An experimental MOSFET approach to characterize (192)Ir HDR source anisotropy.

The dose anisotropy around a (192)Ir HDR source in a water phantom has been measured using MOSFETs as relative dosimeters. In addition, modeling using the EGSnrc code has been performed to provide a complete dose distribution consistent with the MOSFET measurements. Doses around the Nucletron 'classic' (192)Ir HDR source were measured for a range of radial distances from 5 to 30 mm within a 40 x 30 x 30 cm(3) water phantom, using a TN-RD-50 MOSFET dosimetry system with an active area of 0.2 mm by 0.2 mm. For each successive measurement a linear stepper capable of movement in intervals of 0.0125 mm re-positioned the MOSFET at the required radial distance, while a rotational stepper enabled angular displacement of the source at intervals of 0.9 degrees . The source-dosimeter arrangement within the water phantom was modeled using the standardized cylindrical geometry of the DOSRZnrc user code. In general, the measured relative anisotropy at each radial distance from 5 mm to 30 mm is in good agreement with the EGSnrc simulations, benchmark Monte Carlo simulation and TLD measurements where they exist. The experimental approach employing a MOSFET detection system of small size, high spatial resolution and fast read out capability allowed a practical approach to the determination of dose anisotropy around a HDR source.

A parallel plate chamber for calibration of 192Ir LDR and HDR sources.

A good program of quality assurance requires the user to check the calibration of brachytherapy sources. Conventional well-type ionization chambers have restrictions on the length of the source which can be used due to the variation in the relative ionization with distance from the position of maximum sensitivity. We have fabricated a parallel plate chamber, which can be used for both LDR and HDR sources of 192Ir placed centrally inside. The electrodes are made from printed circuit boards. Sources of lengths up to 15 cm can be calibrated with this chamber. It has a good linear response and stability. It costs little and can be used with any electrometer. The chamber, which has a volume of about 40 cm3, has a response of 820 nCmin(-1) per cGy m2 h(-1).

Preoxygenation in children using expired oxygraphy.

We performed preoxygenation on 25 patients, aged 1-12 yr. End-tidal oxygen sampling was used to find the duration of preoxygenation required to reach an end-tidal oxygen fraction of 0.9. All children reached this end-point within 80 s, which was markedly more rapid than that observed in adult subjects. The clinical applications of this form of monitoring in children are discussed.

In situ hybridization for human papillomavirus DNA in uterine adenosquamous carcinoma with glassy cell features ("glassy cell carcinoma").

Eighteen uterine adenosquamous carcinomas that showed focal glassy cell features (33% to 85% of tumor histology) or predominant glassy cell features (greater than 85% of tumor histology) were studied by in situ hybridization for human papillomavirus (HPV). Viral DNA was present in neoplastic cells in five cases: type 18 in four cases (two cervical adenosquamous carcinomas with predominant glassy cell features, two cervical adenosquamous carcinomas with focal glassy cell features) and type 16 in one case (cervical adenosquamous carcinoma with predominant glassy cell features). Positive intranuclear staining for HPV DNA was present within areas of squamous and glandular differentiation and within areas with glassy cell features. The mean age of HPV(+) patients was less than HPV(-) patients (mean, 57 years, compared to 67 years). No significant association between HPV status and prognosis or glassy cell features was detected. Human papillomavirus types 16 and 18 are associated with adenosquamous carcinoma with predominant glassy cell features or focal glassy cell features, "glassy cell carcinoma." Automated colorimetric in situ hybridization is an effective method to detect HPV DNA.

Glassy cell features in adenosquamous carcinoma of the uterine cervix. Histologic, ultrastructural, immunohistochemical, and clinical findings.

