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Background Our aim was to determine sets of reconstruction parameters for the Biograph Vision Quadra (Siemens Healthineers) PET/CT system that result in quantitative images compliant with the European Association of Nuclear Medicine Research Ltd. (EARL) criteria. Using the Biograph Vision 600 (Siemens Healthineers) PET/CT technology but extending the axial field of view to 106 cm, gives the Vision Quadra currently an around fivefold higher sensitivity over the Vision 600 with otherwise comparable spatial resolution. Therefore, we also investigated how the number of incident positron decays—i.e., exposure—affects EARL compliance. This will allow estimating a minimal acquisition time or a minimal applied dose in clinical scans while retaining data comparability. Methods We measured activity recovery curves on a NEMA IEC body phantom filled with an aqueous 18F solution and a sphere to background ratio of 10–1 according to the latest EARL guidelines. Reconstructing 3570 image sets with varying OSEM PSF iterations, post-reconstruction Gaussian filter full width at half maximum (FWHM), and varying exposure from 59 kDecays/ml (= 3 s frame duration) to 59.2 MDecays/ml (= 1 h), allowed us to determine sets of parameters to achieve compliance with the current EARL 1 and EARL 2 standards. Recovery coefficients (RCs) were calculated for the metrics RCmax, RCmean, and RCpeak, and the respective recovery curves were analyzed for monotonicity. The background’s coefficient of variation (COV) was also calculated. Results Using 6 iterations, 5 subsets and 7.8 mm Gauss filtering resulted in optimal EARL1 compliance and recovery curve monotonicity in all analyzed frames, except in the 3 s frames. Most robust EARL2 compliance and monotonicity were achieved with 2 iterations, 5 subsets, and 3.6 mm Gauss FWHM in frames with durations between 30 s and 10 min. RCpeak only impeded EARL2 compliance in the 10 s and 3 s frames. Conclusions While EARL1 compliance was robust over most exposure ranges, EARL2 compliance required exposures between 1.2 MDecays/ml to 11.5 MDecays/ml. The Biograph Vision Quadra’s high sensitivity makes frames as short as 10 s feasible for comparable quantitative images. Lowering EARL2 RCmax limits closer to unity would possibly even permit shorter frames.

A Correction to this paper has been published: 10.1007/s00259-021-05300-8

This study proposes an automated prostate cancer (PC) lesion characterization method based on the deep neural network to determine tumor burden on 68Ga-PSMA-11 PET/CT to potentially facilitate the optimization of PSMA-directed radionuclide therapy. We collected 68Ga-PSMA-11 PET/CT images from 193 patients with metastatic PC at three medical centers. For proof-of-concept, we focused on the detection of pelvis bone and lymph node lesions. A deep neural network (triple-combining 2.5D U-Net) was developed for the automated characterization of these lesions. The proposed method simultaneously extracts features from axial, coronal, and sagittal planes, which mimics the workflow of physicians and reduces computational and memory requirements. Among all the labeled lesions, the network achieved 99% precision, 99% recall, and an F1 score of 99% on bone lesion detection and 94%, precision 89% recall, and an F1 score of 92% on lymph node lesion detection. The segmentation accuracy is lower than the detection. The performance of the network was correlated with the amount of training data. We developed a deep neural network to characterize automatically the PC lesions on 68Ga-PSMA-11 PET/CT. The preliminary test within the pelvic area confirms the potential of deep learning methods. Increasing the amount of training data should further enhance the performance of the proposed method and may ultimately allow whole-body assessments.

PURPOSE Digital PET/CT scanners represent a significant step forward in molecular imaging. We report here the clinical impact of digital PET in PSMA-PET/CT. METHODS In this retrospective study, 88 consecutive patients who underwent [68Ga]Ga-PSMA-11 PET/CT on a digital PET/CT (dPET/CT) scanner for recurrent prostate cancer (PC) were included in a first cohort. In a second step, 88 individuals who underwent an analogue [68Ga]Ga-PSMA-11 PET/CT (aPET/CT) were selected after they were matched to the first cohort for clinical parameters. Following consensus read by two nuclear medicine physicians, the number and type of PC lesions as well as benign, PSMA-positive lesions were recorded. The results were complemented by extensive [68Ga]Ga phantom measurements to determine imaging characteristics of both scanners. RESULTS dPET/CT revealed a greater number of PC lesions compared to aPET/CT (326 versus 142) as well as a proportional increase in benign causes of tracer-uptake (144 versus 65). A greater number of scans were noted as pathological for PC on dPET/CT (74/88) compared to aPET/CT (64/88, p < 0.05). The PSMA positivity rate for PC was significantly higher in dPET/CT for the lowest PSA values (PSA < 2.0 ng/ml, p < 0.05). CONCLUSION dPET/CT detected more PC lesions compared to aPET/CT. A significantly higher rate of pathological PET/CTs was noted in the group with the lowest PSA values. A higher number of benign PSMA-positive lesions were also noted in dPET/CT. The differences could be plausibly explained by the measured imaging characteristics of the scanners.

