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PubMed1998

Combined experimental and Monte Carlo verification of 137Cs brachytherapy plans for vaginal applicators.

Dose rates in a phantom around a shielded and an unshielded vaginal applicator containing Selectron low-dose-rate 137Cs sources were determined by experiment and Monte Carlo simulation. Measurements were performed with thermoluminescent dosimeters in a white polystyrene phantom using an experimental protocol geared for precision. Calculations for the same set-up were done using a version of the EGS4 Monte Carlo code system modified for brachytherapy applications into which a new combinatorial geometry package developed by Bielajew was recently incorporated. Measured dose rates agree with Monte Carlo estimates to within 5% (1 SD) for the unshielded applicator, while highlighting some experimental uncertainties for the shielded applicator. Monte Carlo calculations were also done to determine a value for the effective transmission of the shield required for clinical treatment planning, and to estimate the dose rate in water at points in axial and sagittal planes transecting the shielded applicator. Comparison with dose rates generated by the planning system indicates that agreement is better than 5% (1 SD) at most positions. The precision thermoluminescent dosimetry protocol and modified Monte Carlo code are effective complementary tools for brachytherapy applicator dosimetry.

Administration, Intravaginal↗
PubMed1997

[The verification of optimized 3D-dosage distributions with an 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 gelatin 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 shielded 192Ir 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.

Brachytherapy↗
PubMed1991

A dosimetric analysis of Morris, Fletcher, and Henschke systems for treatment of uterine cervix carcinoma.

The role of intracavitary irradiation in the treatment of uterine cervix carcinoma is well established, and over the years a number of different systems for intracavitary irradiation have been developed. To compare the clinical efficacy of different systems and to develop guidelines for the design of applicators with new sources such as americium-241, we present a dosimetric comparison of three systems: (a) the Morris system, a modified Stockholm technique; (b) the Henschke system; and (c) the Fletcher system. Using a computerized planning system, dose distributions with different configurations of each system were calculated. For each case, doses to point A, B, and a set of reference points representing bladder and rectum were also calculated. Also, the 60 Gy reference volumes, as defined by ICRU Report No. 38, 1985, were calculated for six different treatment regimens. These treatment regimens employ widely different combinations of whole pelvis external beam dose, split pelvis external beam dose, and intracavitary irradiation dose to achieve similar clinical outcomes for the treatment of various stages of cervix carcinoma. From this analysis we observe the following: (a) The Morris system produces a higher dose rate to point A (70 to 90 cGy/hr) compared to the Fletcher or Henschke system (50 to 70 cGy/hr); (b) the doses to point B relative to point A dose are about the same for all three systems at 28 to 32%; (c) the doses to reference rectum and bladder points relative to point A dose for clinically equivalent configurations are about the same for Fletcher and Henschke systems (58-65%) not including the effects of shields in the vaginal ovoids, and somewhat higher for the Morris system (72-79%); (d) the volume treated to a given dose rate by each intracavitary system alone is about the same; and (e) the 60 Gy volume depends critically upon the external beam whole pelvis dose, rising steeply as the external beam whole pelvis dose approaches 30 Gy. Since different groups have used widely different prescriptions of external beam whole pelvis dose, ranging from 0 to 50 Gy depending upon stage, the 60 Gy volumes for these various dose prescriptions are strikingly different. Because the Morris system uses lower values for the external beam whole pelvis dose than the others, its 60 Gy volume for the advanced Stage IIB and IIIB is 2 to 4 times lower than others. This choice makes the Morris system more conservative than others, probably resulting in slightly lower cure rates for the advanced stage disease.

Brachytherapy↗
PubMed1995

Lea's Shield: a phase I postcoital study of a new contraceptive barrier device.

