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M Carrara,
A Bono,
C Bartoli,
A Colombo,
M Lualdi,
D Moglia,
N Santoro,
E Tolomio,
S Tomatis,
G Tragni,
M Santinami, R Marchesini
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ABSTRACT: Various instruments based on acquisition and elaboration of images of pigmented skin lesions have been developed in an attempt to in vivo establish whether a lesion is a melanoma or not. Although encouraging, the response of these instruments, e.g. epiluminescence microscopy, reflectance spectrophotometry and fluorescence imaging, cannot currently replace the well-established diagnostic procedures. However, in place of the approach to instrumentally assess the diagnosis of the lesion, recent studies suggest that instruments should rather reproduce the assessment by an expert clinician of whether a lesion has to be excised or not. The aim of this study was to evaluate the performance of a spectrophotometric system to mimic such a decision. The study involved 1794 consecutively recruited patients with 1966 doubtful cutaneous pigmented lesions excised for histopathological diagnosis and 348 patients with 1940 non-excised lesions because clinically reassuring. Images of all these lesions were acquired in vivo with a multispectral imaging system. The data set was randomly divided into a train (802 reassuring and 1003 excision-needing lesions, including 139 melanomas), a verify (464 reassuring and 439 excision-needing lesions, including 72 melanomas) and a test set (674 reassuring and 524 excision-needing lesions, including 76 melanomas). An artificial neural network (ANN(1)) was set up to perform the classification of the lesions as excision-needing or reassuring, according to the expert clinicians' decision on how to manage each examined lesion. In the independent test set, the system was able to emulate the clinicians with a sensitivity of 88% and a specificity of 80%. Of the 462 correctly classified as excision-needing lesions, 72 (95%) were melanomas. No major variations in receiver operating characteristic curves were found between the test and the train/verify sets. On the same data set, a further artificial neural network (ANN(2)) was then architected to perform classification of the lesions as melanoma or non-melanoma, according to the histological diagnosis. Having set the sensitivity in recognizing melanoma to 95%, ANN(1) resulted to be significantly better in the classification of reassuring lesions than ANN(2). This study suggests that multispectral image analysis and artificial neural networks could be used to support primary care physicians or general practitioners in identifying pigmented skin lesions that require further investigations.
Physics in Medicine and Biology 06/2007; 52(9):2599-613. · 2.83 Impact Factor
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ABSTRACT: The complex inner layered structure of skin influences the photon diffusion inside the cutaneous tissues and determines the reflectance spectra formation. Phantoms are very useful tools to understand the biophysical meaning of parameters involved in light propagation through the skin. To simulate the skin reflectance spectrum, we realized a multilayered skin-like phantom and a multilayered skin phantom with a melanoma-like phantom embedded inside. Materials used were Al(2)O(3) particles, melanin of sepia officinalis and a calibrator for haematology systems dispersed in transparent silicon. Components were optically characterized with indirect techniques. Reflectance phantom spectra were compared with average values of in vivo spectra acquired on a sample of 573 voluntary subjects and 132 pigmented lesions. The phantoms' reflectance spectra agreed with those measured in vivo, mimicking the optical behaviour of the human skin. Further, the phantoms were optically stable and easily manageable, and represented a valid resource in spectra formation comprehension, in diagnostic laser applications and simulation model implementation, such as the Monte Carlo code for non-homogeneous media.
