Abstract P6-17-13: ZW49, a HER2 targeted biparatopic antibody drug conjugate for the treatment of HER2 expressing cancers

Background: HER2-targeted therapies have transformed the treatment of patients with HER2-expressing breast and gastric cancers. Despite this, there remains a need for new treatments that are well tolerated and effective not only for cancers with high HER2 expression levels but also those with lower levels of expression. ZW49 is an antibody drug conjugate (ADC) that combines a novel auristatin payload (potent anti-cancer agent) with the unique mechanisms of action of the anti-HER2 biparatopic antibody, ZW25, which binds to the same domains as trastuzumab and pertuzumab. In preclinical studies in cancer cell lines with low to high levels of HER2 expression, ZW25 is associated with increased binding and internalization compared to trastuzumab, while the novel N-acyl sulfonamide auristatin payload has demonstrated increased in vivo tolerability compared to other microtubule inhibitors. ZW49 therefore has the potential to address unmet medical need across a range of HER2-expressing cancers.

Methods: Multiple in vitro and in vivo experiments were performed to characterize ZW49 as a potential therapeutic candidate. Internalization and cell growth inhibition of ZW49 were evaluated in HER2-expressing cell lines. Anti-tumor activity was assessed in patient-derived xenograft (PDX) tumor models of HER2 low and high expressing breast cancers. Tolerability was assessed in a 6-week repeat-dose non-GLP toxicology study in non-human primates (NHP) with intravenous administration of ZW49 at either 9 mg/kg or 12 mg/kg once every two weeks.

Results: In vitro, ZW49 was more rapidly internalized into HER2-expressing cells compared to a monospecific trastuzumab-ADC. ZW49 also displayed potent in vitro cell growth inhibition in several breast cancer cell lines with a range of HER2 expression. This activity was confirmed in multiple in vivo PDX models, including a HER2 IHC 3+ HBCx-13b xenograft where two doses of ZW49 at 3 mg/kg or higher generated tumor regressions, and a HER2 IHC 1+ ST-910 xenograft where a single dose of ZW49 at 6 mg/kg or higher generated regressions. In both models, regressions occurred at exposures that were well tolerated in NHP. In a repeat dose pilot non-GLP study the highest dose tested (12 mg/kg) was considered to be the no observed adverse effect level (NOAEL) and a GLP repeat-dose toxicology study was ongoing at the time of abstract submission.

Conclusions: ZW49 is a novel biparatopic HER2-targeted ADC that demonstrated anti-tumor activity in low and high HER2-expressing breast cancer cell lines and PDX models. Notably, tumor regressions were observed at exposure levels that were well tolerated in NHP. These results support the potential of ZW49 as a novel therapeutic agent that may help address unmet medical need in patients with high and low HER2-expressing cancers.

Citation Format: Hamblett KJ, Barnscher SD, Davies RH, Hammond PW, Hernandez A, Wickman GR, Fung VK, Ding T, Garnett G, Galey AS, Zwierzchowski P, Clavette BC, Winters GC, Rich JR, Rowse GJ, Babcook JS, Hausman D. ZW49, a HER2 targeted biparatopic antibody drug conjugate for the treatment of HER2 expressing cancers [abstract]. In: Proceedings of the 2018 San Antonio Breast Cancer Symposium; 2018 Dec 4-8; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2019;79(4 Suppl):Abstract nr P6-17-13.

Low Dose Pelvimetry with Biplane Digital Radiography

The digital moving slit technique as used by most CT scanners for overview images, was used for antero-posterior and lateral views of the pelvis for pelvimetry. The method was evaluated in phantom experiments and clinical examinations were performed in 23 patients. The method was compared with conventional pelvimetry in 14 patients. Estimated ovarian dose was reduced by a factor of 14.2. The discrepancy in measurements of the pelvic diameters by computed tomography compared with conventional pelvimetry was considered to be without practical importance from an obstetric point of view. Digital pelvimetry is easier for the patient, faster and the need for repeated exposures is eliminated. Based on these facts it is suggested that digital pelvimetry should replace the conventional method whenever possible.

