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Purpose
In cancer of unknown primary (CUP), positron emission tomography/computed tomography (PET/CT) with the glucose analog [\(^{18}\)F]FDG represents the standard imaging approach for localization of the malignant primary. Frequently, however, [\(^{18}\)F]FDG PET/CT cannot precisely distinguish between small occult tumors and chronic inflammation, especially in Waldeyer’s tonsillar ring. To improve the accuracy for detecting primary tumors in the Waldeyer’s tonsillar ring, the novel PET tracer [\(^{68}\)Ga]Ga-FAPI-4 for specific imaging of fibroblast activation protein (FAP) expression was used as a more specific target for cancer imaging.
Methods
Eight patients with suspicion of a malignant tumor in Waldeyer’s tonsillar ring or a CUP syndrome were examined. PET/CT scans with [\(^{18}\)F]-FDG and [\(^{68}\)Ga]Ga-FAPI-4 were performed for pre-operative tumor localization. After surgical resection, histopathological and immunohistochemical results were compared to PET/CT findings.
Results
Histopathology revealed a palatine or lingual tonsil carcinoma in all patients. In case of lymph node metastases smaller than 7 mm in size, the [\(^{18}\)F]FDG PET/CT detection rate of cervical lymph node metastases was higher than that of [\(^{68}\)Ga]FAPI PET/CT, while both tracers identified the primary tumors in all eight cases. The size of the primary and the lymph node metastases was directly correlated to the respective FAP expression, as detected by immunohistochemistry. The mean SUVmax for the primary tumors was 21.29 ± 7.97 for \(^{18}\)F-FDG and 16.06 ± 6.29 for \(^{68}\)Ga-FAPI, respectively (p = 0.2). The mean SUVmax for the healthy contralateral tonsils was 8.38 ± 2.45 for [\(^{18}\)F]FDG and 3.55 ± 0.47 for [\(^{68}\)Ga]FAPI (p < 0.001). The SUVmax ratio of [68Ga]FAPI was significantly different from [\(^{18}\)F] FDG (p = 0.03). Mean TBRmax for the [\(^{68}\)Ga]Ga-FAPI-4 tracer was markedly higher in comparison to [\(^{18}\)F]FDG (10.90 vs. 4.11).
Conclusion
Non-invasive imaging of FAP expression by [\(^{68}\)Ga]FAPI PET/CT resulted in a better visual detection of the malignant primary in CUP, as compared to [\(^{18}\)F]FDG imaging. However, the detection rate of lymph node metastases was inferior, presumably due to low FAP expression in small metastases. Nevertheless, by offering a detection method for primary tumors with the potential of lower false positive rates and thus avoiding biopsies, patients with CUP syndrome may benefit from [\(^{68}\)Ga]FAPI PET/CT imaging.
Background
CXCR4-directed positron emission tomography/computed tomography (PET/CT) has been used as a diagnostic tool in patients with solid tumors. We aimed to determine a potential correlation between tumor burden and radiotracer accumulation in normal organs.
Methods
Ninety patients with histologically proven solid cancers underwent CXCR4-targeted [\(^{68}\)Ga]Ga-PentixaFor PET/CT. Volumes of interest (VOIs) were placed in normal organs (heart, liver, spleen, bone marrow, and kidneys) and tumor lesions. Mean standardized uptake values (SUV\(_{mean}\)) for normal organs were determined. For CXCR4-positive tumor burden, maximum SUV (SUV\(_{max}\)), tumor volume (TV), and fractional tumor activity (FTA, defined as SUV\(_{mean}\) x TV), were calculated. We used a Spearman's rank correlation coefficient (ρ) to derive correlative indices between normal organ uptake and tumor burden.
Results
Median SUV\(_{mean}\) in unaffected organs was 5.2 for the spleen (range, 2.44 – 10.55), 3.27 for the kidneys (range, 1.52 – 17.4), followed by bone marrow (1.76, range, 0.84 – 3.98), heart (1.66, range, 0.88 – 2.89), and liver (1.28, range, 0.73 – 2.45). No significant correlation between SUV\(_{max}\) in tumor lesions (ρ ≤ 0.189, P ≥ 0.07), TV (ρ ≥ -0.204, P ≥ 0.06) or FTA (ρ ≥ -0.142, P ≥ 0.18) with the investigated organs was found.
