeds of sound, densities and backscatter levels, is described in detail. One of the outstanding features of the phantom is that 30% of the volume of the glandular region consists of tissue-mimicking fat, the remainder being tissue-mimicking glandular (non-adipose) tissue. The presence of these tissue-mimicking fat globules should cause ultrasound beam distortions similar to those found in clinical scans of the breasts of younger women. Halliwell (1977) has presented direct evidence for such beam distortions in real breasts. Other tissues simulated in the phantom are: skin, subcutaneous and retromammary fat, Cooper's ligaments, ducts and (abnormal)masses. The potential areas of usefulness of the phantom are: aiding in the development of more effective ultrasound imaging machines, discovering-- or verifying the causes of--various artifacts in breast imaging, routine testing of instruments being used clinically for breast imaging, and training of ultrasonographers. Ultrasound images of the phantom, made using three different instruments, are displayed and discussed.

Water-based proteinaceous gels, which--with appropriate additives--are stable with time and possess a high melting point, have been used as base materials in ultrasonically tissue-mimicking materials. In the present work, versions of these gels having various concentrations of glycerol and graphite particles were studied regarding their NMR T1 and T2 dependencies at a proton Larmor frequency of 10.7 MHz. It has been found that T1 depends primarily on the concentration of glycerol and T2 depends primarily on the graphite particle concentration. Also, the ranges of T1 and T2 likely span those which exist for soft tissue parenchymae. Thus, these materials are good candidates for use as NMR tissue-mimicking materials. T1 and T2 also vary with gelatin concentration. The latter fact, together with the strong dependence of T2 on graphite concentration, mean that effective contrast-resolution phantoms and anthropomorphic phantoms with stable T1 and T2 distributions can be produced.

The mineralization of 1.0 to 100 ng each of four complexing compounds-oxalate, citrate, nitrilotriacetate (NTA), and EDTA-per ml was tested in media prepared in accordance with equilibrium calculations by a computer program so that the H, Ca, Mg, Fe, or Al complex (chemical species) was predominant. Sewage microorganisms mineralized calcium citrate more rapidly than iron, aluminum, or hydrogen citrate, and magnesium citrate was degraded slowest. Aluminum, hydrogen, and iron oxalates were mineralized more rapidly than calcium oxalate, and magnesium oxalate was decomposed slowest. Sewage microorganisms mineralized calcium NTA but not aluminum, magnesium, hydrogen, or iron NTA or any of the EDTA complexes. Pseudomonas sp. mineralized calcium and iron citrates but had no activity on hydrogen, aluminum, or magnesium citrate. Pseudomonas pseudoalcaligenes mineralized calcium, iron, hydrogen, and aluminum citrates but had little activity on magnesium citrate. Pseudomonas alcaligenes used calcium, iron, hydrogen, and aluminum oxalates readily, but it used magnesium oxalate at a slower rate. Listeria sp. destroyed calcium NTA but had no effect on hydrogen, iron, or magnesium NTA. Increasing the Ca concentration in the medium enhanced the breakdown of NTA by Listeria sp. The different activities of the bacterial isolates were not a result of the toxicity of the complexes or the lack of availability of a nutrient element. NTA mineralization was not enhanced by the addition of Ca to Beebe Lake water, but it was enhanced when Ca and an NTA-degrading inoculum were added to water from an oligotrophic lake. The data show that chemical speciation influences the mineralization of organic compounds by naturally occurring microbial communities and by individual bacterial populations.

A three-dimensional model for production of gray scale texture in ultrasound B-mode images is described. The model computes time-dependent echo signals resulting from scattering of acoustic pulses by particles randomly distributed in an attenuating medium and transforms these signals into a gray scale image. Specific transducer and pulser-receiver characteristics are accounted for, as well as the three-dimensional nature of the problem, without loss of computational efficiency. The model generates texture that closely corresponds to that found experimentally in ultrasound images of tissue-mimicking phantoms. The dependence of the texture upon the depth of the region that was scanned and on the characteristics of the transducer-receiver system were clearly demonstrated. Good agreement between theory and experiment was found for the texture in phantoms containing simulated spherical low-scatter tumors.