Die Positronenemissionstomographie/Computertomographie (PET/CT) mit Liganden des Prostataspezifischen Membranantigens (PSMA) und die PSMA-Therapie haben sich seit ihrer klinischen Einfuhrung in 2011 weltweit rasant ausgebreitet. Aktuelle Erkenntnisse sowohl uber die PSMA-PET/CT als auch uber die PSMA-Therapie werden zusammengefasst. Erkenntnisse aus der Literatur und Erfahrungen der Autoren wurden zusammengetragen. Es zeigt sich eine sehr hohe Sensitivitat und Spezifitat der PSMA-PET/CT sowohl beim Rezidivprostatakarzinom (‑PC) als auch beim Primarstaging des PC mit mittlerem und hohem Risikoprofil. Die Ergebnisse der PSMA-Therapie als Drittlinientherapie bei Patienten mit metastasiertem, kastrationsresistentem PC sind vielversprechend. Die PSMA-PET/CT hat sich mittlerweile als Goldstandard in der Diagnostik des Rezidiv-PC etabliert und ist dabei, dieselbe Rolle auch beim Primarstaging des PC mit mittlerem und hohem Risikoprofil zu ubernehmen. Die PSMA-Therapie wird in einer stets wachsenden Zahl an Zentren als Drittlinientherapie bei metastasiertem, kastrationsresistentem PC routinemasig durchgefuhrt.

PURPOSE Dual-time point PET/CT scanning with [68Ga]Ga-PSMA-11 in the diagnosis of prostate cancer (PC) has been advanced as a method to increase detection of PC lesions, particularly at early stages of biochemical recurrence and as a potential means to aid the discrimination between benign and pathological prostate-specific membrane antigen (PSMA) uptake. However, the assumption that all PC lesions uniformly exhibit increasing tracer uptake at delayed imaging has not yet been investigated, which this present study aims to address. METHODS One hundred consecutive patients with biochemically recurrent PC who received standard and late [68Ga]Ga-PSMA-11 PET/CT (by local protocol at 1.5 h "standard" and 2.5 h p.i. "late") underwent retrospective evaluation. All lesions with a tracer uptake above local background were analysed with regard to their maximum standardised uptake values at standard and late images (SUVmax) and characterised according to their morphological characteristics. RESULTS Seventy-nine of 100 patients had PSMA-positive scans, in whom a total of 185 individual PSMA-positive lesions were identified. These were morphologically characterised as bone lesions (n = 48), solid organ lesions (n = 3), lymph node (LN) lesions (n = 78) and locally recurrent lesions in the prostatic fossa or seminal vesicles (n = 56). The relative uptake between standard and late imaging was considered; all lesions classified as local recurrence presented with increasing (86%) or stable patterns of tracer uptake (14%). In contrast, only 58% of bone lesions exhibited increasing tracer uptake, with 21% exhibiting a stable pattern and 21% exhibiting a decreasing tracer uptake at late imaging. CONCLUSION A heterogeneous pattern of dynamic tracer uptake was observed, with a largely increasing pattern observed for locally recurrent lesions and lymph nodes and a significant proportion of bone lesions exhibiting decreasing tracer uptake. The results are of significance not only in the imaging and identification of PC lesions, but they also have implications for PSMA-directed ligand therapy.

PURPOSE So far, there have been very few studies which provide a direct comparison between MRI and PSMA-ligand PET/CT for the detection of recurrent prostate cancer (rPC). This present study therefore aims to provide further clinical data in order to resolve this urgent clinical question, and thereby strengthen clinical recommendations. METHODS A retrospective analysis was performed for patients who were scanned at our institution with whole-body PSMA-PET/CT (tracer: 68Ga-PSMA-11) between January 2017 and September 2018 in order to detect rPC. Amongst them, 43 underwent an additional pelvic MRI within 2 months. Both modalities were compared as follows: a consensus read of the PET data was performed by two nuclear physicians. All lesions were recorded with respect to their type and localization. The same process was conducted by two radiologists for pelvic MRI. Thereafter, both modalities were directly compared for every patient and lesion. RESULTS Overall, 30/43 patients (69.8%) presented with a pathologic MRI and 38/43 (88.4%) with a pathologic PSMA-PET/CT of the pelvis. MRI detected 53 pelvic rPC lesions (13 of them classified as "uncertain") and PSMA-PET/CT detected 75 pelvic lesions (three classified as "uncertain"). The superiority of PSMA-PET/CT was statistically significant only if uncertain lesions were classified as false-positive. CONCLUSIONS PSMA-PET/CT detected more pelvic lesions characteristic for rPC when compared to MRI. In order to detect rPC, a potential future scenario could be conducting first a PSMA-PET/CT. Combining the advantages of both modalities in hybrid PET/MRI scanners would be an ideal future scenario.

