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Biomedical subjects

M Frigerio

Publications and source records attributed to M Frigerio.

At least 19 recordsLinked to original sources
PubMed1999

Contrast improvement in a new radiotherapy imaging system.

PURPOSE: The aim of this paper is to compare the EC-L Kodak system for radiation therapy beam localization with a conventional one that could be daily employed in a radiotherapy department. BACKGROUND: The main purpose of portal images is to verify the treatment volume in actual clinical conditions. Low contrast is the main constraint affecting portal film image. METHODS: Kodak proposes a new imaging system (film and cassette) characterized by contrast enhancement as imaging standard for radiotherapy. The evaluation of system contrast was carried out by using a step-wedge consisting in 4 60 x 60 mm plexiglas steps and an anthropomorphic phantom. Portal films were exposed to a 6 MV photon beam by a linear accelerator (Varian Clinac 1800) with a 250 x 340 mm field size at the 1000 mm source film distance. The 2 imaging system performances were evaluated analyzing the image optical density. RESULTS: The use of the Kodak system results in a real contrast improvement, so it is satisfactory to describe the field placement as to the region of interest. CONCLUSIONS: The most critical characteristic attaining this method regards low contrast, i. e. the small optical density difference existing between different anatomical regions on the film. Since radiographic techniques can significantly influence quality of portal films, the adequate choice of film and screen combination, as well as the exposure technique is particularly useful in a radiotherapy quality assurance program.

Evaluation Studies as Topic↗
PubMed1998

Radiological findings when very small lung volumes are irradiated in breast and chest wall treatment.

Acute pneumonitis following breast irradiation is a rare and transient phenomenon that can be easily managed by drugs. The aim of this study is to evaluate late sequelae on lung, after postoperative radiotherapy (RT) for breast cancer. We were concerned with investigating late radiological findings when very small lung volumes are involved in the irradiated volume. We studied 28 consecutive patients. They underwent clinical examination and all staging procedures before surgery, evaluation of pulmonary function with spirometry, postoperative chest x-ray and high resolution computed tomography (HRCT) of the lung before RT. Clinical examinations were usually performed every 3 months after RT. A second chest x-ray, HRCT and spirometry were carried out after nearly 7 months from the end of RT. We estimated the irradiated lung volume by measuring the area of the lung surface enclosed by the 50% isodose (LA50) in each profile. We found a significant correlation between LA50 and the score of radiological findings after RT. No correlations were found between other factors (i.e., adjuvant chemotherapy, age, weight, smoking) and lung fibrosis. No woman developed radiation pneumonitis syndrome or respiratory symptoms. Our results indicate that irradiation of the breast and/or chest wall is well tolerated if treatment planning is done accurately. The fibrosis likelihood is strongly correlated to the irradiated lung volume. The use of tangential fields limits radiological changes that can be detected only by HRCT examination and are not associated with clinical symptoms.

Adult↗
PubMed1998

Interphysician variability in defining the planning target volume in the irradiation of prostate and seminal vesicles.

With the improvements in treatment accuracy the risk exists of over-reliance on the capability of the physician to estimate the extent of the tumour. We assessed the variability between six radiotherapists in defining the planning target volume (PTV) on CT slices for three prostate tumour cases. Percentage differences between measured volumes and mean values calculated for each case ranged from -53.64 to +60.48% (SD 36.00%). There is a considerable variation in delineating the PTV, both in the cranio-caudal direction and in the in-slice extension of the areas drawn on each slice (standard deviations ranged from 0.35 to 2.64 cm2). We also checked the uncertainty in the shape and position of the contours on each CT image. The analysis was performed on three slices of one test case. As we expected, the uncertainty seems largest for seminal vesicle slices and smallest for prostatic apex slices. These results endorse the need for uncertainty analysis of all departmental processes in order to define a detailed protocol and consequently to minimize the interphysician differences in PTV delineations.

Analysis of Variance↗
PubMed1998

[Air bubble effect during alloy cooling in shielding blocks radiotherapy].

