Inverse temperature dependent lifetimes of transient S(N)2 ion-dipole complexes

The association and collisional stabilization of the S(N)2 entrance channel complex [Cl(-)...CH3Cl]* is studied in a low-temperature radiofrequency ion trap. The temperature dependence of the ternary rate coefficient is measured and a much stronger inverse temperature dependence than expected from a simple statistical calculation is found. From these data the lifetime of the transient S(N)2 complex has been derived as a function of temperature. It is suggested that the inverse temperature dependent rates of nonsymmetric S(N)2 reactions are related to the observed inverse temperature dependence of the transient ion-dipole complexes.

Nonstandard behavior of a negative ion reaction at very low temperatures

We have studied the negative ion reaction NH2-+H_{2}-->NH_{3}+H- in the temperature range from 300 to 8 K. We observe a strongly suppressed probability for proton transfer at room temperature. With decreasing temperature, this probability increases, in accordance with a longer lifetime of an intermediate anion-neutral complex. At low temperatures, a maximum in the reaction rate coefficient is observed that suggests the presence of a very small barrier at long range or a quantum mechanical resonance feature.

[Stereotactic Mammotome breast biopsy: routine clinical experience and correlation with BI-RADS--classification and histopathology]

BACKGROUND

Stereotactic breast biopsy using the Mammotome system allows minimal invasive tissue sampling of suspicious lesions of the breast cancer, e.g. clustered microcalcifications BI-RADS type 3 and 4, and has widely replaced open surgical biopsies. The aim of this retrospective study was to review the results of these biopsies in regard of technical feasibility and complications as well as to correlate initial BI-RADS assessment with histopathology.

METHODS

One hundred thirty-five vacuum-assisted breast biopsies in 124 patients were evaluated. Before biopsy, the mammograms were classified according to the Breast Imaging Reporting and Data System (BI-RADS). All mammograms were reviewed with knowledge of the final histologic diagnosis. Patients with benign diagnoses underwent mammographic follow-up. Excisional biopsy was recommended for diagnoses of in-situ or invasive carcinoma.

RESULTS

No serious complications of the biopsies were observed. Histopathology revealed 105 (78%) benign lesions. Benign lesions were classified as BI-RADS 3 in 49 (36%) and as suspicious (BI-RADS 4) in 56 (41%). Thirty lesions (22%) were malignant, of which 26 (87%) were classified BI-RADS 4 or 5. The frequency of malignancy in BI-RADS 4 and 5 was 19 of 75 (25%) and 7 of 7 (100%), respectively. Of the 53 BI-RADS 3 lesions, 4 (8%) were malignant.

CONCLUSIONS

Mammotome biopsy was shown to be a safe and well-tolerated technique for the work-up of mammographic lesions. The frequency of malignant histopathologic findings in BI-RADS 3 lesions was higher than expected, reflecting the difficulties in the mammographic differentiation of benign and malignant clustered microcalcifications.

Photodetachment of cold OH- in a multipole ion trap

The absolute photodetachment cross section of OH- anions at a rotational and translational temperature of 170 K is determined by measuring the detachment-induced decay rate of the anions in a multipole radio-frequency ion trap. In comparison with previous results, the obtained cross section shows the importance of the initial rotational-state distribution. Using a tomography scan of the photodetachment laser through the trapped ion cloud, the derived cross section is model-independent and thus features a small systematic uncertainty. The tomography also yields the column density of the OH- anions in the 22-pole ion trap in good agreement with the expected trapping potential of a large field free region bound by steep potential walls.

Quantitative high resolution transmission electron microscopy of nanostructured semiconductors

Peak-finding procedures and the geometric phase method of quantitative high resolution electron microscopy (qHRTEM) were applied to determine the local strain and the chemical composition of nanostructured semiconductor materials. The growth of the structures investigated was induced by minimization of strain energy. The analysis of strain distribution is necessary for the understanding of the self-organized formation of nanostructures. The possibilities and limitations of the methods are discussed in detail by analysing HRTEM images of (Si,Ge) islands and of a double layer of stacked quantum dots of (In,Ga)As and Ga(Sb,As).