Conclusions
In patients with solid tumors imaged with [\(^{68}\)Ga]Ga-PentixaFor PET/CT, no relevant tumor sink effect was noted. This observation may be of relevance for therapies with radioactive and non-radioactive CXCR4-directed drugs, as with increasing tumor burden, the dose to normal organs may remain unchanged.
Background:
Renal scans are among the most frequent exams performed on infants and toddlers. Due to the young age, this patient group can be classified as a high-risk group with a higher probability for developing stochastic radiation effects compared to adults. As there are only limited data on biokinetics and dosimetry in this patient group, the aim of this study was to reassess the dosimetry and the associated radiation risk for infants undergoing \(^{99m}\)Tc-MAG3 renal scans based on a retrospective analysis of existing patient data. Consecutive data were collected from 20 patients younger than 20 months (14 males; 6 females) with normal renal function undergoing \(^{99m}\)Tc-MAG3 scans. To estimate the patient-specific organ activity, a retrospective calibration was performed based on a set of two 3D-printed infant kidneys filled with known activities. Both phantoms were scanned at different positions along the anteroposterior axis inside a water phantom, providing depth- and size-dependent attenuation correction factors for planar imaging. Time-activity curves were determined by drawing kidney, bladder, and whole-body regions-of-interest for each patient, and subsequently applying the calibration factor for conversion of counts to activity. Patient-specific time-integrated activity coefficients were obtained by integrating the organ-specific time-activity curves. Absorbed and effective dose coefficients for each patient were assessed with OLINDA/EXM for the provided newborn and 1-year-old model. The risk estimation was performed individually for each of the 20 patients with the NCI Radiation Risk Assessment Tool.
Results:
The mean age of the patients was 7.0 ± 4.5 months, with a weight between 5 and 12 kg and a body size between 60 and 89 cm. The injected activities ranged from 12 to 24 MBq of \(^{99m}\)Tc-MAG3. The patients' organ-specific mean absorbed dose coefficients were 0.04 ± 0.03 mGy/MBq for the kidneys and 0.27 ± 0.24 mGy/MBq for the bladder. The mean effective dose coefficient was 0.02 ± 0.02 mSv/MBq. Based on the dosimetry results, an evaluation of the excess lifetime risk for the development of radiation-induced cancer showed that the group of newborns has a risk of 16.8 per 100,000 persons, which is about 12% higher in comparison with the 1-year-old group with 14.7 per 100,000 persons (all values are given as mean plus/minus one standard deviation except otherwise specified).
Conclusion:
In this study, we retrospectively derived new data on biokinetics and dosimetry for infants with normal kidney function after undergoing renal scans with \(^{99m}\)Tc-MAG3. In addition, we analyzed the associated age- and gender-specific excess lifetime risk due to ionizing radiation. The radiation-associated stochastic risk increases with the organ doses, taking age- and gender-specific influences into account. Overall, the lifetime radiation risk associated with the \(^{99m}\)Tc-MAG3 scans is very low in comparison to the general population risk for developing cancer.
In 2006, 0.18 Mio pediatric nuclear medicine diagnostic exams were performed worldwide. However, for most of the radiopharmaceuticals used data on biokinetics and, as a consequence on dosimetry, are missing or have not been made publicly available. Therefore, most of the dosimetry assessments presented today for diagnostic agents in children and adolescents rely on the biokinetics data of adults. Even for one of the most common nuclear medicine exams for this patient group, renal scintigraphy with 99mTc-MAG3 for assessing renal function measured data on biokinetics is available only from a study performed on four children of different ages. In particular, renal scans are among the most frequent exams performed on infants and toddlers. Due to the young age, this patient group can be classified as a risk group with a higher probability of developing stochastic radiation effects compared to adults. As there are only limited data on biokinetics and dosimetry in this patient group, the aim of this study is to reassess the dosimetry and the associated radiation risk for a larger number of infants undergoing 99mTc-MAG3 renal scans based on a retrospective analysis of existing patient data.