Physics in Medicine and Biology 06/2007; 52(10):N229-39. · 2.83 Impact Factor
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ABSTRACT: Different technological tools have been developed to aid in the diagnosis of pigmented skin lesions, including cameras working with conventional RGB colour systems, epiluminescence microscopy and spectrophotometric methods using visible and near infrared wavelengths. All the different procedures should provide in an objective and reproducible fashion quantitative measurements of the colour and shape features of a given skin mole. At present, many devices have been introduced in experimental stages for clinical diagnosis, mainly used to provide to the clinicians an objective, computer-assisted second opinion. As for any diagnostic instruments, optical devices should also be subjected to a dedicated quality assurance protocol in order to evaluate the response repeatability of each device (intra-instrument agreement) and to check the accordance among the responses of different devices (inter-instrument agreement). The aim of this study was to design a quality assurance protocol for optical devices dedicated to image analysis of pigmented skin lesions and, in case, to detect cutaneous melanoma by using suitable tissue-like phantoms as standard references that enable testing of both hardware and software components. As an example, we report the results of intra-instrument and inter-instrument agreement when the protocol was applied on a series of 30 SpectroShade instruments, a novel optical device based on multi-spectral image analysis of colour and shape features of pigmented skin lesion.
Physics in Medicine and Biology 01/2007; 51(23):N429-40. · 2.83 Impact Factor
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ABSTRACT: The results obtained utilising radiochromic films (Gafchromic MD-55 and HD-810, ISP Technologies Inc.), radiographic films (Kodak EDR2) and laboratory-made Fricke-xylenol-orange-infused gel dosimeters in form of layers have been intercompared. Dose calibration curves have been attained for all kinds of dosimeters and in-phantom measurements have been performed. From the detected in-phantom dose images, depth-dose profiles have been extracted and compared with reference values obtained with an ionisation chamber. The performance of the different dosimeters, their precision and reliability, are presented.
Physica Scripta 02/2006; 2005(T118):31. · 1.20 Impact Factor
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ABSTRACT: Early detection and prompt excision of cutaneous melanoma is of paramount importance to improve patient survival, and the clinician should be aware of the clinical features that suggest the presence of a malignant lesion. The clinical diagnosis is mainly based on observation of the colour and shape of a given skin lesion. Unfortunately, evaluation of a pigmented lesion is to a large extent subjective and is closely related to the experience of the clinician. To overcome this problem, optical imaging techniques using different instrumentation (i.e. colour video camera, epiluminescence microscopy, reflectance spectrophotometry) and computer image analysis have been proposed in an attempt to provide quantitative measurements in an objective and reproducible fashion. The different procedures employed to perform the diagnosis automatically all have a common denominator: mimicking the eye and the brain of the clinician by image processing and computerized analysis programs, respectively. Sensitivity and specificity data reported in the literature suggest that the computer-based diagnosis of melanoma does not greatly differ from the diagnostic capability of an expert clinician, and is independent of the optical acquisition method employed to analyse the lesions. Most of the computer-processed morphometric variables useful in automated diagnosis are not recognizable nor can be objectively evaluated by the human eye, except that of lesion dimension. However, several questions should be answered before assessing the actual usefulness, including the potential and limitations, of computer-based diagnostic procedures. The purpose of this study was to briefly review the different kinds of instrumentation being used to diagnose melanoma, and to raise questions and whenever possible provide answers in an attempt to establish whether there will be a future for these computerized systems.
Melanoma Research 07/2002; 12(3):279-86. · 2.19 Impact Factor
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ABSTRACT: Modeling of light transport in tissue requires development of theoretical models and experimental procedures, as well as tissue-simulating phantoms. Our purpose was to develop a phantom that matches the optical characteristics of human skin in the visible and near infrared spectral range.
The phantom consists of a transparent silicone rubber in which Al(2)O(3) particles and a cosmetic powder are embedded. Layers with thickness as thin as 0.1 mm can be made. The optical properties of Al(2)O(3) particles and cosmetic powder, i.e., total attenuation, absorption and scattering coefficients, and phase function, have been determined in the visible and near infrared spectral range, by using direct and indirect techniques.
By varying the concentration of scattering and absorbing particles, tissue-like layers can be produced with predictable optical properties. In particular, mixing at suitable concentration Al(2)O(3) particles and cosmetic powder with the silicone rubber, the optical properties of human skin have been simulated over a range of wavelengths from 400 to 1,000 nm. The comparison between the phantom diffuse reflectance spectrum and that of human skin, averaged over a sample of 260 patients, showed a good agreement.