Lea's Shield is a new vaginal barrier contraceptive that may offer advantages over existing methods. It is made of silicone which is resistant to petroleum-based lubricants, does not absorb odors, and does not cause allergic reactions in users with latex sensitivity. It has an anterior loop for ease of insertion and removal and a one-way flutter valve. Its novel design has sufficient volume to fill the posterior fornix, which helps keep it in place and prevent sperm from entering the cervical os. This study evaluated with a standard postcoital test (PCT) the ability of the Lea's Shield used with spermicide or non-spermicidal lubricant to prevent sperm from entering midcycle cervical mucus. Ten sterilized women underwent four PCT cycles: one cycle in which no contraceptive barrier was used (a baseline cycle) and 3 cycles in which one of the following was used: Lea's Shield with spermicide, or with non-spermicidal lubricant, or the contraceptive diaphragm used with spermicide. All volunteers demonstrated more than 5 progressively motile sperm per high power field in the cervical mucus after intercourse in the baseline cycle. No motile sperm were found in the cervical mucus in any cycle in which Lea's Shield or the diaphragm was used with spermicide. No motile sperm were found in cervical mucus in 9 of 10 cycles in which Lea's Shield was used without spermicide. Only two progressively motile sperm were present in the cervical mucus of one volunteer who used the shield with non-spermicidal lubricant.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1994

Lea's Shield, a new barrier contraceptive preliminary clinical evaluations three-day tolerance study.

In this study the Lea's Shield was evaluated for its tolerance by women who wore the device for three consecutive days. Ten women who wore the Lea's Shield for 72 hours completed the tolerance study without adverse effects. Examination of the cervix and vagina revealed that the device did not provoke any significant cellular or microbial changes among the wearers. No major changes in the appearance or prevalence of vaginal flora occurred in the women after three days of wearing the device. A gradient in the pH could be detected between the contents of the vagina, which was more acidic than the contents of the bowl of the device. The range of cervical shapes and vaginal morphology among the study participants has had no influence upon the ability of the device to remain in its proper position. The device "settles in place" as it is pushed in, thereby obviating any special maneuvers for proper positioning. No vaginal nor cervical trauma occurred. We have concluded from these basic clinical evaluations that Lea's Shield is well tolerated during three days of use. Efficacy trials in women at risk recently completed have confirmed the high degree of acceptability and that the device can function adequately as one size fits all.

Cervix Uteri↗
PubMed1994

Determination of active pellets' position in the selectron-HDR vaginal tube using a therados RFA-3 water phantom system.

The method for determination of the active pellets' position in the Selectron vaginal tube is shown. A special steel cap shielding with narrow window mounted above the Therados RFA-3 semiconductor detector was constructed. By scanning along the Selectron line vaginal tube in air and water, for an appropriate distance with mild dose gradient, the actual active pellets' positions can be determined. The resolution was higher during scanning in the air than in water. The minimum number of tries for checking the whole system depends on the total number of pellet sources in the main safe, and the number of active pellets used. Advantages of this method, compared to other conventional methods for determination of the Selectron-HDR source positions, are associated with high resolution and capability of repetition without movement of the tube during checking procedure.

Brachytherapy↗
PubMed1998

Compliance with universal precautions: knowledge and behavior of residents and students in a department of obstetrics and gynecology.

OBJECTIVES: To assess the knowledge of universal precautions for the delivery and operating rooms by residents and students and to evaluate their use of universal precautions. STUDY DESIGN: Obstetrics and gynecology (ob/gyn) residents (n = 30) and students (n = 31) from an inner-city, teaching hospital were polled by anonymous questionnaire to assess their knowledge of the appropriate barrier equipment for certain ob/gyn procedures. To determine actual compliance with universal precautions, 459 ob/gyn procedures were observed. We noted the use of appropriate barrier equipment for each procedure: gloves for pelvic exam and face shields, gowns, gloves, and booties for vaginal delivery, cesarean delivery, and dilation and curettage. The True Epistat statistical software program was used to perform simple regression analysis. RESULTS: Thirty residents (100%) knew the appropriate barrier equipment required for each type of procedure performed. One student (< 1%) did not know that booties were appropriate for the surgical procedures. Rationale for lack of compliance with universal precautions elicited by the questionnaire included time constraints (64%), inconvenience (52%), and presumption that patient was not infected (34%). The observed rate of compliance with universal precautions by participants indicates that individual compliance was inversely related to the years of experience (overall compliance rate of students was 96%; for first-year residents, 92%, second-year residents, 89%, third-year residents, 84%, fourth-year residents, 78%; r = -0.9918, P = 0.0009). CONCLUSIONS: Knowledge regarding universal precautions was nearly 100%, while overall observed compliance was only 89%. Compliance with universal precautions was better among students (96%) than among residents (88%). Compliance with universal precautions was inversely related to years of experience.

