Ferrous sulphate dosimetry by the thiocyanate method

The use of ammonium thiocyanate to estimate ferric ions in the ferrous sulphate dosimeter has been investigated. The spontaneous oxidation rate of ferrous ions increased with increase in thiocyanate ion or ferrous ion concentration and with decrease in ferric ion concentrations. The spontaneous oxidation rate was too fast at the usual ferrous ion concentrations to permit accurate measurements at low doses. However it was slowed down to an acceptable level by using a dosimeter solution of 1 × 10⁻⁴ M FeSO₄/1 × 10⁻³ M NaCl/0.4 M H₂ SO₄ in which the G(Fe³⁺) value was found to be 15.6 and independent of dose up to 5 krad. Two procedures involving different proportions of thiocyanate were used to form the ferric thiocyanate complex. Optical absorbance measurements were made at 477 nm. Details of the method are given for the estimation of doses in the range 200–2600 rad. Only 1 ml of dosimeter solution is required when 10 cm path length spectrophotometer micro-cells which are commercially available are used. A standard error of less than ±1.0% was obtained.     

Ceric/thallous dosimetry at less than 1000 rad

The ceric/thallous system has been investigated as a low level dosimeter using fluorimetry for the radiation-produced cerous ion. Excellent linearity between the increase in the cerous ion concentration and the dose was obtained using an aerated solution of 13 μM Ce(IV), 6μM Ce(III), 20 μM Tl(I) in 0.4 M H₂SO₄. G(Ce³⁺) was found to be 7.56 ± 0.08. The internal filter effect caused by the ceric ions is not a problem provided that the initial concentration is less than 15 μM since the same G(Ce³⁺) value was obtained regardless of whether the results were corrected for the internal filter or not. The most serious disadvantages of the system appear to be light sensitivity and thermal reduction of ceric ions. The thermal reduction is most rapid immediately after solution preparation and requires a delay of about one month before stability is achieved.     

Measurements of the Fe3+ diffusion coefficient in Fricke Xylenol gel using optical density measurements

In Fricke dosimetry, optical density measurements are performed some time after dosimeter irradiation. Values of the diffusion coefficient of Fe³⁺ in Fricke Xylenol gel (FXG) are necessary for determining the spatial distribution of the absorbed dose from measurements of the optical density. Five sets of FXG dosimeters, kept at different constant temperatures, were exposed to collimated 6 MV photons. The optical density profile, proportional to the Fe³⁺ concentration, at the boundary between irradiated and non-irradiated parts of each dosimeter was measured periodically over a period of 60 h. By comparing the experimental data with a function that accounts for the unobserved initial concentration profile of Fe³⁺ in the FXG, we obtained diffusion coefficients 0.30±0.05, 0.40±0.05, 0.50±0.05, 0.60±0.05 and 0.80±0.05 mm²/h for the temperatures 283.0±0.5, 286.0±0.5, 289.0±0.5, 292.0±0.5, and 296.0±0.5 K, respectively. The activation energy of Fe³⁺ diffusion in the gel, 0.54±0.06 eV, was determined from the temperature dependence of the diffusion coefficients.     

Measurement of the G-value for 1·5 keV X-rays

Summary

Although there are several theoretical predictions of the dependence of the G-value on X-ray energy, measurements have not been made below ≈ 7 keV. Using a ferrous sulfate solution modified by the addition of benzoic acid, we have measured the relative G-values for Al_k characteristic X-rays (1·5 keV), ²³⁸Pu α-particles (3·7 MeV), ⁶⁰Co (1·17 MeV) and ¹³⁷Cs (0·66 MeV) γ-rays. This modified ferrous sulfate solution gave a 4-fold increase in sensitivity relative to the conventional solution, making measurements with the Al_k X-rays feasible. The relative ferrous-to-ferric conversions as a function of dose were similar for the two γ-ray energies, yielding G-values of 1·62 and 1·59 µmol J^?1 for the ⁶⁰Co and ¹³⁷Cs radiations, respectively. The α-particle G-value was 0·52 µmol J^?1, or 31 per cent of that for the ⁶⁰Co γ-rays, in good agreement with previous measurements. The Al_k X-rays had a G-value of 0·92 µmol J^?1 or 57 per cent of that of the ⁶⁰Co radiation. This G-value for the 1·5 keV X-rays is within 20 per cent of the values predicted by current theories, and theoretical values are within the error range of our measurement. The consistency between the experimental value reported here and theoretical G-values for ultrasoft X-rays should be valuable for models of radiation action on biological systems.     