How apoptotic cells aid in the removal of their own cold dead bodies

Apoptotic cell clearance facilitates the removal of aged, damaged, infected or dangerous cells although minimizing perturbation of surrounding tissues, and is a vital process in the development and homeostasis of multicellular organisms. Importantly, failure to correctly execute programmed cell death and subsequent corpse clearance is broadly associated with chronic inflammatory and/or autoimmune diseases such as systemic lupus erythematosus. Apoptotic cells develop dramatic morphological changes including contraction, membrane blebbing and apoptotic body formation, which were among the first and most readily identifiable features of cellular suicide. However, understanding the purpose of apoptotic cell morphological changes has proven to be elusive, and recent studies have made somewhat surprising, and occasionally opposing, conclusions about the contribution of blebbing to phagocytic clearance and prevention of inflammatory/autoimmune disease. We review the evidence indicating how apoptotic blebs actively promote corpse recognition, uptake, and generation of auto-reactive antibodies.

Activating ROCK1 somatic mutations in human cancer

Cancer cells acquire characteristics of deregulated growth, survival and increased metastatic potential. Genetic mutations that provide a selective advantage by promoting these characteristics have been termed 'drivers,' whereas mutations that do not contribute to disease initiation/progression are termed 'passengers.' The advent of high-throughput methodologies has facilitated large-scale screening of cancer genomes and the subsequent identification of novel somatic mutations. Although this approach has generated valuable results, the data remain incomplete until the functional consequences of these mutations are determined to differentiate potential drivers from passengers. ROCK1 is an essential effector kinase downstream of Rho GTPases, an important pathway involved in cell migration. The Cancer Genome Project identified three nonsynonymous mutations in the ROCK1 gene. We now show that these somatic ROCK1 mutations lead to elevated kinase activity and drive actin cytoskeleton rearrangements that promote increased motility and decreased adhesion, characteristics of cancer progression. Mapping of the kinase-interacting regions of the carboxy terminus combined with structural modeling provides an insight into how these mutations likely affect the regulation of ROCK1. Consistent with the frequency of ROCK1 mutations in human cancer, these results support the conclusion that there is selective pressure for the ROCK1 gene to acquire 'driver' mutations that result in kinase activation.

Assessment of correlated dose and sensitivity profiles on a multi-slice CT scanner

In the case of computed tomography (CT) scanners as well as other imaging techniques utilising ionising radiation, it is imperative that radiation is confined to the sensitive part of the image detector. Assuring this for a CT scanner requires detailed information about the scanner dose and sensitivity profiles and their spatial correlation. The profiles should ideally be co-centric and tightly fit to each other. Ensuring this inherent performance of the scanner can be seen as one of the fundamental steps in optimising diagnostic examinations with CT. A measurement device using a dedicated liquid ionisation chamber is employed to investigate the performance of a Toshiba Aquilion 16 scanner in this aspect. Dose profile and sensitivity profile pairs for four collimations are presented where each pair of profiles are spatially correlated to each other. The measurement device can be applied to any scanner for fast and accurate assessment of dose and sensitivity profiles and their spatial correlation.

Long-term stability of liquid ionization chambers with regard to their qualification as local reference dosimeters for low dose-rate absorbed dose measurements in water

The long-term sensitivity and calibration stability of liquid ionization chambers (LICs) has been studied at a local and a secondary standards dosimetry laboratory over a period of 3 years. The chambers were transported several times by mail between the two laboratories for measurements. The LICs used in this work are designed for absorbed dose measurements in the dose rate region of 0.1-100 mGy min(-1) and have a liquid layer thickness of 1 mm and a sensitive volume of 16.2 mm3. The liquids used as sensitive media in the chambers are mixtures of isooctane (C8H18) and tetramethylsilane (Si(CH3)4) in different proportions (about 2 to 1). Operating at a polarizing voltage of 300 V the leakage current of the chambers was stable and never exceeded 3% of the observable current at a dose rate of about 1 mGy min(-1). The volume sensitivity of the chambers was measured to be of the order of 10(-9) C Gy(-1) mm3. No systematic changes in the absorbed dose to water calibration was observed for any of the chambers during the test period (sigma < 0.2%). Variations in chamber dose response with small changes in the polarizing voltage as well as sensitivity changes with accumulated absorbed dose were also investigated. Measurements showed that the LIC response varies by 0.15% per 1% change in applied voltage around 300 V. No significant change could be observed in the LIC sensitivity after a single absorbed dose of 15 kGy. The results indicate that the LIC can be made to serve as a calibration transfer instrument and a reference detector for absorbed dose to water determinations providing good precision and long-term reproducibility.

