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(68)Ga-citrate has one of the simplest chemical structures of all (68)Ga-radiopharmaceuticals, and its clinical use is justified by the proven medical applications using its isotope-labeled compound (67)Ga-citrate. To support broader application of (68)Ga-citrate in medical diagnosis, further research is needed to gain clinical data from healthy volunteers. In this work, we studied the biodistribution of (68)Ga-citrate and subsequent radiation exposure from it in healthy men. Methods: (68)Ga-citrate was prepared with an acetone-based radiolabeling procedure compliant with good manufacturing practices. Six healthy men (age 41 ± 12 y, mean ± SD) underwent sequential whole-body PET/CT scans after an injection of 204 ± 8 MBq of (68)Ga-citrate. Serial arterialized venous blood samples were collected during PET imaging, and the radioactivity concentration was measured with a γ-counter. Urinary voids were collected and measured. The MIRD bladder-voiding model with a 3.5-h voiding interval was used. A model using a 70-kg adult man and the MIRD schema was used to estimate absorbed doses in target organs and effective doses. Calculations were performed using OLINDA/EXM software, version 2.0. Results: Radioactivity clearance from the blood was slow, and relatively high radioactivity concentrations were observed over the whole of the 3-h measuring period. Although radioactivity excretion via urine was rather slow (biologic half-time, 69 ± 24 h), the highest decay-corrected concentrations in urinary bladder contents were measured at the 90- and 180-min time points. Moderate concentrations were also seen in kidneys, liver, and spleen. The source organs showing the largest residence times were muscle, liver, lung, and heart contents. The heart wall received the highest absorbed dose, 0.077 ± 0.008 mSv/MBq. The mean effective dose (International Commission on Radiological Protection publication 103) was 0.021 ± 0.001 mSv/MBq. Conclusion: PET imaging with (68)Ga-citrate is associated with modest radiation exposure. A 200-MBq injection of (68)Ga-citrate results in an effective radiation dose of 4.2 mSv, which is in the same range as other (68)Ga-labeled tracers. This suggests the feasibility of clinical studies using (68)Ga-citrate imaging in humans and the possibility of performing multiple scans in the same subjects across the course of a year.

Biologically created subvolumes enable non-uniform dose distributions in prostate cancer radiotherapy (RT) thus potentially improving therapeutic ratio and reducing toxicity. We present the long-term outcome of men receiving focal boosting of carbon-11 acetate (ACE) PET-CT metabolically active areas in prostate carcinoma. Thirty men with hormone na��ve localized prostate carcinoma underwent ACE PET/CT for RT planning. There were five low-, 17 intermediate-, and eight high-risk patients. Based on thresholding of the standardized uptake values (SUVs) metabolic target volumes (MTVs) corresponding to intraprostatic lesions (IPLs) were contoured. Two planning target volumes (PTVs) were applied i.e., PTVlow-risk for the whole prostate with 8���10 mm margin and PTVhigh-risk for the MTV. Pelvic nodes were not irradiated. Late toxicity of biologically guided RT was reviewed after a median of 63 months and outcome after a median follow-up of 124 months. Median doses to PTVlow-risk, PTVhigh-risk, prostate, and MTV were 72.9 Gy, 79.4 Gy, 76.6 Gy, and 80.4 Gy, respectively, in 38 fractions. The 10-year cancer-specific survival was 86% and the biochemical failure-free ratio 68%, respectively. The median biochemical progression-free survival (PFS) was 37, 108, and 119 months in the high, intermediate, and low-risk groups, respectively, the difference being significant between high and intermediate-risk groups (p = 0.02). One patient (3%) presented with locoregional and 5 (17%) with distant nodal metastases. Five patients (17%) had a biochemical relapse. A larger MTV was associated with shorter PFS (r = ���0.41, p = 0.02), but had no influence on OS. No other statistically significant differences in the dose painting parameters were observed between recurrence-free and recurring patients. Biological guidance for dose-escalated prostate RT is feasible with ACE PET/CT. Since a larger MTV may be associated with a higher risk for progression, we encourage further study of dose-escalation to ACE-positive lesions considering the low toxicity of our protocol.