Radiochromic solutions for reference dosimetry

A chemical radiochromic dosimeter using hexa(hydroxyethyl)pararosaniline nitrile (HHEV-CN) dissolved in an aerated mixture of triethyl phosphate and dimethyl sulfoxide can be used over a wide absorbed dose range as a stable reference dosimeter, with useful characteristics, both for steady-state and pulsed radiation fields. Solutions of the leuco dye at 2-mM concentration, containing small amounts of acetic acid, p-nitrobenzoic acid and polyvinylbutyral, show high precision and a linear response for absorbed doses up to 4 kGy. When the leuco dye concentration is increased to 100 mM, the response is also linear, and absorbed doses as low as 0.5 Gy can be read with a precision of 1.3% (95% confidence limits). The radiation chemical yield is constant with changes in absorbed dose rate, but it increases with concentration of the leuco dye up to 10⁻¹ molarity. The radiation chemical yields for dye formation are: for 2-mM solution, G(dye) = 0.015 μmol J⁻¹; for 100-mM solution, G(dye) = 0.28 μmol J⁻¹. The uncertainties for these measured values are ±2.6% (95% confidence limits). The molar linear absorption coefficient at 605–608 nm wavelength is 1.0 × 10⁵ L mol⁻¹ cm⁻¹, the uncertainty (95% confidence limits) being ±2.2%. This dosimeter solution may be used in small sealed glass ampoules or plastic vials and is useful for measuring x- and γ-ray doses of interest in food irradiation and in clinical radiology. The combination of ingredients simulates water and biological tissue (muscle) in terms of radiation interaction cross sections, i.e. mass energy-absorption coefficients for photons (0.1–20 MeV) and mass collision stopping powers for electrons (0.1–50 MeV).     

N-isopropylacrylamide gel dosimeter to evaluate clinical photon beam characteristics

The introduction of beam intensity control concept in current radiotherapy techniques has increased treatment planning complexity. Thus, small-field dose measurement has become increasingly vital. Polymer gel dosimetry method is widely studied. It is the only dose measurement tool that provides 3D dose distribution. This study aims to use an N-isopropylacrylamide (NIPAM) gel dosimeter to conduct beam performance measurements of percentage depth dose (PDD), beam flatness, and symmetry for photon beams with field sizes of 3×3 and 4×4 cm². Computed tomography scans were used to readout the gel dosimeters. In the PDD measurement, the NIPAM gel dosimeter and Gafchromic^TM EBT3 radiochromic film displayed high consistency in the region deeper than the build-up region. The gel dosimeter dose profile had 3% lower flatness and symmetry measurement at 5 cm depth for different fields compared with that of the Gafchromic^TM EBT3 film. During gamma evaluation under 3%/3 mm dose difference/distance-to-agreement standard, the pass rates of the polymer gel dosimeter to the TPS and EBT3 film were both higher than 96%. Given that the gel is tissue equivalent, it did not exhibit the energy dependence problems of radiochromic films. Therefore, the practical use of NIPAM polymer gel dosimeters is enhanced in clinical dose verification.     

Radiation-induced decomposition of aqueous trichloroethylene solutions

In air-saturated reagent grade water, 10 ppm trichloroethylene are decomposed by γ radiation in a roughly first-order reaction; the initial G-value being 5.4 molecules/100 eV. At sub-ppm concentrations the kinetics remain roughly first-order; the initial G-values decrease with decreasing concentration. The main decomposition products are Cl⁻, CO₂ and HCOOH. A tentative reaction scheme in accordance with these results is presented.     

Verifikation optimierter 3D-Dosisverteilungen mittels MR-Fricke-Gel

Purpose

Complex 3D treatment planning techniques require a dose verification throughout the irradiated volume. Conventional dosimetry techniques only unsatisfyingly serve these needs.

Material and Method

The chemical dosimeter FeSO₄ solution can be used for measuring spatial dose distributions with the help of magnetic resonance imaging by fixing the iron ions in a gelatine matrix. A 3D dosimetry method was developed for 3D verification in an homogeneous, anthropomorphic phantom. The verification is achieved by juxtaposition or superposition of measured and calculated isodoses.