Purpose To evaluate the performance of [68Ga]Ga-PSMA-11 PET/CT in the diagnosis of recurrent prostate cancer (PC) after prostatectomy in a large multicentre cohort. Methods The centres, which contributed to this study, were the departments of nuclear medicine of Heidelberg (Germany), Technical University of Munich (Germany) and Albert Einstein Hospital of São Paulo (Brazil). A total of 2533 patients who were scanned with [68Ga]Ga-PSMA-11 PET/CT at 1 h p.i. due to recurrent PC after prostatectomy were included in this retrospective analysis. Exclusion criteria were as follows: patients with untreated primary tumour, previous chemotherapy or Xofigo®; those previously treated with exclusively external beam radiation therapy or HIFU; those referred for PSMA-therapy; and those treated with ADT (including first- and second-generation ADT) within the last 6 months. Potential influences of different factors such as PSA level, PSA doubling-time (PSADT), PSA velocity (PSAVel), Gleason Score (GSC, including the separate analysis of 7a and 7b), age and amount of injected tracer were evaluated in a multivariable analysis. Results The rate of pathologic PET/CT-scans was 43% for PSA ≤ 0.2 ng/ml, 58% for PSA > 0.2 to ≤ 0.5, 72% for PSA > 0.5 to ≤ 1.0 and increased to a maximum of 93% for PSA > 10 ng/ml. A pathological PET/CT was significantly (p = 0.001) associated with PSA level and higher GSC. Amount of injected tracer, age, PSADT and PSAVel were not associated with a higher probability of a pathological scan. Conclusion [68Ga]Ga-PSMA-11 PET/CT at 1 h p.i. confirmed its high performance in the largest patient cohort yet analysed. Tumour detection showed a clear association with higher PSA and higher GSC. No association was found between a pathological [68Ga]Ga-PSMA-11 PET/CT and age, amount of injected tracer, PSADT or PSAVel.

Background Gastrin Releasing Peptide receptor (GRPr)-based radioligands have shown great promise for diagnostic imaging of GRPr-positive cancers, such as prostate and breast. The present study aims at developing and evaluating a versatile GRPr-based probe for both PET/SPECT imaging as well as intraoperative and therapeutic applications. The influence of the versatile chelator AAZTA5 on the radiometal labelling properties and the in vitro performance of the generated radiotracers were thoroughly investigated. The GRPr-based antagonist D-Phe-Gln-Trp-Ala-Val-Gly-His-Sta-Leu-NH2 was functionalized with the chelator 6-[Bis (carboxymethyl)amino]-1,4-bis (carboyxmethyl)-6-methyl-1,4-diazepane (AAZTA5) through the spacer 4-amino-1-carboxymethyl-piperidine (Pip) to obtain AAZTA5-Pip-D-Phe-Gln-Trp-Ala-Val-Gly-His-Sta-Leu-NH2 (LF1). LF1 was radiolabelled with gallium-68 (PET), indium-111 (SPECT, intraoperative applications) and lutetium-177 (therapy, SPECT). In vitro evaluation included stability studies, determination of lipophilicity, protein-binding studies, determination of Kd and Bmax as well as internalization studies using the epithelial human prostate cancer cell line PC3. In vitro monotherapy as well as combination therapy studies were further performed to assess its applicability as a theranostic compound. Results LF1 was labelled with gallium-68, indium-111 and lutetium-177 within 5 min at room temperature (RT). The apparent molar activities (Am) were ranging between 50 and 60 GBq/μmol for the 68Ga-labelled LF1, 10–20 GBq/μmol for the 111In- and 177Lu-labelled LF1. The radiotracers were stable for a period of 4 h post labeling exhibiting a hydrophilic profile with an average of a LogDoctanol/PBS of − 3, while the bound activity to the human serum protein was approximately 10%. 68/natGa-LF1, 177/natLu-LF1 and 111/natIn-LF1 exhibited high affinity for the PC3 cells, with Kd values of 16.3 ± 2.4 nM, 10.3 ± 2.73 nM and 5.2 ± 1.9 nM, respectively, and the required concentration of the radiotracers to saturate the receptors (Bmax) was between 0.5 and 0.8 nM which corresponds to approximately 4 × 105 receptors per cell. Low specific internalization rate was found in cell culture, while the total specific cell surface bound uptake always exceeded the internalized activity. In vitro therapy studies showed that inhibition of PC3 cells growth is somewhat more efficient when combination of 177Lu-labelled LF1 with rapamycin is applied compared to 177Lu-laballed LF1 alone. Conclusion Encouraged by these promising in vitro data, preclinical evaluation of the LF1 precursor are planned in tumour models in vivo.