Purpose To validate a synthetic computed tomography (sCT) software with continuous HUs and large field‐of‐view (FOV) coverage for magnetic resonance imaging (MRI)‐only workflow of general pelvis anatomy in radiotherapy (RT). Methods An sCT software for general pelvis anatomy (prostate, rectum, and female pelvis) has been developed by Philips Healthcare and includes continuous HUs assignment along with large FOV coverage. General pelvis sCTs were generated using a two‐stack T1‐weighted mDixon fast‐field echo (FFE) sequence with a superior‐inferior coverage of 36 cm. Seventy‐seven prostate, 43 rectum, and 27 gynecological cases were scanned by three different institutions. mDixon image quality and sCTs were evaluated for soft tissue contrast by using a confidence level scale from 1 to 5 for bladder, prostate/rectum interface, mesorectum, and fiducial maker visibility. Dosimetric comparison was performed by recalculating the RT plans on the sCT after rigid registration. For 12 randomly selected cases, the mean absolute error (MAE) between sCT and CT was calculated to evaluate HU similarity, and the Pearson correlation coefficients (PCC) between the CT‐ and sCT‐generated digitally reconstructed radiographs (DRRs) were obtained for quantitative comparison. To examine geometric accuracy of sCT as a reference for cone beam CT (CBCT), the difference between bone‐based alignment of CBCT to CT and CBCT to sCT was obtained for 19 online‐acquired CBCTs from three patients. Results Two‐stack mDixon scans with large FOV did not show any image inhomogeneity or fat‐water swap artifact. Fiducials, Foley catheter, and even rectal spacer were visible as dark signal on the sCT. Average visibility confidence level (average ± standard deviation) on the sCT was 5.0 ± 0.0, 4.6 ± 0.5, 3.8 ± 0.4, and 4.0 ± 1.1 for bladder, prostate/rectum interface, mesorectum and fiducial markers. Dosimetric accuracy showed on average

Highlights • Distribution of recurrent HNSCC in relation to radiotherapy volume was evaluated. • Both p16 positive and negative HNSCC recur in high-risk treatment volume. • This indicates potential failure of multimodality imaging to disclose significant disease. • A need for biomarkers other than p16 to predict radiosensitivity continues to exist., Background Locoregional recurrence remains a major cause of failure in head and neck squamous cell carcinoma (HNSCC). Human papilloma virus (HPV)-associated HNSCCs generally have a good prognosis but may recur even after standard photon radiotherapy (RT). Another incentive in observing patterns of recurrence is increased use of highly conformal techniques such as proton therapy. We therefore studied geographic distribution of recurrent tumors in relation to the high-risk treatment volume in a cohort of patients with HNSCC receiving combined modality therapy. Methods Medical records of 508 patients diagnosed with HNSCC in 2010–2015 were reviewed. We identified a subgroup that had local and/or regional recurrence at hybrid positron emission tomography (PET)/computed tomography (CT) and/or magnetic resonance imaging (MRI). We adapted p16 as a surrogate marker for HPV-positivity and only patients with known p16 status were eligible for a detailed analysis where recurrent tumor was copied on the planning CT and the dose received by the recurrent tumor volume was determined using dose-volume histograms. Results Twenty-five patients who had received either cisplatin (n = 23) or cetuximab-enhanced (n = 2) RT were identified. 31 locoregional recurrent tumors were detected among 18 p16 negative and 7 p16 positive patients. Of recurrent tumors 14 (45%) were classified as in-field, 5 (16%) as marginal miss, and 12 (39%) as true miss. p16 positive patients had 4 in-field, 2 marginal, and 1 true miss. By contrast, p16 negative patients had 10 in-field, 3 marginal, and 11 true miss recurrences. Conclusions Both p16 positive and negative HNSCC recur in high-risk treatment volume despite the common view of high radiosensitivity of the former. Biomarkers predicting radioresistance should be characterized in p16 positive tumors before widely embarking on de-escalated CRT protocols. Another concern is how to decrease the number of true or marginal misses in p16 negative cases despite multimodality imaging-based target delineation.