Glassy cell features (GCF) were identified as composing a predominant pattern (more than 85% of histology) in six cases and a focal pattern (33-85% of histology) in 10 cases of a series of 53 adenocarcinomas (AC) and adenosquamous carcinomas (ADSQ) of the uterine cervix. In three cases examined ultrastructurally, GCFs correlated with many cytoplasmic polyribosomes and abundant rough endoplasmic reticulum, but Golgi complexes and tonofilaments were scant and intracytoplasmic lumina were absent. Intracellular mucin was present in the areas showing GCFs of four ADSQs with predominant GCFs and six ADSQs with focal GCFs. Two of three cases examined ultrastructurally showed intracellular electron-dense material that corresponded to mucin secretory material. Immunohistochemical studies of the six ADSQs with predominant GCF cases showed the following pattern of reactivity: monoclonal carcinoembryonic antigen (CEA), 2 of 6 cases; polyclonal CEA, 3 of 6; CA 125, 0 of 6; CA 19-9, 0 of 6; placental alkaline phosphatase, 0 of 6; and vimentin, 1 of 6. Focal GCF areas showed monoclonal CEA, 4 of 9 cases; polyclonal CEA, 3 of 9; vimentin, 4 of 9; while CA 125, CA 19-9, and placental alkaline phosphatase were negative in areas of GCFs. One of three patients with ADSQ with predominant GCFs and five of nine patients with ADSQ with focal GCFs with at least 1 year of follow-up were disease free. No association between GCFs (combined focal and predominant) and recurrent disease was present when compared to the other 29 AC and ADSQ patients with follow-up. Recurrent disease in our series of AC and ADSQ was only associated with stage III or IV disease at presentation (P less than 0.001). There was no association with adenosquamous histology, histologic grade, lymphatic invasion, or age. There were insufficient cases of ADSQ with predominant GCFs with follow-up to evaluate fully prognostic significance of this subgroup. Our study suggests that GCFs are part of the spectrum of differentiation in ADSQ of the cervix rather than a distinct histologic type of carcinoma with unique clinical significance.

Cervicovaginal cytology in uterine adenocarcinoma and adenosquamous carcinoma. Comparison of cytologic and histologic findings.

To investigate the diagnostic accuracy and to characterize the findings in false-negative cases, the results of cervicovaginal cytology in 56 adenocarcinomas and 25 adenosquamous carcinomas (42 cervical, 36 endometrial, 2 metastatic and 1 arising synchronously from both cervix and endometrium) were reviewed, including review of the actual slides in 56 cases. Overall, 80% of the initial cytologic diagnoses resulted in diagnostic curettage (i.e., cytology was effectively positive); 84% of the postreview diagnosis were effectively positive. Nine cytology slides showed no malignant cells; eight of these negative smears showed repair, five were atrophic, two showed a high estrogen effect and one had enlarged atypical bare nuclei. These false-negative diagnoses were associated with an endometrial primary site (P less than .01), endometrioid histology (P less than .005), low-grade or intermediate-grade histology (P less than .005), small size of tumor (P less than .05) and absence of cervical involvement (P less than .005) in those cases in which a hysterectomy was performed. False-negative diagnoses were not associated with an absence of endocervical cells or with scanty cellularity. Of 39 cervical and 28 endometrial carcinomas with a positive cytologic diagnosis (initially or after review of the available slides), cytology correctly identified the primary site in 18% and 54% of the cases, respectively. Cytology incorrectly classified the anatomic site of four cervical and three endometrial carcinomas and considered one case arising in both the endometrium and cervix to be endometrial. Routine cervicovaginal cytology does have a role in screening for uterine glandular carcinoma; to maximize its diagnostic sensitivity, we suggest using a recommendation for curettage in the report of positive cases so that all of the varied cytologic diagnoses associated with glandular carcinomas will receive a uniform clinical response. In those cases with preserved cancer cells, a correlation can be made with the histologic type of the carcinoma, rather than with the anatomic site.

Levels of leakage radiation from electron collimators of a linear accelerator.

The leakage radiation from electron applicators used with our linear accelerator has been measured. For the applicators 6 X 6 to 25 X 25 cm size, the leakage was measured in the plane of the patient and on the sides of the applicators with the available electron energies of 6, 9, 12, 15 and 18 MeV. The levels were significant. The highest leakage on the side was for the combination of 6 X 6-cm applicator and 9-MeV electrons (32%) and in the plane of the patient for 25 X 25-cm applicator with 18 MeV (10%) relative to the peak dose. Adding lead 1-2 mm, at appropriate locations inside the applicators has reduced the leakages to acceptable levels without affecting the beam parameters.