Dose optimization of contrast-enhanced carotid MR angiography

The purpose of this work was to compare the diagnostic performance of a single-contrast or a double-contrast dose of carotid contrast-enhanced MR angiography (MRA). One-hundred nineteen patients (mean age 65+/-14.4 years) underwent carotid contrast-enhanced MRA with a standardized protocol (repetition time/echo 3.73 ms/1.38 ms, flip-angle 25 degrees, acquisition-time 19 s, voxel size 1.2 x 1.2 x 0.9 mm3) on a 1.5-T scanner (Sonata, Siemens-Medical-Systems) using a neck phased-array coil. Contrast agent was administered intravenously at a rate of 3.0 ml/s, either as a single dose (n=57; 0.1 mmol/kg body weight) or as a double dose (n=62; 0.2 mmol/kg body weight) of meglumine gadoterate (0.5 M/l), followed by 30 ml saline. Qualitative image analysis was performed on maximum intensity projections using a five-point scale. Signal intensities were measured at three different vascular levels on both sides to assess the contrast-to-noise ratios (CNRs). Image quality was rated as good or excellent in all cases. A double dose did not influence the efficacy of carotid enhancement (CNR single dose 69.12+/-19.8; CNR double dose 70.01+/-20.7; p = 0.81) compared with a single dose. In both dose groups the mean CNRs were inversely related to bodyweight, despite adjusted contrast volumes (p=0.0005). Double-dose contrast-enhanced carotid MRA is not superior to single-dose MRA, as overall diagnostic performance and quantitative contrast enhancement are equal. Being more cost-efficient, a single-dose administration of contrast agent is recommended for MRA of the carotid arteries.

[Referrer satisfaction as a quality criterion: developing an questionnaire for measuring the quality of services provided by a radiology department]

PURPOSE

To develop a questionnaire for measuring referring physician satisfaction and to conduct a pilot study in which this questionnaire is given to all physicians referring patients to the authors' radiology department.

MATERIALS AND METHODS

After qualitative pre-testing and adjustment of the prototype questionnaire, data were collected using the finalized standardized questionnaire comprising 29 indicators rated on a 4-point ordinal scale mailed with a personalized cover letter to the total referring physician population of a radiology department (n = 727). The replies, rated 1 - 4, were entered into a data entry mask for statistical analysis.

RESULTS

The response rate was 33.8 %. The indicators with the highest satisfaction rating were the range of examinations offered ("very satisfied": 79.3 % mean 3.79), the quality of the technical equipment used for MRI and CT (79.3 %, 3.79) and mammography (82.5 %, 3.82), and the quality of the images yielded by these procedures (74.5 %, 3.73 and 82.2 %, 3.83). Dissatisfaction was relatively high with the indicators "time to receipt of the written report" (28.3 % "not very satisfied" or "not at all satisfied", mean 2.97), "time to receipt of the X-ray images" (18.2 %, 3.07) and "availability of previous findings" (20.9 %, 3.05); satisfaction was higher among external referring physicians (p < 0.05). Physicians rated the importance of these three indicators as relatively high ("very important": 62.4 %, 54.3 % and 49.6 %). Other indicators showing a similar level of dissatisfaction were "car parking availability" (24.1 %, 3.01), "patient waiting time" (27.4 %, 2.87) and "patient environment" (21.2 %, 2.99), although these factors were rated as less important ("very important": 33.0 %, 33.7 % and 40.4 %).

CONCLUSION

This questionnaire constitutes a standardized validated instrument for assessing referring physician satisfaction with a radiology department. The data from this pilot study highlight areas for potential improvement. Deployment of such a questionnaire in different radiology departments could serve to establish best practice benchmarks.

Wie zufrieden sind die klinischen Partner mit der Arbeit eines radiologischen Instituts?

PURPOSE

To develop a questionnaire for measuring referring physician satisfaction and to conduct a pilot study in which this questionnaire is given to all physicians referring patients to the authors' radiology department.

MATERIALS AND METHODS

After qualitative pre-testing and adjustment of the prototype questionnaire, data were collected using the finalized standardized questionnaire comprising 29 indicators rated on a 4-point ordinal scale mailed with a personalized cover letter to the total referring physician population of a radiology department (n = 727). The replies, rated 1 - 4, were entered into a data entry mask for statistical analysis.

RESULTS

The response rate was 33.8 %. The indicators with the highest satisfaction rating were the range of examinations offered ("very satisfied": 79.3 % mean 3.79), the quality of the technical equipment used for MRI and CT (79.3 %, 3.79) and mammography (82.5 %, 3.82), and the quality of the images yielded by these procedures (74.5 %, 3.73 and 82.2 %, 3.83). Dissatisfaction was relatively high with the indicators "time to receipt of the written report" (28.3 % "not very satisfied" or "not at all satisfied", mean 2.97), "time to receipt of the X-ray images" (18.2 %, 3.07) and "availability of previous findings" (20.9 %, 3.05); satisfaction was higher among external referring physicians (p < 0.05). Physicians rated the importance of these three indicators as relatively high ("very important": 62.4 %, 54.3 % and 49.6 %). Other indicators showing a similar level of dissatisfaction were "car parking availability" (24.1 %, 3.01), "patient waiting time" (27.4 %, 2.87) and "patient environment" (21.2 %, 2.99), although these factors were rated as less important ("very important": 33.0 %, 33.7 % and 40.4 %).

CONCLUSION

This questionnaire constitutes a standardized validated instrument for assessing referring physician satisfaction with a radiology department. The data from this pilot study highlight areas for potential improvement. Deployment of such a questionnaire in different radiology departments could serve to establish best practice benchmarks.