Quality control of 99Mo/99Tcm generators: results of a survey of the Radiopharmacy Working Group of the Italian Association of Nuclear Medicine (AIMN).

A multicentre survey of the quality control of 99Tcm generators has been completed: 245 generators from seven different commercial sources were tested over a period of 2 years. The results indicate that the mean pH of the eluates was 5.8 +/- 0.6; the aluminium contents were typically < 10 ppm; the radiochemical purity was 99.8 +/- 0.4% and the median 99Mo content was 3.8 x 10(-4) percent. The elution profiles gave a volume of 1.9 ml to obtain 50% of the total eluted activity and of 4.9 ml to obtain 95%. Other radionuclide impurities and heavy metal breakthrough were evaluated by graphite furnace absorption spectrometry and inductively coupled plasma mass spectrometry. National guidelines for the standardization of radiopharmacy procedures are currently being compiled.

[Quality evaluation of a personal dosimetry service]. / Valutazione della qualità del servizio di dosimetria individuale.

In a hospital environment high quality personal dosimetry is demanded by two different considerations: first, the marked reduction in the radiation exposure levels of hospital workers during the last 10 years and second, the recent decrease in the allowed absorbed dose thresholds for the different categories of workers and for the general population. In fact, according to the new Italian Radioprotection Law (D.L. vo 230/95), the dose equivalent limit for the general population has been decreased to 1 mSv per year. This means that a dosimetric system should be able to measure, with acceptable precision and accuracy, dose levels as low as 0.1 mSv per observation period (generally 1 month or 45 days). This is quite a stringent requirement for this kind of dosimetry. During a tender, the performances of the whole body personal dosimetry systems by four Italian service providers were analyzed by irradiating more than 60 test samples for each provider with four different energies in a wide dose interval (0.01-100 mSv). The results show that all systems perform quite well in the 0.2-100 mSv dose range; on the contrary, in the 0.01-0.2 mSv dose range, significant differences appear between the services and TLD based systems perform better than film based ones. In particular, one of the two TLD based systems measured doses as low as 0.01 mSv. To conclude this very high sensitivity level really opens a new "observation window" on the low doses world. The use of higher quality (and, of course, more expensive) materials by this provider seems to be the key of its success.

[Quality assurance in radiology: quality control of radiographic cassettes]. / Assicurazione della qualità nella radiologia: il controllo della qualità delle cassette radiografiche.

A "quality team" in radiology, whose members are the authors of this paper, has implemented a quality control program to test the cassettes with intensifying screen systems used in radiology departments. 149 systems-124 of them for general purpose radiology and 25 for mammography-were submitted to the following tests: visual inspection of radiographic cassettes and intensifying screens, screen-film contact, intensifying screen cleanliness and relative sensitivity of the intensifying screens. The results of each type of test are reported in detail in the paper, on a 3-point scale: good, sufficient and poor. The overall results of the quality control tests show 78% of general purpose radiology cassettes to qualify as good (69%) or sufficient (9%), while 22% were of poor quality. 88% of the mammographic cassettes qualified as good (76%) or sufficient (12%), while 12% were of poor quality. All tests were easy to perform and required limited resources. The necessary procedures to keep quality high over time are also reported. To conclude, the results obtained with our quality control program could be used as an effective tool to address and plan the turnover of the cassettes with intensifying screens which are usually used in diagnostic radiology practice.

Pulmonary deposition of aerosolised pentamidine using a new nebuliser: efficiency measurements in vitro and in vivo.

