Biomedical subjects

S Carpino

Publications and source records attributed to S Carpino.

At least 19 recordsLinked to original sources

PubMed2006

Proteolysis and microstructure of Piacentinu Ennese cheese made using different farm technologies.

The aim of this study was to provide the biochemical and structural characterization of Piacentinu Ennese cheese and to evaluate the impact of different farm technologies on cheese proteolysis and microstructure. Fifteen cheeses were manufactured according to traditional technology, i.e., from raw milk and farmhouse rennet in the absence of starter culture. Pasteurized milk, commercial rennet, and starter were used for production of 20 nontraditional cheeses. Proteolysis in Piacentinu Ennese cheese was monitored during a 2- to 10-mo ripening time. Low rates of overall proteolysis were observed in cheese, as percentages of total N soluble at pH 4.6 and in 12% trichloroacetic acid were about 11.40 and 8.10%, respectively, after 10 mo of age. Patterns of primary proteolysis by urea-PAGE showed that alpha(s)-caseins were degraded to a larger extent than were beta-caseins, although a considerable amount of both caseins was still intact after 10 mo. Reversed phase-HPLC analysis of the cheese peptide fractions showed a slow decrease in the levels of hydrophobic peptides coupled to increasing levels of hydrophilic compounds as the cheese aged. The structural characteristics of Piacentinu Ennese cheese were evaluated by scanning electron microscopy after 2, 4, and 6 mo of age. The micrographs showed a sponge-like structural network with a well-distributed system of empty spaces, originally occupied by whey and fat. The microstructure changed during cheese ripening to become more compact with cavities of smaller size. Farm technology significantly affected cheese proteolysis and microstructure. Nontraditional cheeses had higher levels of pH 4.6-soluble N and showed a larger hydrolysis of alpha(s)-casein fractions by urea-PAGE analysis than did traditional cheeses. Large differences between cheese-types also concerned the patterns of secondary proteolysis. Nontraditional cheeses had higher levels of 12% trichloroacetic acid-soluble N and showed larger proportions of free amino acids and hydrophilic peptides in the HPLC profiles of the corresponding 70% ethanol-soluble N fraction than traditional cheeses. Nontraditional cheeses also had a more open structure with a coarser and less continuous appearance than did traditional cheeses. A large amount of variability in cheese proteolysis and structure within nontraditional treatment reflected farm-dependent changes in manufacturing conditions related to the use of various types of rennet and starter.

Agriculture↗

PubMed2006

Interaction of brine concentration, brine temperature, and presalting on salt penetration in Ragusano cheese.

Thirty-one 3.6-kg blocks of Ragusano cheese were made on each of 6 different days (in different weeks) starting with a different batch of milk on each day. On d 1, 3, and 5, the cheeses were not presalted and on d 2, 4, and 6, all cheeses were presalted (PS). One of the 31 blocks of cheese was selected at random for analysis before brine salting (i.e., on d 0). The remaining 30 blocks were randomly divided into 2 groups of 15 blocks each; one group was placed in 18% brine (18%B) and the other group was placed in saturated brine (SB). For the 15 blocks within each of the 2 brine concentrations (BC), 5 blocks were placed in a brine tank at 12 degrees C, 5 at 15 degrees C, and 5 at 18 degrees C, and submerged for 24 d. The research objective was to determine the combined impacts (i.e., interactions) of PS the curd before stretching, BC (SB vs. 18%B), and brine temperature (BT; 12, 15, and 18 degrees C) on salt uptake, moisture content, and yield of Ragusano cheese. Although BC, BT, and PS each had their own separate impacts on salt uptake, there was little interaction of these effects on salt uptake when they were used in combination. The PS most quickly delivered salt to the interior of the cheese and was the most effective approach to salting for controlling early gas formation. There were strong separate impacts of BC, BT, and PS on cheese moisture content, moisture loss, and net weight loss, with BC having the largest separate impact on these parameters. Reducing BT reduced salt content and increased moisture, but the effects were small. The more important effect of reduced BT was to reduce growth of gas forming bacteria. The 18%B produced higher moisture, and less moisture and weight loss than SB. The effect of interactions of BC, BT, and PS on moisture loss and net weight loss were small. To achieve the maximum benefit from the various approaches to salting for controlling early gas formation in Ragusano cheese, PS combined with slightly lower BT (i.e., 15 degrees C instead of 18 degrees C) should be used. Although using 18%B instead of SB did increase salt uptake, the point at which improved salt uptake occurred due to use of 18%B did not provide benefit in prevention of early gas formation, as reported separately. However, use of 18%B instead of SB provided a 9.98% increase in cheese yield due to reduced moisture loss during brining; this would be very attractive to cheese makers. The increase in yield needs to be balanced against the risk of growth of undesirable bacteria in the 18%B and the creation of another cheese quality defect.