PURPOSE: The introduction of ligands targeting prostate-specific membrane antigen (PSMA), especially 68Ga-PSMA-11, has changed the management of patients with prostate cancer (PCa). 18F-Labelled ligands can be produced in larger amounts and therefore can improve availability for a larger group of patients. The aim of this study was to evaluate the diagnostic performance of the recently introduced 18F-PSMA-1007 in patients with recurrent PCa. METHODS: This retrospective analysis included 100 consecutive patients with biochemical relapse (mean age 68.75 ± 7.6 years) referred for PSMA PET/CT. Whole-body PET/CT imaging (from the lower limbs to the skull) was performed in all patients 120 min after injection of 338 ± 44.31 MBq 18F-PSMA-1007. Prostatectomy, radiation beam therapy of the prostate bed and androgen-deprivation therapy had been performed in 92%, 45% and 27% of the patients, respectively. Radiation beam therapy of the prostate bed had been performed in addition to surgery in 38 patients (38%) and 10 patients (10%) had received all three therapy modalities. The probability of a 18F-PSMA-1007 PET/CT scan suggestive of pathology was compared with the Gleason score (GS) and PSA level. RESULTS: Of the 100 patients, 95 (95%) showed at least one pathological finding on 18F-PSMA-1007 PET/CT. The overall median PSA level was 1.34 ng/ml (range 0,04-41.3 ng/ml). The rates of pathological scans were 86%, 89%, 100% and 100% among patients with PSA levels ≤0.5, 0.51-1.0, 1.1-2.0 and > 2.0 ng/ml, respectively. The median GS was 7 (range 5-10). The majority of patients (70) with a GS available had a score in the range 7-9. The rate of pathological scans in these patients was 93% (65/70). The median SUVmax values of the pathological findings were 10.25, 14.32, 13.16 and 28.87 in patients with PSA levels ≤0.5, 0.51-1.0, 1.1-2.0 and >2.0 ng/ml, respectively. The median SUVmax in patients with a PSA level of >2.0 ng/ml was significantly higher than in all other PSA groups. CONCLUSION: 18F-PSMA-1007 PET/CT can detect recurrent PCa in a high percentage of patients with biochemical relapse. The probability of a pathological 18F-PSMA-1007 PET/CT scan seems to be high even in patients with a low PSA level ≤0.5 ng/ml, and this may have a significant impact on the management of this relevant group of patients. KEYWORDS: Biochemical relapse; PSMA-1007; Prostate cancer

PSMA-targeted PET in patients with prostate cancer (PCa) has a significant impact on treatment decisions. By far the most frequently used PSMA ligand is 68Ga-labelled PSMA-11. However, due to the availability of larger amounts of activity, 18F-labelled PSMA ligands are of major interest. The aim of the present study was to evaluate the biodistribution and performance of the novel 18F-labelled ligand PSMA-1007 at two different time points. This retrospective analysis included 40 consecutive patients (mean age 68.7 ± 8.1 years) referred for PSMA PET/CT. 18F-PSMA-1007 PET/CT was performed for localization of biochemical relapse, primary staging or therapy follow-up. Circular regions of interest were placed on representative slices of the liver, spleen, kidney, abdominal aortic blood pool, bone marrow (fourth lumbar vertebral body), urinary bladder and gluteus muscle at 60 and 120 min after injection. In malignant lesions the maximum standardized uptake (SUVmax) was measured within volumes of interest at both time points. All SUVs at 60 min were compared with those at 120 min after injection. The activity in the blood pool, urinary bladder and gluteus muscle was very low and decreased significantly over time (P