The proposed technique allows to produce a stable and reproducible phantom, with accurately predictable optical properties, easy to make and to handle. This phantom is a useful tool for numerous applications involving light interaction with biologic tissue.
Lasers in Surgery and Medicine 02/2001; 28(3):237-43. · 2.75 Impact Factor
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ABSTRACT: The dosimetric accuracy of a 3D treatment planning system (TPS) for conformal radiotherapy with a computer-assisted dynamic multileaf collimator (DMLC) was evaluated. The DMLC and the TPS have been developed for clinical applications where dynamic fields not greater than 10 x 10 cm2 and multiple non-coplanar arcs are required. Dosimetric verifications were performed by simulating conformal treatments of irregularly shaped targets using several arcs of irradiation with 6 MV x-rays and a spherical-shaped, tissue-simulating phantom. The accuracy of the delivered dose at the isocentre was verified using an ionization chamber placed in the centre of the phantom. Isodose distributions in the axial and sagittal planes passing through the centre of the phantom were measured using double-layer radiochromic films. Measured dose at the isocentre as well as isodose distributions were compared to those calculated by the TPS. The maximum percentage difference between measured and prescribed dose was less than 2.5% for all the simulated treatment plans. The mean (+/-SD) displacement between measured and calculated isodoses was, in the axial planes, 1.0 +/- 0.6 mm, 1.2 +/- 0.7 mm and 1.5 +/- 1.1 mm for 80%, 50% and 20% isodose curves, respectively, whereas in the sagittal planes it was 2.0 +/- 1.2 mm and 2.2 +/- 2 mm for 80% and 50% isodose curves, respectively. The results indicate that the accuracy of the 3D treatment planning system used with the DMLC is reasonably acceptable in clinical applications which require treatments with several non-coplanar arcs and small dynamic fields.
Physics in Medicine and Biology 09/2000; 45(8):N77-84. · 2.83 Impact Factor
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ABSTRACT: In an attempt to overcome the subjectiveness of clinical observation in the diagnosis of cutaneous melanoma, a computerized method is proposed. Reflectance images of 237 pigmented lesions (67 melanomas and 170 non-melanomas) were analysed using a telespectrophotometric technique. This device consists of a CCD camera with 17 interference filters. Images were acquired at selected wavelengths, from 420 to 1040 nm. Morphological and reflectance related parameters were extracted from the wavelength-dependent images of the lesions. The most significant features in the comparison between benign and malignant lesions were: lesion dimension (P < 10(-8) at 578 nm); mean value (P < 10(-7) at 940 nm) and standard deviation (P < 10(-4) at 904 nm) of lesion reflectance; lesion roundness (P < 10(-5) at 461 nm); and border irregularity (P < 10(-4) at 461 nm). Based on these parameters, a discriminant function between the two populations of lesions (naevi and melanomas) was obtained. By using the results of the analysis of the recruited lesions as 'training data', discriminant functions enabled the assignment of a score, or a 'risk probability', to each studied lesion. By imposing a sensitivity of 80% (a figure that mimics the diagnostic capability of an experienced clinician), entering or not entering the lesion dimension as input data in the discriminant analysis led to a specificity of 51% or 46% respectively. The high number of false-positive cases, which is a consequence of the selection criteria of the lesions, is, at present, the major limitation of the current technique. Nevertheless, our results suggest that an imaging-based computer-assisted device could be capable of discriminating malignant lesions mainly by evaluation of reflectance, especially in the infrared region, and shape properties. The dimension of a lesion should not be essential in the diagnosis of melanoma and, in our opinion, small melanomas should be recognized by a computer system as well as they are on clinical grounds.