Results

Different gel compositions were studied in view of their applicability as clinical 3D dosimeter concerning dose response, linearity and diffusion behaviour. A gel with 5% gelatin and 1 mM of ferrous ions proved to be the most suitable. The inverse spin-spin relaxation time T₂ ^?1 is an indicator of the ferric ion concentration that showed to be linear with the dose in the range between 0 and 40 Gy (R²=0.996). The dose response was 0.057 per second and Gy. The observed diffusion of the iron ions was only influenced little by different gel compositions. To isolate the restrictions in the clinical application, measurements on the disturbing effects like, e. g. the inhomogeneous spatial response and the gel surface effects, were made and eliminated with the subtraction method. The clinical use of the method is demonstrated for the examples of the verification of calculated 3D dose distributions of a shielded¹⁹²Ir afterloading vaginal applicator and a head and neck 3-field plan with the use of asymmetric jaws and compensators.

Conclusion

The study demonstrates the clinical applicability of the method and shows its limitations.     

Self-diffusion of Co2+ ions in CoCl2 and CoSO4, and electrolyte-diffusion of CoSO4 and ZnSO4 in agar gel medium

Self-diffusion of Co²⁺ ions in CoCl₂ and CoSO₄ in the concentration range of 10⁻⁵ to 0.25 M is studied in 1% agar gel at 25°C using zone-diffusion technique. The divergence observed between theoretical and experimental values of diffusion coefficients in both systems is explained on the basis of various types of interactions occurring in the system.The applicability of the transition state theory to the diffusion of ZnSO₄ in agar gel medium is tested by varying the temperature of the system as well as the gel concentration. The activation energy and D₀ value decrease with increasing gel concentration, in agreement with the theory.The obstruction effect determined in terms of α-value, describing the relative lowering of the diffusion coefficient in gel medium in comparison with the pure solution, in the diffusion of ZnSO₄ is found to be independent of temperature. The effect of electrolyte concentration on obstruction effect and on activation energy (E) for diffusion of CoSO₄ is also examined. The decrease in α and E values with electrolyte concentration is explained by considering the competitive hydration between ions and agar molecules and Wang's model respectively.     

Effect of the first row transition metal ions on positronium formation

The effect of various metal ions on positronium formation and the lifetime of orthopositronium (oPs) was investigated in three different kinds of substances. In the fine powders prepared by heat-treatment of Ca and Zn oxalates, there was a substantial amount of surface oPs component while there was no surface oPs component in the heat-treated oxalates of the first row transition metal ions (Mn, Fe, Ni and Cu). The positron lifetime spectrum of allophane, a kind of mixed silica-alumina gel, was also studied. The 3rd and the 4th components have been attributed to oPs within and on the surface of ther particles, respectively. Both I₃ and I₄ were decreased when Fe³⁺ ions were substituted for some of the Al³⁺ ions. λ₃ also increased with increasing amount of Fe³⁺ ion. The unpaired spins have two effects; inhibition of Ps formation and quenching of oPs lifetime. In further experiments, the effect of the metal ions which were incorporated into the chain of a polymeric system was investigated. In this case the effect of the unpaired spins was of minor inportance, and the structural condition of the substance seemed to be more important in determining oPs intensity. A possible explanation for the different experimental results obtained for the fine powders (heat-treated metal oxalates and allophane) and the polymeric systems has been given.     

NATO Advanced Study Institute on ‘Photosensitization: Molecular,Cellular and Medical Aspects’ (Held at the Royal Military College of Canada,Kingston, Canada from 5 to 18 July 1987)