Animals↗

PubMed2005

Evaluation of bitterness in Ragusano cheese.

The appearance of undesirable bitter taste in Ragusano cheese was investigated by comparing the composition of 9 bitter cheeses with that of 9 reference cheeses of good quality by means of chemical, electrophoretic, and chromatographic analyses. Rates of proteolysis were significantly affected in cheeses of different quality. Primary proteolysis, as measured by pH 4.6-soluble N, was significantly greater in bitter cheeses compared with reference samples. Urea-PAGE profiles showed an almost complete breakdown of caseins in bitter cheeses and the further degradation of primary peptides into smaller compounds not detectable by this technique. Cheeses with defects had significantly lower levels of secondary proteolysis as reflected by the percentage of pH 4.6-soluble N soluble in 12% trichloroacetic acid and the amounts of total free amino acids. Peptides separated by reversed phase-HPLC revealed that the large and significant differences in peptide profiles of the soluble fractions between bitter and reference cheeses were mainly due to a much higher proportion of hydrophobic peptides in the former. The occurrence of bitterness in Ragusano cheese was therefore attributable to unbalanced levels of proteolysis and peptidolysis. Extensive degradation of caseins and primary peptides by activities of proteases produced large amounts of small- and medium-sized hydrophobic peptides that were not adequately removed by peptidases of microflora and therefore accumulated in cheese potentially contributing to its bitter taste. The presence of these compounds in bitter cheeses was related to high salt-in-moisture and low moisture contents that limited the enzymatic activities of microflora important in secondary proteolysis. Combining salt-in-moisture and the ratio of hydrophobic-to-hydrophilic soluble peptides resulted in the best logistic partial least squares regression model predicting cheese quality. Although bitterness is known to be rarely encountered in cheese at salt-in-moisture levels >5.0, all of the bitter cheeses analyzed in this study had salt-in-moisture levels much greater than this value. According to the logistic model, a risk of bitterness development may exist for cheeses with a midrange (5 to 10%) salt-in-moisture content but with an inadequate level of secondary proteolysis.

Caseins↗

PubMed2005

Composition, microstructure, and surface barrier layer development during brine salting.

The goal of this study was to characterize the changes in chemical composition, porosity, and structure that occur at the surface of a block of brine-salted cheese and their relationship to the rate at which salt is taken up from the brine. To create a difference in composition, salt uptake, and barrier layer properties, identical blocks of Ragusano cheese were placed in saturated and 18% salt brine at 18 degrees C for 12 d. The overall moisture content and porosity decreased, whereas salt and salt in moisture content increased near the surface of blocks of brine-salted Ragusano cheese for all treatments. The general appearance of the microstructure of the surface of the blocks of brine-salted cheese was much more compact than the microstructure 1 mm inside the block at both brine concentrations. Large differences in porosity of the barrier layer were produced by brine-salting cheese in 18% vs. saturated brine, with cheese in saturated brine having much lower porosity at the surface and taking up much less salt during brining. The macro network of water channels within the microstructure of the cheese was less open near the surface of the block for cheese in both saturated and 18% brine after 4 d. However, no large differences in the size of the macro channels in the cheese structure due to the difference in brine concentration were observed by scanning electron microscopy. It is possible that the shrinkage of the much smaller pore structure within the casein matrix of the cheese is more important and will become more limiting to the rate of salt diffusion. Further microstructure work at higher resolution is needed to answer this question. The calculated decrease in porosity at the exterior 1-mm portion of the block was 50.8 and 29.2% for cheeses that had been in saturated vs. 18% brine for 12 d, respectively. The difference in brine concentration had a very large impact on the salt in moisture content of the cheese. The exterior of the cheese in 18% brine reached a salt in moisture content almost identical to that of the brine very quickly (17.3% at 4 d), whereas the salt in moisture content at the surface of the cheese block in saturated brine was only 11.9% at 4 d. There appears to be some critical concentration of salt in brine above which there is a large negative impact on salt uptake due to the creation of a barrier layer at the surface of the block of cheese.