The therapeutic efficacy of nebulised pentamidine in the prophylaxis of Pneumocystis carinii pneumonia (PCP) depends on the absolute pulmonary deposition of the drug. We studied the performance of a new nebuliser (Pentasave) by comparison both in vitro and in vivo with a standard nebuliser (Respirgard II). In vitro, deposition of pentamidine labelled with technetium-99m human serum albumin was measured indirectly by capturing inhaled particles on an absolute filter and measuring radioactivity with a gamma camera. The nebulisers were initially assessed with a pentamidine dose of 100 mg in 5 ml at 44 psi and an air flow of 10 l/min for Respirgard II and 16 l/min for Pentasave. Nebuliser output, expressed as the percentage of the initial nebuliser radioactivity captured by the inhalation filter, was 15% +/- 2% (mean +/- SD) for Respirgard II, and significantly increased to 23% +/- 3% for an initial version and to 33% +/- 2% for the final version of Pentasave. Measurements with a gamma camera in a group of ten patients with human immunodeficiency virus infection were made in vivo. The results revealed that pulmonary drug distributions are good using both Respirgard II and Pentasave. The literature reports that once-monthly pulmonary deposition of 9 mg pentamidine seems enough to produce prophylactic effects against Pneumocystis carinii. We measured pulmonary pentamidine deposition of 20.22 +/- 4.31 mg (mean +/- SD) using Respirgard II (with 300 mg in 5 ml) and of 16.00 +/- 7.18 mg using Pentasave (with 150 mg in 6 ml). These findings show that the therapeutic dose of pentamidine (9 mg) was widely exceeded with both nebulisers. Further investigations might demonstrate that about 200 mg and 125 mg pentamidine for Respirgard II and Pentasave, respectively, will achieve a pulmonary deposition of therapeutic dose, allowing significant savings in terms of drug and expense.

The choice of radiographic film-screen systems: quality evaluation and purchasing specifications drafting. Report on A.I.F.B. Working Group activity.

The comparative evaluation of radiographic screen-film systems presents several problems from both the theoretical and the experimental points of view. From the theoretical point of view the main difficulties are related to the choice of the parameters best suited to express the "overall quality" of a system. This quantity is expressed as a product of image quality index and system sensitivity. As image quality index we assumed the signal-to-noise power ratio: this index depends in an explicit way on contrast, resolution and noise of the system. From the experimental point of view the main problem is that to measure some basic quantities, sophisticated and expensive equipment, like computer-controlled microdensitometers, is generally required. In this paper, we report the Italian Association of Biomedical Physicists Task group suggestions for measuring the basic physical parameters (with particular reference to the use of cost-effective equipment and for purchasing specification drafting). Using synthetic quality indices, the evaluation criteria of radiographic materials are directly derived from the general theory of radiographic image perception.

[Evaluation of the quality of screen-film radiographic systems: physical principles and methods of measurement]. / Valutazione della qualità di sistemi radiografici schermo-pellicola: principi fisici e metodi di misura.

Comparative evaluation of radiographic film-screen systems presents several problems from both the theoretical and the experimental point of view. From the theoretical point of view the main difficulties are related to the choice of the parameters best suited to express the "overall quality" of a system. From the practical point of view the main problem is that to measure some basic quantities (resolution and noise) sophisticated and expensive instruments are required. This paper deals with both these problems. To express image quality we have assumed the signal-to-noise power ratio: this index depends in a explicit way on contrast, resolution and noise of the system. The dependence on sensitivity is implicit and was derived using literature data. From a knowledge of the dependence of image quality on sensitivity it is possible to develop an "overall quality" index which is considered to express the "technological level" of the system. This index can be used in the comparative evaluation of the different systems. In this work some basic physical quantities (characteristic curve, sensitivity) were evaluated using standard instruments. To measure spatial resolution and noise an inexpensive, PC-based, TV-digitizer system was developed. As an example, both image and overall quality indices were evaluated on three mammographic systems which are typical of the three different "phases" of the development of this technique.

Epidemiological study of urinary tract stones in a northern Italian city.

An epidemiological study of stone disease in a Northern Italian city was carried out by means of a postal questionnaire mailed to 6000 individuals (2.5% of the entire population). It was found that the incidence of stone disease was comparable to that of industrialised Western Europe. There was a relationship between stone disease and gout and stone disease and a positive family history. The frequency of uric acid stones was high (26.5%). Stone-formers showed no alimentary differences from non-stone formers apart from the use of spices and herbs. Stone-formers used less water from public aqueducts and more uncarbonated mineral water, but only 19% of these drank at least 2 litres a day.

Three-dimensional display of myocardial perfusion: detection of ischemic lesions using a new image subtraction method.

A recent, commercially available computer program for the three-dimensional (3D) display of single-photon emission tomography (SPET) data was used to study myocardial perfusion in patients with coronary artery disease (CAD). To enable the detection of small ischemic lesions, the authors proposed a new "distance-substraction" method: after suitable centering of the axial slices, 3D "distance-shaded" images of the stress study were subtracted from the corresponding views of the rest study. With this technique, small changes in surface-to-observer distance were highlighted, thus enabling us to detect nontransmural ischemic areas of the myocardium. General characteristics and possibilities of the subtraction technique were tested on a simple myocardial phantom. Some clinical results of the application of this method on CAD patients are presented and discussed. In CAD patients in whom only nontransmural ischemic lesions are present, the subtraction of "distance-shaded" images is decisive for a correct diagnosis.

