Radiation doses and image information in digital pelvimetry with a phosphorous screen.

PURPOSE: The aim of the investigation was to determine the patient dose in digital pelvimetry by means of a phosphorous screen as compared to a screen-film combination of very high sensitivity. MATERIAL AND METHODS: Entrance dose measurements and absorbed dose determinations in a series of patient exposures were made. In the first series the exposure reduction was achieved by reducing the mAs (tube current x exposure time) for the lateral and the a.p. views as compared with those used for the screen-film system. In the second series the tube potential, kV, was increased for both projections in order to increase the penetration capacity of the radiation. RESULTS AND CONCLUSION: The imaging plate technique can be used in pelvimetry with a dose reduction (and a corresponding reduction of the radiation risk to the foetus) to less than 50% of that achieved with a screen-film system of the very highest sensitivity.

Time-resolved white light transillumination for optical imaging.

PURPOSE: To describe a new breast-imaging method with the potential of multi-spectral optical transillumination based on a time-resolved technique. MATERIAL AND METHODS: A breast phantom was irradiated with ultra-short laser pulses of white light generated by self-phase modulation of an incident high-power laser pulse in water. Time-resolved detection of the transmitted light was performed. Contrast resolution was studied using different absorbers located inside the breast phantom. RESULTS AND CONCLUSION: The results showed that simultaneous, multi-spectral transillumination is possible. The technique can also be used for measurements of optical properties in tissue.

Laser transillumination of breast tissue phantoms using time-resolved techniques.

The objective of this study was to evaluate a pulsed laser transillumination technique based on time-resolved detection on breast-tissue-like phantoms. Experiments have been performed on tissue-like plastic phantoms with different scattering characteristics. The effects of time-gate width, size, localisation and refractive index of hidden objects have been scrutinised. Our study showed that the shorter the time-gate the higher the contrast. The contrast is very dependent on the size of the hole, whereas the full width half maximum is not. Furthermore, the investigation showed that the changes of early detected light in an experimental setting is due to scattering, and not to a higher speed of the transmitted light.

Time-gated viewing studies on tissuelike phantoms.

A time-gated technique to enhance viewing through highly scattering media such as tissue is discussed. Experiments have been performed on tissuelike plastic phantoms to determine the possibilities and limitations of the technique. The effects of the time-gate width and the localization, size, and optical properties of hidden objects have been studied. A computer model to simulate light propagation in tissue is also presented. The predictions of the model are compared with experimental results.

A phase I/II evaluation of metoclopramide as a radiosensitiser in patients with inoperable squamous cell carcinoma of the lung.

The feasibility of administering metoclopramide (MCA) as a radiosensitizer has been evaluated in 23 patients with a pathological or cytological diagnosis of a squamous cell carcinoma of the lung, clinically evaluated as inoperable. All patients received 40-60 Gy radiotherapy fractionated into 1.8 Gy fractions 5 times per week (Monday-Friday). Two MCA treatment regimens were used: (i) MCA at 2 mg/kg administered by intravenous-infusion 1-2 h prior to radiotherapy 3 times per week (Monday, Wednesday, Friday); and (ii) MCA at 1 mg/kg administered by intravenous infusion 1-2 h prior to radiotherapy 5 times per week (Monday-Friday). 11 of the 23 patients treated with radiotherapy and MCA had none to mild pneumonitis or fibrosis and another 8 of the 23 had moderate levels. No patient had their therapy interrupted due to radiation-related side-effects. The MCA-related side-effects were as expected, i.e. 78% of the patients experienced sedation/tiredness and 48% expressed restlessness/anxiety symptoms. Both the total dose and serum levels of MCA were significantly associated to the MCA side-effect profile. Tumour response, duration of tumour response and survival were significantly positively correlated to the total and weekly doses of MCA administered to the patients during their radiotherapy treatment. These favourable phase II data have justified the initiation of a phase II/III randomised multicentred trial being carried out in Europe to evaluate MCA as a radiosensitiser.

Evaluation of the image quality of ink-jet printed paper copies of digital chest radiographs as compared with film: a receiver operating characteristic study.

Paper copies of digital radiographs printed with the continuous ink-jet technique have proved to be of a high enough quality for demonstration purposes. We present a study on the image quality of ink-jet printed paper copies of digital chest radiographs, based on receiver operating characteristic (ROC) analysis. Eighty-three digital radiographs of a chest phantom with simulated tumors in the mediastinum and right lung, derived from a computed radiography (CR) system were presented in two series of hard copies as ink-jet printed paper copies and as laser recorded film. The images, with a matrix of 1,760 x 2,140 pixels, were printed with a spatial resolution of 10 pixels/mm in the CR film recorder as well as in the ink-jet printer. On film, every image was recorded in two versions, one optimized for the mediastinum and one for the lungs. On paper, only one image was printed; this constituted an effort to optimize both the mediastinum and the lungs. The ink-jet printed images, printed on a matt coated paper, were viewed as on-sight images with reflected light. The examinations were reviewed by six radiologists, and ROC curves were constructed. No significant difference was found between the performance of film and that of ink-jet paper prints. Because the cost for a paper copy is only a tenth of that of film, remarkable cost reductions can be achieved by using the ink jet technique instead. Our results show that further quality studies of ink-jet printed images are worthwhile.