Experimental results for the angular distribution of scattered ultrasound in water from a 0.635 mm diameter steel sphere embedded in agar were obtained for interrogating frequencies of 1.0, 2.25, 3.5 and 5.0 MHz. The experimental results compared favorably with theoretical predictions based on the work of Faran. The results for both theory and experiment are presented in the form of the Differential Scattering Cross Section (DSC) for scattering angles from 170 degrees to 44 degrees. The implications of this study on calculating the expected scattering behavior of gelatin based ultrasound phantoms are briefly discussed.

Up until now, no material has been found whose attenuation and speed of sound properties not only mimic those of human soft tissue, but are controllable in magnitude. We have discovered such a material in the form of water-based pharmaceutical gels containing uniform distributions of graphite powder and known concentrations of alcohol. The magnitude of the attenuation coefficient can be controlled easily between 0.2 and 1.5 dB/cm at 1 MHz, by varying the concentration of graphite. These attenuation coefficients are nearly proportional to the frequency. The speed of sound varies between 1520 and 1650 m/s at room temperature, depending primarily upon the concentration of alcohol. Bacterial invasion has been prevented by sterilization procedures and the introduction of appropriate preservatives. The ultrasonic properties exhibit temporal stability and change little over the range of room temperatures.

Fifty-seven patients with painful bone metastases were randomized to receive 4 Gy in 6 fractions over 3 weeks with 2 fractions per week or 10 Gy in 2 fractions with an interval of one week. Pain intensity was assessed by scoring the consumption of analgesics combined with patient self-evaluation on a visual analogue scale. Treatment results were identical in the two treatment groups, with satisfactory pain control in about 48% of the patients. In other studies with physician evaluation of pain control, better results have invariably been reported, suggesting some degree of observer bias. A review of the literature as well as the results of this study indicates that within wide ranges no optimal radiation schedule or dose exist for reducing pain in bone metastases. Therefore short courses of treatment using moderate doses should be preferred for the convenience of the patients.

Measurements were performed on freshly-excised bovine liver and myocardium to determine the ultrasonic scattering nature of the tissues under a variety of experimental conditions. Results for the angular distribution of the differential scattering cross section per unit volume of tissue are reported for scattering angles spanning 170 to 44 degrees for interrogating frequencies of 1.0, 2.25, 3.5 and 5.0 MHz. Fresh and aged tissues, some with abnormally high connective tissue content were analyzed. The results are compared to previously-published works.

Using stable materials capable of mimicking any soft tissues of the human body--quantitatively with respect to speed of sound, density, and attenuation coefficient and semiquantitatively with respect to scatter--we have constructed a torso section phantom containing simulated bowel gas, kidney, kidney fat pad, liver, tumor, cyst, bony structures, and resolution fibers. Simple geometries and precise knowledge of ultrasonic properties allow artifacts to be produced and explained with great confidence. Artifacts due to refraction and reflection are particularly dramatic. Phantoms such as this should be useful as stage one phantoms for training ultrasonographers. Such phantoms should also be of use to those who are doing research in ultrasonic image processing. This might involve, for example, recognizing image artifacts and reducing their effect in the formation of the image.

Three prototype anthropomorphic breast phantoms are discussed. The phantoms were constructed using ultrasonically tissue-mimicking materials; these materials mimic various tissue parenchymae in terms of attenuation, speed of sound, density, and scatter level. Realistic artifacts related to refraction and reflection at interfaces between different simulated parenchymae are produced. The phantoms represent premenopausal breasts, and they complement one another. Two of them represent the dense breasts of women under 30 years of age, and one represents that of a woman between 35 and 40 years of age. Of the former two, one produces what is apparently above-average refraction effects in the region of the peripheral fat layer; the other produces more typical refraction effects. Simulated tumors, cysts, and calcifications of various sizes are suspended in the glandular regions. Such phantoms are valuable for use in developmental testing of state-of-the-art ultrasound machines, quality assurance testing of clinical machines, and training of sonographers in breast imaging.