Sialic acid-binding immunoglubulin-like lectin 9 (Siglec-9) is a ligand of vascular adhesion protein 1 (VAP-1). A gallium 68-labeled peptide of Siglec-9, 68Ga-DOTA-Siglec-9, holds promise as a novel PET tracer for imaging of inflammation. This first-in-human study investigated the safety, tolerability, biodistribution, and radiation dosimetry of this radiopharmaceutical. Methods: Six healthy males underwent dynamic whole-body PET/CT. Serial venous blood samples were drawn from 1–240 min after intravenous injection of 162 ± 4 MBq of 68Ga-DOTA-Siglec-9. In addition to gamma counting, the plasma samples were analyzed by high-performance liquid chromatography to detect intact tracer and radioactive metabolites. Radiation doses were calculated using the OLINDA/EXM 2.2 software. In addition, a patient with early rheumatoid arthritis was studied with both 68Ga-DOTA-Siglec-9 and 18F-FDG PET/CT to determine the ability of the new tracer to detect arthritis. Results:68Ga-DOTA-Siglec-9 was well tolerated by all subjects. 68Ga-DOTA-Siglec-9 was rapidly cleared from blood circulation and several radioactive metabolites were detected. The organs with the highest absorbed doses were the urinary bladder wall (0.38 mSv/MBq) and kidneys (0.054 mSv/MBq). The mean effective dose was 0.022 mSv/MBq (range 0.020–0.024 mSv/MBq). Most importantly, however, 68Ga-DOTA-Siglec-9 was able to detect arthritis comparable to 18F-FDG. Conclusion: Intravenous injection of 68Ga-DOTA-Siglec-9 was safe and biodistribution is favorable for testing of the tracer in larger group of patients with rheumatoid arthritis planned in the next phase of clinical trials. The effective radiation dose of 68Ga-DOTA-Siglec-9 was within the same range as those of other 68Ga-labeled tracers. Injection of 150 MBq of 68Ga-DOTA-Siglec-9 would expose a subject to 3.3 mSv. These findings support the possible repeated clinical use of 68Ga-DOTA-Siglec-9, e.g., in trials aiming to elucidate the treatment efficacy of novel drug candidates.

Purpose Treatment planning for proton therapy requires the relative proton stopping power ratio (RSP) information of the patient for accurate dose calculations. RSP are conventionally obtained after mapping of the Hounsfield units (HU) from a calibrated patient computed tomography (CT). One or multiple CT are needed for a given treatment which represents additional, undesired dose to the patient. For prostate cancer, magnetic resonance imaging (MRI) scans are the gold standard for segmentation while offering dose-less imaging. We here quantify the clinical applicability of converted MR images as a substitute for intensity modulated proton therapy (IMPT) treatment of the prostate. Methods MRCAT (Magnetic Resonance for Calculating ATtenuation) is a Philips-developed technology which produces a synthetic CT image consisting of five HU from a specific set of MRI acquisitions. MRCAT and original planning CT data sets were obtained for ten patients. An IMPT plan was generated on the MRCAT for each patient. Plans were produced such that they fulfill the prostate protocol in use at Massachusetts General Hospital (MGH). The plans were then recomputed onto the nominal planning CT for each patient. Robustness analyses (±5 mm setup shifts and ±3.5 % range uncertainties) were also performed. Results Comparison of MRCAT plans and their recomputation onto the planning CT plan showed excellent agreement. Likewise, dose perturbations due to setup shifts and range uncertainties were well within clinical acceptance demonstrating the clinical viability of the approach. Conclusions This work demonstrate the clinical acceptability of substituting MR converted RSP images instead of CT for IMPT planning of prostate cancer. This further translates into higher contouring accuracy along with lesser imaging dose.

Hypoxia dose painting is a radiotherapy technique to increase the dose to hypoxic regions of the tumour. Still, the clinical effect relies on the reproducibility of the hypoxic region shown in the medical image.Eight HNC patients undergoing twoThe mean (SD) correlation coefficient between DPBN prescription and plan was 0.92 (0.02) and 0.93 (0.02) for sessions A and B, respectively, with corresponding quality factors of 0.02 (0.002) and 0.02 (0.003), respectively. The mean correlation between dose prescriptions at day A and B was 0.72 (0.13), and 0.77 (0.12) for the corresponding plans. A mean correlation of 0.80 (0.08) was found between plan A, recalculated on image basis B, and plan B.Hypoxia DPBN planning based on

