Physical and clinical comparison between a screen-film system and a dual-side reading mammography-dedicated computed radiography system.

BACKGROUND: Digital mammography systems, thanks to a physical performance better than conventional screen-film units, have the potential of reducing the dose to patients, without decreasing the diagnostic accuracy. PURPOSE: To achieve a physical and clinical comparison between two systems: a screen-film plate and a dual-side computed radiography system (CRM; FUJIFILM FCR 5000 MA). MATERIAL AND METHODS: A unique feature of the FCR 5000 MA system is that it has a clear support medium, allowing light emitted during the scanning process to be detected on the "back" of the storage phosphor plate, considerably improving the system's efficiency. The system's physical performance was tested by means of a quantitative analysis, with calculation of the modulation transfer function, detective quantum efficiency, and contrast-detail analysis; subsequently, the results were compared with those achieved using a screen-film system (SFM; Eastmann Kodak MinR-MinR 2000). A receiver operating characteristic (ROC) analysis was then performed on 120 paired clinical images obtained in a craniocaudal projection with the conventional SFM system under standard exposure conditions and also with the CRM system working with a dose reduced by 35% (average breast thickness: 4.3 cm; mean glandular dose: 1.45 mGy). CRM clinical images were interpreted both in hard copy and in soft copy. RESULTS: The ROC analysis revealed that the performances of the two systems (SFM and CRM with reduced dose) were similar (P>0.05): the diagnostic accuracy of the two systems, when valued in terms of the area underneath the ROC curve, was found to be 0.74 for the SFM, 0.78 for the CRM (hard copy), and 0.79 for the CRM (soft copy). CONCLUSION: The outcome obtained from our experiments shows that the use of the dual-side CRM system is a very good alternative to the screen-film system.

Purification by ozonolysis of (18)O enriched water after cyclotron irradiation and the utilization of the purified water for the production of [18F]-FDG (2-deoxy-2-[18F]-fluoro-d-glucose).

The high cost of virgin (18)O-enriched water has forced many researchers to study methods to purify and recycle enriched water after the first irradiation for the production of radiopharmaceuticals. In our study, [(18)O]H(2)O was purified by ozonolysis and distillation. Analyses showed a large decrease in impurities after this treatment. The purification procedure was carried out after the production of 94 batches of [18F]-FDG, which were manufactured using a GE Minitrace cyclotron and a GE Mx TracerLab synthesizer. Saturation yields after bombardment, using virgin and re-purified water were, respectively, 2864+/-204MBq/muA and 2727+/-167MBq/muA, a decrease of 5.5%. The decrease in [18F]-FDG yield, from 67.2+/-0.7% to 65.5+/-0.9%, can be ascribed to the irradiation step only.

Analytical estimation of ultrasound properties, thermal diffusivity, and perfusion using magnetic resonance-guided focused ultrasound temperature data.

For thermal modeling to play a significant role in treatment planning, monitoring, and control of magnetic resonance-guided focused ultrasound (MRgFUS) thermal therapies, accurate knowledge of ultrasound and thermal properties is essential. This study develops a new analytical solution for the temperature change observed in MRgFUS which can be used with experimental MR temperature data to provide estimates of the ultrasound initial heating rate, Gaussian beam variance, tissue thermal diffusivity, and Pennes perfusion parameter. Simulations demonstrate that this technique provides accurate and robust property estimates that are independent of the beam size, thermal diffusivity, and perfusion levels in the presence of realistic MR noise. The technique is also demonstrated in vivo using MRgFUS heating data in rabbit back muscle. Errors in property estimates are kept less than 5% by applying a third order Taylor series approximation of the perfusion term and ensuring the ratio of the fitting time (the duration of experimental data utilized for optimization) to the perfusion time constant remains less than one.

Image quality and dose in computerized tomography: evaluation of four CT scanners.

Spatial resolution, statistical noise, and patient dose are important parameters for the evaluation of the performances of computerized tomography (CT) scanners. These parameters are combined to develop some "synthetic indices," and to be able to describe intrinsic properties of a CT scanner (the maximum obtainable spatial resolution and dose efficiency). This type of analysis has been applied to the evaluation of four CT scanners, three of third, and one of fourth generation.

Radiation transport in a radiotherapy room.

The photoneutron dose equivalent in a linac radiotherapy room and its entrance maze was investigated by means of Monte Carlo simulations under different conditions. Particularly, the effect of neutron absorbers and moderator layers placed on the maze walls was considered. The contribution of prompt gamma rays emitted in absorption reactions of thermal neutrons was also taken into account. The simulation results are compared with some experimental measurements in the therapy room and in the maze.

Transfer kinetics and coefficients of 90Sr, 134Cs, and 137Cs from forage contaminated by Chernobyl fallout to milk of cows.

A experiment was conducted to study kinetics, transfer coefficients, and biological half-lives of 90Sr, 134Cs, and 137Cs from feed to milk. A cow was fed a diet containing alfalfa hay contaminated by Chernobyl fallout for 14.5 wk. The time-dependent activity in milk was approximated by a two-compartment model with fast biological half-lives of 2, 0.9, and 1 d and slow biological half-lives of 36.9, 8.7, and 12.4 d for 90Sr, 134Cs, and 137Cs, respectively. The transfer coefficients determined in the experiment were 0.0008 d L-1 for 90Sr, 0.0029 d L-1 for 134Cs, and 0.0031 d L-1 for 137Cs. The biological elimination phases of 134Cs and 137Cs were described by a two-compartment model while a one-compartment model was proposed for 90Sr.

MRI patterns of invasive lobular cancer: T1 and T2 features.