PSMA ligand imaging with hybrid PET/MRI scanners could be an integral part of the clinical routine in the future. However, the first study about this novel method revealed a severe photopenic artifact (“halo artifact”) around the urinary bladder causing significantly reduced tumor visibility. The aim of this evaluation was to analyze the role of arm truncation on the appearance of the halo artifact in 68Ga-PSMA-11 PET/MRI hypothesizing that this influences the appearance. Twenty-seven consecutive patients were subjected to 68Ga-PSMA-11 PET/CT (1 h p.i.) followed by PET/MRI (3 h p.i.). PET/MRI was first started with scans of the abdomen to pelvis with arms positioned up above the head. Immediately thereafter, additional scans from the pelvis to abdomen were conducted with arms positioned down beside the trunk. All investigations were first analyzed separately and then compared with respect to tumor detection and tumor uptake (SUV) as well as the presence and intensity of the halo artifact. The Wilcoxon signed rank test was used to determine statistical differences including Bonferroni correction. The halo was significantly reduced if the arms were elevated. Lesions inside the halo artifact (n = 16) demonstrated significantly increased SUVmean (p = 0.0007) and SUVmax (p = 0.0024) with arms positioned up. The halo appearance and intensity was not dependent on the total activity and activity concentration of the urinary bladder. Positioning the arms down was shown to be significantly associated with the appearance of the halo artifact in PET/MRI. Positioning the arms up above the head can significantly reduce the halo artifact, thereby detecting more tumor lesions.

Purpose Since the clinical introduction of 68Ga-PSMA-11 PET/CT, this imaging method has rapidly spread and is now regarded as a significant step forward in the diagnosis of recurrent prostate cancer (PCa). The aim of this study was to analyse the influence of several variables with possible influence on PSMA ligand uptake in a large cohort. Methods We performed a retrospective analysis of 1007 consecutive patients who were scanned with 68Ga-PSMA-11 PET/CT (1 h after injection) from January 2014 to January 2017 to detect recurrent disease. Patients with untreated primary PCa or patients referred for PSMA radioligand therapy were excluded. The possible effects of different variables including PSA level and PSA doubling time (PSADT), PSA velocity (PSAVel), Gleason score (GSC, including separate analysis of GSC 7a and 7b), ongoing androgen deprivation therapy (ADT), patient age and amount of injected activity were evaluated. Results In 79.5% of patients at least one lesion with characteristics suggestive of recurrent PCa was detected. A pathological (positive) PET/CT scan was associated with PSA level and ADT. GSC, amount of injected activity, patient age, PSADT and PSAVel were not associated with a positive PET/CT scan in multivariate analysis. Conclusion 68Ga-PSMA-11 PET/CT detects tumour lesions in a high percentage of patients with recurrent PCa. Tumour detection is clearly associated with PSA level and ADT. Only a tendency for an association without statistical significance was found between higher GSC and a higher probability of a pathological PET/CT scan. No associations were found between a pathological 68Ga-PSMA-11 PET/CT scan and patient age, amount of injected activity, PSADT or PSAVel.

Purpose Prostate-specific membrane antigen (PSMA)-targeting radioligand therapy (RLT) was introduced in 2011. The first report described the antitumor and side effects of a single dose. The aim of this analysis was to evaluate toxicity and antitumor activity after single and repetitive therapies. Methods Thirty-four men with metastatic castration-resistant prostate cancer received PSMA-RLT with 131I-MIP-1095. Twenty-three patients received a second, and three patients a third dose, timed at PSA progression after an initial response to the preceding therapy. The applied doses were separated in three groups: 5.0 GBq. Antitumor and side-effects were analyzed by blood samples and other clinical data. Follow-up was conducted for up to 5 years. Results The best therapeutic effect was achieved by the first therapy. A PSA decline of ≥50% was achieved in 70.6% of the patients. The second and third therapies were significantly less effective. There was neither an association between the applied activity and PSA response or the time-to-progression. Hematologic toxicities were less prevalent but presented in a higher percentage of patients with increasing number of therapies. After hematologic toxicities, xerostomia was the second most frequent side effect and presented more often and with higher intensity after the second or third therapy. Conclusion The first dose of RLT with 131I-MIP-1095 presented with low side effects and could significantly reduce the tumor burden in a majority of patients. The second and third therapies were less effective and presented with more frequent and more intense side effects, especially hematologic toxicities and xerostomia. Electronic supplementary material The online version of this article (doi:10.1007/s00259-017-3665-9) contains supplementary material, which is available to authorized users.