Data were collected retrospectively from 34 patients younger than 20 months with normal (20 patients) and abnormal renal function (14 patients) undergoing 99mTc-MAG3 scans. The patient-specific organ activity was estimated based on a retrospective calibration which was performed based on a set of two 3D-printed infant kidneys (newborns: 8.6 ml; 1-year-old: 23.4 ml) filled with known activities. Both phantoms were scanned at different positions along the anteroposterior axis inside a water phantom, providing depth- and size-dependent attenuation correction factors for planar imaging. Time-activity curves were determined by drawing kidney, bladder, and whole body regions-of-interest for each patient, and subsequently applying the calibration factor for conversion of counts to activity. Patient-specific time-integrated activity coefficients were obtained by integrating the organ-specific time-activity curves. Absorbed and effective dose coefficients for each patient were assessed with OLINDA/EXM for the provided newborn and 1-year-old phantom. Based on absorbed dose values, the radiation risk estimation was performed individually for each of the 34 patients with the National Cancer Institute’s Radiation Risk Assessment Tool.
The patients’ organ-specific mean absorbed dose coefficients for the patients with normal renal function were 0.04±0.03 mGy/MBq for the kidneys and 0.27±0.24 mGy/MBq for the bladder. This resulted in a mean effective dose coefficient of 0.02±0.02 mSv/MBq. Based on the dosimetry results, the evaluation of the excess lifetime risk (ELR) for the development of radiation-induced cancer showed that the group of newborns has an ELR of 16.8 per 100,000 persons, which is higher in comparison with the 1-year-old group with an ELR of 14.7 per 100,000 persons. With regard to the 14 patients with abnormal renal function, the mean values for the organ absorbed dose coefficients for the patients were: 0.40±0.34 mGy/MBq for the kidneys and 0.46±0.37 mGy/MBq for the bladder. The corresponding effective dose coefficients (mSv/MBq) was: 0.05±0.02 mSv/MBq. The mean ELR (per 100,000 persons) for developing cancer from radiation exposure for patients with abnormal renal function was 29.2±18.7 per 100,000 persons.
As a result, the radiation-associated stochastic risk increases with the organ doses, taking age- and gender-specific influences into account. Overall, the lifetime radiation risk associated with the 99mTc-MAG3 scans is very low in comparison to the general population risk for developing cancer.
Furthermore, due to the increasing demand for PET-scans in children and adolescents with 68Ga-labelled peptides, in this work published data sets for those compounds were analyzed to derive recommendations for the administered activities in children and adolescents. The recommendation for the activities to be administered were based on the weight-independent effective dose model, proposed by the EANM Pediatric Dosage Card for application in pediatric nuclear medicine. The aim was to derive recommendations on administered activities for obtaining age-independent effective doses. Consequently, the corresponding weight-dependent effective dose coefficients were rescaled according to the formalism of the EANM dosage card, to determine the radiopharmaceutical class of 68Ga-labeled peptides (“multiples”), and to calculate the baseline activities based on the biokinetics of these compounds and an upper limit of the administered activity of 185 MBq for an adult. Analogous to 18F-fluoride, a minimum activity of 14 MBq is recommended. As a result, for those pediatric nuclear medicine applications involving 68Ga-labeled peptides, new values for the EANM dosage card were proposed and implemented based on the results derived in this work.
Overall, despite the low additional radiation-related cancer risk, all efforts should be undertaken to optimize administered activities in children and adolescents for obtaining sufficient diagnostic information with minimal associated radiation risk.
We report on a currently 76-year-old female patient with relapsed/refractory (RR) multiple myeloma (MM) treated at our institution. This patient had received six lines of therapy including tandem autologous stem cell transplant, proteasome inhibitor, immunomodulatory drugs and CD38 antibody MOR202. At the last relapse, she progressed during treatment with pomalidomide and MOR202. In an individualized therapy concept, we started a multi-agent salvage therapy with pomalidomide, bortezomib, doxorubicin, dexamethasone, and CD38 antibody daratumumab (“Pom-PAD-Dara”), which resulted in a stringent complete remission with minimal residual disease (MRD) negativity after nine cycles. So far, our patient shows a progression free survival of more than 12 months. Our case demonstrates the feasibility of successful CD38 antibody retreatment in a patient with heavily pretreated CD38 antibody resistant MM.
