In vivo spectrophotometric evaluation of neoplastic and non-neoplastic skin pigmented lesions--I. Reflectance measurements.

Reflectance spectrophotometry from 400 to 800 nm on different cutaneous pigmented lesions, including primary and metastatic malignant melanoma, pigmented nevi, lentigo and seborrhoeic keratosis, has been performed by using an external integrating sphere coupled to a spectrophotometer. Measurements show that reflectance spectra of the different lesions manifest dissimilar patterns, particularly in the near IR region. Comparison of reflectance of nevi with that of malignant melanomas results in a highly significant difference (P less than 10(-6)) between the two samples. Though interpretation of the spectra remains difficult as a result of the complexity of the optical processes of scattering and absorption, our results suggest that a detailed analysis of the reflectance spectrum may give clinically useful information, and could be utilized as an aid in clinical diagnosis of cutaneous pigmented lesions, especially where malignant melanoma is concerned.

In vivo spectrophotometric evaluation of neoplastic and non-neoplastic skin pigmented lesions. III. CCD camera-based reflectance imaging.

Reflectance spectroscopy, which allows an objective evaluation of the color of surfaces, has recently been proposed as a useful tool to discriminate cutaneous melanoma from other pigmented cutaneous lesions. A novel spectrophotometric system based on the use of a charge coupled device camera provided with a set of interference filters has been developed to acquire images of cutaneous pigmented lesions at selected wavelengths ranging from 420 to 1040 nm. For each filter, an image was captured, digitized by a frame grabber and stored in a personal computer to perform off-line data handling. Reflectance images were acquired of 22 cutaneous pigmented lesions including melanoma and dysplastic, compound and junctional nevus. From each spectral image, three parameters, i.e. mean reflectance, variegation index and lesion area; were derived at the corresponding wavelength. The wavelength dependence of the three parameters was significantly different when melanoma was compared to the other investigated lesions. Although preliminary, our results suggest that telespectrophotometry gives useful information and could be utilized as an aid in the clinical diagnosis of cutaneous pigmented lesions.

Dose-response curve slope improvement and result reproducibility of ferrous-sulphate-doped gels analysed by NMR imaging.

Ferrous sulphate gel analysed by relaxation time measurements with NMR imaging is considered a useful dosimeter for 3D determinations of absorbed dose. A protocol for the gel preparation with agarose SeaPlaque that leads to a dosimeter with very high dose sensitivity is described. The dose-response curve slope is about 0.2 s(-1) Gy(-1) and the G factor turns out to be approximately 185 ions per 100 eV of absorbed energy. A method for making the measurements and analysing the results that brings about good result reproducibility is suggested. A thorough experimental study of the dependence of the dosimeter response on the elapsed time from preparation to irradiation and from irradiation to NMR measurement has revealed good reproducibility. The above characteristic of the gel system is very interesting, because it shows the possibility of utilizing the dosimeter for absolute dose determinations with satisfactory reliability.

Potential and limitations of magnetic resonance imaging for real-time monitoring of interstitial laser phototherapy.

RATIONALE AND OBJECTIVES: Magnetic resonance (MR) imaging has been suggested as a method to monitor interstitial laser phototherapy (ILP) in deep tissues. Unfortunately, a reliable relation between temperature and MR parameters has not yet been demonstrated. In this study, we examined whether such a relation exists and whether MR imaging can measure absolute temperature or temperature changes. METHODS: We evaluated, in the range of 21 degrees C to 80 degrees C, the temperature dependence of the MR imaging signal and T1 in samples of liver, water, CuSO4, and oil. Spin-echo and fast low-angle shot (FLASH) sequences were used. RESULTS: The MR imaging signal of liver, CuSO4, and water continuously decreased when the temperature was increased from 21 degrees C to 80 degrees C. By contrast, the MR imaging signal of the oil increased with increasing temperature up to 40-50 degrees C and then decreased at higher temperatures. We observed a reliable linear relation only between T1 and temperature in a range' of 30-60 degrees C for oil and CuSO4. CONCLUSION: MR imaging has the potential to measure thermal variations with an uncertainty of approximately +/- 10 degrees C. However, the use of MR imaging to monitor the real-time thermal effect induced in biologic tissues during laser irradiation requires further investigation before it can be applied clinically.

