Appropriate use criteria for dementia amyloid imaging in Switzerland - mini-review and statement on behalf of the Swiss Society of Nuclear Medicine and the Swiss Memory Clinics.

While FDG-PET imaging of the brain for the differential diagnosis of dementia has been covered by the compulsory health insurance in Switzerland for more than a decade, beta-amyloid-PET just recently has been added to the catalogue of procedures that have been cleared for routine use, provided that a set of appropriate use criteria (AUC) be followed. To provide guidance to dementia care practitioners, the Swiss Society of Nuclear Medicine and the Swiss Memory Clinics jointly report a mini-review on beta-amyloid-PET and discuss the AUC set into effect by the Swiss Federal Office of Public Health, as well as their application and limitations.

Early metabolic responses in temozolomide treated low-grade glioma patients.

Amino acid transport and protein synthesis are important steps of tumor growth. We investigated the time course of tumor metabolism in low-grade gliomas (LGG) during temozolomide chemotherapy, and compared metabolic responses as measured with positron emission tomography (PET) with volume responses as revealed by magnetic resonance imaging (MR). A homogeneous population of 11 patients with progressive non-enhancing LGG was prospectively studied. Imaging was done at 6-months intervals starting six months, and in a second series starting three months after treatment initiation. F-18 fluoro-ethyl-L-tyrosine (FET) uptake was quantified with PET as metabolically active tumor volume, and was compared with the tumor volume on MR. Response was defined as >or=10% reduction of the initial tumor volume. Eight patients showed metabolic responses. Already 3 months after start of chemotherapy the active FET volumes decreased in 2 patients to a mean of 44% from baseline. First MR volume responses were noted at 6 months. Responders showed a volume reduction to 31 +/- 23% (mean +/- SD) from baseline for FET, and to 73 +/- 26% for MR. The time to maximal volume reduction was 8.0 +/- 4.4 months for FET, and 15.0 +/- 3.0 months for MR. The initial metabolic response correlated with the best volume response on MR (Spearman Rank P = 0.011). Deactivation of amino acid transport represents an early indicator of chemotherapy response in LGG. Response assessment based on MR only has to be reconsidered. The time window obtained from PET may assist for individual treatment decisions in LGG patients.

Comparing Two Imaging Methods for Follow-Up of Lung Cancer Treatment: A Randomized Pilot Study.

BACKGROUND: Scientific data on the image modality to be used in postcurative treatment surveillance of non-small cell lung cancer patients are scarce. This prospective randomized pilot trial compared the performance of integrated 18F-fluorodeoxyglucose positron emission tomography-computed tomography (PET-CT) and contrast-enhanced computed tomography (CE-CT). METHODS: After termination of curative-intent treatment, patients were randomly assigned to the PET-CT or the CE-CT group. Imaging was performed every 6 months for 2 years. If suspicious radiologic findings were detected or patients became symptomatic, a diagnostic workup was initiated. Sensitivity, specificity, and positive predictive value for detecting cancer recurrence were calculated for both imaging procedures. RESULTS: The study enrolled 96 patients. In 14 of 50 patients (28%) in the PET-CT group and in 14 of 46 patients (30%) in the CE-CT group, a suspicious radiologic finding was confirmed as cancer recurrence after diagnostic workup. False-positive findings were detected in 11 patients (22%) of the PET-CT group and in 8 patients (17%) of the CE-CT group. The sensitivity, specificity, and positive predictive value for detecting cancer recurrence (95% confidence interval) were 0.88 (0.62 to 0.98), 0.62 (0.42 to 0.79), and 0.56 (0.35 to 0.76) for PET-CT and 0.93 (0.68 to 1.00), 0.72 (0.53 to 0.87), and 0.64 (0.41to 0.83) for CE-CT, respectively. CONCLUSIONS: The results of our study suggest that PET-CT is not superior to CE-CT in detecting cancer recurrence during 2 years after curative-intent treatment of non-small cell lung cancer.

Image analysis in posttreatment non-small cell lung cancer surveillance: specialists' interpretations reviewed by the thoracic multidisciplinary tumor board.