Clinical Competence↗
PubMed2002

Use of MRI to determine the in vivo position of a silicone vaginal barrier contraceptive device.

This study was performed to determine the location of a silicone rubber vaginal barrier contraceptive device, the Lea's Shield, in vivo. Two women, one parous and one nulligravid, were enrolled in the study. Surface coil, multiplanar Magnetic Resonance Imaging (MRI) was performed immediately following insertion of the contraceptive device, and was repeated following 35-40 min of normal ambulation by the participant.The contraceptive device was markedly hypointense to pelvic structures on both T1 and T2 weighted images. Its position within the vagina and relationship to the cervix were readily identifiable on MR images. The device was located in the upper vagina and completely covered the cervix in both patients. The valve appeared closed, and there was no apparent pressure on the urethra. The position was not altered by ambulation. In conclusion, MRI was a reproducible and rapid means for noninvasively determining the intravaginal location and orientation of a barrier contraceptive device. After insertion, the Lea's Shield occupies the upper vagina and completely covers the cervix.

Adult↗
PubMed1996

Measurement and calculation of heterogeneity correction factors for an Ir-192 high dose-rate brachytherapy source behind tungsten alloy and steel shields.

Shields made of high atomic number material are commonly used in vaginal applicators with high dose-rate (HDR) 192Ir remotely afterloaded brachytherapy sources. However little data is available for the dose distribution around such shields. Heterogeneity correction factors (HCFs) are defined as the ratio of the dose to a point with the heterogeneity (shield) in place, divided by the dose to the same point with no heterogeneity. Using thermoluminescent dosimeters (TLDs) in solid water phantom we have measured the HCFs behind 6 and 20 mm diam tungsten alloy disks, 4 and 2 mm thick and a 4 mm thick steel disk, positioned 15 mm from the source. For each measurement point, the heterogeneity correction factors were also inferred from Monte Carlo simulations, which accurately modeled the experimental geometry. The agreement between measured and calculated HCFs on the average was within 6%. Tungsten alloy disks resulted in about two times greater dose reduction in water (HCF approximately 0.4, for 20 x 4 mm disk) than for a steel disk with the same dimensions (HCF approximately 0.85). Reducing the disk diameter to 6 mm increased the dose transmission up to about 25%. Increasing the source-to-detector distance from 4 to 7 cm caused a change in HCF from 2% to more than 20%, depending on disk material and diameter. The detector artifact effects arising from the finite size and different composition of the TLD chips were determined.

Alloys↗
PubMed1981

Fatal peritonitis following IUD-associated salpingitis.

Previous reports have implicated the Dalkon shield intrauterine device (IUD) in septic second trimester abortion and maternal death from sepsis. In the case reported here, Fusobacterium necrophorum, a rarely pathogenic vaginal anaerobe, gained access to the uterus in a woman wearing a Dalkon shield and caused acute parametritis, overwhelming peritonitis, systemic sepsis, and death. It is well known that IUDs can contribute to the development of serious pelvic infections, and in this case it is possible that the Dalkon shield was the cause of the ascending infection into the uterus.

Adult↗
PubMedDate not supplied

High dose rate intracavitary brachytherapy for recurrent or residual lesions in the vaginal cuff: results in post-hysterectomy patients with carcinoma of the cervix.