Visual Abstract, Sialic acid–binding immunoglubulinlike lectin 9 (Siglec-9) is a ligand of vascular adhesion protein 1. A 68Ga-labeled peptide of Siglec-9, 68Ga-DOTA-Siglec-9, holds promise as a novel PET tracer for imaging of inflammation. This first-in-humans study investigated the safety, tolerability, biodistribution, and radiation dosimetry of this radiopharmaceutical. Methods: Six healthy men underwent dynamic whole-body PET/CT. Serial venous blood samples were drawn from 1 to 240 min after intravenous injection of 162 ± 4 MBq of 68Ga-DOTA-Siglec-9. In addition to γ-counting, the plasma samples were analyzed by high-performance liquid chromatography to detect intact tracer and radioactive metabolites. Radiation doses were calculated using the OLINDA/EXM software, version 2.2. In addition, a patient with early rheumatoid arthritis was studied with both 68Ga-DOTA-Siglec-9 and 18F-FDG PET/CT to determine the ability of the new tracer to detect arthritis. Results: 68Ga-DOTA-Siglec-9 was well tolerated by all subjects. 68Ga-DOTA-Siglec-9 was rapidly cleared from the blood circulation, and several radioactive metabolites were detected. The organs with the highest absorbed doses were the urinary bladder wall (0.38 mSv/MBq) and kidneys (0.054 mSv/MBq). The mean effective dose was 0.022 mSv/MBq (range, 0.020–0.024 mSv/MBq). Most importantly, however, 68Ga-DOTA-Siglec-9 was comparable to 18F-FDG in detecting arthritis. Conclusion: Intravenous injection of 68Ga-DOTA-Siglec-9 was safe and biodistribution was favorable for testing of the tracer in larger group of patients with rheumatoid arthritis, as is planned for the next phase of clinical trials. The effective radiation dose of 68Ga-DOTA-Siglec-9 was within the same range as the effective radiation doses of other 68Ga-labeled tracers. Injection of 150 MBq of 68Ga-DOTA-Siglec-9 would expose a subject to 3.3 mSv. These findings support the possible repeated clinical use of 68Ga-DOTA-Siglec-9, such as in trials to elucidate the treatment efficacy of novel drug candidates.

Hypoxia contributes to radiotherapy resistance and more aggressive behaviour of several types of cancer. This study was designed to evaluate the repeatability of intratumour uptake of the hypoxia tracer [18F]EF5 in paired PET/CT scans. Ten patients with newly diagnosed head and neck cancer (HNC) received three static PET/CT scans before chemoradiotherapy: two with [18F]EF5 a median of 7 days apart and one with [18F]FDG. Metabolically active primary tumour volumes were defined in [18F]FDG images and transferred to co-registered [18F]EF5 images for repeatability analysis. A tumour-to-muscle uptake ratio (TMR) of 1.5 at 3 h from injection of [18F]EF5 was used as a threshold representing hypoxic tissue. In 10 paired [18F]EF5 PET/CT image sets, SUVmean, SUVmax, and TMR showed a good correlation with the intraclass correlation coefficients of 0.81, 0.85, and 0.87, respectively. The relative coefficients of repeatability for these parameters were 15%, 17%, and 10%, respectively. Fractional hypoxic volumes of the tumours in the repeated scans had a high correlation using the Spearman rank correlation test (r = 0.94). In a voxel-by-voxel TMR analysis between the repeated scans, the mean of Pearson correlation coefficients of individual patients was 0.65. The mean (± SD) difference of TMR in the pooled data set was 0.03 ± 0.20. Pretreatment [18F]EF5 PET/CT within one week shows high repeatability and is feasible for the guiding of hypoxia-targeted treatment interventions in HNC.

Using magnetic resonance imaging (MRI) as the only imaging method for radiotherapy treatment planning (RTP) is becoming more common as MRI-only RTP solutions have evolved. The geometric accuracy of MR images is an essential factor of image quality when determining the suitability of MRI for RTP. The need is therefore clear for clinically feasible quality assurance (QA) methods for the geometric accuracy measurement.This work evaluates long-term stability of geometric accuracy and the validity of a 2D geometric accuracy QA method compared to a prototype 3D method and analysis software in routine QA. The long-term follow-up measurements were conducted on one of the 1.5 T scanners over a period of 19 months using both methods. Inter-scanner variability of geometric distortions was also evaluated in three 1.5 T and three 3 T MRI scanners from a single vendor by using the prototype 3D QA method.The geometric accuracy of the magnetic resonance for radiotherapy (MR-RT) platform remained stable within 2 mm at distances of250 mm from isocenter. All scanners achieved good geometric accuracy with mean geometric distortions of1 mm at150 mm and2 mm at250 mm from the isocenter. Both measurement methods provided relevant information about geometric distortions.Geometric distortions are often considered a limitation of MRI-only RTP. Results indicate that geometric accuracy of modern scanners remain within acceptable limits by default even after many years of clinical use based on the 3D QA evaluation.