This paper presents an adaptation of a method for determining acoustic backscatter coefficients to produce quantitative ultrasound images. Backscattered echo signals are recorded from a region to be imaged and backscatter coefficients are determined and related to spatial position. The values of the backscatter coefficients are then translated into a gray scale image. Testing of this imaging technique has been performed using tissue-mimicking phantoms which contain sections having backscatter coefficients different from that of the surrounding material. The technique has also been tested using a phantom in which a fat-mimicking layer is interposed between the acoustic window and the main body of the phantom. The images produced were found to be quantitatively accurate throughout the phantom, including the sections with differing backscatter. Quantitative accuracy did not suffer when the fat-mimicking layer was present.

Determinations of shear wave speeds of sound and attenuation coefficients are reported for soft tissues, a silicone rubber reference material, and a gel used in manufacturing ultrasonically tissue-mimicking materials. Fresh bovine tissues were investigated, including calfskin, liver, cardiac muscle, and striated muscle. Because of the very large shear wave attenuation coefficients, reasonably accurate determinations of shear wave properties are difficult to make. The quantity measured directly was the complex reflection coefficient for shear waves at a planar interface between the sample and fused silica. Measurements were made at frequencies spanning the range 2-14 MHz. The shear wave attenuation coefficients increase with frequency and are of the order of 10(4) times the longitudinal wave attenuation coefficients. The shear wave speeds of sound also increase with frequency but are only a few percent of the longitudinal wave speeds of sound. The results are accurate enough to allow frequency dependencies to be proposed.

The acoustic backscattering coefficients of a tissue-mimicking (TM) material have been measured using a modified Sigelmann-Reid technique in order to assess the similarity of its acoustic properties to those of soft tissues. A simple reference scatter material was used to probe the strengths and the limitations of the measurement technique. Backscatter coefficients measured from the TM material exhibit a frequency dependence of the form fm in the range 1.0-8.0 MHz where 3.5 less than or equal to m less than or equal to 3.8. The backscatter coefficient is also found to be approximately proportional to the particle concentration in the TM material up to concentrations that yield an attenuation coefficient of 0.9 db/cm/MHz. Comparisons of backscatter coefficients measured from the TM material are made with published values for liver, myocardium, and blood.

Two anthropomorphic phantoms, simulating the breast as it is compressed against the chest wall during ultrasonic imaging, are described in detail regarding structural configurations and distributions of ultrasonic properties. The external shape of each phantom is that of a rectangular parallelepiped; this simple shape is consistent with the breast in the compressed configuration and also facilitates the inclusion of a considerable variety of simulated lesions including comparisons of imaging as a function of depth. One of the phantoms was completed about 4 1/2 years prior to this writing, and images made with scanners which were state-of-the-art in late 1983 and 1984 are compared with images made with two current state-of-the-art imagers. Improvements in imager quality over that period are apparent. The more recently produced phantom contains a simulated tumor with a complex structure as well as realistic simulated calcifications of various sizes. The tumor has a necrotic core and an irregularly shaped boundary. This boundary possesses a roughness intended to give rise to diffuse reflection.

A new variety of tissue-mimicking materials for use in 1H nuclear magnetic resonance (NMR) phantoms has been developed and extensively tested, principally at 10 MHz and at room temperature. The materials can be formed with a broad range of T1's and T2's representative of soft tissues. They are mixtures of various percentages of agar, animal hide gelatin, water, and glycerol. Small concentrations of formaldehyde and n-propanol prevent melting through 100 degrees C and prevent bacterial invasion. The materials are easily produced. A thorough description of compositions and production procedures is given. T1's exhibit about a 5%/degrees C rise in temperature. T2's exhibit less than a 1% rise/degrees C. Long-term (12 months) stability is exhibited both for NMR properties and for absence of fluid extrusion. Preliminary results indicate that T1's depend on the Larmor frequency in a similar way to that observed in soft tissues.

Phantoms were used to compare imaging of various masses in the glandular region for two types of breasts. In one type, normal glandular tissue contains no fat clumps; in the other type, randomly distributed spherical fat clumps exist. The size distribution and number of fat clumps per unit volume in the phantoms represented those found in actual normal glandular tissue. For a 5-cm path length between the scanning window of the phantom and the centers of the masses, the presence of the fat clumps caused distortions and deviations of the beam, resulting in image distortion. This degradation was reduced when successive slabs of the material containing the fat clumps were removed. Image degradation appeared to be less severe when a 2.25 (rather than a 3.5) MHz transducer was used. The results show that the thickness of tissue containing fat clumps between the scanning transducer and a mass plays a role in the detectability of masses and diagnostic usefulness of the image of a breast. This suggests that imaging of the breast in the compressed configuration should be performed regardless of whether the freely suspended breast is imaged. Also, transducers of lower nominal frequency may have an important role in breast imaging.