BACKGROUND: Data show that the initial specialist's image interpretation and final multidisciplinary tumor board (MTB) assessment can vary substantially in the pretherapeutic cancer setting. The aim of this post hoc analysis was to investigate the concordance of the specialist's and MTB's image interpretations in patients undergoing systematic posttreatment lung cancer image surveillance. METHODS: In the initial prospective study, lung cancer patients who had received curative-intent treatment were randomly assigned to undergo either contrast-enhanced computed tomography (CE-CT) or integrated 18F-fluorodeoxyglucose positron emission tomography-computed tomography (PET-CT). Imaging was performed every 6 months for 2 years, and all imaging studies were finally assessed by our MTB. This post hoc analysis assessed differences between the initial specialist's image interpretation and the final MTB's image interpretation. RESULTS: In 89 patients, 266 imaging studies (129 PET-CT, 137 CE-CT) were analyzed. In 87.2% (88.4, 86.1%) of the studies, complete concordance was found. Out of the 12.8% (11.6, 13.9%) with discordant results, 7.5% (6.9, 8.0%) had implications for alterations in patient management (major disagreements).Twenty major disagreements were detected in 17 study patients. Retrospectively, in eight out of these 17 (47%) patients, in contrast to the MTB's view, the specialist's interpretation was more appropriate, whereas in nine out of 17 patients (53%), the MTB's interpretation was more accurate. CONCLUSIONS: In an experienced MTB, the agreement between imaging specialists and the rest of the MTB with regard to the interpretation of images is high in a setting of posttreatment lung cancer image surveillance. It seems that in cases of disagreements, the rates of more accurate interpretation are well balanced between imaging specialists and the MTB. TRIAL REGISTRATION: ISRCTN16281786, Date 23. February 2017.

Do you want to participate in a clinical study as a healthy control? - Risk or benefit?

A healthy woman volunteered to participate as "healthy control" in a study. An increased level of procalcitonin (PCT) was detected and remained elevated on follow-up measurements. As calcitonin levels were elevated as well, thyroid ultrasound was performed which revealed nodes in both thyroid lobes, one of them showing metabolic activity in positron emission tomography-computed tomography scan. To exclude a malignant thyroid cancer despite the negative findings in a fine needle aspiration the patient underwent thyroidectomy and a medullary thyroid carcinoma (MTC) was detected in the right lobe. MTC is a rare endocrine tumor with a poor prognosis once having spread, therefore early detection remains a priority for the outcome. Screening parameter is serum calcitonin, in absence of infection the pro-hormone PCT can be used as a screening parameter as well with high sensitivity.

Assessment of hypoxia and perfusion in human brain tumors using PET with 18F-fluoromisonidazole and 15O-H2O.

UNLABELLED: Hypoxia predicts poor treatment response of malignant tumors. We used PET with (18)F-fluoromisonidazole ((18)F-FMISO) and (15)O-H(2)O to measure in vivo hypoxia and perfusion in patients with brain tumors. METHODS: Eleven patients with various brain tumors were investigated. We performed dynamic (18)F-FMISO PET, including arterial blood sampling and the determination of (18)F-FMISO stability in plasma with high-performance liquid chromatography (HPLC). The (18)F-FMISO kinetics in normal brain and tumor were assessed quantitatively using standard 2- and 3-compartment models. Tumor perfusion ((15)O-H(2)O) was measured immediately before (18)F-FMISO PET in 10 of the 11 patients. RESULTS: PET images acquired 150-170 min after injection revealed increased (18)F-FMISO tumor uptake in all glioblastomas. This increased uptake was reflected by (18)F-FMISO distribution volumes >1, compared with (18)F-FMISO distribution volumes <1 in normal brain. The (18)F-FMISO uptake rate K(1) was also higher in all glioblastomas than in normal brain. In meningioma, which lacks the blood-brain barrier (BBB), a higher K(1) was observed than in glioblastoma, whereas the (18)F-FMISO distribution volume in meningioma was <1. Pixel-by-pixel image analysis generally showed a positive correlation between (18)F-FMISO tumor uptake at 0-5 min after injection and perfusion ((15)O-H(2)O) with r values between 0.42 and 0.86, whereas late (18)F-FMISO images (150-170 min after injection) were (with a single exception) independent of perfusion. Spatial comparison of (18)F-FMISO with (15)O-H(2)O PET images in glioblastomas showed hypoxia both in hypo- and hyperperfused tumor areas. HPLC analysis showed that most of the (18)F-FMISO in plasma was still intact 90 min after injection, accounting for 92%-96% of plasma radioactivity. CONCLUSION: Our data suggest that late (18)F-FMISO PET images provide a spatial description of hypoxia in brain tumors that is independent of BBB disruption and tumor perfusion. The distribution volume is an appropriate measure to quantify (18)F-FMISO uptake. The perfusion-hypoxia patterns described in glioblastoma suggest that hypoxia in these tumors may develop irrespective of the magnitude of perfusion.

Measurement of the extracellular space in brain tumors using 76Br-bromide and PET.