Hypoxia contributes to radiotherapy resistance and more aggressive behaviour of several types of cancer. This study was designed to evaluate the repeatability of intratumour uptake of the hypoxia tracer [Ten patients with newly diagnosed head and neck cancer (HNC) received three static PET/CT scans before chemoradiotherapy: two with [In 10 paired [Pretreatment [

Purpose: The aim of this study was to compare dosimetric characteristics, monitor unit, and delivery efficiency of 4 different stereotactic body radiotherapy techniques for the treatment of prostate cancer. Methods: This study included 8 patients with localized prostate cancer. Dosimetric assets of 4 delivery techniques for stereotactic body radiotherapy were evaluated: robotic CyberKnife, noncoplanar intensity-modulated radiotherapy, and 2 intensity-modulated arc therapy techniques (RapidArc and Elekta volumetric-modulated arc therapy). All the plans had equal treatment margins and a prescription dose of 35 Gy in 5 fractions. Results: Statistically significant differences were observed in homogeneity index and mean doses of bladder wall and penile bulb, all of which were highest with CyberKnife. No significant differences were observed in the mean doses of rectum, with values of 15.2 ± 2.6, 13.3 ± 2.6, 13.1 ± 2.8, and 13.8 ± 1.6 Gy with CyberKnife, RapidArc, volumetric-modulated arc therapy, and noncoplanar intensity-modulated radiotherapy, respectively. The highest dose conformity was realized with RapidArc. The dose coverage of the planning target volume was lowest with noncoplanar intensity-modulated radiotherapy. Treatment times and number of monitor units were largest with CyberKnife (on average 34.0 ± 5.0 minutes and 8704 ± 1449 monitor units) and least with intensity-modulated arc therapy techniques (on average 5.1 ± 1.1 minutes and 2270 ± 497 monitor units). Conclusion: Compared to CyberKnife, the RapidArc, volumetric-modulated arc therapy, and noncoplanar intensity-modulated radiotherapy produced treatment plans with similar dosimetric quality, with RapidArc achieving the highest dose conformity. Overall, the dosimetric differences between the studied techniques were marginal, and thus, the choice of the technique should rather focus on the delivery accuracies and dose delivery times.

Background. In postmastectomy radiotherapy (PMRT), the dose coverage of the planning target volume (PTV) with additional margins, including the chest wall, supraclavicular, interpectoral, internal mammary and axillar level I–III lymph nodes, is often compromised. Electron fields may improve the medial dose coverage while maintaining organ at risk (OAR) doses at an acceptable level, but at the cost of hot and cold spots at the electron and photon field junction. To improve PMRT dose coverage and uniformity, an isocentric technique combining tangential intensity-modulated (IM)RT fields with one medial electron field was implemented.Material and methods. For 10 postmastectomy patients isocentric IMRT with electron plans were created and compared with a standard electron/photon mix and a standard tangent technique. PTV dose uniformity was evaluated based on the tolerance range (TR), i.e. the ratio of the standard deviation to the mean dose, a dice similarity coefficient (DSC) and the 90% isodose coverage and the hot spot volumes. OAR and contralateral breast doses were also recorded.Results. IMRT with electrons significantly improved the PTV dose homogeneity and conformity based on the TR and DSC values when compared with the standard electron/photon and tangent technique (p < 0.02). The 90% isodose coverage improved to 86% compared with 82% and 80% for the standard techniques (p < 0.02). Compared with the standard electron/photon mix, IMRT smoothed the dose gradient in the electron and photon field junction and the volumes receiving a dose of 110% or more were reduced by a third. For all three strategies, the OAR and contralateral breast doses were within clinically tolerable limits.Conclusion. Based on these results two-field IMRT combined with an electron field is a suitable strategy for PMRT.

Purpose 11C-labelled 1-[(S)-1-(2,3-dihydrobenzo[1,2]dioxin-2-yl)methyl]-4-(3-methoxy-methylpyridin-2-yl)-piperazine (11C-ORM-13070) is a novel PET tracer for imaging of α2C-adrenoceptors in the human brain. Brain α2C-adrenoceptors may be therapeutic targets in several neuropsychiatric disorders, including depression, schizophrenia and Alzheimer’s disease. To validate the use of 11C-ORM-13070 in humans, we investigated its radiometabolism, pharmacokinetics, whole-body distribution and radiation dose.

