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P Delogu

Publications and source records attributed to P Delogu.

14 recordsLinked to original sources
PubMed2006

Comparison of two portable solid state detectors with an improved collimation and alignment device for mammographic x-ray spectroscopy.

We describe a portable system for mammographic x-ray spectroscopy, based on a 2 X 2 X 1 mm3 cadmium telluride (CdTe) solid state detector, that is greatly improved over a similar system based on a 3 X 3 X 2 mm3 cadmium zinc telluride (CZT) solid state detector evaluated in an earlier work. The CdTe system utilized new pinhole collimators and an alignment device that facilitated measurement of mammographic x-ray spectra. Mammographic x-ray spectra acquired by each system were comparable. Half value layer measurements obtained using an ion chamber agreed closely with those derived from the x-ray spectra measured by either detector. The faster electronics and other features of the CdTe detector allowed its use with a larger pinhole collimator than could be used with the CZT detector. Additionally, the improved pinhole collimator and alignment features of the apparatus permitted much more rapid setup for acquisition of x-ray spectra than was possible on the system described in the earlier work. These improvements in detector technology, collimation and ease of alignment, as well as low cost, make this apparatus attractive as a tool for both laboratory research and advanced mammography quality control.

Calibration↗
PubMed2005

GPCALMA: a Grid-based tool for mammographic screening.

OBJECTIVES: The next generation of high energy physics (HEP) experiments requires a GRID approach to a distributed computing system: the key concept is the Virtual ORGANISATION (VO), a group of distributed users with a common goal and the will to share their resources. METHODS: A similar approach, applied to a group of hospitals that joined the GPCALMA project (Grid Platform for Computer Assisted Library for MAmmography), will allow common screening programs for early diagnosis of breast and, in the future, lung cancer. The application code makes use of neural networks for the image analysis and is useful in improving the radiologists' diagnostic performance. GRID services allow remote image analysis and interactive online diagnosis, with a potential for a relevant reduction of the delays presently associated with screening programs. RESULTS AND CONCLUSIONS: A prototype of the system, based on AliEn GRID Services [1], is already available, with a central server running common services [2] and several clients connecting to it. Mammograms can be acquired in any location; the related information required to select and access them at any time is stored in a common service called Data Catalogue, which can be queried by any client. Thanks to the PROOF facility [3], the result of a query can be used as input for analysis algorithms, which are executed on the nodes where the input images are stored,. The selected approach avoids data transfers for all the images with a negative diagnosis and allows an almost real time diagnosis for the set of images with high cancer probability.

Algorithms↗
PubMed2001

[Application of a computer-aided detection (CAD) system to digitalized mammograms for identifying microcalcifications].