Cheese↗

PubMed2004

Contribution of native pasture to the sensory properties of Ragusano cheese.

Ragusano is a Protected Denomination of Origin cheese produced in the Hyblean area of Sicily. Sixteen samples of Ragusano cheese from two different treatments [pasture and total mixed ration (TMR)] were evaluated after 4 and 7 mo of aging. The color of the cheeses produced from milk of cows consuming fresh native pasture plants was much more yellow than cheeses from TMR fed cows (i.e., higher Hunter b value). This was due to transfer of beta-carotene and related compounds from the diet and demonstrated that compounds from native pasture plants changed the sensory characteristics of Ragusano cheese. To avoid a "halo" effect in a trained panel, quantitative descriptive analysis sensory evaluation of these cheeses for odor, taste, consistency, and mouth structure, color differences among cheeses were masked. A unique approach in sensory analysis was developed using sunglasses with lenses designed to block light at the specific wavelengths at which panelists would detect differences in color among samples. Testing was conducted every 2-wk period (15-d increments) with two tests per week using 11 trained panelists. All the panelists tasted all the products. Panelists were able to detect significant differences in the sensory characteristics of cheeses produced from milk of cows consuming native pastures versus TMR even when the color difference was masked.

Animal Feed↗

PubMed2004

Composition and aroma compounds of Ragusano cheese: native pasture and total mixed rations.

Raw milk from 13 cows fed TMR supplemented with native pasture and from 13 cows fed only TMR on one farm was collected separately 4 times with an interval of 15 d between collections. Two blocks (14 kg each) of cheese were made from each milk. The objective was to determine the influence of consumption of native plants in Sicilian pastures on the aroma compounds present in Ragusano cheese. Milk from cows that consumed native pasture plants produced cheeses with more odor-active compounds. In 4-mo-old cheese made from milk of pasture-fed cows, 27 odor-active compounds were identified, whereas only 13 were detected in cheese made from milk of total mixed ration-fed cows. The pasture cheeses were much more rich in odor-active aldehyde, ester, and terpenoid compounds than cheeses from cows fed only total mixed ration. A total of 8 unique aroma-active compounds (i.e., not reported in other cheeses evaluated by gas chromatography olfactory) were detected in Ragusano cheese made from milk from cows consuming native Sicilian pasture plants. These compounds were 2 aldehydes ([E,E]-2,4-octadienal and dodecanal), 2 esters (geranyl acetate and [E]-methyl jasmonate), 1 sulfur compound (methionol), and 3 terpenoid compounds (1-carvone, L(-) carvone, and citronellol). Geranyl acetate and (E)-methyl jasmonate were particularly interesting because these compounds are released from fresh plants as they are being damaged and are part of a possible plant defense mechanism against damage from insects. Most of the odor-active compounds that were unique in Ragusano cheese from pasture-fed cows appeared to be compounds created by oxidation processes in the plants that may have occurred during foraging and ingestion by the cow. Some odor-active compounds were consistently present in pasture cheeses that were not detected in the total mixed ration cheeses or in the 14 species of pasture plants analyzed. Either these compounds were present in other plants not analyzed, created in the rumen or in cheese after the pasture-plant material had been consumed, or the compounds were lost in the method of sample extraction used for the plant analysis (i.e., steam distillation) versus the solid-phase microextraction method used for the cheeses. This research has demonstrated clearly that some unique odor-active compounds found in pasture plants can be transferred to the cheese.

Animal Feed↗

PubMed2004

Lipolysis and proteolysis in Ragusano cheese during brine salting at different temperatures.

