[en] Radiomics, machine learning, and, more generally, artificial intelligence (AI) provide unique tools to improve the performances of nuclear medicine in all aspects. They may help rationalise the operational organisation of imaging departments, optimise resource allocations, and improve image quality while decreasing radiation exposure and maintaining qualitative accuracy. There is already convincing data that show AI detection, and interpretation algorithms can perform with equal or higher diagnostic accuracy in various specific indications than experts in the field. Preliminary data strongly suggest that AI will be able to process imaging data and information well beyond what is visible to the human eye, and it will be able to integrate features to provide signatures that may further drive personalised medicine. As exciting as these prospects are, they currently remain essentially projects with a long way to go before full validation and routine clinical implementation. AI uses a language that is totally unfamiliar to nuclear medicine physicians, who have not been trained to manage the highly complex concepts that rely primarily on mathematics, computer sciences, and engineering. Nuclear medicine physicians are mostly familiar with biology, pharmacology, and physics, yet, considering the disruptive nature of AI in medicine, we need to start acquiring the knowledge that will keep us in the position of being actors and not merely witnesses of the wonders developed by other stakeholders in front of our incredulous eyes. This will allow us to remain a useful and valid interface between the image, the data, and the patients and free us to pursue other, one might say nobler tasks, such as treating, caring and communicating with our patients or conducting research and development.

[en] 9-[(3-[¹⁸F]Fluoro-1-hydroxy-2-propoxy)methyl]guanine ([¹⁸F]FHPG, 2) has been synthesized by nucleophilic substitution of N²-(p-anisyldiphenylmethyl)-9-{[1-(p-anisyldiphenylmethoxy)-3 -toluenesulfonyloxy-2-propoxy]methyl}guanine (1) with potassium [¹⁸F]fluoride/Kryptofix 2.2.2 followed by deprotection with 1 N HCl and purification with different methods in variable yields. When both the nucleophilic substitution and deprotection were carried out at 90 deg. C and the product was purified by HPLC (method A), the yield of compound 2 was 5-10% and the synthesis time was 90 min from EOB. However, if both the nucleophilic substitution and deprotection were carried out at 120 deg. C and the product was purified by HPLC, the yield of compound 2 decreased to 2%. When compound 2 was synthesized at 90 deg. C and purified by Silica Sep-Pak (method B), the yield increased to 10-15% and the synthesis time was 60 min from EOB. Similarly, 9-(4-[¹⁸F]fluoro-3-hydroxymethylbutyl)guanine ([¹⁸F]FHBG, 4) was synthesized with method A and method B in 9% and 10-15% yield, respectively, in a synthesis time of 90 and 60 min, respectively, from EOB. Compound 2 was relatively unstable in acidic medium at 120 deg. C while compound 4 was stable under the same condition. Both compound 2 and compound 4 had low lipid/water partition coefficient (0.126±0.022, n=5 and 0.165±0.023, n=5, respectively). Although it contains non-radioactive ganciclovir (∼5-30 μg) as a chemical by-product, compound 2 synthesized by method B has a similar uptake in 9L glioma cells as that synthesized by method A, and is a potential tracer for imaging herpes simplex virus thymidine kinase gene expression in tumors using PET. Similarly, compound 4 synthesized by method B contains ∼10-25 μg of penciclovir as a chemical by-product. Thus, the simplified one pot synthesis (method B) is a useful method for synthesizing both compound 2 and compound 4 in good yield for routine clinical use, and the method is readily amenable for automation

[en] The Annual Congress of the European Association of Nuclear Medicine took place in Copenhagen on October 13-17, 2007. The event is the major scientific and professional effort in the field of nuclear medicine in Europe. The most important developments in the fields of instrumentation, radionuclide production, radiochemistry, radiotherapy, as well as the clinical imaging fields of neurology, cardiology, oncology, and general sciences were reported. This paper emphasizes the major findings and trends at this important gathering. This review is, however, only a brief summary of the large amount of data discussed. (orig.)

