High dose brachytherapy with non sealed 188Re (rhenium) resin in patients with non-melanoma skin cancers (NMSCs): single center preliminary results.

BACKGROUND AND AIM: High dose brachytherapy using a non sealed 188Re-resin (Rhenium-SCT®, Oncobeta® GmbH, Munich, Germany) is a treatment option for non-melanoma skin cancer (NMSC). The aim of this prospective study was to assess the efficacy and the safety of a single application of Rhenium-SCT® in NMSC. MATERIALS AND METHOD: Fifty consecutive patients (15F, 35 M, range of age 56-97, mean 81) showing 60 histologically proven NMSCs were enrolled and treated with the Rhenium-SCT® between October 2017 and January 2020. Lesions were located on the face, ears, nose or scalp (n = 46), extremities (n = 9), and trunk (n = 5). Mean surface areas were 7.0 cm2 (1-36 cm2), mean thickness invasion was 1.1 mm (0.2-2.5 mm), and mean treatment time was 79 min (21-85 min). Superficial, mean, and target absorbed dose were 185 Gy, 63 Gy, and 31 Gy respectively. Patients were followed-up at 14, 30, 60, 90, and 180 days posttreatment, when dermoscopy and biopsy were performed. Mean follow-up was 20 months (range 3-33 months). Early skin toxicity was classified according to Common Terminology Criteria for Adverse Events (CTCAE). Cosmetic results were evaluated after at least 12 months according to Radiation Therapy Oncology Group (RTOG) scale. RESULTS: At 6 months follow-up, histology and dermoscopy were available for 54/60 lesions, of which 53/54 (98%) completely responded. One patient showed a 1-cm2 residual lesion that was subsequently surgically excised. Twelve months after treatment, 41/41 evaluable lesions were free from relapse. Twenty four months after treatment, 23/24 evaluable lesions were free of relapse. In 56/60 lesions early side effects, resolving within 32 days were classified as grades 1-2 (CTCAE). In the remaining 4/60 lesions, these findings were classified as grade 3 (CTCAE) and lasted up to 8-12 weeks but all resolved within 90 days. After at least 12 months (12-33 months), cosmetic results were excellent (30 lesions) or good (11 lesions). CONCLUSION: High dose brachytherapy with Rhenium-SCT® is a noninvasive, reasonably safe, easy to perform, effective and well-tolerated approach to treat NMSCs, and it seems to be a useful alternative option when surgery or radiation therapy are difficult to perform or not recommended. In our population 98% of the treated lesions resolved completely after a single application and only one relapsed after 2 years. Larger patients' population and longer follow-up are needed to confirm these preliminary data and to find the optimal dose to administer in order to achieve complete response without significant side effects.

Hepatobiliary Scintigraphy in the Preoperative Evaluation of Potential Living Liver Donors.

BACKGROUND: Graft selection strategy in living donor liver transplantation (LDLT) is usually multifactorial, but special attention is paid to the determination of donor liver volumes to minimize any risk of posthepatectomy liver failure (PHLF). Hepatobiliary scintigraphy (HBS) with single-photon-emission computed tomography allows for the measurement of total and future liver remnant function (FLR-F) and has been shown to predict the risk of PHLF more accurately than liver volumetry. METHODS: Since November 2016, HBS has been performed at our Institution in every candidate to major hepatectomy, including potential living liver donors. RESULTS: Thirty-seven consecutive patients were submitted to HBS, of whom 7 were potential living liver donors. After completed hepatectomy (n = 27), the median FLR-F of patients who developed PHLF (n = 9) was 1.72%/min/m2 (range 1.40-2.78) compared to that of patients who did not (n = 18), which was 4.02%/min/m2 (range 1.15-12.08). Three donors underwent operations (1 right hepatectomy and 2 left hepatectomies). In the only donor who developed PHLF, the FLR accounted for the 37% of the total liver volume, whereas the FLR represented only the 31% of the total liver function (TL-F = 11.29%/min) with a resulting FLR-F of 2.05%/min/m2. CONCLUSIONS: The present study suggests that a non-invasive low-cost exam such as HBS may be a promising tool to predict PHLF not only in neoplastic patients but also to evaluate potential living donors. Larger studies are needed to draw any conclusion regarding the benefits of HBS in the living liver donor workup.

Low dose radiation 18F-fluoride PET/CT in the assessment of Unilateral Condylar Hyperplasia of the mandible: preliminary results of a single centre experience.