Vascular adhesion protein-1 (VAP-1) is an endothelial glycoprotein mediating leukocyte trafficking from blood to sites of inflammation. BTT-1023 is a fully human monoclonal anti-VAP-1 antibody developed to treat inflammatory diseases. In this study, we preclinically evaluated radioiodinated BTT-1023 for inflammation imaging. Methods: Rabbits were intravenously injected with radioiodinated BTT-1023. Distribution and pharmacokinetics were assessed by PET/CT up to 72 h after injection. Human radiation dose estimates for 124I-BTT-1023 were extrapolated. Additionally, rabbits with chemically induced synovitis were imaged with 123I-BTT-1023 SPECT/CT. Results: Radioiodinated BTT-1023 cleared rapidly from blood circulation and distributed to liver and thyroid. Inflamed joints were delineated by SPECT/CT. The estimated human effective dose due to 124I-BTT-1023 was 0.55 mSv/MBq, if blockage of thyroid uptake is assumed. Conclusion: The radioiodinated BTT-1023 was able to detect mild inflammation in vivo. Clinical 124I-BTT-1023 PET studies with injected radioactivity of 0.5–0.7 MBq/kg may be justified.

Background: The clinical feasibility of using pseudo-computed tomography (pCT) images derived from magnetic resonance (MR) images for external bean radiation therapy (EBRT) planning for prostate cancer patients has been well demonstrated. This paper investigates the feasibility of applying an MR-derived, pCT planning approach to additional types of cancer in the pelvis. Material and methods: Fifteen patients (five prostate cancer patients, five rectal cancer patients, and five gynecological cancer patients) receiving EBRT at Turku University Hospital (Turku, Finland) were included in the study. Images from an MRCAT (Magnetic Resonance for Calculating ATtenuation, Philips, Vantaa, Finland) pCT method were generated as a part of a clinical MR-simulation procedure. Dose calculation accuracy was assessed by comparing the pCT-based calculation with a CT-based calculation. In addition, the degree of geometric accuracy was studied. Results: The median relative difference of PTV mean dose between CT and pCT images was within 0.8% for all tumor types. When assessing the tumor site-specific accuracy, the median [range] relative dose differences to the PTV mean were 0.7 [−0.11;1.05]% for the prostate cases, 0.3 [−0.25;0.57]% for the rectal cases, and 0.09 [−0.69;0.25]% for the gynecological cancer cases. System-induced geometric distortion was measured to be less than 1 mm for all PTV volumes and the effect on the PTV median dose was less than 0.1%. Conclusions: According to the comparison, using pCT for clinical EBRT planning and dose calculation in the three investigated types of pelvic cancers is feasible. Further studies are required to demonstrate the applicability to a larger cohort of patients.

Carbon-11 labeled N-butan-2-yl-1-(2-chlorophenyl)-N-methylisoquinoline-3-carboxamide ([11C]PK11195) is a peripheral benzodiazepine receptor (PBR) antagonist that is used as a positron emission tomography (PET) radiopharmaceutical for neuroinflammatory imaging. This study was designed to investigate the radiation dosimetry of [11C]PK11195.Whole-body distribution kinetics of intravenously administered [11C]PK11195 in rats was assessed by means of dynamic PET imaging, and estimates for human radiation dosimetry were calculated. Rat plasma and various tissue homogenates obtained at different time points after intravenous injection of [11C]PK11195 were analyzed by reversed-phase gradient radio-HPLC method using online radiodetection. In addition, in vitro stability of [11C]PK11195 was determined in rat brain homogenate by incubation at +37 degrees C.PET imaging of rats showed the highest radioactivity levels in heart, kidneys, thyroid gland, liver, and lungs. The radioactivity cleared rapidly from lungs and slowly from heart and liver. However, much of the radioactivity retained in kidneys, which was in concordance with the observed low urinary excretion of [11C]PK11195. Extrapolating from the rat data, the effective dose of [11C]PK11195 for a 70-kg man was estimated to be 4.2 +/- 0.3 microSv/MBq. Five different radiometabolites were detected in rat plasma, and the level of intact [11C]PK11195 decreased from 80% +/- 11% (mean +/- SD) at 10 min to 44% +/- 5% at 40 min after injection. In rat heart, brain, kidney, and lung homogenates, more than 90% of total radioactivity originated from intact [11C]PK11195. In liver, however, the amount of [11C]PK11195 was approximately 70% and decreased over time, indicating metabolism by liver enzymes.[11C]PK11195 showed a fast uptake in many rat tissues and it was metabolized relatively fast in vivo, but not in brain in vitro. The estimated effective dose for humans speaks for the use of [11C]PK11195 in human PET imaging.