[en] The aim of this study was to assess the usefulness of fluorine-18 fluoro-2-deoxy-D-glucose positron emission tomography (FDG PET) in the post-therapy surveillance of endometrial carcinomas. Forty-one fully corrected whole-body PET studies were performed in 34 women with previously treated endometrial cancers as a part of their follow-up programme. In 28 studies, FDG PET was indicated to localise a recurrence suspected at the control visits on the basis of clinical examination and/or radiological abnormalities (chest X-ray, CT or MRI) and/or elevated tumour marker levels (CA125, CEA). Another 13 studies were performed as a simple surveillance procedure. Overall, in 26 studies PET detected recurrent disease, which was confirmed either by histology (n=7) or by clinical and radiological outcomes (n=19). In 88% of the cases, the PET findings confirmed recurrence suggested by routine follow-up. In the remaining 12% of cases, PET detected asymptomatic recurrences that were unsuspected at the control visits. Whole-body PET accurately localised the site of confirmed recurrences as being above and below the diaphragm in 50%, only below the diaphragm in 35% and only above the diaphragm in 15%. In one patient, however, PET missed microscopic lung metastases shown on thoracic CT, and in three studies, metabolic imaging results were not confirmed. In 11 of 12 negative PET studies, no subsequent clinical or radiological recurrences were observed with a median follow-up of 10 months. Overall, the results of PET agreed well with the final diagnosis (Cohen's kappa coefficient =0.78). In 9/26 patients (35%) with confirmed recurrences, the PET findings significantly altered the treatment choice by detecting either clinically or radiologically unsuspected distant metastases. The sensitivity, specificity, diagnostic accuracy and positive and negative predictive values of FDG PET imaging in the post-therapy surveillance of endometrial carcinomas were 96%, 78%, 90%, 89% and 91%, respectively. Indeed, the high likelihood ratio for a positive test result (4.5) and the low likelihood ratio for a negative test result (0.05) demonstrated the clinical utility of metabolic imaging in ''ruling in'' disease as well as ''ruling out'' recurrence. In conclusion, whole-body FDG PET appears useful in the post-therapy surveillance of endometrial cancers, both for the accurate localisation of suspected recurrences and for the detection of asymptomatic recurrent disease. (orig.)

[en] The aim of this study is to determine whether ${}^{99m}$Tc-MAA SPECT/CT-based dosimetry could predict the actual absorbed dose in hepatocellular carcinoma (HCC) or liver metastases, treated by glass or resin microspheres. Fifty-seven patients who underwent selective internal radiation therapy (SIRT) were retrospectively included in the study, for a total of 59 treatments. Nineteen HCC were treated by resin microspheres (HCC-SIR), 20 HCC with glass microspheres (HCC-Thera), and 20 liver metastases with resin microspheres (Metastases-SIR). The mean absorbed doses in tumoral liver (Dm) and non-tumoral liver (DmNTL) were determined on the ${}^{99m}$Tc-MAA SPECT/CT and the ${}^{90}$Y PET/CT, and compared with each other. DmNTL was < 50 Gy in the 3 groups, with a strong correlation in all population, albeit slightly lower in Metastases-SIR than HCC-SIR and HCC-Thera (CCC 0.8, 0.94 and 0.96, respectively). In tumoral liver, Dm was higher in HCC than metastases (159 ± 117 Gy versus 63 ± 31 Gy). ${}^{99m}$Tc-MAA SPECT/CT proved to be a better indicator of Dm in HCC compared with metastases, with similar ${}^{99m}$Tc-MAA-${}^{90}$Y concordance in resin and glass microspheres (CCC HCC-SIR 0.82, CCC HCC-Thera 0.82, and CCC Metastases-SIR 0.52). ${}^{99m}$Tc-MAA SPECT/CT is a reasonably reliable tool for predicting the dose to the non-tumoral liver in both HCC and metastases, regardless of the type of microspheres. It is also fairly reliable for predicting the tumor dose in HCC, again regardless of the type of spheres, although individual variations are observed.

[en] Fluorine-18 fluorodeoxyglucose positron emission tomography (¹⁸FDG PET) plays a major role in the management of oncology patients. Owing to the singular properties of the glucose tracer, many patients suffering from non-malignant diseases such as inflammatory or infectious diseases may also derive clinical benefit from the appropriate use of metabolic imaging. Large vessel vasculitides such as giant cell arteritis and Takayasu arteritis are other examples that may potentially extend the field of ¹⁸FDG PET indications. The purpose of the present article is to assess the feasibility of metabolic imaging in vasculitis on the basis of the current literature data. In particular, the clinical context and the ¹⁸FDG imaging patterns seen in patients with large vessel vasculitis are analysed in order to identify potential indications for metabolic imaging. (orig.)

[en] Highlights: • Radiation recall pneumonitis (RRP) is a delayed radiation-induced lung toxicity. • RRP was detected in 15 out of 80 (18.8%) lung cancer patients under immunotherapy. • RRP was associated in one third of the cases with immune checkpoint inhibitor-related pneumonitis. • RRP was mistaken for cancer progression on imaging in 53% of the cases. Radiation recall pneumonitis (RRP) is a delayed radiation-induced lung toxicity triggered by systemic agents, typically anticancer drugs. Immune checkpoint inhibitors (ICIs) have recently been identified as potential causal agents of RRP but its real incidence and potential risk factors remain unknown.