BACKGROUND: Unilateral condylar hyperplasia (UCH) of the mandible, or Hypercondylia, is a pathological condition that determines an abnormal growth of the affected condyle.Bone SPECT with Tc99m-diphosphonates is a successful tool in the diagnosis of UCH. EANM guidelines also suggest the use of 18F-NaF PET/CT, though it leads to a higher radiation exposure. AIM: As UCH patients are young, we aimed to develop a low dose 18F-Fluoride PET/CT protocol and compare it to a standard injected activity scan, to assess if the image quality remains unchanged. MATERIALS AND METHODS: We prospectively enrolled 20 patients (7 males, 13 females, mean age 23.2) with UCH, who underwent 18F-NaF PET/CT to assess the hypercondylia. We administered a low activity of 18F-NaF (2.9 MBq/kg) in 15 patients and a standard activity (5.3 MBq/kg) in 5 patients. Activity range was chosen according to 2015 EANM guidelines.To determine if the scans with low radiotracer activity were "diagnostic" such as those with standard activity, two expert nuclear medicine physicians, unaware of the administered activity, independently reviewed the scans and expressed a final qualitative judgment in terms of "diagnostic"/"non-diagnostic" scan. Furthermore, we compared the effective dose of a low injected activity PET/CT to the standard one and to a Bone SPECT performed with standard injected activity of Tc99m-diphosphonates. RESULTS: Reviewers classified 19 of 20 scans as "diagnostic". Only one of them was classified as "non diagnostic" due to condylar arthrosis that disturbed the correct evaluation of condylar radiotracer uptake. The effective dose of a 18F-Fluoride PET/CT, in patient of 70 kg, is about 3.5 mSv in scans performed with 2.9 MBq/kg [0.017 mSv/MBq × 2.9 MBq/kg × 70 kg] and about 6.3 mSv in ones performed with 5.3 MBq/kg [0.017 mSv/MBq × 5.3 MBq/kg × 70 kg]. The effective dose of 99mTc-MDP bone SPECT is about 3.2 mSv [0.0043 mSv/MBq × 740 MBq of 99mTc-MDP]. DISCUSSION: 18F-NaF PET/CT performed with a low radiotracer activity allows a good assessment of UCH similar to that performed with an ordinary activity. The effective radiation dose of a low-injected activity PET/CT is significantly lower than an ordinary-injected activity and is not significantly higher than the most used Bone SPECT. Moreover PET/CT is performed in 1.5 h while Bone SPECT requires at least 3.5 h. CONCLUSIONS: The 18F-Fluoride PET/CT procedure could be performed with 2.9 MBq/Kg (minimum 185 MBq, recommended at least 200 MBq) of 18F-NaF to minimize the effective radiation dose received, maintaining the quality of the scan. Further studies including a larger number of patients and clinical follow-up are needed to confirm our preliminary findings.

First results of an eye lens dosimetry survey in an interventional cardiology department.

The eye lens annual dose limit for exposed personnel to ionizing radiation has recently been revised by the ICRP--International Commission on Radiological Protection and the proposed new limit has been accepted by European legislation through the Council Directive 2013/59/EURATOM 2013. Among medical exposed personnel, the staff performing interventional cardiology are usually affected by relevant doses. For this reason a survey, employing dosemeters characterized in terms of H(p)(3), was performed in order to get the order of magnitude of the doses received by the eye lens, at least as a first guess.The survey showed that the annual dose limit can easily be reached if a proper radiation protection approach is not implemented.

Improving PET spatial resolution and detectability for prostate cancer imaging.

Prostate cancer, one of the most common forms of cancer among men, can benefit from recent improvements in positron emission tomography (PET) technology. In particular, better spatial resolution, lower noise and higher detectability of small lesions could be greatly beneficial for early diagnosis and could provide a strong support for guiding biopsy and surgery. In this article, the impact of improved PET instrumentation with superior spatial resolution and high sensitivity are discussed, together with the latest development in PET technology: resolution recovery and time-of-flight reconstruction. Using simulated cancer lesions, inserted in clinical PET images obtained with conventional protocols, we show that visual identification of the lesions and detectability via numerical observers can already be improved using state of the art PET reconstruction methods. This was achieved using both resolution recovery and time-of-flight reconstruction, and a high resolution image with 2 mm pixel size. Channelized Hotelling numerical observers showed an increase in the area under the LROC curve from 0.52 to 0.58. In addition, a relationship between the simulated input activity and the area under the LROC curve showed that the minimum detectable activity was reduced by more than 23%.

Development and validation of RAYDOSE: a Geant4-based application for molecular radiotherapy.

We developed and validated a Monte-Carlo-based application (RAYDOSE) to generate patient-specific 3D dose maps on the basis of pre-treatment imaging studies. A CT DICOM image is used to model patient geometry, while repeated PET scans are employed to assess radionuclide kinetics and distribution at the voxel level. In this work, we describe the structure of this application and present the tests performed to validate it against reference data and experiments. We used the spheres of a NEMA phantom to calculate S values and total doses. The comparison with reference data from OLINDA/EXM showed an agreement within 2% for a sphere size above 2.8 cm diameter. A custom heterogeneous phantom composed of several layers of Perspex and lung equivalent material was used to compare TLD measurements of gamma radiation from (131)I to Monte Carlo simulations. An agreement within 5% was found. RAYDOSE has been validated against reference data and experimental measurements and can be a useful multi-modality platform for treatment planning and research in MRT.