Effects of tamoxifen on oxyhemoglobin-induced cerebral vasoconstriction

The effect of tamoxifen on oxyhemoglobin-mediated cerebral vasoconstriction was examined. Tamoxifen caused a concentration-dependent relaxation of cerebral artery preparations contracted with oxyhemoglobin and phorbol myristate acetate with the IC(50) values 0.66+/-0.1 and 1.1+/-0.1 microM, respectively. In cerebrovascular smooth muscle cells, oxyhemoglobin and phorbol myristate acetate induced protein kinase C activation, which was 220+/-7% and 203+/-8% of control, respectively. The increase in protein kinase C activity was prevented by tamoxifen. The results suggest that the ability of tamoxifen to reverse vasoconstriction is mediated, at least in part, via inhibition of protein kinase C.

General collection efficiency in liquid iso-octane and tetramethylsilane used as sensitive media in a thimble ionization chamber

The general collection efficiency in the dielectric liquids iso-octane (CaH18; 2-2-4 trimethylpentane) and tetramethylsilane (Si(CH3)4), used as sensitive media in a thimble liquid ionization chamber (LIC) with a liquid layer thickness of 1 mm, has been studied. Measurements were made for continuous radiation at varying dose rates using 140 keV photons from the decay of 99mTc for chamber polarizing voltages of 50, 100 and 500 V. The maximum dose rate in each measurement session was about 150 mGy min(-1). The experimental results were compared with theoretical general collection efficiencies calculated by the equation for the general collection efficiency in gases. The results show that the general collection efficiency in a thimble LIC for continuous radiation can be calculated with the equation for the general collection efficiency in gas ionization chambers, using the same chamber geometry correction factors and analogous characteristic ion recombination parameters for the dielectric liquids.

Assessment of the relative dose distribution around an 192Ir line source using a liquid ionization chamber

The relative absorbed dose distribution in water around an 192Ir line source of 50 mm length and 0.3 mm diam has been measured using a liquid ionization chamber (LIC). The sensitive volume of the chamber is a cylinder with 3.0 mm diam and a thickness of 1.0 mm. The sensitive medium in the LIC consists of a mixture of two dielectric liquids, tetramethylsilane and isooctane. The mixture has been optimized so that the LIC provides an almost energy-independent response for the radiation qualities present at different distances from the source in water. The measurements were carried out at distances of 2.5-50.0 mm along the source bisector and at distances of 0.0 to +/-40.0 mm along the source axis. The results were compared with measurements made with LiF chips in Solid Water and with calculated data based on an analytical solution to the Sievert integral as well as with Monte Carlo calculations of absolute dose rate in water. Considering the uncertainties involved, the dose distribution measured by the LIC is in reasonably good agreement with the theoretical data as well as the results held with LiF. In comparison with the Monte Carlo calculations the discrepancies range from 0.1% to 18% with the largest differences at points close to the source. This work demonstrates the ability of the LIC for mapping the dose distribution around a low-dose-rate brachytherapy source emitting photons of intermediate energies.

Liquid ionization chambers for absorbed dose measurements in water at low dose rates and intermediate photon energies

Two new liquid ionization chamber (LIC) designs, consisting of cylindrical and plane-parallel configurations, are presented. They are designed to be suitable for high-precision measurements of absorbed dose-to-water at dose rates and photon energies typical for LDR intermediate photon energy brachytherapy sources. The chambers have a sensitive liquid layer thickness of 1 mm and sensitive volumes of 7 mm3 (plane-parallel) and 20 mm3 (cylindrical). The liquids used as sensitive media in the chambers are either isooctane (C8H18), tetramethylsilane (Si(CH3)4) or mixtures of these two liquids in the approximate proportions 2 to 1. A chamber filled with such a liquid mixture and with a polarizing voltage of 300 V, provides a volume sensitivity of about 10(-9)C Gy(-1) mm(-3) for absorbed dose measurements in water in an x-ray radiation field with an effective photon energy of 120 keV. In the interval 30 to 140 keV, the relative change in sensitivity is less than +/- 2.5%. The leakage current of the chambers is low and stable, which implies that absorbed dose measurements can be done with good reproducibility at dose-rates as low as 50 microGy min-1 (sigma < 3%). The long-term calibration stability was tested for a set of five chambers over a period of more than 1 year. No systematic change in their sensitivity could be observed. The general recombination at a polarizing voltage of 300 V is less than 2% for dose-rates up to about 100 mGy min-1. The temperature dependence at room temperature is 0.5% per degree C. The response is almost independent of the direction of the radiation for the plane-parallel LIC.