To illustrate the [18F]FDG-PET/CT findings in patients affected by cancer with clinical diagnosis of Covid-19 METHODS: We retrospectively reviewed the cases of patients who showed pulmonary involvement unrelated to cancer metastases on March 13 and 16 2020. We reviewed the scans, collected medical history, and exposure information.Among the 13 scans, we identified 5 cases with imaging findings suspicious for viral infection. Peripheral lung consolidations and/or ground-glass opacities in two or more lobes were found. Lung abnormalities displayed increased [18F]FDG uptake (SUVmax 4.3-11.3). All the patients on the day of PET/CT acquisition were asymptomatic, and they did not have fever or cough. In view of the PET/CT findings, home isolation, symptom surveillance, and treatment (in 3/5 patients) were indicated. At 1-week follow-up, 2/5 patients experienced the onset of mild respiratory symptoms.The [18F]FDG-PET/CT can identify probable Covid-19 disease in the absence or before symptoms onset and can guide patient management. Nuclear medicine staff needs to be aware of the possibility of contact with patients affected by the SARS-CoV-2 infection even if they do not present any symptom. Therefore, safety measures need to be adopted for other patients and hospital staff in order to block the spread of infection.

The positron emission tomography (PET) tracer 68Ga-PSMA-11, targeting the prostate-specific membrane antigen (PSMA), is rapidly excreted into the urinary tract. This leads to significant radioactivity in the bladder, which may limit the PET-detection of local recurrence (LR) of prostate cancer (PC) after radical prostatectomy (RP), developing in close proximity to the bladder. Here, we analyze if there is additional value of multi-parametric magnetic resonance imaging (mpMRI) compared to the 68Ga-PSMA-11-PET-component of PET/CT or PET/MRI to detect LR. One hundred and nineteen patients with biochemical recurrence after prior RP underwent both hybrid 68Ga-PSMA-11-PET/CTlow-dose (1 h p.i.) and -PET/MRI (2-3 h p.i.) including a mpMRI protocol of the prostatic bed. The comparison of both methods was restricted to the abdomen with focus on LR (McNemar). Bladder-LR distance and recurrence size were measured in axial T2w-TSE. A logistic regression was performed to determine the influence of these variables on detectability in 68Ga-PSMA-11-PET. Standardized-uptake-value (SUVmean) quantification of LR was performed. There were 93/119 patients that had at least one pathologic finding. In addition, 18/119 Patients (15.1%) were diagnosed with a LR in mpMRI of PET/MRI but only nine were PET-positive in PET/CT and PET/MRI. This mismatch was statistically significant (p = 0.004). Detection of LR using the PET-component was significantly influenced by proximity to the bladder (p = 0.028). The PET-pattern of LR-uptake was classified into three types (1): separated from bladder; (2): fuses with bladder, and (3): obliterated by bladder). The size of LRs did not affect PET-detectability (p = 0.84), mean size was 1.7 ± 0.69 cm long axis, 1.2 ± 0.46 cm short-axis. SUVmean in nine men was 8.7 ± 3.7 (PET/CT) and 7.0 ± 4.2 (PET/MRI) but could not be quantified in the remaining nine cases (obliterated by bladder). The present study demonstrates additional value of hybrid 68Ga-PSMA-11-PET/MRI by gaining complementary diagnostic information compared to the 68Ga-PSMA-11-PET/CTlow-dose for patients with LR of PC.

Purpose Radiotherapy is the main therapeutic approach besides surgery of localized prostate cancer. It relies on risk stratification and exact staging. This report analyses the potential of [68Ga]Glu-urea-Lys(Ahx)-HBED-CC (68Ga-PSMA-11), a new positron emission tomography (PET) tracer targeting prostate-specific membrane antigen (PSMA) for prostate cancer staging and individualized radiotherapy planning. Methods A cohort of 57 patients with prostate cancer scanned with 68Ga-PSMA-11 PET/CT for radiotherapy planning was retrospectively reviewed; 15 patients were at initial diagnosis and 42 patients at time of biochemical recurrence. Staging results of conventional imaging, including bone scintigraphy, CT or MRI, were compared with 68Ga-PSMA ligand PET/CT results and the influence on radiotherapeutic management was quantified. Results 68Ga-PSMA ligand PET/CT had a dramatic impact on radiotherapy application in the presented cohort. In 50.8 % of the cases therapy was changed. Conclusion The presented imaging technique of 68Ga-PSMA PET/CT could be a key technology for individualized radiotherapy management in prostate cancer.