The purpose of this study was to assess the long-term survival, disease control, and complication rates of high dose rate intracavitary brachytherapy (HDR-ICR) alone or combined with external beam irradiation (HDR-ICR + EBRT) in patients with pathologically involved or close surgical margin in the vagina (Group 1) and recurrent lesions in the vaginal cuff (Group 2) following hysterectomy for cervical carcinoma. In Group 1, 10 patients received HDR-ICR only, and 11 patients received HDR-ICR + EBRT with or without paravaginal shielding. In Group 2, 8 patients received HDR-ICR only, and 11 patients received HDR-ICR + EBRT with or without paravaginal shielding. The HDR-ICR dose per fraction planned at the Apical Vaginal Point was 5-6 Gy per week. In Group 1, the 5-year absolute survival rates (AS), disease-free survival rates (DFS), and vaginal control rates (VC) were 81.0%, 76.2%, and 100%, respectively. The 5-year AS was lower in patients with parametrial infiltration or adenocarcinoma. In Group 2, the 5-year AS, DFS, and VC were 73.3%, 77.4% and 88.8%, respectively. The 5-year AS was lower when tumors were larger than 3 cm or infiltrated. Late complications occurred in 10 patients. In all but one patient, the complications were acceptable. All patients with cystitis, ileus, or leg edema received EBRT + HDR-ICR. We recommend a treatment regimen of 25-30 Gy of HDR-ICR alone for Group 1 patients without pathologically high risk of recurrence or Group 2 patients with superficial recurrent lesions, and a treatment regime of 50 Gy whole pelvis EBRT combined with 10-15 Gy HDR-ICR for Group 1 patients with pathologically high risk of recurrence or Group 2 patients with infiltrated recurrent lesions.

Adult↗
PubMedDate not supplied

Analysis of correlation between rectal complications and rectal dose following high dose rate intracavitary radiotherapy in patients with uterine cervix cancer: in vivo dosimetric analysis.

PURPOSE: To investigate the correlation between late rectal complications and rectal dose in uterine cervix cancer patients treated with high dose rate intracavitary radiotherapy (HDR ICR) and to analyze dose factors reducing complications. METHODS: A retrospective analysis was done of 74 patients treated with external beam RT and HDR ICR between 1995 and 1997. Radiotherapy (RT) consisted of a median 50.4 Gy external beam plus six fractions of HDR ICR given two times per week, concurrent with the last three weeks of external beam therapy, to a total dose of median 24 Gy to point A or the reference point. Rectal doses were calculated at rectal reference points using barium contrast criteria. In vivo measurement of rectal dose was performed with thermoluminescent dosimeters (TLD) immediately prior to the first fraction of HDR ICR. RESULTS: Eight patients developed rectal complications (11%). There was a significant difference between measured rectal doses for patients with rectal complications and those without (p < 0.05), and the doses were higher in complicated patients. A significant increase in the probability of development of complications was found for patients receiving measured rectal doses of ICR fractional dose 320 cGy or more, ICR total dose 2000 cGy or more, and ICR% to point A 80% or more. CONCLUSIONS: This study showed that in vivo dosimetry using TLD during HDR ICR could have a useful role as a predictor of late rectal complications. Dose limitation to the rectum could possibly be achieved by thorough vaginal packing or use of an applicator with proper shielding while maintaining a high dose to the tumor.

Adult↗
PubMed1991

Radiotherapy alone for medically inoperable carcinoma of the cervix: stage IA and carcinoma in situ.