Liquid ionization chamber measurements of dose distributions in small 6 MV photon beams

A new liquid ionization chamber (LIC) design optimized for high spatial resolution was used for measurements of dose distributions in radiation fields intended for stereotactic radiosurgery (SRS). This work was mainly focused on the properties of this detector in radiation fields from linear accelerators for clinical radiotherapy (pulsed radiation with dose rates from approximately 0.5 to 5 Gy min-1 and beam diameters down to 8 mm). The narrow beams used in stereotactic radiosurgery require detectors with small sizes in order to provide a good spatial resolution. The LIC is investigated to see whether it can be used as a detector for dose measurements in beams currently used for stereotactic radiosurgery. Its properties are compared with those of silicon diodes. The comparisons include output factor (OF), depth dose and profile measurements in 6 MV photon fields of different sizes. For OF measurements, an NACP air ionization chamber was also used in the comparison. The dependence of the response on the detector orientation in the photon beam is also investigated for the diodes and the LIC. The results suggest that LICs can provide better properties than diodes for measuring dose distributions in narrow photon beams.

General collection efficiency for liquid isooctane and tetramethylsilane in pulsed radiation

The general collection efficiency in pulsed radiation was studied for isooctane (C8H18) and tetramethylsilane (Si(CH3)4). These two liquids were used as sensitive media in a parallel-plate liquid ionization chamber with a 1 mm sensitive layer. Measurements were carried out using 20 MV photon radiation from a linear accelerator with a pulse repetition frequency of 30 pulses/second and a pulse length of 3.5 microseconds. The general collection efficiency was determined for polarizing voltages in the interval 1000-2000 V for isooctane and 500-2000 V for tetramethylsilane and for pulse doses in the interval 0.06-1.9 mGy/pulse. An air ionization chamber was used as a pulse dose reference monitor. The experimental results were compared with those predicted by the equation for the general collection efficiency for gases in pulsed radiation, using the permittivity of each of the liquids. It was found that for general collection efficiencies down to 80% the differences between the predicted and experimental general collection efficiencies in the two liquids were within +/- 1% at electric field strengths exceeding 10(6) V m-1.

General collection efficiency for liquid isooctane and tetramethylsilane used as sensitive media in a parallel-plate ionization chamber

The general collection efficiency has been measured in liquid isooctane (C8H18) and tetramethylsilane (Si(CH3)4) used as the sensitive media in a parallel-plate ionization chamber, with an electrode distance of 1 mm, intended for photon and electron dosimetry applications. The liquid ionization chamber was irradiated at different dose rates by 140 keV photons from the decay of radioactive 99mTc. The measurements were made at potential differences of 50, 100, 200 and 500 V. Measurements were performed for each liquid and electric field strength, with the decay rate of 99mTc used as the dose-rate reference. The maximum dose rate was about 150 mGy min-1 in each experiment. When the measured general collection efficiency values are compared with the theoretical predictions for collection efficiency in gases, it is found that the latter also describe the general collection efficiency in the two liquids within 1% of the saturation current for collection efficiencies down to 60% when using experimentally determined recombination rate constants and on mobilities characteristic of each of the liquids.

Properties of liquid ionization chambers at LDR brachytherapy dose rates

Properties such as sensitivity, general recombination and reproducibility of liquid-filled parallel-plate ionization chambers for dosimetry in low-dose-rate brachytherapy radiation fields have been evaluated. Two different dielectric liquids, isooctane (C8H(1)8) and tetramethylsilane (Si(CH3)4), have been used as sensitive media in chambers having a coin-shaped sensitive volume of 3 mm in diameter and 1 mm thickness. An electric field strength of 300 kV m-1 was found to be optimal with respect to sensitivity, leakage current and general recombination. At absorbed dose rates from 0.1-100 mGy min-1 the ionization charge measurements at an irradiation time of 1 min showed a reproducibility better than 1%, and a general recombination not exceeding 0.5%. The calibration--absorbed dose to water against ionization charge at a 60Co reference source--did not show any significant change over an observation time of one year for any of the chambers.