The goal of our study was to quantify the expression of the somatostatin receptors (SSTR2) using the maximum standardized uptake value (SUVmax) of [(68)Ga]DOTA(0)-Phe(1)-Tyr(3)-octreotide (DOTATOC) positron emission tomography (PET)-computed tomography (CT) in liver metastases of patients with neuroendocrine tumors (NETs) prior to peptide receptor radiation therapy (PRRT) and compare the initial tumor uptake with the final treatment outcome.SSTR2 expression of the 60 liver metastases in 30 NET patients was assessed at baseline and after PRRT by measuring SUVmax, tumor to spleen ratio (T/S ratio), and tumor to liver ratio (T/L ratio). Based on morphological changes and tumor size measured at baseline and follow-up contrast-enhanced CT (after three cycles of PRRT), lesions were divided into two groups by the following: (i) responding (n = 40) and (ii) non-responding (n = 20).Statistically significant differences were observed in the mean SUVmax for non-responding vs. responding lesions at baseline (18.00 ± 3.59 vs. 33.55 ± 4.62, p 0.05) and for the mean T/S ratio (1.20 ± 0.37 vs. 1.90 ± 0.45, p 0.05) and the mean T/L ratio (3.15 ± 0.53 vs. 4.97 ± 0.62, p 0.05). Using the receiver operating characteristic curves, SUVmax was found a better metric than both T/L ratio and T/S ratio (area under the curve (AUC) of SUVmax 0.87; T/L ratio 0.78; T/S ratio 0.73) as a stratification criterion. Using a threshold value of16.4 for SUVmax, the sensitivity and specificity in predicting responding lesions were 95 and 60 %, respectively.We propose a SUVmax cutoff of16.4 from [(68)Ga]DOTATOC-PET-CT to select patients for PRRT. A T/L ratio2.2 might present a scanner-independent criterion that enables the translation of our results to other institutions. However, the robustness of this arbitrary unit still needs to be evaluated with different PET scanners.

Purpose Positron emission tomography (PET) with choline tracers has found widespread use for the diagnosis of prostate cancer (PC). However, choline metabolism is not increased in a considerable number of cases, whereas prostate-specific membrane antigen (PSMA) is overexpressed in most PCs. Therefore, a 68Ga-labelled PSMA ligand could be superior to choline tracers by obtaining a high contrast. The aim of this study was to compare such a novel tracer with standard choline-based PET/CT. Methods Thirty-seven patients with biochemical relapse of PC [mean prostate-specific antigen (PSA) 11.1 ± 24.1 ng/ml, range 0.01–116] were retrospectively analysed after 18F-fluoromethylcholine and 68Ga-PSMA PET/CT within a time window of 30 days. Radiotracer uptake that was visually considered as PC was semi-quantitatively analysed by measuring the maximum standardized uptake values (SUVmax) of the scans acquired 1 h after injection of 68Ga-PSMA complex solution (median 132 MBq, range 59–263 MBq) and 18F-fluoromethylcholine (median 237 MBq, range 114–374 MBq), respectively. In addition, tumour to background ratios were calculated. Results A total of 78 lesions characteristic for PC were detected in 32 patients using 68Ga-PSMA PET/CT and 56 lesions were detected in 26 patients using choline PET/CT. The higher detection rate in 68Ga-PSMA PET/CT was statistically significant (p = 0.04). In five patients no lesion was found with both methods. All lesions detected by 18F-fluoromethylcholine PET/CT were also seen by 68Ga-PSMA PET/CT. In 68Ga-PSMA PET/CT SUVmax was clearly (>10 %) higher in 62 of 78 lesions (79.1 %) and the tumour to background ratio was clearly (>10 %) higher in 74 of 78 lesions (94.9 %) when compared to 18F-fluoromethylcholine PET/CT. Conclusion 68Ga-PSMA PET/CT can detect lesions characteristic for PC with improved contrast when compared to standard 18F-fluoromethylcholine PET/CT, especially at low PSA levels. Electronic supplementary material The online version of this article (doi:10.1007/s00259-013-2525-5) contains supplementary material, which is available to authorized users.

Das Ziel besteht in der Verbesserung der Detektion und Staging des Prostatakarzinoms mittels innovativer Bildgebungstechnik wie PET/MRT. Die Modalitat der Wahl zur Detektion des Prostatakarzinoms ist die multiparametrische MRT. Des Weiteren wird die PET/CT insbesondere zum Staging und zur Detektion von Fernmetastasten/Rezidivdiagnostik eingesetzt. Zur Darstellung von Knochenmetastasen ist das am haufigsten eingesetzte Verfahren die Szintigraphie. Die Entwicklung einer simultanen, hybriden PET/MRT stellt die letzte grose „Vereinigung“ der bekannten Schnittbildmodalitaten dar. Zusatzlich ermoglicht die Synthese von neuen innovativen Tracern wie 18F-FACBC und 68Ga-PSMA (PSMA prostataspezifisches Membranantigen) spezifischere Detektion des Prostatakarzinoms. Die hybride PET/MRT-Bildgebung hat das Potenzial, in der Zukunft konventionelle Techniken abzulosen. Das Verfahren steht erst am Anfang der breiten Anwendung. Die Studienlage muss ausgebaut werden, um den zusatzlichen Nutzen zu belegen. Aktuell besteht noch eine geringe Verbreitungslage, da es sich um ein neues und kostenintensives Verfahren handelt. Zugleich existiert noch keine einheitliche Losung des Kostenersatzes durch die Kassen. Die Bedeutung fur die Praxis steigt erst mit Klarung der Vergutungssituation und Beleg des Nutzens durch grosere Studien.