Physics in Medicine and Biology 06/2000; 45(5):1243-54. · 2.83 Impact Factor
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ABSTRACT: In stereotactic radiosurgery the choice of appropriate detectors, whether for absolute or relative dosimetry, is very important due to the steep dose gradient and the incomplete lateral electronic equilibrium. For both linac-based and Leksell Gamma Knife radiosurgery units, we tested the use of calibrated radiochromic film to measure absolute doses and relative dose distributions. In addition a small diode was used to estimate the relative output factors. The data obtained using radiochromic and diode detectors were compared with measurements performed with other conventional methods of dosimetry, with calculated values by treatment planning systems and with data prestored in the treatment planning system supplied by the Leksell Gamma Knife (LGK) vendor. Two stereotactic radiosurgery techniques were considered: Leksell Gamma Knife (using gamma-rays from 60Co) and linac-based radiosurgery (LR) (6 MV x-rays). Different detectors were used for both relative and absolute dosimetry: relative output factors (OFs) were estimated by using radiochromic and radiographic films and a small diode; relative dose distributions in the axial and coronal planes of a spherical polystyrene phantom were measured using radiochromic film and calculated by two different treatment planning systems (TPSs). The absolute dose at the sphere centre was measured by radiochromic film and a small ionization chamber. An accurate selection of radiochromic film was made: samples of unexposed film showing a percentage standard deviation of less than 3% were used for relative dose profiles, and for absolute dose and OF evaluations this value was reduced to 1.5%. Moreover a proper calibration curve was made for each set of measurements. With regard to absolute doses, the results obtained with the ionization chamber are in good correlation with radiochromic film-generated data, for both LGK and LR, showing a dose difference of less than 1%. The output factor evaluations, performed using different methods, are in good agreement with a maximum difference of 1.5% for all field sizes considered (LGK and LR) except the 4 mm helmet used in the LGK unit. In this case, differences exist between diode and radiochromic film measurements and both detectors show data values larger than the prestored OF value of 0.80. Dose profiles measured by radiochromic film and calculated are in excellent agreement for both LGK and LR with a maximum deviation of less than 1.0 mm, when full widths of the dose profiles at 20%, 50%, 80% levels are considered. When external photon beams are used in stereotactic radiosurgery, the 'well selected' radiochromic films are very accurate detectors both for relative and absolute dosimetry. The experimental results, obtained using both radiochromic and diode detectors, show that the 4 mm helmet relative output factor could be underestimated.
Physics in Medicine and Biology 05/1999; 44(4):887-97. · 2.83 Impact Factor
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ABSTRACT: The propagation of light emitted by a linear light diffuser in a cylindrical hollow organ was investigated by means of the Monte Carlo (MC) method. The height and radius of the cavity, scattering (mu(s)) (or reduced scattering, mu'(s)) and absorption (mu(a)) coefficients, anisotropy (g), and refractive indices of the media involved (n1, n2) are required as input data by the MC code, as are characteristics of the light diffuser (length, delivered power and emission profile). Results of our MC model were tested by measuring the light fluence rate in a tissue-simulating phantom (mu(a) = 0.5 cm(-1), mu(s) = 23 cm(-1) and g = 0.75) irradiated at 633 nm with a cylindrical diffuser. Since geometric and optical parameters determine the behaviour of light propagation in tissue, MC simulations with different sets of input parameters were carried out to provide qualitative as well as quantitative data useful in planning photodynamic therapy. Data are reported on light penetration and fluence rate build-up at mu(a) and mu'(s) values ranging between 0.1 and 5 cm(-1) and 2.5 and 50 cm(-1), respectively. Furthermore, results suggest that a shift and spread could occur in the isofluence curves along the symmetry axis, which depend on the diameter of the treated lumen as well as on the emission profile of the light diffuser. Using our data it is possible to estimate how inaccuracy in knowledge of the optical coefficients can affect (i.e. usually by increasing) the light dose scheduled at a certain depth into tissue.
Physics in Medicine and Biology 02/1999; 44(1):1-11. · 2.83 Impact Factor
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ABSTRACT: A problem for clinicians is to mentally integrate information from multiple diagnostic sources, such as computed tomography (CT), magnetic resonance (MR), and single photon emission computed tomography (SPECT), whose images give anatomic and metabolic information.