The objective of this study was to define the role of radiotherapy alone for medically inoperable patients with Carcinoma in Situ (CIS) and Stage IA carcinoma of the uterine cervix. At the Mallinckrodt Institute of Radiology, Radiation Oncology Center from January 1959 through December 1986 21 patients with CIS and 34 with Stage IA were treated. All patients had histologically proven disease. The average age was 56 years for CIS and 51 years for Stage IA patients. Therapy for patients with CIS consisted of a single intracavitary insertion with a uterine tandem and colpostats. The average radiation doses were 4612 cGy to point A, 9541 cGy to the surface of the cervix, and 5123 milligram-hours (mgh). Radiotherapy for Stage IA tumors was delivered with intracavitary irradiation alone in 13 (average doses were 5571 cGy to point A, 10,430 cGy vaginal surface dose, and 6488 mgh). The other 21 patients were treated with external beam and intracavitary irradiation. The average whole pelvis dose was 1443 cGy with an additional 2354 cGy boost to the parametria with a midline stepwedge shield. The average intracavitary doses were 5200 cGy to point A, 10234 cGy to the vaginal surface, and 6293 mgh. None of the patients with CIS developed recurrent disease and none had severe sequelae of therapy. Only one patient with Stage IA developed recurrent disease in the pelvis. None developed metastatic disease. The severe complication rate was 5.9% (2/34) for Stage IA and only occurred in those receiving intracavitary irradiation and external beam irradiation. We conclude that irradiation consisting of intracavitary implants alone is excellent treatment for patients with medically inoperable Stage IA and CIS of the cervix.

Adult↗
PubMed2002

Radiation dose measurements with alanine/agarose gel and thin alanine films around a 192Ir brachytherapy source, using ESR spectroscopy.

Alanine/agarose gel and alanine films in stacks have been used for measurements of absorbed dose around an HDR 192Ir source in a vaginal cylinder-applicator, with and without a 180 degrees tungsten shield. The gel and the films were analysed by means of ESR spectroscopy and calibrated against an ion chamber in a 4 MV photon beam to obtain absolute dose values. The gel serves as both dosimeter and phantom material, and the thin (130 microm) films are used to achieve an improved spatial resolution in the dose estimations. Experimental values were compared with Monte Carlo simulations using two different codes. Results from the measurements generally agree with the simulations to within 5%, for both the alanine/agarose gel and the alanine films.

Alanine↗
PubMed2005

Lea's Shield: colposcopic and microbiological testing during 8 weeks of use.

OBJECTIVES: The aims of this study were to assess the effects of Lea's Shield(R) plus nonoxynol-9 spermicide on signs and symptoms of female genital irritation and cervical and vaginal microflora during 8 weeks of use with intercourse and to analyze problems associated with the use of the device. METHODS: In this open-label, single-arm study, participants were evaluated by pelvic examination, colposcopy and vaginal and cervical cultures. RESULTS: About 13% of women (4/30) reported symptoms of irritation, and minor product-related colposcopic findings were seen in about one third (11/30). Although average colony counts for enterococcus, Escherichia coli and anaerobic gram-negative rods increased during product use, no clinical diagnoses of infection were made. Most users reported at least one problem using Lea's Shield. CONCLUSION: Lea's Shield, when used for 8 weeks during intercourse, is associated with evidence of genital irritation in a minority of users and with changes in vaginal microflora that do not appear to correlate with clinical infections.

Adolescent↗
PubMed2001

An inexpensive meter to measure differences in electrical resistance in the rat vagina during the ovarian cycle.