Usefulness of 124I PET/CT imaging to predict absorbed doses in patients affected by metastatic thyroid cancer and treated with 131I.

AIM: The aim of this work was the evaluation of the usefulness of 124I PET/CT sequential scans to predict absorbed doses to metastatic thyroid cancer in patients undergoing 131I therapy. METHODS: From July 2011 until April 2012 8 patients affected by metastatic thyroid cancer were enrolled. Each patient underwent 4 PET/CT scans at 4, 24, 48, 72 h after the administration of about 74 MBq of 124I. Blood samples and whole body exposure measurements were obtained to calculate blood and red marrow doses. Activity concentrations and lesion volumes obtained from PET/CT images were used to evaluate tumour doses with MIRD formalism and spheres model. The average administered 131I therapeutic activity was 6475 MBq (range: 3700-9250 MBq). RESULTS: 124I PET/CT images showed, with a very good resolution, all 131I avid lesions detected by post therapy whole body scans. The average dose rates for blood, red marrow and lesions were respectively: 6.58E-02 ± 1.64E-02 mGy/MBq, 5.73E-02 ± 1.57E-02 mGy/MBq, 2.22E+01 ± 1.62E+01 mGy/MBq. Three out of eight patients did not show any uptake of 124I in all PET/CT scans, despite high level of TSH and CT detectable lesions. Post-therapy 131I whole body scan confirmed the absence of focal iodine uptake. CONCLUSION: Negative 124I PET/CT images probably could be used as predictive of real absence of iodine avidity, avoiding all toxicity from useless 131I therapy. A higher number of patients is necessary to validate these preliminary results and a project is ongoing to compare MIRD results to voxel dosimetry based on Monte Carlo simulation.

68Ga-DOTANOC: biodistribution and dosimetry in patients affected by neuroendocrine tumors.

OBJECTIVES: The aim of this work was the evaluation of biodistribution and radiation dosimetry of (68)Ga-DOTANOC in patients affected by neuroendocrine tumors. MATERIALS AND METHODS: We enrolled nine patients (six male and three female) affected by different types of neuroendocrine tumors (NETs). Each patient underwent four whole body positron emission tomography (PET) scans, respectively, at 5, 20, 60, and 120 min after the intravenous injection of about 185 MBq of (68)Ga-DOTANOC. Blood and urine samples were taken at different time points post injection: respectively, at about 5, 18, 40, 60, and 120 min for blood and every 40-50 min from injection time up to 4 h for urine. The organs involved in the dosimetric evaluations were liver, heart, spleen, kidneys, lungs, pituitary gland, and urinary bladder. Dosimetric evaluations were done using the OLINDA/EXM 1.0 software. RESULTS: A physiological uptake of (68)Ga-DOTANOC was seen in all patients in the pituitary gland, the spleen, the liver, and the urinary tract (kidneys and urinary bladder). Organs with the highest absorbed doses were kidneys (9.0E-02+/-3.2E-02mSv/MBq). The mean effective dose equivalent (EDE) was 2.5E-02+/-4.6E-03 mSv/MBq. DISCUSSION AND CONCLUSIONS: The excretion of the compound was principally via urine, giving dose to the kidney and the urinary bladder wall. As SSTR2 is the most frequently expressed somatostatin receptor and (68)Ga-DOTANOC has high affinity to it, this compound might play an important role in PET oncology in the future. The dosimetric evaluation carried out by our team demonstrated that (68)Ga-DOTANOC delivers a dose to organs comparable to, and even lower than, analogous diagnostic compounds.

Artefacts of PET/CT images.

Positron emission tomography (PET) is a non-invasive imaging modality, which is clinically widely used both for diagnosis and accessing therapy response in oncology, cardiology and neurology.Fusing PET and CT images in a single dataset would be useful for physicians who could read the functional and the anatomical aspects of a disease in a single shot.The use of fusion software has been replaced in the last few years by integrated PET/CT systems, which combine a PET and a CT scanner in the same gantry. CT images have the double function to correct PET images for attenuation and can fuse with PET for a better visualization and localization of lesions. The use of CT for attenuation correction yields several advantages in terms of accuracy and patient comfort, but can also introduce several artefacts on PET-corrected images.PET/CT image artefacts are due primarily to metallic implants, respiratory motion, use of contrast media and image truncation. This paper reviews different types artefacts and their correction methods.PET/CT improves image quality and image accuracy. However, to avoid possible pitfalls the simultaneous display of both Computed Tomography Attenuation Corrected (CTAC) and non corrected PET images, side by side with CT images is strongly recommended.