Simple Summary
Prostate cancer often relapses after initial radical prostatectomy, and salvage radiotherapy offers a second chance of cure for relapsed patients. Modern imaging techniques, especially prostate-specific membrane antigen positron emission tomography/computed tomography (PSMA PET/CT), enable radiation oncologists to target radiotherapy at the involved sites of disease. In a group of patients, PSMA PET/CT imaging can detect a macroscopic local recurrence with or without locoregional lymph node metastasis. In these cases, an escalation of the radiotherapy dose is often considered for controlling the visible tumor mass. As the evidence for dose-escalated salvage radiotherapy for macroscopic recurrent prostate cancer after PSMA PET/CT imaging is still limited, we address this topic in the current analysis. We found that the outcome of patients with dose-escalated salvage radiotherapy for macroscopic prostate cancer recurrence is encouragingly favorable, while the toxicity is very limited.
Abstract
Background: The purpose of this study was to access the oncological outcome of prostate-specific membrane antigen positron emission tomography (PSMA PET/CT)-guided salvage radiotherapy (SRT) for localized macroscopic prostate cancer recurrence. Methods: Between February 2010 and June 2021, 367 patients received SRT after radical prostatectomy. Out of the 367 screened patients, 111 patients were staged by PSMA PET/CT before SRT. A total of 59 out of these 111 (53.2%) patients were treated for PSMA PET-positive macroscopic prostatic fossa recurrence. Dose-escalated SRT was applied with a simultaneous integrated boost at a median prescribed dose of 69.3 Gy (IQR 69.3–72.6 Gy). The oncological outcome was investigated using Kaplan-Meier and Cox regression analyses. The genitourinary (GU)/gastrointestinal (GI) toxicity evaluation utilized Common Toxicity Criteria for Adverse Events (version 5.0). Results: The median follow-up was 38.2 months. The three-year biochemical progression-free survival rate was 89.1% (95% CI: 81.1–97.8%) and the three-year metastasis-free survival rate reached 96.2% (95% CI: 91.2–100.0%). The cumulative three-year late grade 3 GU toxicity rate was 3.4%. No late grade 3 GI toxicity occurred. Conclusions: Dose-escalated PSMA PET/CT-guided salvage radiotherapy for macroscopic prostatic fossa recurrence resulted in favorable survival and toxicity rates.
Simple Summary
Patients, who suffer from oligorecurrent prostate cancer with limited nodal involvement, may be offered positron emission tomography (PET)-directed salvage nodal radiotherapy to delay disease progression. This current analysis aimed to access salvage radiotherapy for nodal oligorecurrent prostate cancer with simultaneous integrated boost to PET-involved lymph nodes as metastasis-directed therapy. A long-term oncological outcome was favorable after salvage nodal radiotherapy and severe toxicity rates were low. Androgen deprivation therapy plays a major role in recurrent prostate cancer management and demonstrates a positive influence on the rate of biochemical progression in patients receiving salvage nodal radiotherapy. The present long-term analysis may help clinicians identify patients who would benefit from salvage nodal radiotherapy and androgen deprivation therapy, as a multimodal treatment strategy for oligorecurrent prostate cancer.
Abstract
Background: The study aimed to access the long-term outcome of salvage nodal radiotherapy (SNRT) in oligorecurrent prostate cancer. Methods: A total of 95 consecutive patients received SNRT for pelvic and/or extrapelvic nodal recurrence after prostate-specific membrane antigen (PSMA) or choline PET from 2010 to 2021. SNRT was applied as external beam radiotherapy with simultaneous integrated boost up to a median total dose of 62.9 Gy (EQD2\(_{1.5Gy}\)) to the recurrent lymph node metastases. The outcome was analyzed by cumulative incidence functions with death as the competing risk. Fine–Gray regression analyses were performed to estimate the relative hazards of the outcome parameters. Genitourinary (GU)/gastrointestinal (GI) toxicity evaluation utilized Common Toxicity Criteria for Adverse Events (v5.0). The results are as follows: the median follow-up was 47.1 months. The five-year biochemical progression rate (95% CI) was 50.1% (35.7–62.9%). Concomitant androgen deprivation therapy (ADT) was adminstered in 60.0% of the patients. The five-year biochemical progression rate was 75.0% (42.0–90.9%) without ADT versus 35.3% (19.6–51.4%) with ADT (p = 0.003). The cumulative five-year late grade 3 GU toxicity rate was 2.1%. No late grade 3 GI toxicity occured. Conclusions: Metastasis-directed therapy through SNRT for PET-staged oligorecurrent prostate cancer demonstrated a favorable long-term oncologic outcome. Omittance of ADT led to an increased biochemical progression.