INTRODUCTION: Shaped fields are widely used in radiotherapy to protect critical organs and to avoid unnecessary normal tissue irradiation. The most common system for photon beam shaping consists in a low melting point alloy. We studied the air bubbles which can occur during alloy cooling with both new and remelted alloys and when different cooling techniques are chosen. MATERIAL AND METHODS: Forty cone samples (18 of remelted alloy and 22 of new alloy) were prepared to evaluate the frequence of air bubble recurrence, with reproducible geometric sizes (height = 70 mm, major base surface diameter = 60 mm, minor base surface diameter = 40 mm). Air bubble sizes and dose inhomogeneity were evaluated by reproducing 60Co radiograph of each sample (two orthogonal projections: 6 x 7 cm). The samples were cooled at a constant temperature, following three different modalities: high (25 degrees C), medium (5 degrees C), low (-20 degrees C) temperature. Owing to the small geometrical magnification, air bubble sizes were determined by measuring their surface on samples lateral projections, taking into account the sight detectable bubble edges. RESULTS: Up to 300 mm2 lateral surface bubbles are always present in all castings. Casting inhomogeneities can produce a film-density inhomogeneity ranging from 9% to 40%. The spatial distribution of bubbles seems to be random. CONCLUSIONS: Bubble recurrence is independent of both the metal alloy (repeatedly used castings) and the different block cooling modalities. The effect of air bubbles on the shielded areas dose inhomogeneity is generally of no relevant importance. However, these inhomogeneities can produce hot spots which must be taken into accurate consideration only in the particular treatments where critical small size organ dose sparing represents a basic issue (i.e. the shielding of eye lens).

Air↗
PubMed1997

Restrictive criteria for heart transplantation candidacy maximize survival of patients with advanced heart failure.

BACKGROUND: The shortage of organ donors and the amelioration of medical management of advanced heart failure mandate strict selection of heart transplant candidates on the basis of the need and probability of success of transplantation, with the aim of maximizing survival of patients with advanced heart failure, both with and without transplantation. This study analyzes the impact of restricting the criteria for heart transplantation candidacy on the outcome of patients with advanced heart failure referred for transplantation. METHODS: Survival and freedom from major cardiac events (death, resuscitated cardiac arrest, transplantation while supported with inotropes or mechanical devices) were compared between patients listed during 1990 to 1991, when standard criteria were applied (group 1, n = 118), and patients listed during 1993 to 1994, when only patients requiring continuous/recurrent intravenous inotrope therapy in spite of optimized oral medications and outpatients showing actual progression of the disease were admitted to the waiting list (group 2, n = 88). Survival and freedom from cardiac events (defined as above plus listing in urgent status) were also calculated in stable outpatients evaluated in 1993 to 1994, who were potential heart transplant candidates according to standard criteria but were not listed because of restrictive criteria (group 3, n = 52, New York Heart Association functional class > or = III, mean echocardiographic ejection fraction 0.22 +/- 0.05, mean peak oxygen consumption 12.3 +/- 1.5 ml/kg/min, mean follow-up 19 +/- 10 months). RESULTS: Thirty-one percent, 40%, and 50% of group 1 patients versus 58%, 65%, and 77% of group 2 patients underwent transplantation within 3, 6, and 12 months after listing (p < 0.0007). The 1- and 2-year survival rates after listing were 80% and 71% in group 1 versus 85% and 84% in group 2 (p < 0.0001). Freedom from death/urgent transplantation was lower in group 2 than in group 1 (55% and 48% versus 72% and 59% at 6 and 12 months, respectively; p < 0.0001). In patients undergoing transplantation, the postoperative survival rate was similar (87% and 91% at 2 years in group 1 and group 2, respectively). Two years after heart transplantation candidacy was denied, 86% of group 3 patients were alive, and 74% were event-free. CONCLUSIONS: Restricting the admissions to the waiting list to patients with refractory/progressive heart failure improved survival rates after listing by increasing the probability to undergo transplantation in a short time. Selection of most severely ill candidates did not affect postoperative survival. Survival and freedom from cardiac events were good in patients with advanced but stable heart failure, in spite of their severe functional limitation. Thus restrictive criteria for heart transplantation candidacy allows maximal survival benefit from both medical therapy and transplantation.

Adolescent↗
PubMed1997

[Heart transplantation 1985-1995: 10 years experience at the "Angelo De Gasperis" center. Improvement of results by progress in operative criteria].