UNLABELLED: Brain edema significantly contributes to the clinical course of human brain tumor patients. There is evidence that an enlargement of the extracellular space (ECS) is involved in the development of brain edema. Although T2-weighted magnetic resonance (T2-MR) images represent brain edema by its increased water content, they do not differentiate ECS enlargement from increased intracellular water content. METHODS: On the basis of the known distribution of bromide in the ECS, we used (76)Br-bromide and PET to measure the regional ECS in 9 brain tumor patients. Transport rate constants and the distribution volume (DV) of (76)Br-bromide in normal brain and tumor were derived from dynamic PET scans and the measured (76)Br-bromide concentration in arterial plasma. We evaluated different models regarding their reliability in estimating the ECS. RESULTS: Assuming that the DV of (76)Br-bromide represents the ECS, robust estimates were possible for all investigated regions. In normal brain, ECS was within a narrow range-for example, occipital lobe, 19.9% +/- 3.1%-and was lower in 2 dexamethasone-treated patients compared with untreated patients. In 7 of 9 tumors, increased ECS ranged between 43.8% and 61.1%. ECS increases were confined to the tumor mass and did not extend into peritumoral edematous brain. Two patients with large hyperintense lesions according to T2-MR images showed normal ECS values within the lesion. CONCLUSION: (76)Br-Bromide PET allows a quantitative measurement of the ECS in brain edema and in normal brain. The discrepancies between lesions shown by T2-MRI and regional ECS enlargement as measured with PET challenge the concept of tumor-induced brain edema.

Preclinical evaluation of a new, stabilized neurotensin(8--13) pseudopeptide radiolabeled with (99m)tc.

UNLABELLED: The rapid degradation of neurotensin (NT) limits its clinical use in cancer imaging and therapy. Thus, a new NT(8--13) pseudopeptide, NT-VIII, was synthesized. Some changes were introduced in the sequence of NT(8--13) to stabilize the molecule against enzymatic degradation: Arg(8) was N-methylated, and Lys and Tle replaced Arg(9) and Ile(12), respectively. Finally, (NalphaHis)Ac was coupled to the N-terminus for (99m)Tc(CO)(3) labeling. This peptide was characterized both in vitro and in vivo. METHODS: The new analog was labeled with (99m)Tc(CO)(3). Its metabolic stability was analyzed both in human plasma and in HT-29 cells. Binding properties, receptor downregulation, and internalization were tested with HT-29 cells. Biodistribution was evaluated in nude mice with HT-29 xenografts. RESULTS: (99m)Tc(CO)(3)NT-VIII showed a high stability in plasma, where most of the peptide remained intact after 24 h of incubation at 37 degreesC. However, the degradation in HT-29 cells was more rapid (46% of intact (99m)Tc(CO)(3)NT-VIII after 24 h at 37 degreesC). Binding to NT1 receptors (NTR1) was saturable and specific. Scatchard analysis showed a high affinity for (99m)Tc(CO)(3)NT-VIII, with a dissociation constant similar to (125)I-NT (1.8 vs. 1.6 nmol/L). After interacting with NTR1, (99m)Tc(CO)(3)NT-VIII was rapidly internalized, with more than 90% internalized after 30 min. It also distributed and cleared rapidly in nude mice bearing HT-29 xenografts. The highest rates of accumulation were found in kidney and tumor at all time points tested. Tumor uptake was highly specific because it could be blocked by coinjection with a high dose of (NalphaHis)Ac-NT(8--13). Tumors were clearly visualized in scintigraphy images. CONCLUSION: The changes that were introduced stabilized the molecule against enzymatic degradation without affecting binding properties. Moreover, the increase in stability enhanced tumor uptake, making this derivative a promising candidate for clinical use.

Stabilization of neurotensin analogues: effect on peptide catabolism, biodistribution and tumor binding.

Neurotensin (NT) receptors in pancreatic and other neuroendocrine tumors are promising targets for imaging and therapeutic purposes. Here, we report on the effect of distinct changes in the peptide chain on catabolism in vitro for five radiolabeled [99mTc] neurotensin analogues having high affinity for neurotensin receptors. Substitution of NT(1-7) by (NalphaHis)Ac--the Tc-binding moiety--combined with a reduced bond 8-9 (CH2NH), N-methylation of peptide bonds or replacement of Ile(12) by tertiary leucin (Tle) led to peptide stabilization of various degrees. Biodistribution studies in nude mice bearing HT29 xenografts showed higher tumor uptake with more stable peptides, yielding high tumor to blood ratios of up to 70.

Focal changes in diffusivity on apparent diffusion coefficient MR imaging and amino acid uptake on PET do not colocalize in nonenhancing low-grade gliomas.