[en] Introducing a hybrid imaging method such as single photon emission computed tomography (SPECT)/CT greatly alters the routine in the nuclear medicine department. It requires designing new workflow processes and the revision of original scheduling process and imaging protocols. In addition, the imaging protocol should be adapted for each individual patient, so that performing CT is fully justified and the CT procedure is fully tailored to address the clinical issue. Such refinements often occur before the procedure is started but may be required at some intermediate stage of the procedure. Furthermore, SPECT/CT leads in many instances to a new partnership with the radiology department. This article presents practical advice and highlights the key clinical elements which need to be considered to help understand the workflow process of SPECT/CT and optimise imaging protocols. The workflow process using SPECT/CT is complex in particular because of its bimodal character, the large spectrum of stakeholders, the multiplicity of their activities at various time points and the need for real-time decision-making. With help from analytical tools developed for quality assessment, the workflow process using SPECT/CT may be separated into related, but independent steps, each with its specific human and material resources to use as inputs or outputs. This helps identify factors that could contribute to failure in routine clinical practice. At each step of the process, practical aspects to optimise imaging procedure and protocols are developed. A decision-making algorithm for justifying each CT indication as well as the appropriateness of each CT protocol is the cornerstone of routine clinical practice using SPECT/CT. In conclusion, implementing hybrid SPECT/CT imaging requires new ways of working. It is highly rewarding from a clinical perspective, but it also proves to be a daily challenge in terms of management. (orig.)

[en] 2-[¹⁸F]fluoro-2-deoxy-d-glucose (FDG) is currently the only fluorinated tracer used in routine clinical positron emission tomography (PET). Fluorine-18 is considered the ideal radioisotope for PET imaging owing to the low positron energy (0.64 MeV), which not only limits the dose rate to the patient but also results in a relatively short range of emission in tissue, thereby providing high-resolution images. Further, the 110-min physical half-life allows for high-yield radiosynthesis, transport from the production site to the imaging site and imaging protocols that may span hours, which permits dynamic studies and assessment of potentially fairly slow metabolic processes. The synthesis of fluorinated tracers as an alternative to FDG was initially tested using nucleophilic fluorination of the molecule, as performed when radiolabelling with iodine-124 or bromide-76. However, in addition to being long, with multiple steps, this procedure is not recommended for bioactive molecules containing reactive groups such as amine or thiol groups. Radiochemical yields are also often low. More recently, radiosynthesis from prosthetic group precursors, which allows easier radiolabelling of biomolecules, has led to the development of numerous fluorinated tracers. Given the wide availability of¹⁸F, such tracers may well develop into important routine tracers. This article is a review of the literature concerning fluorinated radiotracers recently developed and under investigation for possible PET imaging in cancer patients. Two groups can be distinguished. The first includes ''generalist'' tracers, i.e. tracers amenable to use in a wide variety of tumours and indications, very similar in this respect to FDG. These are tracers for non-specific cell metabolism, such as protein synthesis, amino acid transport, nucleic acid synthesis or membrane component synthesis. The second group consists of ''specific'' tracers for receptor expression (i.e. oestrogens or somatostatin), cell hypoxia or bone metabolism. (orig.)

[en] The aim of this study was to assess rheumatoid arthritis (RA) synovitis with positron emission tomography (PET) and¹⁸F-fluorodeoxyglucose (¹⁸F-FDG) in comparison with dynamic magnetic resonance imaging (MRI) and ultrasonography (US). Sixteen knees in 16 patients with active RA were assessed with PET, MRI and US at baseline and 4 weeks after initiation of anti-TNF-α treatment. All studies were performed within 4 days. Visual and semi-quantitative (standardised uptake value, SUV) analyses of the synovial uptake of FDG were performed. The dynamic enhancement rate and the static enhancement were measured after i.v. gadolinium injection and the synovial thickness was measured in the medial, lateral patellar and suprapatellar recesses by US. Serum levels of C-reactive protein (CRP) and metalloproteinase-3 (MMP-3) were also measured. PET was positive in 69% of knees while MRI and US were positive in 69% and 75%. Positivity on one imaging technique was strongly associated with positivity on the other two. PET-positive knees exhibited significantly higher SUVs, higher MRI parameters and greater synovial thickness compared with PET-negative knees, whereas serum CRP and MMP-3 levels were not significantly different. SUVs were significantly correlated with all MRI parameters, with synovial thickness and with serum CRP and MMP-3 levels at baseline. Changes in SUVs after 4 weeks were also correlated with changes in MRI parameters and in serum CRP and MMP-3 levels, but not with changes in synovial thickness. (orig.)