Summary

Experiments were performed to calibrate a recently developed pulsed field gel electrophoresis assay, the asymmetric field inversion gel electrophoresis (AFIGE), for the measurement of double-strand breaks (dsb) in the DNA of mammalian cells. Calibration was carried out by means of ¹²⁵I decay accumulation, under conditions preventing repair, and is based on the observation that each ¹²⁵I decay in the DNA produces approximately one dsb. Iodine was incorporated into DNA in the form of 5′-iododeoxyuridine and decay accumulation was allowed in cells kept frozen at ? 80°C. Since widely different DNA damage dose-response curves were obtained in cells exposed to X-rays in various phases of the cell cycle, calibration was performed using synchronized populations of cells that were allowed to accumulate DNA damage in G₁, G₁/S, mid-S, and G₂ + M. For this purpose the fraction of activity (in DNA) released from the plug (FAR) was measured and correlated to the number of ¹²⁵I decays accumulated during the elapsed period of time. Fluctuations in the FAR per ¹²⁵I decay were observed throughout the cell cycle that were similar to those previously reported for the FAR per Gy of X-rays. Comparison of the FAr per ¹²⁵I decay with the FAR per Gy gave an induction of 21 ± 3, 31 ± 3, 21 ± 3 and 26 ± 8 dsb per Gy per diploid DNA complement for G₁, G₁/S, S, and G₂ + M cells, respectively. The results suggest that the observed fluctuations in the FAR per Gy throughout the cycle reflect cell-cycle-associated differences in the physicochemical properties of the DNA molecules that alter their electrophoretic mobility, rather than variations in the induction of dsb per Gy, i.e. the sensitivity of the assay fluctuates throughout the cycle. We propose that similar phenomena underlie the observed fluctuations throughout the cell cycle in the fraction of activity eluted per Gy in the non-unwinding filter elution assay. ¹²⁵I decays accumulated at 4°C in partly purified DNA from cells embedded in agarose plugs and lysed immediately, gave FAR identical to those obtained with cells kept frozen. This finding suggests that indirect effects do not significantly contribute to DNA damage induction by ¹²⁵I decay, and indicate that calibration of electrophoresis techniques for dsb measurements can be carried out using this simplified protocol.     

Effects of Calmodulin Antagonists on Radiation-induced Lipid Peroxidation in Microsomes

Summary

Rat liver microsomes were irradiated with γ-rays at a dose rate of 1·31 Gy s^?1. The extent of lipid peroxidation, measured in terms of malondialdehyde (MDA) formed, increased with radiation dose. The presence of calmodulin antagonists during irradiation decreased lipid peroxidation. The order of their protective efficiency was: chlorpromazine (CPZ) > promethazine (PMZ) > trimeprazine (TMZ). Their protective effect was diminished in the presence of ferrous (Fe²⁺) ions and was restored on addition of EDTA. However, calmodulin antagonists considerably inhibited radiation-induced lipid peroxidation in the presence of ferric (Fe³⁺) ions. Calmodulin antagonists also decreased the cytochrome P-450 content of microsomes. These results are discussed with respect to their applicability to radiotherapy. A possible mechanism for the inhibition of radiation-induced lipid peroxidation is suggested.     

The degradation of triazo dye chlorantine fast green BLL in aqueous solutions by gamma radiation—III

The radiation degradation yield (G_{d values}) of Chlorantine Fast Green BLL (CFGBLL), G_d, i.e. the value of moles of dye molecules degraded per joule of energy absorbed (sometimes given in units of the number of molecules decomposed per 100 eV of radiation energy absorbed) was measured in aerated, oxygen- and nitrogen-saturated aqueous solutions. The G_d values were found to be 0.063, 0.0715 and 0.033 μmol/J or (0.61, 0.69 and 0.32/100 eV) respectively. The relatively low degradation yield indicates the absence of chain reactions and probably the poor efficiency and economics, in terms of the practical application of the radiation process. For applications in the radiation treatment of waste water, it is noted that in the presence of oxygen and at higher concentration of CFGBLL, the value of G_d increases markedly, so that it may be practical to monitor the extent of sterilization of water. In addition the radiation processing of CFGBLL waste water may also become economically feasible. The specific bimolecular rate constant of the reaction of CFGBLL with the ^.OH was determined by studying the effect of ethanol concentration on G_d using competition kinetics. This rate constant was found to be k = 2.32 × 10¹⁰ and 1.65 × 10¹⁰ L mol/s at 610 and 380 nm wavelengths, respectively. Suggestions are made for the possible use of CFGBLL aqueous solution as a chemical dosimeter in the range of absorbed dose from 0.1 to 5 kGy.     

A comparison of high b-value vs standard b-value diffusion-weighted magnetic resonance imaging at 3.0?T for medulloblastomas

Objective:

To investigate the utility of diffusion-weighted (DW) MRI using high b-value vs standard b-value for patients with medulloblastoma (MB). Minimum apparent diffusion coefficient (ADC_MIN) values were also compared with tumour cellularity.