Quality control of a hyperthermia system.

Characterization of the applicators, of the thermometers and of the cooling (bolus) system of hyperthermic apparatus must be made before starting hyperthermic treatment and also starting with a frequency depending on the technical features of equipments that make up the whole system. This data gives the radiotherapist some useful parameters for the selection of applicators and general knowledge of the accuracy of the system.

How thick should CT/MR slices be to plan conformal radiotherapy? A study on the accuracy of three-dimensional volume reconstruction.

AIM AND BACKGROUND: The aim of this experimental study was to correlate the thickness of acquired CT slices (2, 4 and 8 mm) or MR slices (4 and 7 mm) with the accuracy of three-dimensional volume reconstruction as performed by a commercially available radiation therapy planning system. METHODS: We used a cylindrical phantom, with a 15-cm diameter and 20-cm height, containing 5 spheres (12.7-31.8 mm diameter) of solid Plexiglas sunk in a 3% agar jelly solution. The phantom was scanned by the CT scan with 3 different slice thicknesses (2, 4 and 8 mm and a distance of 0 mm between the slices). Two different acquisition techniques (slice thickness of 4 and 7 mm with 0.8 and 1.4 mm slice distance, respectively) were compared in the MR study. The volume values calculated from measurements were compared with the known true volume values of the spheres. RESULTS: The average percentage volume difference between calculated and true values for the smaller spheres reconstructed with CT images 2 and 4 mm thick was generally less than 8%, whereas the error for volumes reconstructed with 8-mm-thick CT slices was more than 20%. For the large spheres, the error was generally less than 5%. The data produced by MR acquisition agreed with those obtained using CT sections. CONCLUSIONS: For targets less than 1.5 cm in diameter on our system it is reasonable to acquire CT images with the smallest thickness available. For targets between 1.5 and 3 cm, it seems sufficient to acquire the localization images with a slice thickness of 4 mm. For targets more than 4 cm in diameter, considering that with our radiation therapy planning system the time spent for manual contouring and for isodose calculation highly increased with the number of acquired images, we suggest that the acquisition of CT-MR slices 8-10-mm thick is totally adequate even for conformal radiotherapy treatments.

[External exposure of hot cell operators in nuclear medicine]. / Esposizione esterna degli operatori della cella calda nelle attività di medicina nucleare.

PURPOSE: 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. MATERIAL AND METHODS: 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. RESULTS: 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. DISCUSSION: 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

[3-dimensional automatic dosimetry in curietherapy]. / Dosimetria automatica tridimensionale in Curieterapia.

Isodose curves can be viewed on multiple planes along with the radioactive implant and anatomical structures by projecting them on a video-display. The main options offered are the parallel projection of the implant selecting all the possible rotations, zooming and shifting, calculation of distance between two points of a selected plane, stereoscopic display.

[Use of fast electrons in oncologic therapy. More than a decade's experience]. / Sull'uso degli elettroni veloci in terapia oncologica. Esperienza di oltre un decennio.

Criteria of choice in the utilization of fast electrons in radiotherapy on the basis of 2400 cases and 13 years of experience in the radiotherapy department of Cancer Institute in Milan are discussed. In the opinion of the authors fast electrons represent the most rational treatment to homogenize or differentiate the dose distribution according to space as a complementary technique after first time treatments by different ionizing radiation. Authors demonstrate also that fast electron treatment is the most rational technique for metastases in the retina and for recurrence of rhinopharynx cancer. Radiotherapy by fast electrons allows to deliver to the patient's body on integral dose lesser than with ionizing radiation of other type. Sequelae are regarding in most of the cases soft tissues and are caused by an unrecognized distribution of dose delivered by the ionizing radiations of other type in the first time treatment more than by difficulty im dosimetry of post-electrons.

Extinction and absorption coefficients and scattering phase functions of human tissues in vitro.