UNLABELLED: Low-grade gliomas (LGGs) may harbor malignant foci, which are characterized by increased tumor cellularity and angiogenesis. We used diffusion-weighted MR imaging (apparent diffusion coefficient [ADC]) and PET with the amino acid O-(2-(18)F-fluorethyl)-L-tyrosine ((18)F-FET) to search for focal changes of diffusion (ADC) and amino acid uptake and to investigate whether focal changes in these parameters colocalize within LGGs. METHODS: We retrospectively selected 18 patients with nonenhancing LGG. All patients had undergone (18)F-FET PET and MR imaging for preoperative evaluation or for therapy monitoring in recurrent or progressive LGG. Region-of-interest analysis was performed to compare (18)F-FET uptake and ADC values in areas with focal intratumoral maximum metabolic activity and diffusion restriction and between tumor and normal brain. (18)F-FET uptake was normalized to the mean cerebellar uptake (ratio). ADC values were also compared with the (18)F-FET uptake on a voxel-by-voxel basis across the whole tumor. RESULTS: The mean focal maximum (mean ± SD, 1.69 ± 0.85) and global (18)F-FET uptake in tumors (1.14 ± 0.41) exceeded that of normal cortex (0.85 ± 0.09) and cerebrospinal fluid (0.82 ± 0.20). ADC values in the area with most restricted diffusion (1.07 ± 0.22 × 10(-3) mm(2)/s) and in the whole tumor (1.38 ± 0.27 × 10(-3) mm(2)/s) were in the range between normal cortex (0.73 ± 0.06 × 10(-3) mm(2)/s) and cerebrospinal fluid (2.84 ± 0.09 × 10(-3) mm(2)/s). (18)F-FET uptake did not correlate with corresponding (colocalizing) ADC values, either in the area with focal maximum metabolic activity or in the area with most restricted diffusion or in the whole tumor. CONCLUSION: There is no congruency between (18)F-FET uptake and diffusivity in nonenhancing LGG. Diffusion restriction in these tumors most likely represents changes in brain and tumor cell densities as well as alteration of water distribution and is probably not directly correlated with the density of tumor cells.

F-18 choline PET does not detect increased metabolism in F-18 fluoroethyltyrosine-negative low-grade gliomas.

PURPOSE: Positron emission tomography (PET) with radiolabeled amino acids provides information on biopsy target and chemotherapy response in patients with low-grade gliomas (LGG). In this article, we addressed whether PET with F-18 choline (CHO) detects increased metabolism in F-18 fluoroethyltyrosine (FET)-negative LGG patients. METHODS: Six LGG patients with nongadolinium-enhancing (magnetic resonance) FET-negative LGG were imaged with CHO PET. Regions of interest were positioned over tumor and contralateral brain. Uptake of FET and CHO was quantified as count ratio of tumor to contralateral brain. RESULTS: The mean FET uptake ratio for FET-negative LGG was 0.95 ± 0.03 (mean ± standard deviation). Five tumors did not show increased uptake ratios for CHO (0.96 ± 0.12). Slightly increased CHO uptake was found in 1 patient (1.24), which, however, was not associated with tumor visualization. CONCLUSIONS: Amino acid and choline uptake appear to behave similar in nongadolinium-enhancing LGG. For clinical purposes, CHO PET is not superior to FET PET.

Measurement of tumor hypoxia in spontaneous canine sarcomas.

We used positron emission tomography (PET) with [18F]fluoromisonidazole ([18F]FMISO) to study tumor hypoxia in six dogs with spontaneous sarcomas. The tumors were regarded as hypoxic if [18F]FMISO uptake exceeded normal tissue radioactivity by 40% (tumor/muscle ratio > 1.4) or if kinetic analysis indicated a positive [18F]FMISO tissue influx rate (Ki > 0) by a Patlak plot. Using these criteria, we found hypoxia in a fibrosarcoma grade II, an undifferentiated sarcoma, and an ostoeosarcoma, but not in a fibrosarcoma grade I, another osteosarcoma, and a myxosarcoma. In three animals, the tumor oxygen partial pressure (pO2) was also measured invasively using Eppendorf needle electrodes. In these cases, the Eppendorf measurements were confirmed by the [18F]FMISO PET results. In addition, [15O]H2O PET was performed in four dogs in order to assess tumor perfusion. Comparisons of the [18F]FMISO with [15O]H2O PET images in two cases showed that tumor hypoxia occurred in the tumor center with low perfusion, whereas perfusion was heterogeneous in a nonhypoxic tumor.