[Myocardial perfusion visualized with SPECT: three-dimensional representation]. / Perfusione del miocardio con SPECT: rappresentazione tridimensionale.

A recently developed computer program for three-dimensional (3D) reconstruction of SPECT images has been employed to study myocardial perfusion in coronaropathic patients using MIBI-99mTc or 201Tl chloride. By subtracting after-stress from at-rest 3D reconstructed images, even small ischemic lesions could be located in the myocardium, with good morphological definition. The general characteristics of the method and some clinical results are here presented.

[Radiation exposure of the embryo and the fetus: real risks or unjustified fears?]. / Esposizione alle radiazioni dell'embrione e del feto: rischi reali o ingiustificati timori?

The authors discuss the problem of radiation damage to the individual developing in utero, and summarize the information available in the literature on the subject. Additional risks induced by ionizing radiations are classified with reference to gestational age and dose absorbed by the fetus. Such risks concern the possibility of mental retardation from the 8th to the 15th gestational week, and of developing a malignant disease from the 3rd to the 15th gestational week. We report the dose values received by the fetus as a result of both radiodiagnostic examinations and the Chernobyl nuclear accident: the doses were generally very low, which leads us to the conclusion that additional risks are of the same order of magnitude as the fluctuations in the natural congenital malformations. Thus, prenatal irradiation for diagnostic examinations does not generally represent a reason to recommend therapeutic abortion. However, it is always important to carry out a careful evaluation of the dose absorbed by the fetus and to correctly inform the mother about eventual radiation-induced risks.

Left ventricular diastolic filling rate assessed by gated radionuclide angiography in patients with coronary artery disease.

This study was undertaken to determine the significance of diastolic left ventricular function in 26 normal subjects and in 74 patients with coronary artery disease (CAD). Gated radionuclide left ventriculography in supine position and left anterior oblique projection was performed at rest in both groups considered and during exercise in 11 normal subjects and in 35 patients with CAD. Compared with the normal subjects, the group of patients with CAD showed lower values of global and regional ejection fraction as well as of peak ejection and filling rates. 33 patients with CAD, presenting an ejection fraction greater than 54%, showed similar values of global and regional ejection fraction, compared with the group of normal subjects, while peak filling rate was significantly lower. During exercise peak filling rate significantly increased in normal subjects and in patients with CAD; this increase was constant and similar in the various subgroups considered among patients with CAD. We conclude that peak filling rate represents a more sensitive index than ejection fraction in evaluating left ventricular function in patients with CAD, as shown by the comparison between normal subjects and patients with CAD, who had an ejection fraction greater than 54%.

Antimuscarinic compounds and gastric kinetics: a study with pirenzepine on healthy subjects.

A study has been made on the modifications that appear after acute dosage of pirenzepine in a series of eight healthy subjects of both sexes who had shown, by radioisotopic evaluation, a physiological pattern of gastric kinetics. The acute dosage of the drug was continued for three days at therapeutic doses and, a few hours after the last administration, the same study was repeated. As a test meal, a whole fried egg containing 99mTc-labelled serum albumin was used. The kinetics of the gastric content was scanned by a gamma-camera. The difference in gastric kinetics between the baseline situation and that after administration of the drug is reported and discussed.

Left-to-right shunts. (Quantification, mathematical methods and their statistical comparison).

This work describes a non-traumatic technique for quantitative determination of left-to-right shunts. Various mathematical methods to evaluate the radioisotope concentration lung curve are considered. Data were collected with a gamma camera system connected to a computer. The first results were obtained from 18 patients at the Ospedali Riuniti in Parma, Italy. All the mathematical processes are described. The three methods used were based on: 1. the count ratio (C2/C1) between two pulmonary activity concentrations, 2. the gamma function fitting, 3. decreasing exponential. A comparison of the three methods shows that the gamma function method is the most reliable. In this kind of investigation the patient's radiation dose is low enough for it to be repeated so that the course of the disease can be followed.