Methods:

High and standard b-value DW images were obtained for 17 patients with MB. The number and location of the lesions, signal intensities (SIs), signal-to-noise ratios (SNRs), contrast-to-noise ratios, contrast ratios (CRs) and ADCs of the lesions were compared. Tumour cellularity was also measured and compared with ADC_MIN values.

Results:

All 20 lesions were hyperintense on the DW MR images with high and standard b-values. Four additional lesions were revealed on high b-value, and all 24 lesions were more conspicuous at high b-value. SI, SNR and ADC values for the lesions were lower in the high b-value images than in the standard b-value images. The ADC_MIN value at b = 3000 s mm⁻² was more significantly associated with tumour cellularity than that at b = 1000 s mm⁻². CR values were significantly higher in the high b-value images than in the standard b-value images.

Conclusion:

DW imaging using high b-value may be beneficial for detecting additional, less prominent lesions and may improve the contrast between MB lesions and normal tissue. A stronger inverse correlation with tumour cellularity was identified using the ADC_MIN values at high b-value.

Advances in knowledge:

This study demonstrates the superiority of high b-value DW imaging compared with standard b-value imaging for the detection of MB lesions, especially those with subtle foci.     

DNA strand breakage by bivalent metal ions and ionizing radiation

Purpose: To investigate mechanisms of DNA breakage via the interaction of bivalent metal ion, thiol reducing agent and ionizing radiation, in ?OH scavenging abilities comparable to those in cells.

Materials and methods: We measured the effects of 10 min exposure to 200 μM Fe²⁺ vs. Fe³⁺ on the induction of single (SSB) and double (DSB) strand breaks in unirradiated and oxically irradiated SV40 DNA, in aqueous solution containing 75 or 750 mM glycerol and/or 5 mM glutathione (GSH).

Results: Fe²⁺ or GSH alone produced little DNA damage. However, their combination produced a dramatic increase in the production of both SSB and DSB. Experiments with ferric ion suggest that it produces DNA damage only after partial reduction to ferrous by GSH. Induction efficiencies for SSB in the presence of Fe²⁺/GSH showed additivity of the effects of radiation alone with those from Fe²⁺/GSH. However, the corresponding induction efficiencies for DSB demonstrated a 2.5-fold enhancement.

Conclusions: Our results are consistent with a model in which reduced bivalent metal ions plus thiols, in the presence of O₂, produce DSB in DNA primarily via local clusters of hydroxyl radicals arising from site specific Fenton reactions. The synergism observed between DSB production by Fe/GSH and by ionizing radiation, also believed to occur via local clusters of hydroxyl radicals, is consistent with this model. Our results suggest that both normally present intracellular iron and ionizing radiation may be important sources of oxidative stress in cells.     

Routine kilogray dosimetry with dichromate solutions

The potential advantages of dichromate solutions for routine kilogray dosimetry are reviewed. A new approach to the measurement of dichromate dosimeters is described. On irradiation, dichromate solutions yield Cr³⁺. This reduces ceric solutions quantitatively enabling potentiometric measurements to be made with the resultant ceric/cerous redox couples, using simple measuring equipment. One single dosimeter solution and procedure can cover a very wide dose range. The sensitivity and accuracy can be varied after the irradiation by choosing proportions of ceric and dosimeter solutions which suit selected narrower dose ranges. Examples illustrate the use of this technique with a dosimeter consisting of 0.005 M K₂Cr₂O₇ in 0.4 M H₂SO₄, and doses in the range 0.5–100 kGy. For doses of about 10 kGy and more, small volume dichromate dosimeters can be evaluated by direct measurement of Cr³⁺, using a simple potentiometric titration method. Alternatively, the disappearance of dichromate ion can be measured spectrophotometrically; since the absorption peak is at 350 nm, relatively inexpensive equipment can be used. With this choice of simple measurement techniques, dichromate solutions may prove a useful alternative to ceric-cerous solutions for routine kilogray dosimetry.     

Thermoluminescence of magnesium oxide and its trapping kinetics

MgO (Norton), on u.v. and γ irradiation, exhibits TL glow peaks around 88, 150, 172, 195 and 250°C (heating rate 55°C min⁻¹). TL emission is observed around 340, 390, 445, 705 nm can be attributed to the impurities Fe³⁺ and Cr³⁺, which act as luminescence centers. ESR studies rule out any participation of Mn²⁺ ions. The glow peak around 88°C has E = 1.055 eV, s = 4.3 × 10¹³ s⁻¹ and has order of kinetics b = 1.7.     