PURPOSE: It is estimated that during mammographic screening programs radiologists fail to detect approximately 25% of breast cancers visible on retrospective review; this percentage rises to 50% if minimal signs are considered. Independent double reading is now strongly recommended as it allows to reduce the rate of false negative examinations by 5-15%. Recent technological progress has allowed to develop a number of computer-aided detection (CAD) systems. The aim of CAD is to help radiologists interpret lesions by serving as a second reader. In this study the authors developed and applied a CAD system to measure its ability to microcalcifications detect and compare its performance with that of a human observer. MATERIAL AND METHODS: The study was performed as part of the CALMA (computer-aided library for mammography) project of the Pisa section of the National Institute of Nuclear Physics. The aim of this project is to set up a large database of digital mammograms and to develop a CAD system. Our study series consisted of 802 mammograms - corresponding to 213 patients - digitalized between March and June 2000. We performed traditional mammography and then digitalized the mammograms using a CCD linear scanner (pixel size of 85 x 85 microm2, 12 bits). The images were evaluated by two radiologists with similar experience and then by the CAD system. This CAD system searches for microcalcifications by using ad hoc algorithms and an artificial neural network (Sanger type). RESULTS: The number of clusters in our database was 141 corresponding to 140 images; 692 images were non pathological. The CAD system identified a variable number of clusters depending on the threshold values. The threshold value is a number over which the probability of finding a lesion is highest. With thresholds of 0.13 and 0.14 the CAD system identified 140/141 clusters (99.3%); with a threshold of 0.15 it identified 139/141 clusters (98.6%); with a threshold of 0.16, 137/141 (97.2%); with a threshold of 0.18, 133/141 (94.3%); with thresholds of 0.18 and 0.20, 130/141 (92.2%). With threshold values of 0.13, 0.14, 0.15, 0.16 and 0.17 the system's sensitivity was greater than 82%, whereas with values of 0.18 and 0.20 it was greater than 80%. The number of false positive region of interest (ROI) / image was greater with low threshold values: in particular, thresholds of 0.13 and 0.14 yielded 16 false positives /image, thresholds of 0.15 and 0.16 yielded 9 and 7 false positives/image, and both 0.18 and 0.20 only 5/image. DISCUSSION: ROC curve shows how the use of high threshold values determined a very high specificity despite very low sensitivity rates. Conversely, low threshold values allowed to have a high sensitivity and a very low specificity. The best performance of our CAD system was obtained with threshold values at 0.15 and 0.16. In fact these thresholds resulted in a high sensitivity (greater than 82%) with an acceptable number of false positives/image, 9 and 7/image, respectively. It is not yet known how radiologists can deal with large numbers of false positives in screening programmes but in our opinion the most important feature of a good CAD system is a high sensitivity. CONCLUSIONS: In the near future the use of CAD systems will be widespread and easier to apply to everyday practice above all in centers where digital mammography is performed. Mammograms could be directly shown to radiologists after the CAD system has selected the ROI and analysed the images. Thanks to its high sensitivity and despite its low specificity CAD represents a concrete aid for radiologists.

Breast Diseases↗
PubMed2000

Conversion of bis(trichloromethyl) carbonate to phosgene and reactivity of triphosgene, diphosgene, and phosgene with methanol(1)

Triphosgene was decomposed quantitatively to phosgene by chloride ion. The reaction course was monitored by IR spectroscopy (React-IR), showing that diphosgene was an intermediate. The methanolysis of triphosgene in deuterated chloroform, monitored by proton NMR spectroscopy, gave methyl chloroformate and methyl 1,1, 1-trichloromethyl carbonate in about a 1:1 ratio, as primary products. The reaction carried out in the presence of large excess of methanol (0.3 M, 30 equiv) was a pseudo-first-order process with a k(obs) of 1.0 x 10(-)(4) s(-)(1). Under the same conditions, values of k(obs) of 0.9 x 10(-)(3) s(-)(1) and 1.7 x 10(-)(2) s(-)(1) for the methanolysis of diphosgene and phosgene, respectively, were determined. The experimental data suggest that, under these conditions, the maximum concentration of phosgene during the methanolysis of triphosgene and diphosgene was lower than 1 x 10(-)(5) M. Methyl 1,1,1-trichloromethyl carbonate was synthesized and characterized also by the APCI-MS technique.

Journal Article↗
PubMed1987

The surgical management of childhood cholesteatoma.

The results of treatment of 124 cases of childhood cholesteatoma are reported in the present study and compared with an adult group of patients. Intact canal wall tympanoplasty was performed in over 90 per cent of cases in children and the procedure was staged in nearly 80 per cent of cases. The children had a 43.8 per cent incidence of residual cholesteatoma and an 8.8 per cent incidence of recurrent cholesteatoma in intact canal wall tympanoplasty cases. Intact canal wall tympanoplasty remains the technique of choice in our hands for the treatment of childhood cholesteatoma; pre-planned staging of the operation is mandatory for the detection and elimination of residual cholesteatoma which occurs more frequently in children.

Adolescent↗
PubMed1985

Autologous fitted incus versus Plastipore PORP in ossicular chain reconstruction.