Delineation of gross tumour volume in 3D is a critical step in the radiotherapy (RT) treatment planning for oropharyngeal cancer (OPC). Static [Five patients with OPC underwent dynamic [Some dynamic features showed a trend towards discrimination of different metabolic areas but lack of consistency means that clinical application is not recommended based on these results alone.Impact of inflammatory tissue remains a problem for volume delineation in RT of OPC, but a simple dynamic imaging protocol proved practicable and enabled simple data analysis techniques that show promise for complementing the information in static uptake values.

(11)C-labelled 1-[(S)-1-(2,3-dihydrobenzo[1,2]dioxin-2-yl)methyl]-4-(3-methoxy-methylpyridin-2-yl)-piperazine ((11)C-ORM-13070) is a novel PET tracer for imaging of α2C-adrenoceptors in the human brain. Brain α2C-adrenoceptors may be therapeutic targets in several neuropsychiatric disorders, including depression, schizophrenia and Alzheimer's disease. To validate the use of (11)C-ORM-13070 in humans, we investigated its radiometabolism, pharmacokinetics, whole-body distribution and radiation dose.Radiometabolism was studied in a test-retest setting in six healthy men. After intravenous injection of (11)C-ORM-13070, blood samples were drawn over 60 min. Plasma samples were analysed by radio-HPLC for intact tracer and its radioactive metabolites. Metabolite-corrected plasma time-activity curves were used for calculation of pharmacokinetics. In a separate group of 12 healthy men, the whole-body distribution of (11)C-ORM-13070 and radiation exposure were investigated by dynamic PET/CT imaging without blood sampling.Two radioactive metabolites of (11)C-ORM-13070 were detected in human arterial plasma. The proportion of unchanged (11)C-ORM-13070 decreased from 81 ± 4 % of total radioactivity at 4 min after tracer injection to 23 ± 4 % at 60 min. At least one of the radioactive metabolites penetrated into red blood cells, while the parent tracer remained in plasma. The apparent elimination rate constant and corresponding half-life of unchanged (11)C-ORM-13070 in arterial plasma were 0.0117 ± 0.0056 min(-1) and 73.6 ± 35.8 min, respectively. The organs with the highest absorbed doses were the liver (12 μSv/MBq), gallbladder wall (12 μSv/MBq) and pancreas (9.1 μSv/MBq). The mean effective dose was 3.9 μSv/MBq, with a range of 3.6 - 4.2 μSv/MBq.(11)C-ORM-13070 was rapidly metabolized in human subjects after intravenous injection. The effective radiation dose of (11)C-ORM-13070 was in the same range as that of other (11)C-labelled brain receptor tracers. An injection of 500 MBq of (11)C-ORM-13070 would expose a subject to 2.0 mSv of radiation. This supports the use of (11)C-ORM-13070 in repeated PET scans, for example, in receptor occupancy trials with novel drug candidates.

This first-in-human study investigated the safety, tolerability, metabolism, pharmacokinetics, biodistribution, and radiation dosimetry of 68Ga-bombesin antagonist 68Ga-DOTA-4-amino-1-carboxymethylpiperidine-d-Phe-Gln-Trp-Ala-Val-Gly-His-Sta-Leu-NH2 (BAY 86-7548). Methods: Five healthy men underwent dynamic whole-body PET/CT after an intravenous injection of BAY 86-7548 (138 ± 5 MBq). Besides total radioactivity, plasma samples were analyzed by radio–high-performance liquid chromatography for metabolism of the tracer. Dosimetry was calculated using the OLINDA/EXM software. Results: Three radioactive plasma metabolites were detected. The proportion of unchanged BAY 86-7548 decreased from 92% ± 9% at 1 min after injection to 19% ± 2% at 65 min. The organs with the highest absorbed doses were the urinary bladder wall (0.62 mSv/MBq) and the pancreas (0.51 mSv/MBq). The mean effective dose was 0.051 mSv/MBq. BAY 86-7548 was well tolerated by all subjects. Conclusion: Intravenously injected BAY 86-7548 is safe, and rapid metabolism is demonstrated. A 150-MBq injection of BAY 86-7548 results in an effective dose of 7.7 mSv, which could be reduced to 5.7 mSv with frequent bladder voids.