To combine this different imaging procedure information, and to overlay correspondent slices, we used commercially available software packages (SRS PLATO and IFS). The algorithms utilize a fiducial-based coordinate system (or frame) with 3 N-shaped markers, which allows coordinate transformation of a clinical examination data set (9 spots for each transaxial section) to a stereotactic coordinate system. The N-shaped markers were filled with fluids visible in each modality (gadolinium for MR, calcium chloride for CT, and 99mTc for SPECT). The frame is relocatable, in the different acquisition modalities, by means of a head holder to which a face mask is fixed so as to immobilize the patient. Position errors due to the algorithms were obtained by evaluating the stereotactic coordinates of five sources detectable in each modality.
SPECT and MR position errors due to the algorithms were evaluated with respect to CT: deltax was < or = 0.9 mm for MR and < or = 1.4 mm for SPECT, deltay was < or = 1 mm and < or = 3 mm for MR and SPECT, respectively. Maximal differences in distance between estimated and actual fiducial centers (geometric mismatch) were in the order of the pixel size (0.8 mm for CT, 1.4 mm for MR, and 1.8 mm for SPECT). In an attempt to distinguish necrosis from residual disease, the image fusion protocol was studied in 35 primary or metastatic brain tumor patients.
The image fusion technique has a good degree of accuracy as well as the potential to improve the specificity of tissue identification and the precision of the subsequent treatment planning.
International Journal of Radiation OncologyBiologyPhysics 02/1999; 43(1):227-34. · 4.11 Impact Factor
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ABSTRACT: The ABCD (Asymmetry, Border, Color, and Dimension) criteria represent a commonly used clinical guide for the diagnosis of early melanoma. The authors revised these criteria in the light of objective measurements of the features of pigmented skin lesions obtained by telespectrophotometric analysis (TS) in the visible and near-infrared wavelengths.
This study involves a consecutive series of 186 patients with 195 cutaneous pigmented lesions (53 melanomas and 142 nonmelanoma lesions). Each lesion was subjected to TS in vivo, before surgery. For this purpose, the authors used four spectrophotometric parameters that could be closely related to the four criteria of the ABCD guide, namely, roundness (an estimate of how a lesion contour resembles a circle), smoothness (an indicator of the regularity of a lesion border), mean reflectance (the ability of a lesion to diffuse or reflect the incident light), and size (the greatest dimension of a lesion).
When melanomas and nonmelanoma lesions were compared by univariate analysis, all four spectrophotometric parameters considered proved to be significantly different (P=0.05). Multivariate logistic analysis showed that mean reflectance in the infrared (P < 0.01) and size (P=0.03) were parameters independently associated with melanoma. Melanoma showed lower reflectance and greater size than benign lesions.
Information provided by TS substantially validates the importance of the ABCD clinical guide and suggests that color is the most important parameter in discriminating melanoma from nevi. In particular, melanoma appears darker than other pigmented lesions.
Cancer 02/1999; 85(1):72-7. · 4.77 Impact Factor
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ABSTRACT: The coming into effect of decrees No. 626/94, 242/96 and 230/95 has once again brought out the problem of the radiation exposure of hot cell operators in nuclear medicine.
With regard to the activity of the Division of Nuclear Medicine of the Istituto Nazionale Tumori in Milan, a map has been produced of the radiation fields in the hot cell in- and outside the working station by measuring the rate of exposure and evaluating the radiation energy using film dosimeters in multifilter containers. The individual doses were measured with film dosimeters for the sternum, the back of the hand and the wrist, and with thermoluminescent dosimeters for the fingers and forehead. The thermoluminescent ring was worn with the detector towards the palm and towards the back of the hand in order to identify the side that was exposed most; the film dosimeter on the sternum was worn both underneath and above the lead apron to reveal a possible reduction in overall exposure due to attenuation of the lower-energy components.