Selective salpingography and fluoroscopic transcervical salpingoplasty for diagnosis and treatment of proximal fallopian tube occlusions

In 25 women with primary or secondary infertility, primary hysterosalpingography (HSG) or laparoscopy with chromopertubation indicated 33 proximal and 2 distal tubal obstructions. Four salpingectomies had been performed earlier. All patients were considered for transcervical catheter salpingoplasty (TCSP) to reconstruct tubal patency. Secondary examination with repeat HSG or selective osteal salpingography confirmed 26 proximal and 3 distal tubal occlusions while 17 tubes were patent. Selective osteal salpingography was performed successfully in 32 of 33 (97%) tubes. Sixteen of 26 (61.5%) proximally occluded tubes were successfully recanalized by coaxial catheter and guidewire technique while two of three distally occluded tubes were reopened by forceful flushing of contrast medium. So far, one ectopic and five intrauterine pregnancies were achieved in ten patients with observation time more than four months. Three patients have had normal deliveries. The favorable results, lack of complications and low costs seem to justify the recommendation to use selective salpingography and fallopian tube recanalization as the first intervention in patients with obstruction of the proximal fallopian tube.

Polarity effect in plane-parallel ionization chambers using air or a dielectric liquid as ionization medium

A plane-parallel ionization chamber having a sensitive volume of 2 mm3 and using the dielectric liquid tetramethylsilane as the sensitive medium instead of air is described. In the design of the chamber special attention was given to the factors that can cause unwanted currents in the cable, stem, or the chamber dielectric material. The chamber has been tested with respect to the polarity effect in regions of radiation fields where ordinary plane-parallel ionization chambers will often fail. These regions are the build-up region in photon fields, and the region close to the practical range for electrons where nonelectronic equilibrium is significant. Experimental results show that, despite the extremely small ionization volume in the liquid ionization chamber, the polarity effect never exceeds a few tenths of a percent in field positions where well-known commercially available chambers with much less spatial resolution designed for measurements in radiation therapy fields can show polarity effects of 5% to 30%. The origin of spurious currents and how they must be minimized in the design of either a liquid- or gas-filled ionization chamber is discussed.

Absorbed dose in water. Comparison of several methods using a liquid ionization chamber

In the present investigation a liquid ionization chamber has been used as a transfer instrument for the quantity absorbed dose in water in a cobalt-60 gamma-ray beam. The characteristics of the liquid ionization chamber are described. The transferred dosimetric information has been compared with absorbed-dose determination using air-ionization-chamber dosimetry, water calorimetry and ferrous-sulphate dosimetry. The agreement between the different measured absorbed-dose values is very good, i.e. within 0.2%. This is an indication that the consistency in the methods used to determine absorbed dose in water is good. The impact of the new standard for air kerma in air, introduced in 1986 by the BIPM, on the air-ionization-chamber dosimetry is investigated. It is shown that any differences in the dosimetry when using the old or the new set of data cancel out for the cobalt-60 beam. The investigation also shows that the value of epsilon mG for the ferrous-sulphate dosimeter recommended in ICRU 35 for electrons can be used also in cobalt-60 beams.

Low field (0.02 T) MR imaging of the whole body

The diagnostic utility of extremely low field magnetic resonance (MR) (0.02 T) was evaluated in various parts of the body outside the head. The areas investigated included the spine (104 patients), kidneys (19 patients), female pelvis (21 patients), and hips (15 patients). The results were compared with those of other imaging modalities, e.g., ultrasound, CT, and scintigraphy. Available pulse sequences and typical examination times for different types of studies are reported. Poor spatial resolution and long imaging times limit the application of this technique to the whole body. Due to poor signal-to-noise ratio, image quality is not comparable with that obtained at higher field strengths. In spite of these restrictions it was possible to demonstrate lumbar disk herniations, to differentiate renal and ovarian cysts from tumors, and to detect early avascular necrosis of the femoral head. Extremely low field MR imaging may eventually be used in screening spinal pathology and in the diagnosis of early avascular necrosis of the femoral head. At present, this technique can not replace ultrasound or CT in abdominal examinations.

Magnetic resonance imaging of renal masses at 0.02 tesla

To determine the usefulness of extremely low field magnetic resonance imaging (MRI) in the evaluation of renal masses 19 patients with 15 tumors (13 renal and 2 renal pelvic carcinomas) and 8 cysts were examined in a 0.02 tesla MRI unit. The findings were compared with results of computed tomography (CT) and ultrasound. Cavography was performed in 6 patients. MRI enabled differentiation between cysts and solid tumors. Tumor extension into the inferior vena cava could be demonstrated in one case and liver metastases in two patients. The image quality was inferior to that reported at higher field strengths and the tumors were more precisely staged by CT and ultrasound. At present, it is unlikely that low field MRI will play any substantial role in the evaluation of renal masses.