Background and purpose Stereotactic lung radiotherapy (SLRT) has emerged as a curative treatment for medically inoperable patients with early-stage non-small cell lung cancer (NSCLC) and the use of intensity-modulated radiotherapy (IMRT) and volumetric modulated arc treatments (VMAT) have been proposed as the best practical approaches for the delivery of SLRT. However, a large number of narrow field shapes are needed in the dose delivery of intensity-modulated techniques and the probability of underdosing the tumour periphery increases as the effective field size is decreased. The purpose of this study was to evaluate small lung tumour doses irradiated by intensity-modulated techniques to understand the risk for dose calculation errors in precision radiotherapy such as SLRT. Materials and methods The study was executed with two heterogeneous phantoms with targets of Ø1.5 and Ø4.0 cm. Dose distributions in the simulated tumours delivered by small sliding window apertures (SWAs), IMRT and RapidArc treatment plans were measured with radiochromic film. Calculation algorithms of pencil beam convolution (PBC) and anisotropic analytic algorithm (AAA) were used to calculate the corresponding dose distributions. Results Peripheral doses of the tumours were decreased as SWA decreased, which was not modelled by the calculation algorithms. The smallest SWA studied was 2 mm, which reduced the 90% isodose line width by 4.2 mm with the Ø4.0 cm tumour as compared to open field irradiation. PBC was not able to predict the dose accurately as the gamma evaluation failed to meet the criteria of ±3%/±1 mm on average in 61% of the defined volume with the smaller tumour. With AAA the corresponding value was 16%. The dosimetric inaccuracy of AAA was within ±3% with the optimized treatment plans of IMRT and RapidArc. The exception was the clinical RapidArc plan with dose overestimation of 4%. Conclusions Overall, the peripheral doses of the simulated lung tumours were decreased by decreasing the SWA. To achieve adequate surface dose coverage to small lung tumours with a difference less than 1 mm in the isodose line radius between the open and modulated field, a larger than 6 mm SWA should be used in the dose delivery of SLRT.

Background High-grade gliomas (HGGs) express somatostatin receptors (SSTR), rendering them candidates for peptide receptor radionuclide therapy (PRRT). Our purpose was to evaluate the potential of 68Ga-DOTA-1-Nal3-octreotide (68Ga-DOTANOC) or 68Ga-DOTA-Tyr3-octreotide (68Ga-DOTATOC) to target SSTR subtype 2 (SSTR2) in HGGs, and to study the association between SSTR2 expression and established biomarkers. Methods Twenty-seven patients (mean age 52 years) with primary or recurrent HGG prospectively underwent 68Ga-DOTA-peptide positron emission tomography/computed tomography (PET/CT) before resection. Maximum standardized uptake values (SUVmax) and receptor binding potential (BP) were calculated on PET/CT and disruption of blood–brain barrier (BBB) from contrast-enhanced T1-weighted magnetic resonance imaging (MRI-T1-Gad). Tumor volume concordance between PET and MRI-T1-Gad was assessed by Dice similarity coefficient (DC) and correlation by Spearman’s rank. Immunohistochemically determined SSTR2 status was compared to receptor imaging findings, prognostic biomarkers, and survival with Kruskal-Wallis, Pearson chi-square, and multivariate Cox regression, respectively. Results All 19 HGGs with disrupted BBB demonstrated tracer uptake. Tumor SUVmax (2.25 ± 1.33) correlated with MRI-T1-Gad (r = 0.713, P = 0.001) although DC 0.41 ± 0.19 suggested limited concordance. SSTR2 immunohistochemistry was regarded as positive in nine HGGs (32%) but no correlation with SUVmax or BP was found. By contrast, SSTR2 expression was associated with IDH1 mutation (P = 0.007), oligodendroglioma component (P = 0.010), lower grade (P = 0.005), absence of EGFR amplification (P = 0.021), and longer progression-free survival (HR 0.161, CI 0.037 to 0.704, P = 0.015). Conclusions In HGGs, uptake of 68Ga-DOTA-peptides is associated with disrupted BBB and cannot be predicted by SSTR2 immunohistochemistry. Thus, PET/CT shows limited value to detect HGGs suitable for PRRT. However, high SSTR2 expression portends favorable outcome along with established biomarkers such as IDH1 mutation. Trial registration ClinicalTrials.gov NCT01460706