Purpose Prostate-specific membrane antigen (PSMA) is a cell surface protein with high expression in prostate carcinoma (PC) cells. Recently, procedures have been developed to label PSMA ligands with 68Ga, 99mTc and 123/124/131I. Our initial experience with Glu-NH-CO-NH-Lys-(Ahx)-[68Ga(HBED-CC)](68Ga-PSMA) suggests that this novel tracer can detect PC relapses and metastases with high contrast. The aim of this study was to investigate its biodistribution in normal tissues and tumour lesions.

PET imaging with somatostatin receptor ligands, such as 68Ga-DOTATOC, is a well-established method for detection and target volume definition of meningiomas prior to radiotherapy. Since DOTATOC PET delivers a higher contrast between meningiomas and surrounding tissues than MRI, we conducted a retrospective analysis to compare the diagnostic accuracy of contrast-enhanced MRI (CE-MRI) with 68Ga-DOTATOC PET/CT in patients with cranial meningiomas prior to radiotherapy. Over a period of 6 years, 134 patients (20–82 years of age, 107 women and 27 men) underwent cranial CE-MRI and 68Ga-DOTATOC PET/CT. To compare the two methods, the lesions considered typical of meningiomas visually were counted and analysed with respect to their location and SUVmax. In the 134 patients investigated by both modalities, 190 meningiomas were detected by 68Ga-DOTATOC PET/CT and 171 by CE-MRI. With knowledge of the PET/CT data, the MRI scans were reinvestigated, which led to the detection of 4 of the 19 incidental meningiomas, resulting in an overall detection rate of 92 % of the meningioma lesions that were found by PET/CT. Ga-DOTATOC PET/CT demonstrated an improved sensitivity in meningioma detection when compared to CE-MRI. Tumours adjacent to the falx cerebri, located at the skull base or obscured by imaging artefacts or calcification are particularly difficult to detect by MRI. Therefore 68Ga-DOTATOC PET/CT may provide additional information in patients with uncertain or equivocal results on MRI or could help to confirm a diagnosis of meningioma based on MRI or could help to confirm MRI-based diagnosis of meningiomas in cases of biopsy limitations. It is possible that not only radiotherapy and surgical planning, but also follow-up strategies would benefit from this imaging modality.

Klinisches/methodisches Problem Konventionelle Methoden des Stagings, Therapiemonitorings und -Kontrolle bei Lymphomerkrankungen basieren auf morphologische Veranderungen, in der Regel dem Lasionsdurchmesser. Hierbei ist jedoch eine Vitalitat des Tumors in diesen Herden nicht evaluierbar.

Prostate-specific membrane antigen (PSMA) is a cell surface protein, which is expressed at higher levels in prostate cancer compared to other tissues. This protein provides a promising target for specific imaging and therapy due to its transmembrane location and internalization after ligand binding [1]. PSMA is also expressed in the neovasculature of many solid tumours [2, 3]. Recently procedures have been developed to label PSMA with Ga and I for positron emission tomography (PET) imaging [4, 5]. We present for the first time PET/CT images obtained with Ga-labelled HBED-CC conjugate of the PSMA-specific pharmacophore Glu-NH-CO-NH-Lys (Ga-PSMA). The images were compared with [F]FECH PET/CT of the same patient. The 67-year-old patient had undergone previous radiotherapy of the prostate due to carcinoma and had received androgen therapy since 2002. The patient presented with a continuous increase of PSA values (from 1 ng/ml in 2002 to 7.4 ng/ml in May 2011) and was referred to our department for further analysis using PET/CT. F-FECH PET/CT was unable to detect any lesions. However, Ga-PSMA PET/CT did show a lesion adjacent to the urinary bladder compatible with tumour relapse (figure). Our initial experience with Ga-PSMA PET/CT strongly suggests that this novel method can detect prostate carcinoma relapses and metastases with significantly improved contrast compared to F-FECH PET/CT. Further clinical studies should confirm this observation and determine if PSMA PET/CT can replace F-FECH PET/CT in the diagnosis of prostate carcinoma.