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Biomedical subjects

A Crespi

Publications and source records attributed to A Crespi.

18 recordsLinked to original sources
PubMed2006

Grayscale calibration and quality assurance of diagnostic monitors in a PACS system.

PURPOSE: The aim of this study was to calibrate monitors used in soft-copy review of diagnostic images in a pictures archiving and communication system (PACS) and to assess critical quality assurance (QA) parameters through appropriate checks. MATERIALS AND METHODS: Barco [cathode ray tube (CRT) and liquid crystal display (LCD)] and EIZO (LCD) monitors were evaluated. Calibration and QA controls were carried out during acceptance tests on the systems and every 6 months according to the Task Group 18 (TG18) report by the American Association of Physicists in Medicine (AAPM). The parameters in question include: maximum luminance, contrast ratio, luminance response, spatial resolution and angular response. A subjective evaluation of image quality was also conducted by a number of radiologists. RESULTS: Barco medical monitors' results were well within tolerances, with significant parameters persisting over time. EIZO nonmedical monitors showed rapid performance deterioration below the minimum requirements. Calibration had to be repeated only in a few cases. Radiologists' evaluations showed that monitor quality is equal to or even better than that of conventional films. CONCLUSIONS: Medical monitors turned out to be fully adequate to the task. Periodic QA tests are, however, absolutely necessary to ensure constant quality levels.

Calibration↗
PubMed2006

Effect of a sustained silver-releasing dressing on ulcers with delayed healing: the CONTOP study.

OBJECTIVE: To compare the effect of the sustained silver-releasing foam dressing Contreet Foam (ColoplastA/S) with local best practice (LBP) on delayed healing ulcers using a real-life setting. METHOD: A total of 619 patients with ulcers of varying aetiologies were treated for four weeks with either the silver foam dressing or LBP. RESULTS: Wound area was reduced by 50% with the silver foam and 34% with LBP Less slough and maceration, a faster reduction in exudate level and more positive wound progress was achieved with the silver foam. In addition, exudate handling, ease of use, odour and pain improved. Less time was spent on dressing changes, and mean wear time was longer for the silver foam (3.1 days) than for LBP (2.1 days). All differences were statistically significant (p < 0.05). The silver foam dressing outperformed all of the other dressing categories including moist wound healing products and other silver dressings. CONCLUSION: This large-scale comparative real-life study shows that the silver foam dressing supports faster healing of delayed healing wounds.

Aged↗
PubMed2001

Accuracy of stereotactic localisation with magnetic resonance compared to CT scan: experimental findings.

BACKGROUND: Stereotactic localisation of proper targets can be obtained with Magnetic Resonance imaging (MRI), pending correction of the well-known inaccuracy of MRI in reproducing exact geometrical dimension. The aim of the experimental work was to determine the real extent of the MRI distortion and to correct it. METHODS: PVC phantoms and fixed human brains were used as target simulators: stereotactic targeting was obtained with CT and MRI: the results were compared and, finally, the real stereotactic values were measured on a commercial stereotactic device. To optimise MRI targeting it was necessary to abate the "chemical-shift", to modify the head-coil receiver (tuning the "off-resonance" frequencies) and to correct the targeting directly on the images (especially for the Y axis values); careful quality control and environmental tests were also necessary to maintain good performances along the time. RESULTS: 172 measurements were carried out using both CT, plain X-ray and MRI on PVC phantom. The values obtained from CT were considered as reference. Significant geometrical accuracy was found with CT targeting, except for the Z co-ordinate, due to the slice thickness. Mean value differences between the targets on MRI and their real geometric position are about 1 mm on X and Z axises and about 2 mm on Y axis. Similar results were obtained on fixed brains, where absolute values of X and Y co-ordinates of the simulators were measured using a millimetre grid placed over the brain slice. INTERPRETATION: Experimental findings concerning stereotactic targeting with MRI suggest accuracy adequate for clinical practice, even when extreme geometrical precision is required, such as in radiosurgery or functional stereotaxy. Careful quality control and intensive experimental setting of the MRI device are mandatory to obtain satisfactory results.

Data Interpretation, Statistical↗
PubMed1996

[The evaluation of the physical characteristics of a volumetric computer tomograph].