The influence of temperature (12, 15, 18, 21, and 24 degrees C) of saturated brine on lipolysis and proteolysis in 3.8-kg blocks of Ragusano cheese during 24 d of brining was determined. Twenty-six 3.8-kg blocks were made on each day. The cheese making was replicated on 3 different days. All blocks were labeled and weighed prior to brining. One block was sampled and analyzed prior to brine salting. Five blocks were placed into each of 5 different brine tanks at different temperatures. One block was removed from each brine tank after 1, 4, 8, 16, and 24 d of brining, weighed, sampled, and analyzed. Both proteolysis and lipolysis in Ragusano cheese increased with increasing brine temperature (from 12 to 24 degrees C), with the impact of brine temperature on proteolysis and lipolysis becoming progressively larger. Proteolysis was highest in the interior of the blocks where salt in moisture content was lowest and temperature had more impact on proteolysis in the interior position of the block than the exterior position. However, the opposite was true for lipolysis. The total free fatty acid content was higher and temperature had more impact on lipolysis at the exterior position of the block where salt in moisture was the highest. This effect of increased salt concentration on lipolysis was confirmed with direct salted cheeses in a small follow-up experiment. Lipolysis increased with increasing salt in the moisture content of the direct salted cheeses. It is likely that migration of water-soluble FFA from the brine into the cheese and from the interior portion of the cheese to the exterior portion of the cheese also contributed to a higher level of FFA at the exterior portion of the blocks. As brine temperature increased the profile of individual free fatty acids released from triglycerides changed, with the proportion of short-chain free fatty acids increasing with increasing brine temperature. This effect was largest at high salt in moisture content.

Cheese↗

PubMed2004

Chemometric analysis of proteolysis during ripening of Ragusano cheese.

Chemometric modeling of peptide and free amino acid data was used to study proteolysis in Protected Denomination of Origin Ragusano cheese. Twelve cheeses ripened 3 to 7 mo were selected from local farmers and were analyzed in 4 layers: rind, external, middle, and internal. Proteolysis was significantly affected by cheese layer and age. Significant increases in nitrogen soluble in pH 4.6 acetate buffer and 12% trichloroacetic acid were found from rind to core and throughout ripening. Patterns of proteolysis by urea-PAGE showed that rind-to-core and age-related gradients of moisture and salt contents influenced coagulant and plasmin activities, as reflected in varying rates of hydrolysis of the caseins. Analysis of significant intercorrelations among chemical parameters revealed that moisture, more than salt content, had the largest single influence on rates of proteolysis. Lower levels of 70% ethanol-insoluble peptides coupled to higher levels of 70% ethanol-soluble peptides were found by reversed phase-HPLC in the innermost cheese layers and as the cheeses aged. Non-significant increases of individual free amino acids were found with cheese age and layer. Total free amino acids ranged from 14.3 mg/g (6.2% of total protein) at 3 mo to 22.0 mg/g (8.4% of total protein) after 7 mo. Glutamic acid had the largest concentration in all samples at each time and, jointly with lysine and leucine, accounted for 48% of total free amino acids. Principal components analysis and hierarchical cluster analysis of the data from reversed phase-HPLC chromatograms and free amino acids analysis showed that the peptide profiles were more useful in differentiating Ragusano cheese by age and farm origin than the amino acid data. Combining free amino acid and peptide data resulted in the best partial least squares regression model (R(2) = 0.976; Q(2) = 0.952) predicting cheese age, even though the peptide data alone led to a similarly precise prediction (R(2) = 0.961; Q(2) = 0.923). The most important predictors of age were soluble and insoluble peptides with medium hydrophobicity. The combined peptide data set also resulted in a 100% correct classification by partial least squares discriminant analysis of cheeses according to age and farm origin. Hydrophobic peptides were again discriminatory for distinguishing among sample classes in both cases.

Amino Acids↗

PubMed2003

Influence of presalting and brine concentration on salt uptake by Ragusano cheese.