BACKGROUND: At 10-years from beginning of transplant experience in our Center we analyzed the overall results in an attempt to identify risk factors for early (3 months) and late (over 3 months) mortality after heart transplantation (HTx). METHODS: The data of 313 patients transplanted from November 1985 to June 1995 were studied and analyzed with a multivariate logistic regression and Cox's proportional hazard model. Seventy pre, intra and postoperative variables were considered: demographics, clinical status, hemodynamic parameters, donor characteristics, donor-recipient mismatch, complications, immunosuppressive protocols. In this paper we compared results in patients operated on from 1985 to 1990 (Group I) and from 1991 to 1995 (Group II) in order to assess improvements due to changes in HTx indication and in perioperative treatments. RESULTS: Overall mortality in the entire group was 19.8% (62/313): 30-days, 3 months and late mortality rates were 8.0%, 10.2%, 10.7% respectively. In Group II mortality rates were 7.1%, 8.6% and 2.8% respectively despite significant increase in Status I patients (21.5% in Group I vs 40.1% in Group II, p = 0.0008). Main causes of early death were: graft failure (46.9%), infection (28.1%), acute- rejection (12.5%). Main causes of late death were: cardiac allograft vasculopathy (40.0%) and neoplasm (23.3%). The mean follow-up of the 281 survivors more than 3 months is 45.6 +/- 30.0 months (range 3 to 120 months). Actuarial survival is 86.9 +/- 1.9%, 78.4 +/- 2.7% and 70.7 +/- 3.9% at 1, 5 and 10 years respectively. The difference in the 5-years actuarial survival between Group I and Group II patients is statistically significant (70.7 +/- 4.2% vs 84.5 +/- 4.5%, p = 0.005). TPG (OR 1.19), RAP (OR 1.13) and MD-HD inotropic support of donor (OR 3.81) were identified as independent risk factors for early mortality. Number of moderate rejection at biopsy (OR 1.56) and early postTx infection (OR 3.37) were identified as independent risk factors for late mortality. CONCLUSIONS: The overall results of our ten-year experience are very satisfying in relation to early and late mortality, with a significant favourable trend between patients transplanted in the early era (1985-1990) and those transplanted in the recent era (1991-1995). The study confirm that morbidity and mortality have the highest incidence during the early post-transplantation phase. Pulmonary hypertension and elevated preoperative right filling pressure appear to indicate a significantly increased risk of early death and only marginally influence late survival that is principally related to the severe postoperative complications. Differently from other observations, among the donor-related and recipient-donor matching variables, this analysis evidenced as significant only the need for MD-HD catecolamines during donor-management.

Actuarial Analysis↗
PubMed1997

A semiquantitative approach to the evaluation of acute cardiac allograft rejection at endomyocardial biopsy.

BACKGROUND: Histopathologic criteria for grading of acute cardiac allograft rejection are focused on the most severe lesion that is recognized among the myocardial fragments provided by each endomyocardial biopsy specimen. Considering the distribution of rejection lesions among all the fragments improved the accuracy in characterizing the severity of rejection in pathologic studies. This study was undertaken to verify the usefulness of a semiquantitative evaluation of endomyocardial biopsy specimens, consisting of the calculation of the proportion of fragments showing rejection in the clinical setting. METHODS: Of the 2386 biopsy specimens obtained during the first posttransplantation year in 168 consecutive cardiac allograft recipients, 290 biopsy specimens constituted by > or = 3 adequate fragments and showing rejection not followed by treatment (n = 159) or being the first biopsy specimen prompting treatment with augmented immunosuppression for that rejection episode (n = 131) were selected. These biopsy specimens (index biopsy specimens) were grouped according to whether rejection was present in < or = 33%, > 33% to < or = 67%, and > 67% of the fragments. The rejection grade (according to the standardized grading system) and the proportion of fragments positive for rejection were correlated with the occurrence of clinical symptoms and signs of rejection at index biopsy and with the results of the next biopsy. RESULTS: Rejections graded > or = 3A were more frequently symptomatic (36% vs 9% for those graded < 3, p < 0.0001), as were those involving increasing proportions of fragments (< or = 33%: 5 of 124, 4%; > 33 to < or = 67%: 13 of 99, 13%; > 67%: 19 of 67, 28% [p < 0.0001]). Spontaneous resolution after untreated biopsies was more frequent in focal (grade 1A and 2) than in diffuse mild (1B) rejections (68% vs 38% [p < 0.04]), whereas progression to grade 3A or greater was less frequent (4% vs 27% [p < 0.01]). Increasing proportions of positive fragments were associated with lower frequencies of spontaneous resolution (p < 0.05) and higher frequencies of worsening (9%, 22%, 43% [p < 0.009]) or progression to grade 3A or greater (2%, 6%, 28% [p < 0.005]). Complete resolution after treatment was less frequent for increasing proportions of positive fragments at index biopsy (80%, 66%, 49% [p < 0.05]). CONCLUSIONS: Diffuse versus focal rejection pattern and the proportion of positive fragments seem to be clinically relevant in terms of occurrence of symptoms, spontaneous evolution, and response to treatment.

Adolescent↗
PubMed1997

[Errors in positioning the patient during transcutaneous radiotherapy of the pelvis].