PURPOSE: The aim of this study was to describe magnetic resonance imaging (MRI) patterns in 21 patients with histologically proven invasive lobular cancer (ILC) of the breast. MATERIALS AND METHODS: We retrospectively reviewed MR images of 21 out of 24 women with ILC of the breast. Three women were excluded from the study because they underwent neoadjuvant chemotherapy after MRI. Thirteen of the 24 women had positive clinical findings. All 24 patients underwent mammography, sonography and MRI. MRI was performed to evaluate disease extent and multifocality/multicentricity before modified radical mastectomy (n=5) or quadrantectomy (n=16). Two experienced radiologists reviewed the MRI scans and described the tumour patterns. RESULTS: We identified five morphological patterns of ILC: a solitary mass with irregular margins (n=8); a mass with smooth margins (n=5); multiple small enhancing foci with interconnecting enhancing strands (n=4); dominant lesion surrounded by small foci (n=3); one MR examination was negative. CONCLUSIONS: Architectural and dynamic features are important in the interpretation of breast MRI findings. ILC may be detected on MRI as solitary or multiple lesions that correspond to tumour morphology on pathologic examination. False-negative MRI findings do occur in a small percentage of ILC.

[Dosimetry problems in irradiation of mediastinal tumours (author's transl)]. / Problemi dosimetrici nell'irradiazione dei tumori mediastinici.

Various physical parameters are described for evaluation of the quality of the irradiation plane. Of these, the integral dose and the dose gradient index are regarded as particularly significant and their calculation is included in a computerised dosimetry programme. Examples are drawn from the comparison of various mediastinum irradiation techniques: 60Co, high energy X-rays, fast electrons.

[White and black in nuclear magnetic resonance (NMR). Impulse sequences and their significance in the NMR image]. / Bianco e nero in risonanza nucleare magnetica (RNM). Sequenze di impulsi e loro significato nell'immagine RNM.

In order to understand how pulse sequences affect what is black and what is white in Nuclear Magnetic Resonance (NMR) images, the tissue parameters (proton density; relaxation times T1 and T2) are related to the operator selectable controls (type of pulse sequence; repetition time TR; interpulse delay TI; echo delay TE). The pulse sequences "Saturation Recovery"; "Inversion Recovery"; "Spin Echo" are discussed. The authors also analyze the effect of flowing blood on NMR images.

[Analytical expressions of the energy dissipation of high energy electron beams (author's transl)]. / Espressioni analitiche della dissipazione di energia di elettroni veloci

The energy dissipation of high energy electron beams in water, assuming a "continuous slowing down", is expressed by means of the "transport" and "age diffusion" equations: this allows the automatic calculation of the dose distribution in space. The agreement between calculated and measured values is discussed.

[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.

[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.

[En-bloc treatment of tumors of the hypopharyngeal-laryngeal-tracheal tract with a new isocentric multipendular technic]. / Trattamento in blocco dei tumori del tratto ipofaringo-laringo-tracheale con una nuova tecnica multipendolare isocentrica.

The authors propose a new technique for the treatment of hypopharyngeal-laryngeal-tracheal tract tumors using cobalt-60 irradiation. This technique allows the simultaneous irradiation of both primary tumor and cervical lymph nodes. Therapeutically effective doses can be administered without affecting the spinal cord. The above-mentioned technique consists of 3 isocentric rotations, the widest one carried out by interposing a small lead bar shielding in the middle of the field. Dose distributions obtained in an Alderson-Rando phantom and in a patient are reported.

High-resolution 1H NMR spectroscopy in the diagnosis of breast cancer.

Surgical specimens from 22 patients with infiltrating ductal carcinoma of the breast were analyzed by high-resolution 1H NMR spectroscopy at 80 and 300 MHz. Results were compared with those obtained from 9 benign (proliferative dysplasia without atypia) breast samples. NMR spectra at 80 MHz showed well-resolved water and lipid peaks so it was possible to calculate specific T1 and T2 relaxation times. The longitudinal T1 relaxation process of the water was found to be properly represented by a monoexponential function, whereas the transverse T2 decay was well accounted for by a biexponential model. Relaxation time measurements of the water were found to be a valuable tool in breast tissue characterization, in particular (a) mean T1 values from malignant and control populations are well distinguished (P less than 0.0008); (b) mean T2 values of both fast and slow components from the two populations are statistically different (P less than 0.0001) and no overlap exists in the distributions of the second component. Three-hundred-megahertz spectra allowed a detailed analysis of the lipidic component of the sample: malignant tumors were found to present in the region 1.3-1.2 ppm a species characterized by a very slow transverse relaxation time (T2 = 200-1000 ms).

[Analytical expressions for the dose distribution of 42 MV X-rays from a betatron (author's transl)]. / Espressioni analitiche per la distribuzione di dose dei fasci di raggi X prodotti da un betatrone da 42 MV.

Absorption in water of 42 MV X-rays is described by means of equations whose parameters have been determined in such a way as to best fit the experimental data. The results obtained are employed in a general program for the calculation of dose distribution in external radiotherapy.

[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.

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.

[Computerized tomography: analysis of the characteristics of various pieces of equipment]. / Tomografia computerizzata: analisi delle caratteristiche di alcune apparecchiature.

Spatial resolution, statistical noise and patient dose are important parameters for the evaluation of the performances of CT-scanners. These parameters may be combined to develope some "synthetic indices", able to describe intrinsic properties of a CT-scanner (the maximum obtainable spatial resolution and dose efficiency). This type of analysis has been applied to the evaluation of four CT-scanners, three of 3rd and one of 4th generation.