An apparatus and method of experimentation for measuring frequency-dependent angle scattering from in vitro tissue samples and tissue-like scattering media have been developed. Distinguishing features of this method are that data collection is rapid, data reduction is simple, and results, given in the form of the differential scattering cross section per unit volume, are accurate and absolute. Reported are the results of tests to determine the overall accuracy of the method. Also, results of the differential scattering cross section per unit volume from female human breast tissue are presented.

A set of test samples, all containing ultrasonically equivalent tissue-mimicking material, was produced and measurements of ultrasonic speed and ultrasonic attenuation coefficients were made at seven laboratories using various techniques. The ultrasonic speed values agree well with one another, having a spread of about 0.3 per cent; thus, speed values for tissue parenchyma appearing in the literature are likely to be accurate. Values of ultrasonic attenuation coefficients agree fairly well with one another, with differences between individual values and the group mean of generally less than 20 per cent of the group mean.

The accuracy of a new method for measuring ultrasonic backscatter coefficients was tested, using narrow-band pulses and well-defined media having scatterers randomly distributed in space. Experimentally determined values agree very well with theoretical values for wide ranges of experimental parameters, these ranges being applicable in measurements made on human soft tissues. An important outcome is that the method yields accurate results for scattering media positioned anywhere from the nearfield through the farfield of the nonfocused transducers employed. In addition, backscatter coefficients can be determined for a broad range of gate durations.

A three-dimensional model for gray scale texture in ultrasound B-mode images has been extended to enable absolute quantitative predictions of echo signal levels and texture characteristics. The quantitative aspects of the model are tested with a phantom in which the ultrasonic scattering properties as well as the ultrasonic attenuation coefficient and the speed of sound are known as functions of frequency. Good agreement between theoretical predictions and experimental results was found in the overall brightness of B-mode images, in pixel value histograms, and in an autocorrelation function analysis of images. Passing quantitative tests is additional evidence that the model is a reliable tool for computer simulations involving many important facets of ultrasound B-mode imaging and tissue characterization.

A form of tissue-mimicking material is reported in which oil droplets are dispersed in a water-based gelatin. Broad ranges of ultrasonic parameters, including speed of sound, attenuation coefficient, density and backscatter level, exist for this material. Very important, the attenuation coefficients are nearly proportional to the frequency as in the case of mammalian tissue and the available attenuation coefficient slopes span the range of mammalian tissues. The available range of slopes is 0.1 dB/cm/MHz through at least 2.0 dB/cm/MHz. The available speeds of sound range from a minimum below that of mammalian fat (approximately 1460 m/s) to a maximum above the accepted average for human tissue (154o m/s). Densities available range from below that of fat (approximately 0.92 gm/cm3) through about 1.00 gm/cm3. Backscatter levels are easily made negligible compared to clinical levels and compared to those exhibited in previously reported tissue-mimicking materials in which the suspended particles are solid (Madsen et al. 1978; Burlew et al., 1980). Addition of solid or hollow glass scatterers allows backscatter levels to be made comparable to those clinically observed.

The influence of physiological and environmental factors on the accumulation of oxindole during anaerobic indole metabolism was investigated by high-performance liquid chromatography. Under methanogenic conditions, indole was temporarily converted to oxindole in stoichiometric amounts in media inoculated with three freshwater sediments and an organic soil. In media inoculated with methanogenic sewage sludge, the modest amounts of oxindole detected at 35 degrees C reached higher concentrations and persisted longer when the incubation temperature was decreased from 35 to 15 degrees C. Also, decreasing the concentration of sewage sludge used as an inoculum from 50 to 1% caused an increase in the accumulation of oxindole from 10 to 75% of the indole added. Under denitrifying conditions, regardless of the concentration or source of the inoculum, oxindole appeared in trace amounts but did not accumulate during indole metabolism. In addition, denitrifying consortia which previously metabolized indole degraded oxindole with no lag period. Our data suggest that oxindole accumulation under methanogenic, but not under denitrifying conditions is caused by differences between relative rates of oxindole production and destruction.