Spiral or volumetric computed tomography (CT) is a new scanning technique which allows the scanning of body regions with a continuously rotating system based on the slip ring technology; the patient is also moved continuously, synchronously with data acquisition. The physical characteristics of spiral CT image acquisition were compared with those of conventional CT images. The modulation transfer function (MTF) has the same values for medium-resolution filters, but lower values for spiral CT for high-resolution and frequency-enhancement filters. The slice sensitivity profile (SSP) describes the longitudinal image resolution for multiplanar reconstructions and was measured in terms of FWHM of the SSP curve. We obtained, for 10-mm slice thickness, a FWHM = 10.4 mm (conventional CT), versus 10.7 mm (Spiral CT), while, for 5-mm slice thickness, the corresponding values were 5.2 mm (conventional CT) and 5.5 mm (spiral CT). Noise was evaluated simply by measuring the standard deviation of the CT numbers, in a region of interest, of a uniform image and with the power spectrum or Wiener spectrum of the same image. To assess overall image quality and yield, the noise equivalent quanta (NEQ) value was also calculated. The values were a little lower for the spiral technique, particularly with high-resolution and enhancement or convolution filters. Dosimetric evaluation of the computed tomography dose index (CTDI) and of the multiple scan average dose (MSAD) was done using an acquisition protocol for average lung dose, in an anthropomorphic phantom and with TL dosimeters. The MSAD was 6.17 +/- 0.20 cGy for conventional CT and 5.98 +/- 0.23 cGy for Spiral CT, while lung dose was 3.25 +/- 0.12 cGy and 3.01 +/- 0.16 cGy, respectively.

Artifacts↗
PubMed1994

[Digital storage phosphor radiography. Doses and image quality].

Digital radiography (DR) based on storage phosphor technology is progressively replacing conventional screen-film system radiographic techniques (CR). However, many questions about image quality and dose reduction are still open. Thus, since DR spatial resolution is always lower than that of high quality screen-film images and image noise is conversely higher, for general radiography examinations especially, the signal-to-noise ratio is always lower with DR than with CR at the same dose level. However, the wide dynamic range, the linear response of storage phosphor detectors and the automatic read-out control of the digital system, enable lower DR X-ray imaging efficiency to be overcome, producing a nearly perfect readout of the image data every time an exposure is made. Moreover, post-processing can make the detection of abnormalities easier. This is why in many ROC clinical accuracy studies DR performed equally or better than CR. Good quality DR images, similar to conventional ones at the same dose levels, are therefore achievable in chest, abdomen, bone and soft-tissues examinations. Dose evaluation protocols are strongly needed in DR since overexposures due to technical mistakes may be overlooked; moreover, doses can be adjusted to the peculiar diagnostic need. The S values shown on any hard-copy image can be used to this purpose, even though it must be pointed out that they do not express the actual mean dose to the detector.

Humans↗
PubMed1994

[The detectability of osteoarticular lesions of the extremities on the television monitor].

The diagnostic accuracy of the light-box reading of conventional (film screen) radiographs of the extremities was compared with that of the same set of images displayed on a 1 k x 1 k interactive monitor after laser digitization. 389 alterations (23 nondisplaced fractures, 129 soft-tissue calcifications and 237 articular bone erosions), identified by two experienced radiologists on 66 conventional radiographs, were the reference standard. ROC statistical analysis was performed on 1,556 observations expressed by four readers. The overall diagnostic performance of the two display modalities were substantially equivalent: no statistically significant differences resulted on the whole, but two individual readers performed better with conventional images. No overall nor individual statistically significant difference was reobserved for the subset of articular erosions either. Light-box reading of conventional radiographs allowed a higher number of calcifications in the soft-tissues and of proximal (carpal) abnormalities to be detected. Although our results indicate the overall high fidelity of monitor-displayed laser-digitized images, major improvements in the performance of digital diagnostic workstations are still required before adopting monitors for routine radiologic activity.

Evaluation Studies as Topic↗
PubMed1993

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.

Physical Phenomena↗
PubMed1992

[Squamous papillomas of the esophagus].

The paper reports 14 cases of squamous papilloma of the esophagus which were removed using an endoscopic method: this is a comparatively rare benign pathology of which an increasing number of cases have been recently observed. Endoscopic controls were carried out in all cases and the results of the follow-up are reported.