The diffuse radiation field in the hot cell during the usual working activity amounts to 1 microSv/h. Assessment of the energy of the radiation fields within the working station revealed a higher energy (90 to 140 keV) in the source storage area than in the area where the syringes are prepared, the latter being affected by diffuse radiation with components of approximately 35, 90 and 110 keV. The hand of the operator is unevenly exposed to the diffuse radiation field and the fingers are more exposed than the back of the hand and the wrist: when the thermoluminescent ring was worn with the detector towards the palm of the hand the measured values did not show a higher exposure than when it was worn with the detector towards the back of the hand. The equivalent of the overall dose measured underneath the lead apron did not show any relevant reduction of the exposure due to attenuation of the lower-energy component (approx. 35 keV). We report the dosimetric findings regarding the total and partial exposure of four different operators during their regular weekly shift, with the dosimeters for the sternum, ring finger and forehead being replaced daily. The average equivalent of the dose to the hand for the manipulation of 37 GBq of 99mTc, measured with a thermoluminescent ring on the proximal phalanx of the ring finger, ranged 3.9 mSv to 2.0 mSv. Except in one case, the sternum and forehead proved to be well protected by the shielding of the working station.
The operator who stay in the hot cell for 5 hours/week accumulates, due to the presence of diffuse radiation, 5 microSv/week to the whole body; when his/her hands are inside the working station for 2.5 hours/week in the most unfavorable conditions as regards the presence of radioactive sources, they will be exposed to 1250 microSv/week, independently of dose preparation. The exposure of hot cell personnel is highly dependent on the ergonomics of the operator (build, height, arm spread, hand size, etc.) with respect to the position of the apertures and the inspection windows of the working station; as a consequence, the three dosimetric values (exposure of the sternum, the hands and the forehead) cannot be correlated. The fingers are the most exposed part of the hand, which confirms the appropriateness of our choice of the thermoluminescent ring to measure the partial exposure of the hands. Our results have been compared with those reported in the literature and with statistical data relative to three years of regular activity (1994-1996), during which the hot cell operators were monitored according to the same parameters; female operators proved to be more exposed than males, with average yearly equivalents of the total dose of 2764 microSv and 860 microSv, respectively, and average yearly equivalents of the partial dose to the hands of 32,288 microSv and 9460 microSv, respectively. The average total partial dose equivalent rati
La radiologia medica 01/1999; 96(6):612-7. · 1.44 Impact Factor
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ABSTRACT: The characteristics of a prototype computer-assisted dynamic multileaf collimator (DMLC), specifically designed for small-field conformal radiotherapy, were evaluated at the Istituto Nazionale Tumori of Milan. The collimating device consists of two opposing banks of 16 pairs of 8 cm thick, 3.6 mm wide tungsten leaves and allows shaping of a radiation field up to a size of 10 x 10 cm2 at the isocentre. The screening thickness of each leaf is 6.25 mm at the accelerator gantry isocentre. The leaves have a trapezoidal cross section and move along an arched path, thus providing a 'double focused' collimation system. The DMLC was installed on the head of a Varian Clinac 2100C linear accelerator. Mechanical and dosimetric evaluations were performed to test the stability of the mechanical isocentre and to determine leaf leakage, penumbra width, accuracy of leaf positions and uniformity of leaf speed. Displacement of the mechanical isocentre was less than 1 mm at all gantry angles. Standard radiographic films exposed to 6 MV x-ray radiation were used for dosimetric evaluations. Leakage between leaves was less than 2.5%, and leakage through abutted leaves was less than 5.5%. The penumbra width between 20% and 80% isodose at different positions of leaf banks was 2.7 mm in the direction of the leaf motion and 3.1 mm along the side of the leaf with a standard deviation of 0.2 mm in both directions. Accuracy in the positioning of the leaf was 0.3 mm, whereas the maximum repositioning error was less than 0.2 mm. Finally, during movement of the leaves at the maximum speed of 0.5 mm s(-1), the standard deviation of the leaf positioning error was 0.2 mm, proving an accurate uniformity of leaf speed.