The impact of presalting and nonsaturated brine on salt uptake by Ragusano cheese was determined. The study included four treatments: 1) the traditional method using no presalting and saturated brine, 2) presalting and saturated brine, 3) no presalting and 18% brine for 8 d followed by 16 d in saturated brine, and 4) presalting and 18% brine for 8 d followed by 16 d in saturated brine. Cheese blocks were weighed and sampled before brine salting (time 0) and after 1, 4, 8, 16, and 24 d of brining for each treatment. Presalting delivered 60% of the normal level of salt in the center of the block prior to brine salting without decreasing the rate of uptake of salt from either saturated or 18% brine. Use of 18% salt brine for the first 8 d of 24 d of brine salting increased the rate of salt uptake, compared with 24 d in saturated brine. The increased rate of salt uptake with 18% brine compared with saturated brine was related to the impact of salt brine on the moisture content and porosity of the cheese near the surface of the block. Brine with higher salt content causes a rapid loss of moisture from cheese near the surface of the block. Moisture loss causes shrinkage of the cheese structure and decreases porosity, which impedes moisture movement out and salt movement into the block. The use of 18% salt brine for the first 8 d delayed the moisture loss and cheese shrinkage at the exterior of the block and allowed more salt penetration.

Cheese↗

PubMed2003

Influence of the temperature of salt brine on salt uptake by Ragusano cheese.

The influence of temperature (12, 15, 18, 21, and 24 degrees C) of saturated brine on salt uptake by 3.8-kg experimental blocks of Ragusano cheese during 24 d of brining was determined. Twenty-six 3.8-kg blocks were made on each of three different days. All blocks were labeled and weighed prior to brining. One block was sampled and analyzed prior to brine salting. Five blocks were placed into each of five different brine tanks at different temperatures. One block was removed from each brine tank after 1, 4, 8, 16, and 24 d of brining, weighed, sampled, and analyzed for salt and moisture content. The weight loss by blocks of cheese after 24 d of brining was higher, with increasing brine temperature, and represented the net effect of moisture loss and salt uptake. The total salt uptake and moisture loss increased with increasing brine temperature. Salt penetrates into cheese through the moisture phase within the pore structure of the cheese. Porosity of the cheese structure and viscosity of the water phase within the pores influenced the rate and extent of salt penetration during 24 d of brining. In a previous study, it was determined that salt uptake at 18 degrees C was faster in 18% brine than in saturated brine due to higher moisture and porosity of the exterior portion of the cheese. In the present study, moisture loss occurred from all cheeses at all temperatures and most of the loss was from the exterior portion of the block during the first 4 d of brining. This loss in moisture would be expected to decrease porosity of the exterior portion and act as a barrier to salt penetration. The moisture loss increased with increasing brine temperature. If this decrease in porosity was the only factor influencing salt uptake, then it would be expected that the cheeses at higher brine temperature would have had lower salt content. However, the opposite was true. Brine temperature must have also impacted the viscosity of the aqueous phase of the cheese. Cheese in lower temperature brine would be expected to have higher viscosity of the aqueous phase and slower salt uptake, even though the cheese at lower brine temperature should have had a more porous structure (favoring faster uptake) than cheese at higher brine temperature. Therefore, changing brine concentration has a greater impact on cheese porosity, while changing brine temperature has a larger impact on viscosity of the aqueous phase of the cheese within the pores in the cheese.

Cheese↗

PubMed2002

Chemometric analysis of Ragusano cheese flavor.

Ragusano cheeses were produced in duplicate from milk collected from pasture-fed and total mixed ration (TMR)-fed cattle at four time intervals. The cheeses were subjected to chemical analysis, conventional sensory testing, and gas chromatography-olfactometry (GCO). Data from each type of analysis were examined by principal component and factor analysis and by pattern recognition (SIMCA) to see if sufficient information for classification into pasture-fed and TMR-fed groups was contained therein. The results clearly indicate that there are significant differences in sensory panel and chemical analysis results between the two cheeses. The data were also examined to see if models of sensory responses as a function of analytical or GCO results or both could be constructed with the modeling technique partial least-squares regression (PLS). Strong PLS models of some sensory responses (green and toasted odor; salt, pungent, bitter, and butyric sensations; and smooth consistency) were obtained.