Adult↗
PubMed1991

[Nephrobronchial fistula].

Nephrobronchial fistula is a rare pathology both in absolute terms and in relation to the complications of renal inflammatory processes. Clinical symptoms may be varied but pulmonary complications, which may mask renal symptoms, are generally predominant; cough, hemoptysis and the expectoration of calculi are rarely found. Occasionally, as in the case reported here, the most evident sign is an infective process due to the contemporaneous fistulization of subcutaneous tissues. Instrumental diagnosis is based on chest and abdomen X-ray, fistulography, retrograde pyelography and abdominal CT. CAT may be useful above all in the study of pararenal abscesses.

Bronchial Fistula↗
PubMed1991

[Primary torsion of the omentum].

The paper reports a case of spontaneous torsion of the omentum. Following a review of the international literature on the topic, the Authors discuss the pathogenesis, clinical symptoms and surgical therapy of this pathology.

Adult↗
PubMed1991

[Detection of small bone lesions with digital radiography using storage phosphors].

To date, the skeletal imaging capabilities of digital radiography with storage phosphors have been poorly investigated, and the diagnostic accuracy of this technique has not been thoroughly assessed. To evaluate the performance of storage phosphor digital radiography we compared 66 conventional and 66 digital radiographs of small abnormalities of the extremities (fractures, erosions, calcifications). Conventional images were obtained with a low-speed screen-film system while digital ones were acquired with high-resolution (5 lp/mm max) phosphors and laser-printed on a 8" x 10" film. Two experienced radiologists defined the gold standard (389 abnormalities) and four radiologists scored the findings (1,556 observations) on a five-point discrete scale. ROC analysis indicated film and storage radiography to be equally effective in the overall detection of abnormalities. No difference was found in the individual performances of the four readers, in the site subclasses (wrist, hand), and in the specific detection of fractures and erosions. Digital radiography proved to be superior to conventional radiography in the detection of calcifications in all sites and particularly in the wrist (p less than 0.05). Storage phosphor radiography may replace conventional radiography of the extremities without causing any significant decrease in diagnostic accuracy.

Bone Diseases↗
PubMed1989

[Digital radiography with phosphorus memory: verification of the centering of the patient in high-energy radiotherapy].

A digital radiographic system using storage phosphor detectors was employed in order to verify radiotherapy treatments with high energy photon beams (60Co-18 MV X-rays). The wide range linearity of the detectors and also the possibility of digital image post-processing allowed portal films to be obtained with sufficient contrast in all treatment techniques, particularly in the case of mantle fields. The use of digital radiography may become an easy and valuable procedure for therapy verification.

Algorithms↗
PubMedDate not supplied

[Digital radiography in urography].

The clinical utility was evaluated of a computed radiographic system in urography. The system (FCR 101, Philips Medical Systems, Inc., Shelton, CT) is based on a photo-stimulatable phosphor screen (imaging plate) for X-ray image detection and storage. The X-ray information recorded on the imaging plate is converted into digital from and processed by means of a computer. After processing is completed, the digitized image is reversed back to analogic signals, which modulate the intensity of a laser beam scanning the image on a single-emulsion film (Fuji CR 633). Two hundred IVP's were obtained in four groups, of 50 patients each, with normal azotemic values by rapid infusion of a low osmolality contrast medium (iopamidol 150 mgI/ml). While conventional radiographs were performed on the first group of patients with the injection of 0.6 gI/kg body weight of contrast medium, digital examinations were carried out, in the remaining three groups, with the injection of 0.6, 0.3 and 0.12 gI/kg, respectively. The digital images were processed with the "Abdomen-routine" program. A specific algorithm was implemented in order to reduce the excessive contrast resolution of the bladder, which is due to the characteristics of the nonionic contrast medium and enhanced by the reading program. The image details were evaluated by two observers and then statistically analyzed with nonparametric tests. Statistical analysis did not show any difference in the quality of digital and screen-film images. Image processing improved some inadequate images, by reducing the contrast resolution of the bladder, and allowed a better detection of some details. Low doses (0.3 gI/kg) of a low osmolality (150 mgI/kg) contrast medium were enough to obtain good images. Another biological advantage was obtained by a consistent radiation dose reduction (about 40%).

Adolescent↗