Optical properties of different human tissues in vitro have been evaluated by measuring extinction and absorption coefficients at 635- and 515-nm wavelengths and a scattering angular dependence at 635 nm. Extinction was determined by the on-axis attenuation of light transmitted through sliced specimens of various thicknesses. The absorption coefficient was determined by placing samples into an integrating sphere. The Henyey-Greenstein function was used for fitting experimental data of the scattering pattern. The purpose of this work was to contribute to the study of light propagation in mammalian tissues. The results show that, for the investigated tissues, extinction coefficients range from ~200 to 500 cm(-1) whereas absorption coefficients, depending on wavelength, vary from 0.2 to 25 cm(-1). Scattering is forward peaked with an average cosine of ~0.7.

[Treatment technic and clinical dosimetry in whole-body irradiation]. / Tecnica di trattamento e dosimetria clinica nella panirradiazione corporea.

At the Istituto Nazionale Tumori, Milan, total-body irradiation (TBI) is delivered by a 15 MV linear accelerator, with two lateral opposed beams. Maximum build-up at the skin is achieved by lateral slabs of perspex 3 cm thick. Attenuation filters or bolus are used for dose compensation, or reduction, to the head and lungs. The dose delivered to clinically relevant anatomic regions is determined by "in vivo" dosimetry. For this purpose, calibrated diodes are employed, which are positioned at the entrance and at the exit of the beams. "In vivo" dosimetry data show our TBI technique to allow an homogeneous irradiation of all body areas, with maximum deviation of the mean dose value from reference point dose of -11% in the posterior abdomen, at the spinal cord shielded by arms.

[Computerized dosimetry in curie therapy]. / Dosimetria computerizzata in curieterapia.

Automatic treatment planning for calculation of absorbed dose in curietherapy has been performed at the Istituto Nazionale Tumori of Milano on a routine for some years. The radioactive implant is reconstructed from orthogonal or stereo-roentgenograms, a tabular listing of doses or dose rates can be obtained on the grid of points and the isodose curves are automatically drawn with the projection of sources onto the selected planes of calculation by an interactive plotter.

[Design, development, and dosage control of individual compensatory filters for 6 MV X-ray radiotherapy]. / Progettazione, realizzazione e controllo dosimetrico di filtri compensatori individuali per radioterapia con raggi X da 6 MV.

An automated system for the design and manufacturing of individual compensators has been implemented. The system based on computed tomography enables 3D compensation of missing tissue and tissue heterogeneities. The relationship between Hounsfield numbers and electron densities was obtained empirically. Compensator design is based on the calculation of the water equivalent thicknesses between the compensation plane and the patient surface. After calculation a styrofoam mould is cut by a computer driven machine and filled with bee's wax or tin granules. Compensator thickness is calculated by means of the conversion ratio tau, which is defined as t/x, where t is the compensator thickness equivalent to the missing tissue in the treatment geometry. Relations between tau and field size, depth of compensation plane and focus-compensation plane distance were assessed. The conversion ratio is a linear function of the missing tissue and depends markedly on field size; for a 10-cm-deep compensation plane at 1 m from the accelerator target the tau value, calculated for bee's wax, decreases by 25% from 7 x 7 cm2 to 23 x 23 cm2 field size. Conversion ratio rises by approximately 10% for a 3-cm increase in compensation plane depth and reduces by about 5% when increasing the focus-compensation plane distance from 100 cm to 140 cm. It must be stressed that a 10% variation of tau, for bee's wax, involves only a 2% dose variation in the compensation plane. Therefore, for compensator design it is enough to consider tau as depending on field size only. Compensation effectiveness has been tested by a film-densitometric technique using phantoms with tilted incident surfaces and heterogeneities. The results show that the compensators reduce the flatness of the beam profile below 4% and increase the relative dose uniformity on the compensation plane from 18% to 60%.

Ex vivo optical properties of human colon tissue.

Using a spectrophotometer equipped with an internal integrating sphere, the absorption (mu a) and the reduced scattering (microseconds') coefficients of ex vivo human colon tissues were evaluated from reflectance and transmittance measurements. Mu a and microseconds' varied from 47.7 to 1.0 cm-1 and from 14.2 to 6.2 cm-1, respectively, on passing from 300 nm to 800 nm. These results can be used to estimate the optical penetration depths when photodynamic therapy or light-induced fluorescence procedures are used.