Low dose pelvimetry with biplane digital radiography

The digital moving slit technique as used by most CT scanners for overview images, was used for antero-posterior and lateral views of the pelvis for pelvimetry. The method was evaluated in phantom experiments and clinical examinations were performed in 23 patients. The method was compared with conventional pelvimetry in 14 patients. Estimated ovarian dose was reduced by a factor of 14.2. The discrepancy in measurements of the pelvic diameters by computed tomography compared with conventional pelvimetry was considered to be without practical importance from an obstetric point of view. Digital pelvimetry is easier for the patient, faster and the need for repeated exposures is eliminated. Based on these facts it is suggested that digital pelvimetry should replace the conventional method whenever possible.

Bone mineral content in the proximal tibia measured by computer tomography

With a slight modification of the EMI MK1 scanner a sensitive method for examination of the bone mineral content in the proximal tibia was achieved. The method allows an estimation of the amount of trabecular and cortical bone as well as their mineral content. The anatomic structure of the bone substance is demonstrated, differing in osteoporosis and osteomalacia. The reproducibility is acceptable.

Experimental and clinical evaluation of cholangiography with xeroradiography

Conventional screen film radiography is compared with xeroradiography in an experimental model for cholangiography. The wider exposure latitude of the xerographic technique confers certain diagnostic advantages. However, the actual clinical application presents practical difficulties, which, combined with low sensitivity, are of such a nature that the method can hardly be considered suitable at the present time. If certain improvements can be made, xeroradiography could become a superior method for radiography of the bile ducts.

Mean energy imparted in relation to the focus to object distance

The relationship between the energy absorbed by the patient at the exposure of a radiographic image and the focus to object distance is analysed. It is found that the mean energy imparted, or the integral absorbed dose, is the same irrespective of the focus to object distance when the energy fluence and the field size are both normalized at the film plane. When the field size is kept constant within the object whilst the focus to object distance is varied a limited increase in the mean energy imparted occurs when the focus to object distance is decreased; this statement is valid for the focus to object distances which are usually applied in diagnostic radiology. When estimating radiation risks the importance of the focus to object distance is found to be of limited interest.

Image distortion in narrow beam rotation radiography. A mathematical analysis

A general mathematical analysis of the image distortion in narrow beam rotation radiography has been performed. Distortion effects are often evident in panoramic images exposed in clinical practice. It is found that in spite of this general experience panoramic images, exposed with the aid of a rotating narrow beam, are reliable for ordinary clinical demands when the object morphology is to be assessed. This statement is valid provided that the object has been properly positioned at the exposure.

Elliptical narrow beam rotation radiography

The basic mathematics for elliptical narrow beam rotation radiography are deduced and exemplified. An analysis of the functioning principle of elliptical systems shows that the essential factor in the image formation is the form of the evolute of the ellipse, which determines the projection of the object. The image layer does not necessarily coincide with the ellipse.

Blurring and layer thickness in narrow beam rotation radiography

The definition of the blurring of narrow beam rotation radiography is revived. The relative value of the blurring is considered to be the most reliable measurement. Calculations of the layer thickness should be based on the definition of the relative blurring. Experimental tests were performed, which confirm the mathematically presented hypothesis and also confirm the validity of the mathematical model of narrow beam rotation radiography presented by WELANDER (1974).

A substitute for the water box in the original EMI brain scanner

A modified water box for the EMI brain scanner is described. The modified box permits parts of the body other than the brain to be scanned. The patient setup for brain scans is simplified, and motion artifacts have almost disappeared.

Absorbed dose in mammary radiography

By exposure measurements in an alcohol-water mixture simulating breast tissue, the absorbed dose, and dose distribution in the breast at the radiation qualities commonly used in mammary radiography have been calculated. The absorbed doses for different recording media have been compared at those radiation qualities which result in similar image qualities in the different recording media.

Experimental evaluation of tube potential and contrast medium concentration for cholangiography

Model cholangiographic experiments were performed in which the relationship between contrast medium concentration, duct diameter, calculus size and tube potential was analysed. The same degree of diagnostic reliability was obtained by increasing the tube potential as by diluting the contrast medium. A tube potential of 100 to 110 kV and a contrast medium concentration of 45 per cent were found to give the best result if the background density of the film was held constant.