Hearing results and causes of failure with three types of ossicular reconstruction techniques over an intact stapes, during second-stage intact canal wall tympanoplasty, are reported herein. The three types of reconstruction are: fitted autologous incus (38 cases); Plastipore PORP with cartilage (41 cases); Plastipore PORP without cartilage (32 cases). A residual air-bone gap within 15 dB. was found in 63.2 per cent of fitted includes, in 41.5 per cent of PORPs with cartilage, and in only 37 per cent of PORPs without cartilage. Eighty-four per cent fitted incudes, 63 per cent PORPs with cartilage and 44 per cent PORPs without cartilage yielded a residual air-bone gap within 25 dB. Extrusion has been the main cause of failure among Plastipore prostheses.

Biocompatible Materials↗
PubMed1985

Molded tympanic heterograft. An eight-year experience.

Between 1974 and 1983 the molded tympanic heterograft has been employed in over 1500 cases of tympanic membrane reconstruction at the Second ENT Clinic of the University of Parma, Italy. The results obtained in 1042 patients operated on from July 1974 to December 1981 are reported herein. The tympanic heterograft offered our patients a 90% chance of cure and anatomic restoration of the middle ear; a functional recovery and serviceable hearing can be expected in more than 85% of cases. The heterograft is available in sealed sterilized vials that can be stored at room temperature; its sterility can be maintained for up to five years. There is no need for a graft bank because the heterograft can be kept in the operating theater among the other prostheses that are readily available to the surgical team.

Animals↗
PubMed1985

Surgical treatment of brain herniation into the middle ear and mastoid.

A series of thirty-five patients operated on for brain herniation into the middle ear and mastoid is presented. The etiologic factor was felt to be previous surgery in twenty-six cases, head trauma in four cases, chronic otomastoiditis in four cases, congenital dehiscence of the tegmen in one case, and subdural empyema in one case. Diagnosis and treatment of brain herniation are discussed. The mastoid approach for repair of tegmen defects from below with the use of homologous cartilage or autologous cortical bone is advocated. A combined procedure using the transmastoid approach plus a mini-craniotomy of the temporalis squama is suggested as an alternative treatment to middle cranial fossa repair for larger cerebral hernias.

Adolescent↗
PubMed1984

Management of the labyrinthine fistula in cholesteatoma surgery.

The presence of a labyrinthine fistula has remained one of the major problems in cholesteatoma surgery. Confronted with this problem, the surgeon may ultimately base his choice of procedure on four basic conditions: the size of the fistula, its location in the ear, the condition of the other ear, and the cochlear function. Our attitude has been changing, and currently we prefer to perform a staged closed tympanoplasty. When a closed technique is performed, we either remove the cholesteatoma matrix and then cover the fistula immediately or we leave the matrix in situ and re-explore the mastoid process 5 or 6 months later. The series consists of 88 cases out of a total of 701 patients with cholesteatoma operated on between January 1971 and June 1982. In 20 patients the matrix was left over the fistula at the first stage. The results suggest that a staged operation, i.e. closed tympanoplasty, is to be preferred even in cases with an extensive labyrinthine fistula.

Cholesteatoma↗
PubMedDate not supplied

Prevention of recurrent cholesteatoma in closed tympanoplasty.

Recurrent cholesteatoma in a series of 534 staged intact canal wall tympanoplasties performed over a 10-year period has been reviewed for the present study. Overall detected incidence of recurrent cholesteatoma is 5.2% (28 of 534 operated ears). A steady decrease of recurrent cholesteatoma was found, however, in the second period of our surgical experience (1978 to 1982) when prevention techniques were adopted in all operations, resulting in a 1.07% incidence (four of 373 operated ears). Our present policy for prevention of recurrent cholesteatoma in intact canal wall tympanoplasties with mastoidectomy includes the use of plastic sheeting with thick Silastic, the repair of bony sulcus defects with cartilage shavings, staging of the operation with preplanned reexploration of the middle ear and mastoid, and transtympanic ventilation tube insertion in cases of refractory tubal insufficiency.

Adult↗