The accuracy of a method of data reduction for determining acoustic backscatter coefficients was tested using focused transducers and narrow-band pulses. Two phantoms with well-defined scattering properties were the bases of the tests, one having low attenuation and one with tissue-mimicking attenuation. The experimentally determined backscatter coefficients were found to be independent of transducer-to-scattering-volume distance and to agree very well with theoretical values, typically within 10%.

X-ray linear attenuation coefficients for simulated fat and glandular parenchyma used in ultrasound breast phantoms were measured at 15.2, 20.3, 30.0, 40.0, and 60.0 keV and values compared with published figures calculated from the experimentally determined elemental composition of excised breast parenchyma. Agreement was excellent. These ultrasonic tissue-mimicking (TM) materials can be used in radiographic or ultrasound phantoms for testing imaging instruments as well as for training personnel.

In previous methods of data reduction used to determine ultrasonic backscatter coefficients, various approximations were made. One frequently used is that there is an abrupt cutoff in the lateral extent of the scattering volume interrogated. Another approximation in all previous methods is that the effect of time gating the received echo signals can be written as a function of the distance along the axis of the interrogating beam. In the present paper we show that the backscatter coefficient can be derived from experimental data without making such approximations. The cases of narrow-band and broadband pulses are treated, and the method is applicable whatever the distance between the interrogated volume of scatterers and the transducer face. It is shown that, for a given pulse form, the gate duration must be sufficiently long in order to attain a specified accuracy for the measured backscatter coefficient. A test of the method was done using a phantom with well-defined scattering properties. Very good agreement was found between measured values of backscatter coefficients and those calculated using a first-principles theory.

The influence of postoperative radiation therapy on ipsilateral shoulder function following mastectomy was evaluated from a series of 52 women with primarily operable carcinoma of the breast. Mastectomy and partial axillary dissection were carried out in all patients. In addition, 29 of the patients received postoperative irradiation with 36.6 Gy applied mid-axillarily in 12 fractions with irradiation twice a week. A significant impairment of the active shoulder mobility was found in the irradiated group (p less than 0.01). The passive mobility did not differ significantly between the two groups. The impairment of active shoulder mobility is suggested to be caused by radiation induced subcutaneous fibrosis.

When indole was incubated under methanogenic conditions with an inoculum of sewage sludge, the chemical was metabolized with 10 days and temporary formation of an intermediate was observed. The metabolite was isolated by thin-layer chromatography and determined to be 1,3-dihydro-2H-indol-2one (oxindole) by UV spectroscopy (lambdaMAX, 247 nm) and mass spectrometry (m/z, 133). The methane produced (net amount) indicated nearly complete mineralization of indole.

Two limitations on the animal-hide gelatin and graphite powder tissue equivalent (TE) materials are that they cannot be produced consistently with speeds of sound less than 1,570 m/s at room temperature (22 degrees C) and that irreparable damage can result if the materials are raised to temperatures above 32.5 degrees C. An acceptable substitute polysaccharide gel (agar) has a high melting point (78 degrees C) and can be made to exhibit speeds of sound over the range 1,498 m/s to over 1,600 m/s at 22 degrees C. Thus TE material made with agar is environmentally stable and can be manufactured to exhibit the important speed of sound, 1,540 m/s.

An automatic, three-dimensional, ultrasound beam profiling system was developed and incorporated into a radiotherapy planning minicomputer system with few modifications and at minimal cost. This profiler was invaluable in assessing the characteristics of beams emitted by ultrasound transducers.

The ploidy level was investigated by flow cytometric analysis in 143 cases of invasive intraductal mammary carcinoma. Aneuploidy was found in 70% of the tumours. Comparison of ploidy level with histopathologic features, hormone receptor status and clinical characteristics indicated that aneuploid tumours were mostly poorly differentiated (grade III) and oestrogen receptor negative (p less than 0.05). However, this applied only to postmenopausal patients. No correlation appeared between the progesterone receptor status and the ploidy level, but this parameter tended to predict the frequency of lymph node metastases. The possible prognostic significance of these findings is discussed.