Animal Feed↗

PubMed2002

An empirical method for prediction of cheese yield.

Theoretical cheese yield can be estimated from the milk fat and casein or protein content of milk using classical formulae, such as the VanSlyke formula. These equations are reliable predictors of theoretical or actual yield based on accurately measured milk fat and casein content. Many cheese makers desire to base payment for milk to dairy farmers on the yield of cheese. In small factories, however, accurate measurement of fat and casein content of milk by either chemical methods or infrared milk analysis is too time consuming and expensive. Therefore, an empirical test to predict cheese yield was developed which uses simple equipment (i.e., clinical centrifuge, analytical balance, and forced air oven) to carry out a miniature cheese making, followed by a gravimetric measurement of dry weight yield. A linear regression of calculated theoretical versus dry weight yields for milks of known fat and casein content was calculated. A regression equation of y = 1.275x + 1.528, where y is theoretical yield and x is measured dry solids yield (r2 = 0.981), for Cheddar cheese was developed using milks with a range of theoretical yield from 7 to 11.8%. The standard deviation of the difference (SDD) between theoretical cheese yield and dry solids yield was 0.194 and the coefficient of variation (SDD/mean x 100) was 1.95% upon cross validation. For cheeses without a well-established theoretical cheese yield equation, the measured dry weight yields could be directly correlated to the observed yields in the factory; this would more accurately reflect the expected yield performance. Payments for milk based on these measurements would more accurately reflect quality and composition of the milk and the actual average recovery of fat and casein achieved under practical cheese making conditions.

Animals↗

PubMed2000

Composition of Ragusano cheese during aging.

Ragusano cheese is a brine-salted pasta filata cheese. Composition changes during 12 mo of aging were determined. Historically, Ragusano cheese has been aged in caves at 14 to 16 degrees C with about 80 to 90% relative humidity. Cheeses (n = 132) included in our study of block-to-block variation were produced by 20 farmhouse cheese makers in the Hyblean plain region of the Province of Ragusa in Sicily. Mean initial cheese block weight was about 14 kg. The freshly formed blocks of cheese before brine salting contained about 45.35% moisture, 25.3% protein, and 25.4% fat, with a pH of 5.25. As result of the brining and aging process, a natural rind forms. After 12 mo of aging, the cheese contained about 33.6% moisture, 29.2% protein, 30.0% fat, and 4.4% salt with a pH of 5.54, but block-to-block variation was large. Both soluble nitrogen content and free fatty acid (FFA) content increased with age. The pH 4.6 acetate buffer and 12% TCA-soluble nitrogen as a percentage of total nitrogen were 16 and 10.7%, respectively, whereas the FFA content was about 643 mg/100 g of cheese at 180 d. Five blocks of cheese were selected at 180 d for a study of variation within block. Composition variation within block was large; the center had higher moisture and lower salt in moisture content than did the outside. Composition variation within blocks favored more proteolysis and softer texture in the center.

Cheese↗

PubMed1994

Study on the reference dose level in radiotherapy treatment planning.

PURPOSE: The reference dose level of the dose distribution in the tumor volume is studied. METHODS AND MATERIALS: The study is performed using a formula based on the Linear Quadratic (LQ) model. The calculated reference dose level to which the prescribed dose must be referred, for the eradication of a homogeneous tumor, is investigated by varying the dose distribution, that is, the dose volume histogram shape, its range, the prescribed total dose, the fraction size and the linear quadratic model parameters, alpha and beta. RESULTS: For all the simulated dose volume histograms the calculated reference dose level is lower than the mean dose level, depending on the range of dose variation and the considered tumor sensitivity. When the dose nonuniformity is not too great the reference dose level is very near to the mean dose level; when the inhomogeneity of dose distribution is high the reference level is clearly lower than the mean level but not necessarily equal to the minimum level in the tumor. For the dose volume histograms derived from the actual dose distributions obtained from a two tangential beams technique, a four beams technique and a moving beam technique, the reference levels are calculated and compared with the ICRU 29 reference point dose level. In two cases the reference levels are lower than the level at the ICRU 29 reference point. In the case of the four beams technique, the two levels are equal. CONCLUSION: These theoretical results show the possibility of administering the prescribed dose to a dose level higher than the minimum in the tumor, with the same value of Tumor Control Probability (TCP) as the one corresponding to a uniform tumor irradiation. The application of the proposed study can offer a general support to the choice of the reference dose level, based on the actual dose distribution in the tumor volume.