INTRODUCTION: Quality controls in radiotherapy allow to check the correct running of treatment units and to test our procedures. Portal films taken during the first treatment session are used in quality assurance programs to compare scheduled to administered doses. MATERIAL AND METHODS: To analyze the accuracy of patient positioning in pelvic cancer irradiation, a retrospective study was carried out on 50 treatment schedules carried out at the Radiotherapy Department of S. Anna Hospital (Como, Italy) from June to December, 1996. We checked field mispositioning for correlations with patient or treatment variables, such as patient age, sex, weight, thickness, or unit type. We took one portal film at the first treatment session and checked field positioning by measuring the distance of the isocenter from fixed anatomical structures on the simulation film and on the portal film taken in anteroposterior and lateral projections. RESULTS: Four vectors were defined to evaluate field mispositioning along right-left (ADS), craniocaudal (ACC, LCC) and anteroposterior (AP) directions. The average values of these four vectors were respectively 2.94, 5.23, 5.54 and 3.20 mm. We found a major shift in field centering leftward and toward the patient's feet. To obtain more information about the total isocenter displacement, a vector T was calculated by summing the vectors ADS, ACC and LAP; a further evidence of field mispositioning is given by the vector T mean value (8.66 +/- 4.95 mm). No correlation was found between vector T values and any patient or treatment variable. DISCUSSION: The acquaintance with uncertainties requires adequate statistical tools. A single check at treatment beginning could show a systematic error, but not the random fluctuations which can be recognized only with periodic portal films. To correct a possible systematic error without likely worsening set-up conditions, an adequate threshold value must be chosen for field mispositioning, according to each center's historical data. CONCLUSION: One portal film at the beginning of treatment is the minimum requirement in a quality assurance program. We feel the need to change our protocol and acquire more than one portal film, because the higher the number of portal films the easier the distinction of systematic from random errors. Using serial portal films, all at the first session, we will be able to introduce quantitative criteria for various action levels.

Female↗
PubMed1995

Significance of pericardial effusion after heart transplantation.

The aim of this study was to evaluate the clinical significance of pericardial effusion after heart transplantation and to assess its correlation with acute rejection. One hundred fifty transplanted patients were followed up for the first year: serial echocardiographic studies were performed on the same day as were the endomyocardial biopsies; hemodynamic studies and coronary angiographies were performed 1 year after transplant. Ten days after surgery, pericardial effusion was absent in 77 patients, small in 52, moderate in 14, and large in 7, and was significantly related to severe postoperative bleeding (p < 0.001). Patients were classified according to the presence and the course of pericardial effusion in group A (absence or disappearance of previous pericardial effusion within 1 month, 107 patients) and in group B (onset, persistence, or increase in pericardial effusion, 43 patients). One hundred nineteen patients experienced > or = 1 acute rejection episode. The evolution of pericardial effusion was different (p < 0.0001) according to the number of acute rejection episodes and biopsy specimens showing acute rejection, histologic grading and time of the first episode, and histologic grading of the most severe acute rejection episode. Furthermore, there was a significant correlation with the cumulative duration of acute rejection episodes (p < 0.005) and the presence of previous cardiac surgical history (p < 0.007), but no correlation with cardiac transplant vasculopathy or with a positive weight mismatch. This study suggests that pericardial effusion in transplant recipients is associated with a higher incidence and more severe histologic grading of acute rejection episodes; its presence indicates the need for stricter monitoring of acute rejection.

Acute Disease↗
PubMed1995

An ICRU 50 radiotherapy treatment chart.

We illustrate a radiotherapy treatment chart elaborated to fulfil the necessity for clarity in reporting information about radiotherapeutic treatment. The schematic configuration of the chart results from the experience and the cooperation of physicists, physicians and technicians, and an effort has been made to satisfy Levels 2/3 of the ICRU 50 recommendations. The chart has been divided into four sections corresponding to different kinds of information: a cover sheet, a section containing data about the treatment planning geometry and the console parameters adopted, a section showing dosimetric data, and a section showing treatment data. The chart seems to give a good level of accuracy in reporting treatment plan information.

Humans↗
PubMed1995

An equivalent square method for irregular photon fields.

A quick formula is proposed for calculating equivalent squares of irregularly shaped photon fields. No complex calculations are required. Three different energies (60Co; 6 MV and 18 MV x-rays) were investigated. Comparison with results utilizing the Clarkson technique (60Co) and with experimental measurements (6 MV and 18 MV x-rays) indicates that the method is accettable in a wide variety of clinical situations. The applied procedure introduces an indetermination lower than 4%, with maximum absolute percentage errors of 3%, 2.7%, and 3.6% for 6 MV, 18 MV, and 60Co photon fields respectively.

