Our objective was to evaluate the biodistribution, kinetics, and radiation dosimetry of CuCl in humans and to assess the ability of CuCl PET/CT to detect prostate cancer (PCa) recurrence in patients with biochemical relapse. We prospectively evaluated 50 PCa patients with biochemical relapse after surgery or external-beam radiation therapy. All patients underwentCuCl PET/CT, F-choline PET/CT, and multiparametric MRI within 15 d of each other. Experienced readers interpreted the images, and the detection rate (DR) of each imaging modality was calculated. Histopathology, when available; clinical or laboratory response; and multidisciplinary follow-up were used to confirm the site of disease. In parallel, biodistribution, kinetics of the lesions, and radiation dosimetry ofCuCl were evaluated. From a dosimetric point of view, an administered dose of 200 MBq forCuCl translated into a 5.7-mSv effective dose. Unlike F-choline,CuCl was not excreted or accumulated in the urinary tract, thus allowing thorough pelvic exploration. The maximum CuCl uptake at the sites of PCa relapse was observed 1 h after tracer injection. In our cohort, CuCl PET/CT proved positive in 41 of 50 patients, with an overall DR of 82%. The DRs of F-choline PET/CT and multiparametric MRI were 56% and 74%, respectively. The difference between the DRs ofCuCl PET/CT and F-choline PET/CT was statistically significant ( < 0.001). Interestingly, on considering prostate-specific antigen (PSA) value, CuCl PET/CT had a higher DR than F-choline PET/CT in patients with a PSA of less than 1 ng/mL. The biodistribution of CuCl is more suitable than that of F-choline for exploring the pelvis and prostatic bed. TheCuCl effective dose is like those of other established PET tracers. In patients with biochemical relapse and a low PSA level, CuCl PET/CT shows a significantly higher DR than F-choline PET/CT.
The preliminary results of this study demonstrate the high potential of Cu-PSMA ligand PET/CT imaging in patients with recurrent disease and in the primary staging of selected patients with progressive local disease. The acquired PET images showed an excellent resolution of the detected lesions with very high lesion-to- background contrast. Furthermore, the long half-life ofCu allows distribution of the tracer to clinical PET centers that lack radiochemistry facilities for the preparation of Ga-PSMA ligand (satellite concept).
The Novac7 and Liac are linear accelerators (linacs) dedicated to intraoperative radiation therapy (IORT), which produce high energy, very high dose‐per‐pulse electron beams. The characteristics of the accelerators heads of the Novac7 and Liac are different compared to conventional electron accelerators. The aim of this work was to investigate the specific characteristics of the Novac7 and Liac electron beams using the Monte Carlo method. The Monte Carlo code BEAMnrc has been employed to model the head and simulate the electron beams. The Monte Carlo simulation was preliminarily validated by comparing the simulated dose distributions with those measured by means of EBT radiochromic film. Then, the energy spectra, mean energy profiles, fluence profiles, photon contamination, and angular distributions were obtained from the Monte Carlo simulation. The Spencer‐Attix water‐to‐air mass restricted collision stopping power ratios (normalsW,air) were also calculated. Moreover, the modifications of the percentage depth dose in water (backscatter effect) due to the presence of an attenuator plate composed of a sandwich of a 2 mm aluminum foil and a 4 mm lead foil, commonly used for breast treatments, were evaluated. The calculated normalsW,air values are in agreement with those tabulated in the IAEA TRS‐398 dosimetric code of practice within 0.2% and 0.4% at zref (reference depth in water) for the Novac7 and Liac, respectively. These differences are negligible for practical dosimetry. The attenuator plate is sufficient to completely absorb the electron beam for each energy of the Novac7 and Liac; moreover, the shape of the dose distribution in water strongly changes with the introduction of the attenuator plate. This variation depends on the energy of the beam, and it can give rise to an increase in the maximum dose in the range of 3%–9%.PACS number: 87.56.‐v
BackgroundThe aim of the present study is to evaluate the kinetics and dosimetry of 64CuCl2 in human prostate cancer (PCa) lesions.We prospectively evaluated 50 PCa patients with biochemical relapse after surgery or external beam radiation therapy. All patients underwent 64CuCl2-PET/CT to detect PCa recurrence/metastases. Volumes of interest were manually drawn for each 64CuCl2 avid PCa lesion with a diameter > 1 cm on mpMRI in each patient. Time-activity curves for all lesions were obtained. The effective and biological half-life and the standard uptake values (SUVs) were calculated. Tumour/background ratio (TBR) curves as a function of time were considered. Finally, the absorbed dose per lesion was estimated.ResultsThe mean effective half-life of 64CuCl2 calculated in the lymph nodes (10.2 ± 1.7 h) was significantly higher than in local relapses (8.8 ± 1.1 h) and similar to that seen in bone metastases (9.0 ± 0.4 h). The mean 64CuCl2 SUVmax calculated 1 h after tracer injection was significantly higher in the lymph nodes (6.8 ± 4.3) and bone metastases (6.8 ± 2.9) than in local relapses (4.7 ± 2.4). TBR mean curve of 64CuCl2 revealed that the calculated TBRmax value was 5.0, 7.0, and 6.2 in local relapse and lymph node and bone metastases, respectively, and it was achieved about 1 h after 64CuCl2 injection. The mean absorbed dose of the PCa lesions per administrated activity was 6.00E-2 ± 4.74E-2mGy/MBq. Indeed, for an administered activity of 3.7 GBq, the mean dose absorbed by the lesion would be 0.22 Gy.ConclusionsDosimetry showed that the dose absorbed by PCa recurrences/metastases per administrated activity was low. The dosimetric study performed does not take into account the possible therapeutic effect of the Auger electrons. Clinical trials are needed to evaluate 64Cu internalization in the cell nucleus that seems related to the therapeutic effectiveness reported in preclinical studies.Electronic supplementary materialThe online version of this article (10.1186/s13550-018-0373-9) contains supplementary material, which is available to authorized users.
Very high dose per pulse (3-13 cGy/pulse) high energy electron beams are currently produced by special linear accelerators (linac) dedicated to Intra Operative Radiation Therapy (IORT). The electron beams produced by such linacs are collimated by special Perspex applicators of various size and cylindrically shaped. The biggest problems from the dosimetric point of view are caused by the high dose-per-pulse values and the use of inclined applicators. In this work measurements of absolute dose for the inclined applicators were done by using a small cylindrical ionization chamber, type CC01 (Wellhofer), a parallel plane ionization chamber type Markus (PTW 23343) and radiochromic films type EBT. We show a method which allows calculating the quality correction factors for CC01 chamber with an uncertainty of 1% and the absolute dose value for the inclined applicators using CC01 with an uncertainty of 3.1% for electron beams of energy of 6 and 7 MeV produced by the linac dedicated to IORT Novac7.
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