Humans↗

PubMed1994

Magnetic resonance guided radiosurgery in children: tridimensional extrapolation from isodose neuroimaging superimposition.

In stereotactic radiosurgery, thin external beams of ionizing radiation concentrated in a single dose onto a sharply defined target are employed to treat lesions within the brain, avoiding doses which may produce unwanted damage to the surrounding healthy tissue. The dynamic irradiation technique used with the linear accelerator employs variable arcs of irradiation rotating around the isocenter of the target. The technique of stereotactic magnetic resonance (MR) guided radiosurgery is supported by a dedicated computerized system for treatment planning simulation. The system, based on a personal computer, allows the acquisition, reconstruction, and visualization of the target volume from MR images, and permits calculation and visualization of a three-dimensional dose distribution directly superimposed upon MR images of the lesion. The desired goal of destroying neoplastic tissue without damaging cerebral parenchyma is of particular importance in children. Consequently, adapting the three-dimensional isodose profiles to the morphology of the lesion to be treated is crucial. From this, the importance of the computer simulation is evident, as it permits one to go deeply into the study of isodose distribution, changing beam collimation, and the number and amplitude of arcs of irradiation.

Brain Neoplasms↗

PubMed1993

Estimate of normal tissue damage in treatment planning for stereotactic radiotherapy.

A personal computer (PC) system was developed to perform treatment planning for radiosurgery and stereotactic radiotherapy. These techniques of irradiation of the brain may be accomplished with a linear accelerator by performing several non-coplanar arcs of a highly collimated beam focused at a fixed point. The PC system allows the acquisition, reconstruction and the visualization of the target volume from CT or MR images, and then it permits to calculate a three-dimensional (3-D) dose distribution due to small photon beams and to visualize it. The software calculates not only total dose distribution, administered fractionated or in single fraction, but also the NTD2 (normalized total dose) predicted to have a biological effect equivalent to the single irradiation. The choice of the best technique is supported by the dose volume histograms (DVH) calculation and by an estimate of complication probability to the brain normal tissue (NTCP). The algorithm for NTCP calculation is based on two models: the linear quadratic and the logistic. A comparison of three different dose calculations for a typical cerebral target volume is presented to demonstrate the system performances.

Algorithms↗

PubMed1992

Ideal dose level in treatment planning optimization.

The biological response of the tumor is expressed in terms of tumor control probability (TCP) and its dependence on the inhomogeneous dose distribution throughout the tumor volume is studied. The ideal dose level to which the prescribed dose must be referred is derived, by employing a formula based on the linear quadratic model. To administer the prescribed dose to the ideal dose level renders the tumor control probability equal to that one corresponding to a uniform irradiation of the tumor. For the normal tissue irradiated a normal tissue complication probability index (NTCPI) is also defined and calculated. The comparison between NTCPIs of competing plans supports the optimization. In general the resulting ideal dose level is lower than the mean dose level, but not necessarily equal to the minimum in the tumor. This result shows the possibility of administering the prescribed dose to a dose level higher than the minimum, maintaining the tumor control probability at a good level and consequently lowering the complications to the normal tissue. The method offers a general support for the choice of the reference dose level and of the better technique. An example of application of the method is shown.

Humans↗

PubMed1990

[Leiomyosarcoma of the small intestine].

Three cases of leiomyosarcomas of the small bowel, two localized in the jejunum and one in the ileum are reported. In the light of reported data, stress is laid on the anatomicopathological aspects and it is pointed out that the symptomatology is not specific and is comparable to that characterising the other neoplasms of the small bowel. The usefulness of the various diagnostic investigations are analysed and it is maintained that surgery plays a primary role in the treatment of such neoformations. It is maintained, finally, that further studies are needed to pinpoint the factors that may be correlated with the prognosis.

Adult↗