Algorithms↗
PubMed1995

[Short-term survival after heart transplantation: the relationships between preoperative hemodynamics, organ function and postoperative clinical events].

AIM OF THE STUDY: Pulmonary hypertension is known to affect prognosis of cardiac allograft recipients. Aim of this study is to elucidate the mechanisms relating preoperative hemodynamics to early post-transplant mortality. METHODS: Hemodynamic and pre- and postoperative clinical data of 122 heart transplant recipients were reviewed with respect to early mortality (within 1 month or in-hospital). The relationships between hemodynamics and mortality were studied by means of univariate and multivariate analysis of absolute data and at different cut-off values of hemodynamic parameters. RESULTS: The following hemodynamic parameters were significantly different between survivors (n = 107) and non-survivors (n = 15): right atrial pressure (7.7 +/- 4.7 vs. 12.1 +/- 8.6 mm Hg, p < 0.004), pulmonary vascular resistance (2.57 +/- 1.44 vs. 3.72 +/- 1.88 Wood units, p < 0.007), pulmonary vascular resistance index (4.43 +/- 2.53 vs. 6.53 +/- 3.28 Wood units x m2, p < 0.005), and transpulmonary gradient (8.8 +/- 4.8 vs. 12.3 +/- 6.4 mm Hg, p < 0.02). Right atrial pressure and pulmonary vascular resistance index showed an independent value at stepwise multiple logistic regression analysis (p < 0.008 and < 0.03 respectively). When mortality was tested using cut-off values, it was significantly higher with right atrial pressure > or = 12 (7/28 vs 8/94, p < 0.05), pulmonary vascular resistance index > or = 8 (6/13 vs 9/109, p < 0.0005), and transpulmonary gradient > or = 15 (5/13 vs 10/109, p < 0.01). High right atrial pressure, pulmonary vascular resistance index, and transpulmonary gradient were associated with higher preoperative bilirubin (p < 0.03), which was significantly superior in non-survivors (1.44 +/- 1.53 vs. 0.83 +/- 0.61 mg/dl, p < 0.02). Postoperatively, severe right ventricular failure, severe renal failure and infections within 1 month were all strongly associated with an increased mortality (p < 0.00003); they were more common in patients with high preoperative right filling pressure (9% vs. 43%, p < 0.00002) and/or high pulmonary vascular resistance index (14% vs. 38%, p < 0.03), in those with high right atrial pressure (9% vs. 35%, p < 0.0009), and in those with high pulmonary vascular resistance index (17% vs. 58%, p < 0.002) respectively. Mortality after acute rejection within 1 month was significantly higher in patients with high preoperative right atrial pressure (8% vs. 57%, p < 0.006). CONCLUSIONS: Besides pulmonary hypertension, elevated preoperative right filling pressure appears to indicate an increased risk of early death after transplantation; pre- and postoperative end-organ dysfunction and post-transplant complications are more common or more threatening in this setting.

Adult↗
PubMed1994

Acute rejection after heart transplantation: noninvasive echocardiographic evaluation.

OBJECTIVES: The purpose of this study was to assess the reliability of echocardiography in the noninvasive diagnosis of acute rejection in heart transplant recipients. BACKGROUND: Although echocardiographic results seem to correlate well with allograft rejection, published data are limited and contradictory. METHODS: In 130 transplant recipients, 1,400 serial echocardiograms were recorded within 24 h of endomyocardial biopsy. Increased wall thickness, myocardial echogenicity, pericardial effusion, shorter pressure half-time, isovolumetric relaxation time and a decrease in left ventricular ejection fraction were considered markers of rejection. RESULTS: The distribution of echocardiographic markers revealed highly significant differences between bioptically graded moderate, mild and no rejection and between untreated and treated rejection episodes (both chi-square test, p < 0.0001). Specificity was 98.6% for two markers, but sensitivity was good (80%) for only moderate rejection because of the large number of false negatives in untreated patients with mild rejection. In untreated patients, there was a highly significant difference in the number of echocardiographic criteria between a benign and nonbenign outcome (chi-square test, p < 0.0001). In treated patients, the significant difference in the variation in echocardiographic criteria between favorable and unfavorable responses after 1 week was more pronounced after 2 weeks (t test, p < 0.01 vs. < 0.001). Diastolic indexes and pericardial effusion at 2 weeks seemed to be predictive of therapeutic response. CONCLUSIONS: Poor sensitivity to mild rejection indicates that serial echocardiography cannot supplant endomyocardial biopsy in the early diagnosis of acute rejection, but it seems to be a reliable noninvasive means of identifying acute rejection requiring intensified immunosuppressive therapy and of evaluating outcome.

Acute Disease↗