P53在电离辐射诱导的细胞周期解耦联中的作用

目的 探讨p53基因在电离辐射(IR)诱导的MCF-7细胞周期解耦联中的作用。 方法 构建RNAi表达载体,经磷酸钙共沉淀法转染293T细胞形成病毒包装颗粒,感染MCF-7后采用Western blot检测P53蛋白的表达,建立p53基因沉默模型。将p53野生型(+ +)和沉默模型(- -)经电离辐射处理后,采用流式细胞术分别测定细胞周期并分析细胞多倍体的变化。结果 与p53^{+ +}组比较,p53^{- -}模型组G₀ G₁期细胞百分数减少,S期、G₂期增加(P<0.01),倍体分析表明二倍体数减少,四倍体、八倍体均增加(P<0.01)。在p53^{+ +}和p53^{- -}细胞中,与假照射组比较,4 Gy照射后G₀ G₁期、S期细胞百分数减少,而G₂期增多(P<0.01);倍体分析表明,照射后二倍体数减少,四倍体、八倍体均增加(P<0.01)。与p53^{+ +}+IR组比较,p53^{- -}+IR 组发生G₀ G₁期、S期细胞百分数减少,G₂+M期增多(P<0.01),二倍体数减少,四倍体增多(P<0.01),八倍体无明显差别。结论 电离辐射可以诱导细胞发生G₂期阻滞和细胞周期解耦联;P53在电离辐射诱导的MCF-7细胞G₂期阻滞中发挥作用,而在细胞周期解耦联中可能不发挥作用。     

Polymer gels for in-phantom dose imaging in radiotherapy

Normoxic polymer gel dosimeters are studied, with the aim of achieving a valid and advantageous method for in-phantom 3D dose determinations. Developments were carried out in the application of such dosimetric material to the method based on dosimeter gel layers that has shown good reliability for absorbed dose imaging in radiotherapy. The technique has been improved, in particular taking care of minimizing the oxygen infiltration into the gel matrix in order to suitably avoid its effect of inhibiting the polymerization process after exposure. A suitable choice of the material of dosimeter walls has brought to achieve good steadiness in time of dosimeter sensitivity and satisfactory results in dose imaging and depth-dose profiling.     

In vivo high-resolution magnetic resonance elastography of the uterine corpus and cervix

Objectives

To apply 3D multifrequency MR elastography (3DMMRE) to the uterus and analyse the viscoelasticity of the uterine tissue in healthy volunteers considering individual variations and variations over the menstrual cycle.

Methods

Sixteen healthy volunteers participated in the study, one of whom was examined 12 times over two menstrual cycles. Pelvic 3DMMRE was performed on a 1.5-T scanner with seven vibration frequencies (30–60 Hz) using a piezoelectric driver. Two mechanical parameter maps were obtained corresponding to the magnitude (|G ^* |) and the phase angle (φ) of the complex shear modulus.

Results

On average, the uterine corpus had higher elasticity, but similar viscosity compared with the cervix, reflected by |G ^* |_{uterine corpus}?=?2.58?±?0.52 kPa vs. |G ^* |_cervix?=?2.00?±?0.34 kPa (p?φ _{uterine corpus}?=?0.54?±?0.08, φ _cervix?=?0.57?±?0.12 (p?=?0.428). With 2.23?±?0.26 kPa, |G ^* | of the myometrium was lower in the secretory phase (SP) compared with that of the proliferative phase (PP, |G ^* |?=?3.01?±?0.26 kPa). For the endometrium, the value of |G ^* | in SP was 68 % lower than during PP (PP, |G ^* |?=?3.34?±?0.42 kPa; SP, |G ^* |?=?1.97?±?0.34 kPa; p?=?0.0061).

Conclusion

3DMMRE produces high-resolution mechanical parameter maps of the uterus and cervix and shows sensitivity to structural and functional changes of the endometrium and myometrium during the menstrual cycle.

Key Points

? MR elastography provided for the first time spatially resolved viscoelasticity maps of uterus. ? Uterine corpus had a higher elasticity, but similar viscosity compared with cervix. ? The stiffness of both endometrium and myometrium decreases during the menstrual cycle.