Physics in Medicine and Biology 11/1998; 43(10):3149-55. · 2.83 Impact Factor
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ABSTRACT: Doses to the gonads and skin of adult people were evaluated during the study of functional anorectal disorders with defecography.
The radiologic procedure relies heavily on fluoroscopy with lateral and anteroposterior projections for a mean time of 2.4 minutes; the stages of interest are recorded on a mean of 6 films. Absorbed doses to the gonads and to the skin were measured with LiF thermoluminescence dosimeters placed inside and outside the anthropomorphic "Rando" phantom. The administered doses during the different examination phases (anteroposterior and lateral fluoroscopy and radiography) were measured. Digital and conventional radiography were compared.
Gonadal absorbed doses in a standard DSI examination were: 5.0 +/- .1 mGy to the right ovary, 25.2 +/- .7 mGy to the left ovary and 2.7 +/- .1 mGy to testes when at the margin of the irradiation field. Doses to gonads and skin are about 15% higher when the examination is performed with conventional radiography.
The considerable radiation dose to ovaries shows that defecography can cause radiation-induced genetic effects in women younger than 40 years with a probability of the order of one thousandth of the natural incidence genetic defects.
Defecography must be correctly indicated in fertile women, because of the relatively high absorbed dose to ovaries. In fact, the ovaries absorb about twice as many radiations during defecography than radiologic examinations of the lower gastrointestinal tract.
La radiologia medica 12/1997; 94(5):520-3. · 1.44 Impact Factor
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ABSTRACT: The aim of this study was to determine the non-extremity gamma dose received by a technician while performing an ordinary nuclear medicine procedure or a static (i.e. without blood sampling) fluorine-18 fluorodeoxyglucose (FDG) positron emission tomography (PET) study. The dose per patient was measured by means of a commercial electronic pocket Geiger Mueller dosimeter, worn in the upper left pocket of the overalls. This was previously tested by exposure to known point sources of technetium-99m, gallium-67, iodine-131 and fluorine-18 in the air. A further test was performed with 99mTc, 131I and 18F sources inserted in a water phantom to simulate the condition of high scattering degradation of the primary radiation due to the patient's tissues. Subsequently, the dose was measured by two technicians for a total of 314 clinical cases, covering the most common nuclear medicine procedures, including 44 static, two-level FDG PET studies with repositioning of the patient on the couch between the transmission and the emission scan and seven whole-body PET studies. The dose read by the dosimeter was corrected for environmental background and for detector efficiency measured with sources in the air. For a limited subset of cases, the time spent close to patients was also measured. Doses were then estimated by a crude non-absorbing point source approximation and by using experimental dose rates. A comparison between experimental and estimated doses, as well as with previously published data, completed the work. For most of the conventional procedures, the measured dose per procedure proved to be within the range 0.2-0.4 microSv, except for equilibrium angiocardioscintigraphy (1.0+/-0.5 microSv) and 99mTc-sestamibi single-photon emission tomography (1. 7+/-1.0 microSv). Comparison with data published in the last 20 years shows that our values are generally lower. The current more favourable working conditions are a result of technological improvements (for instance two-head gamma cameras capable of whole-body studies), and safer shielding and distance from patients. Two-level PET gave 11.5+/-4.4 microSv and whole-body PET 5.9+/-1.2 microSv. In a subset of patients these values could be subdivided into the separate contributions from each phase of the procedure. They were: 0.11+/-0.04 microSv for daily quality assurance, 2.9+/-3.0 microSv for two transmission scans, 0.3+/-0.1 microSv for syringe preparation, 2.8+/-1.8 microSv for injection and escorting the patient to the waiting room, 1.7+/-1.5 microSv for a whole-body emission scan, 7.7+/-5.2 microSv for two emission scans, and 0.8+/-0. 2 microSv for patient departure. The higher value from PET by comparison with conventional procedures is attributable to the higher specific gamma constant of 18F, as well as the longer time required for accurate positioning.
European Journal of Nuclear Medicine 12/1997; 24(11):1380-9.