Ziel:
Abschätzung der Risiken des Rezidivs des differenzierten Schilddrüsenkarzinoms, der Karzinom-bedingten Mortalität und der Karzinom-bedingten Reduktion der Lebenserwartung in Abhängigkeit von der Anzahl der zum Erreichen eines krankheitsfreien Zustands benötigten I-131-Therapien (Radioiodtherapien) und der für die Krankheitsfreiheit benötigten kumulativen Aktivität.
Methoden:
Analyse anhand von in der Würzburger Schilddrüsenkarzinom-Datenbank erfassten Verlaufsdaten unter Berücksichtigung eigener zusätzlicher Erhebungen zum follow-up.von 896 Patienten, die nach einer oder mehreren Radioiodtherapien im Therapieverlauf Erkrankungsfreiheit erreichten (negative TSH-stimulierte Thyreoglobulin-Messung in Kombination mit einer negativen I-131-Ganzkörperszintigraphie).
Ergebnisse:
Die erfassbare Nachsorgedauer betrug in Median 9.0 Jahre (Spannbreite 0.1-31.8 Jahre). Rezidiv-Raten nach 5 und 10 Jahren und am Ende der Nachsorge betrugen 1,0±0,3%, 4,0±0,7% und 6,2±1,1%. Die Schilddrüsenkarzinom-bedingte Sterberate betrug jeweils 0,1±0,1%, 0,5±0,3% und 3,4±1,1%.
Mit einer zunehmenden Anzahl von benötigten Radioiodtherapien nahm die Rezidivrate zu (p=0.001). Die Schilddrüsenkarzinom-bedingte Sterblichkeitsrate ist ab 4 benötigten Radioiodtherapien erhöht. Bei Patienten, die nach einer Radioiodtherapie krankheitsfrei waren, finden sich zwischen Niedrig- und Hochrisikopatienten keine Unterschiede bezüglich Rezidiv- und Sterblichkeitsrate. Bei Patienten, die zwei Radioiodtherapien benötigten, waren Rezidiv- und Sterblichkeitsrate der Hochrisikopatienten erhöht.
Bezüglich der kumulativ benötigten Aktivität zeigten sich nur bei Patienten, die eine kumulative Aktivität von über 22,2 GBq benötigten, erhöhte Rezidiv- und Sterberaten.
Im vorliegenden Studienkollektiv mit einer inhärent guten Prognose zeigte sich eine uneingeschränkte Lebenserwartung unabhängig von der benötigen Anzahl der Radioiodtherapien oder der benötigten kumulativen Aktivität.
Fazit:
Falls mehr als eine Radioiodtherapie oder eine hohe kumulative I-131 Aktivität benötigt wird, um einen krankheitsfreien Zustand zu erreichen, muss mit einer Rezidiv- und Schilddrüsenkarzinom-bedingten Sterblichkeits-Rate gerechnet werden, vor allem bei Hochrisikopatienten.