The inherent electrical resistance of the rat vaginal wall rises markedly near the beginning of estrus and then falls again to low levels for the remainder of the ovarian cycle. Accordingly, special instruments have been developed to measure such resistances (within seconds) on simply inserting a small probe fitted with a pair of recording electrodes into the vagina (i.e., the MK-10A impedance checker and the EC40 estrus cycle monitor). As described herein, these two instruments are far more convenient for monitoring individual cycles than more laborious methods in which vaginal smears are inspected for changes in numbers of cornified (C), nucleated (N), and leukocytic (L) cells. However, they are also expensive and their use has essentially remained uncited in the literature. Thus we sought to determine whether a simple, inexpensive electrical meter (with resistance-measuring capacity), as commonly used by professional electricians, would serve the same purpose. We chose a standard multifunctional meter (model 22-178, RadioShack) and attached leads to it fabricated from the internal wiring of a shielded audio cable (model 42-2387A, RadioShack), one male terminal of which was used as a vaginal probe. In rats from which vagina smears revealed cell numbers in the order of C > N > L (typical of early estrus) electrical resistances were high, 488 +/- 130 k Omega (18 rats). In rats from which vagina smears revealed all other possible cell distributions, electrical resistances (combined) were much lower (P < 0.05), 124 +/- 23 k Omega (32 rats). Thus readily accessible, inexpensive electrical meters may be useful in assessing the status of estrus in female rats, either to improve reproductive efficiencies and/or for other purposes involving experiments in which such information is desirable.

Animals↗
PubMed2002

Postoperative intravaginal brachytherapy for endometrial cancer; dosimetric analysis of vaginal colpostats and cylinder applicators.

PURPOSE: To investigate the dosimetric differences between colpostats and cylinder applicators for intravaginal brachytherapy. METHODS AND MATERIALS: Dose distributions near vaginal colpostats and dome cylinders were computed with a commercial high-dose-rate treatment-planning system and verified by spot measurements by using LiF thermoluminescent dosimeters. Taking source anisotropy into account, dwell times were optimized by the computer by using the polynomial optimization on dose points method to give uniform doses along the lateral surfaces of the applicators. In addition, the effects of vaginal packing and the separation distance between colpostats were studied by computing the dose to the vaginal mucosa, assuming 0.5 and 1.0 cm of vaginal packing and colpostat separation, respectively. RESULTS: The computed and measured doses agreed within +/- 7%. Surface doses were similar for both types of applicators when the effect of shielding in the colpostats was neglected. However, percent depth doses in the anterior/posterior and lateral directions were higher for the cylinder, whereas the dose fall-off along the longitudinal patient axis was less pronounced for the colpostats. When vaginal packing at the anterior and posterior surface of the colpostats was increased from 0 to 5, 10, and 15 mm, the corresponding vaginal dose decreased from 97% of the prescription dose to 60%, 39%, and 26%, respectively. Separating the colpostats from 0 to 5 and 10 mm reduced the surface dose near the bladder/rectum to 80% and 67%, respectively, whereas the respective apex dose decreased from 105% of prescription to 91% and 77%. CONCLUSIONS: Colpostats and cylinder applicators for intracavitary brachytherapy have their advantages and disadvantages in depth dose distribution and clinical use. If treatment is confined to the vaginal apex, either applicator can be used. However, the colpostat separation should be kept to a minimum, and vaginal packing should be applied with great care to avoid generating cold spots along the upper vaginal surface and vaginal cuff.

Brachytherapy↗
PubMed1991

Percutaneous mitral balloon valvotomy in pregnancy using the Inoue balloon technique.

We describe a 40-year-old female who was 27 weeks pregnant and had severe rheumatic mitral valve stenosis. The patient presented with severe biventricular heart failure and fast atrial fibrillation. Soon after admission the patient sustained a cardiac arrest and was successfully resuscitated. Despite maximal medical therapy the patient was still in pulmonary edema. Beta blockers were contraindicated as the patient had bronchial asthma. Balloon mitral valvotomy using an Inoue 26 mm balloon catheter was done. The procedure was done with pelvic and abdominal shielding. To minimize radiation exposure no angiography was done and the procedure was done with echo-Doppler guided stepwise mitral valve dilatation. The mitral valve area after balloon valvotomy increased from 0.9 to 2 cm2. The total fluoroscopy time was 14 minutes. At 6-week follow-up the patient was virtually asymptomatic. Vaginal delivery was uneventful. Balloon mitral valvotomy using the Inoue technique in pregnancy with echo guided stepwise dilatation is accomplished with minimal radiation exposure, provided abdominal shielding is implemented throughout the procedure.

Adult↗