Use of GAFCHROMIC XR type R films for skin-dose measurements in interventional radiology: Validation of a dosimetric procedure on a sample of patients undergone interventional cardiology

The Gafchromic XR type R film is a suitable dosimeter to determine the map of the skin dose in patients undergone complex interventional radiological procedures, such as cardiology ones. The need of preventing or locating possible skin injuries due to high doses administered to patients-as recommended by international organizations-wants the introduction in patient dosimetry of a dosimeter easy to handle, with low dependence of the response on energy in the typical radiological range, and extended measurable dose range. XR type R films fulfil all these requirements and moreover may be quickly analyzed by cheap commercial scanners. In order to determine skin-dose values by XR-R, a film calibration curve is required. In this work, validation of the XR-R dosimetry has been performed for the determination of the skin dose: maximum skin-dose values in 14 patients undergone radiofrequency ablation and pacemaker implant procedures have been determined by XR-R calibrated films. A comparison between skin-dose values determined by XR-R films and retrospective ionometric measurements has pointed out some discrepancies in the results, due to difficulties in retrospectively reproducing the real procedure settings, where XR-R film dosimetry is related to the specific patient procedure, even, in very complex interventional settings.

In vivo EBT radiochromic film dosimetry of electron beam for Total Skin Electron Therapy (TSET)

EBT radiochromic films were used to determine skin-dose maps for patients undergone Total Skin Electron Therapy (TSET). Gafchromic EBT radiochromic film is one of the newest radiation-induced auto-developing photon and electron-beam analysis films available for therapeutic radiation dosimetry in radiotherapy applications. EBT films can be particularly useful in TSET; due to patient morphology, underdosed regions typically occur, and the radiochromic film represents a suitable candidate for monitoring them. In this study, TSET was applied to treat cutaneous T-cell lymphoma. The technique for TSET was implemented by using an electron beam with a nominal energy of 6MeV. The patient was treated in a standing position using dual angled fields in order to obtain the greatest dose uniformity along the patient's longitudinal axis. The electron beam energy was degraded by a PMMA filter. The in vivo dose distribution was determined through the use of EBT films, as well as of thermoluminescent dosimeters for comparison (TLDs). EBT results showed a reasonable agreement with TLDs data.

Theoretical models to evaluate hazard due to organochlorine compounds (OCs) in Mediterranean striped dolphin (Stenella coeruleoalba)

Many studies document the chemical stress related to organochlorine (OC) xenobiotics in Mediterranean cetaceans. The aim of this study was to establish a theoretical model to evaluate the hazard to Mediterranean striped dolphins (Stenella coeruleoalba) due to HCB, DDTs and PCB congeners. Differences in OC levels in blubber of stranded and free-ranging specimens enabled us to evaluate the hazard associated with different chlorinated xenobiotics, taking the live population as control sample, assumed to be in good health. For the most toxic compounds, with teratogenic, mutagenic, carcinogenic and endocrine disrupting capacity, we indicate levels beyond which there can be toxicological hazard for the striped dolphin. Using a mathematical formula derived from knowledge of the length and age of 62 stranded specimens, the age of dolphins was estimated and sexual maturity was identified at nine years. This evaluation was important for understanding differences in contaminant burden between males and females.

Dosimetric, mechanical, and geometric verification of conformal dynamic arc treatment

A conformal dynamic arc (CD-arc) technique has been implemented at the S. Giovanni Calibita-Fatebenefratelli Hospital Radiotherapy Center. This technique is performed by rotational beams and a dynamic multileaf collimator (DMLC): during the treatment delivery the gantry rotates and the field shape, formed by the DMLC changes continuously. The aim of this study was to perform dosimetric, mechanical, and geometric verification to ensure that the dose calculated by a commercial treatment planning system and administered to the patient was correct, before and during the clinical use of this technique. Absolute dose values, at the isocenter and at other points placed in dose heterogeneity zone, have been verified with an ionization chamber in a solid homogeneous phantom. In uniform dose regions measured dose values resulted in agreements with the calculated doses within 2%. Isodose distributions have also been determined by radiographic films and compared with those predicted by the planning system. Distance to agreement between calculated and measured isodoses in dose gradient zone was within 2 mm. In conclusion, our results demonstrated the feasibility and the accuracy of the CD-arc technique for achieving highly conformal dose distributions. Up till now 20 patients have been treated with CD-arc therapy.

99mTc-MIBI scintimammography using a dedicated nuclear mammograph

This study reports on a prototype single-photon emission mammograph (SPEM) dedicated to 99mTc-hexakis-2-methoxyisobutile isonitrile (MIBI) scintimammography. Main technical features are reported together with physical performance. Preliminary patient data are also reported.

METHODS

The SPEM detector head is composed of a CsI(T1) scintillating array coupled to a Hamamatsu R3292 position-sensitive photomultiplier tube with crossed-wire anode. The high-resolution collimator is 35-mm thick with a 1.7-mm hole diameter and a 0.2-mm septal thickness. The electronic acquisition system is composed of five integrated cards with computation based on high-speed programmable microprocessors. The readout electronics include correction maps for on-line energy correction and spatial uniformity. The small size of the detector head allows the use of mechanical breast compression to minimize detection distance and tissue scatter. After physical SPEM performance evaluation in vivo scintimammography was performed in 29 patients and was compared with a state-of-the-art Anger camera.

RESULTS

The SPEM showed an intrinsic spatial resolution of 2 mm, an energy resolution of 23% FWHM at 122 keV and spatial uniformities of 18% (integral) and 13.5% (differential). The SPEM imaged one 0.4-cm carcinoma missed by the Anger camera and resolved as separate lumps an irregular focal uptake on the Anger camera image. The remaining cases yielded concordant results.

CONCLUSION

The SPEM prototype presented in this study shows adequate physical characteristics for 99mTc-MIBI scintimammography.

A contribution to the study of the regulatory system of local immune response in "Gallus domesticus"

The "priming effect" is studied to ascertain whether a regulatory system of local immune response exists and, if it does, what its function is. Bursectomized, bursa-ligated and silica-treated chicks were used, together with control birds (silica selectively damages the follicle associated epithelial -FAE- cells). Agglutinins and direct plaque forming cells (PFC)/spleen were checked. The results confirm that contact between the antigen and the bursal tissue acts as a primary stimulus for immune response and that extrabursal lymphoid sites are unable to act in the same way as the bursa of Fabricius. It seems quite probable, then, that a regulatory system of local immune response exists.

[Immune response in the chicken after intrabursal administration of silica: preliminary observations]

Immune response was studied in various experimental conditions using silica, a macrophage-toxic substance, in order to assess the role attributable to FAE cells, which have been demonstrated to be sensitive to this substance. Antibody response was tested in four different groups comprising seven animals each; the priming effect was studied in particular. It was observed that the silica considerably reduced the priming effect when the dose of antigen was administered in the bursal lumen at times immediately subsequent to the administration of the silica. The priming effect, on the contrary, was still present and was more marked when six hours elapsed between the administration of the silica and the priming dose.