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G Zonca,
V Fossati,
S Basso Ricci, R Marchesini,
C Stucchi,
E Pignoli,
A Somigliana,
S Borelli,
M Fantini,
F Santoni,
A Soriani,
L Begnozzi
Frontiers of radiation therapy and oncology 02/1997; 31:60-4.
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ABSTRACT: The effect of topotecan, a topoisomerase I inhibitor, on ionizing radiation-induced cytotoxicity was studied in 2 human tumor cell lines characterized by a different expression of the target enzyme. The cytotoxicity of topotecan alone or in combination with radiation was assessed in exponentially growing non-small-cell lung cancer (H460) and glioblastoma (GBM) cells using the colony-forming assay. An isobologram method was used to evaluate the treatment interaction. An apparent supra-additive effect in cell killing following drug-radiation-combined treatment was observed only in GBM cells exposed to topotecan for 24 hr. In the case of H460 cells, interaction varied from a strong infra-additive effect at low radiation doses to a slight supra-additive effect when cells were exposed to radiation doses greater than 3 Gy. Northern blot analysis indicated that topoisomerase I expression in H460 cells was 8-fold higher than that of GBM cells. Although the H460 cell line exhibited an increased sensitivity to topotecan, only in the GBM cell line (which expressed a lower level of topoisomerase I) did the drug potentiate the radiation cytotoxicity. The observation that the radiosensitization by topotecan was related to topoisomerase I level is consistent with a putative role of the enzyme in processes involved in the repair of radiation damage. It is conceivable that the modulation of enzyme function results in an effective reduction of cellular capability for repair of radiation damage only if the enzyme is not over-expressed. Although a precise role of topoisomerase I in the cellular response to ionizing radiations (in particular, in DNA repair) remains to be documented, such results suggest the potential interest of topoisomerase I inhibitors in combination with radiation therapy for tumors expressing low topoisomerase I levels.
International Journal of Cancer 06/1996; 66(3):342-6. · 5.44 Impact Factor
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ABSTRACT: Reflectance images of 43 pigmented lesions of the skin (18 melanomas, 17 common melanocytic naevi and eight dysplastic naevi) were acquired by a telespectrophotometric system and were analysed in the spectral range from 420 to 1040 nm, to discriminate melanoma from benign melanocytic entities. Different evaluations were carried out considering the whole spectrum, the visible and the near infra-red. A total of 33 (76.7%) lesions were correctly diagnosed by the telespectrophotometric system, compared with 35 (81.4%) correct clinical diagnoses. Reflectance in the infra-red band appears diagnostically relevant. A larger study is needed to prove the validity of this diagnostic method.
European Journal of Cancer 05/1996; 32A(4):727-9. · 5.54 Impact Factor
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ABSTRACT: Two novel porphyrin-bisacridine conjugates (1 and 2) were designed as bifunctional antitumour agents to combine the DNA-binding character of the acridines and the photosensitizing capacity of porphyrin, and have been subjected to biophysical and biological evaluation. The interactions of the conjugates with calf thymus DNA were evaluated using viscometric, spectrophotometric and stopped-flow sodium dodecyl sulphate (SDS) sequestration methods. Both conjugates acted as bis-intercalators via the two acridine chromophores and displayed a longer residence time on DNA relative to the parent acridine ligand. Their biological activity in vitro was studied against the C6 rat glioma, MCF-7, GBM and A431 cell lines. Both conjugates were cytotoxic to all four cell lines. The ID50 (C6 glioma) was essentially the same as that of the parent acridine for one conjugate, but was increased 20-fold for the other, while both conjugates were approximately 10-fold more cytotoxic than the parent porphyrin component. The tissue distribution of the two conjugates was assessed in nude mice xenografted with a human small cell lung carcinoma (POVD). There were large differences in the tissue distribution of the two conjugates, with conjugate 2 localizing 8-fold more in the tumour than conjugate 1.
Anti-cancer drug design 05/1996; 11(3):205-20. · 2.38 Impact Factor