Breast imaging: a comparison of digital luminescence radiographs displayed on TV-monitor and film-screen mammography.

The purpose of this study was to compare the diagnostic accuracy of conventional film-screen mammograms with the corresponding digital luminescence mammograms saved on optical disk and viewed on a 1240-line monitor. One hundred mammograms from 100 patients, including 17 biopsy-proven cancers and one cancer confirmed by cytology, were reviewed. Five radiologists with different mammography experience served as observers, and receiver operating characteristic (ROC) curves were constructed. The result of the monitor interpretation was not inferior to the conventional mammogram interpretation. One observer with vast mammography experience obtained excellent results with a digital interpretation.

Medical transillumination imaging using short-pulse diode lasers.

The recently introduced time-resolved technique for enhanced medical transillumination imaging has been demonstrated for the important case of a diode laser transmitter. This type of gated-viewing technique utilizes early received light only to reject multiply scattered, delayed light, normally blurring the image. Human breast-cancer detection is demonstrated in vitro, and the observations are explained by using theoretical modeling and tissue phantom experiments.

Relation between lightscanning and the histologic and mammographic appearance of malignant breast tumors.

The relation between real-time transillumination (lightscanning) and the histologic appearance of 243 breast carcinomas was evaluated. Lightscanning mainly failed in identifying ductal and lobular carcinomas in situ. The result of lightscanning was also poor regarding small, invasive carcinomas. The absorption patterns in elastosis and scar tissue associated with carcinoma played no important role in the ability of lightscanning to identify a cancer. The relation between the lightscanning and mammographic appearance of 85 breast cancers from the same material was also evaluated. Lightscanning performed poorly in identifying tumors characterized by classifications as compared to tumors with other mammographic appearances. However, the difference was not significant.

Diagnostic accuracy of lightscanning and mammography in women with dense breasts.

The diagnostic accuracy of lightscanning and mammography in 610 breasts with mammographically dense parenchymal patterns was investigated. Lightscanning identified 31 out of 36 cancers and mammography 32. Lightscanning and mammography were in agreement in 28 cases of cancer. One noninvasive lobular carcinoma was not identified by either modality. Four cancers were not correctly identified with lightscanning alone and 3 cancers with mammography alone. Of the 574 breasts without cancer, lightscanning falsely denoted 101 (18%) as possibly being cancerous (false-positives). The corresponding figure for mammography was 25 (4%). Thus, lightscanning, as performed in this study, has the same sensitivity as mammography in detecting cancer in mammographically dense breasts. However, its usefulness is limited by a low predictive value of a positive test (high rate of false-positives).

Digital luminescence mammography. Early clinical experience.

In a pilot study, mammography using digital luminescence was compared to conventional film-screen mammography regarding detectability of micro-calcifications and malignant tumors. The data processing algorithms were designed by the manufacturer to produce an image with characteristics close to conventional mammograms. Three observers reviewed 99 digital and their corresponding conventional mammograms. There was no difference in the detectability of micro-calcifications between digital and conventional mammography. On the digital mammograms, however, artifacts were misjudged as micro-calcifications. In an ROC analysis regarding malignant breast tumors, no significant difference was found between the 2 systems. There was a slight, but not significant, difference between the results of different observers regarding the digital system.

Lightscanning versus mammography for the detection of breast cancer in screening and clinical practice. A Swedish multicenter study.

State of the art lightscanning of the breast was tested against mammography in 2568 women in a Swedish multicenter study. The study was in two parts. One was in women with symptoms from the breasts (the clinical study) comprising 3178 examined breasts with 198 cancers; the other in asymptomatic women (the screening study) comprising 1909 examined breasts with 126 cancers. In women with symptoms from the breasts, lightscanning did not contribute to clinical examination and mammography. In the screening situation, it was poor to pick up small cancers. Mammography alone falsely diagnosed cancer in 6.9% of the patients whereas lightscan falsely diagnosed cancer in 19.1%. Lightscan was not better than mammography in young women. The study shows that lightscanning in its current form is inferior to standard mammography.

Time-resolved transillumination for medical diagnostics.

A time-gated technique to improve the possibility of localizing spatial differences in absorption when transilluminating a turbid, highly scattering medium, such as human tissue, is demonstrated. When transmitting picosecond laser pulses and detecting photons on the opposite side of the object, the contrast can be strongly enhanced by detecting only the photons with the shortest traveling time. Measurements on a 35-mm-thick tissue phantom with 5-mm-diameter absorbing objects inside are reported with data for a human hand in vivo. Implications for optical mammography (diaphanography) are discussed.

Prevalence of mammary carcinoma in patients with gynaecologic cancer.

Six hundred and forty-four patients with primary malignant tumours of the female genital tract were subject to a two-stage screening program on admission, with clinical examination in all and mammography in 380. Clinical examination alone revealed 4 cancers, while supplementary mammography screening of 369 patients with normal clinical examination revealed an additional 6 tumours, of which 5 were invasive. The prevalence rate was about three times that found in two mass-screening programs in different parts of Sweden. Thus, it could be concluded that there is an increased risk for mammary carcinoma in patients with gynaecologic malignancies. It seems reasonable therefore, to recommend mammography routinely in this group of patients.