Nach wie vor sind die Einflussfaktoren auf den Langzeiterfolg der Radioiodtherapie bei der Autoimmunthyreopathie vom Typ Morbus Basedow bei Ersttherapie umstritten. Ziel dieser Dissertation war es, den Langzeiterfolg der Radioiodtherapie bei der Autoimmunthyreopathie vom Typ Morbus Basedow bei Zweit- und Dritttherapie am Beispiel des Krankengutes der Klinik und Poliklinik für Nuklearmedizin der Julius-Maximilians-Universität Würzburg zu analysieren und einen Bezug zu den weiterhin kontrovers diskutierten Einflussfaktoren bei einer Ersttherapie herzustellen. In dieser retrospektiven Studie wurden die Daten von 106 Patienten, die in der Klinik und Poliklinik für Nuklearmedizin im Zeitraum 1998 bis 2000 mit einem Rezidiv nach einer Radioiodtherapie eines Morbus Basedow mit einer 2. bzw. 3. Radioiodtherapie behandelt wurden, uni- und multivariaten Analysen unterzogen. Als prädiktive Einflussfaktoren auf den Langzeiterfolg bei einer 2. Radioiodtherapie lassen sich Volumen, Iodumsatz und thyreostatische Medikation eruieren. Mangels ausreichender Fallzahlen wurde nicht untersucht ob ein bestimmtes Geschlecht oder Alter für ein Rezidiv und damit eine 2. bzw. eine 3. Radioiodtherapie prädisponieren. Ebenfalls hatte die thyreoidale Stoffwechsellage keine Vorraussagekraft. Aufgrund eines feststellbar erhöhten Iodumsatzes bei Hyperthyreose ist aber eine ausgeglichene Hormonlage anzustreben. Die Ergebnisse lassen den Schluss zu, dass weitere, zum Teil noch nicht bekannte und in dieser Dissertation nicht untersuchte Variablen den Ausgang der Radioiodtherapie wesentlich mitbeeinflussen. Als Konsequenz dieser Untersuchung scheint eine Anhebung der angestrebten Dosis bei einer 1. Radioiodtherapie auf 250 – 300 Gy sinnvoll, da dies bei einer 2. Radioiodtherapie wirksam war und somit zu einer Reduktion der Rezidivrate führen könnte.
Vibrational spectroscopy can detect characteristic biomolecular signatures and thus has the potential to support diagnostics. Fabry disease (FD) is a lipid disorder disease that leads to accumulations of globotriaosylceramide in different organs, including the heart, which is particularly critical for the patient’s prognosis. Effective treatment options are available if initiated at early disease stages, but many patients are late- or under-diagnosed. Since Coherent anti-Stokes Raman (CARS) imaging has a high sensitivity for lipid/protein shifts, we applied CARS as a diagnostic tool to assess cardiac FD manifestation in an FD mouse model. CARS measurements combined with multivariate data analysis, including image preprocessing followed by image clustering and data-driven modeling, allowed for differentiation between FD and control groups. Indeed, CARS identified shifts of lipid/protein content between the two groups in cardiac tissue visually and by subsequent automated bioinformatic discrimination with a mean sensitivity of 90–96%. Of note, this genotype differentiation was successful at a very early time point during disease development when only kidneys are visibly affected by globotriaosylceramide depositions. Altogether, the sensitivity of CARS combined with multivariate analysis allows reliable diagnostic support of early FD organ manifestation and may thus improve diagnosis, prognosis, and possibly therapeutic monitoring of FD.
In recent years, a paradigm shift from single-photon-emitting radionuclide radiotracers toward positron-emission tomography (PET) radiotracers has occurred in nuclear oncology. Although PET-based molecular imaging of the kidneys is still in its infancy, such a trend has emerged in the field of functional renal radionuclide imaging. Potentially allowing for precise and thorough evaluation of renal radiotracer urodynamics, PET radionuclide imaging has numerous advantages including precise anatomical co-registration with CT images and dynamic three-dimensional imaging capability. In addition, relative to scintigraphic approaches, PET can allow for significantly reduced scan time enabling high-throughput in a busy PET practice and further reduces radiation exposure, which may have a clinical impact in pediatric populations. In recent years, multiple renal PET radiotracers labeled with C-11, Ga-68, and F-18 have been utilized in clinical studies. Beyond providing a precise non-invasive read-out of renal function, such radiotracers may also be used to assess renal inflammation. This manuscript will provide an overview of renal molecular PET imaging and will highlight the transformation of conventional scintigraphy of the kidneys toward novel, high-resolution PET imaging for assessing renal function. In addition, future applications will be introduced, e.g. by transferring the concept of molecular image-guided diagnostics and therapy (theranostics) to the field of nephrology.
Introduction
Commissioning, calibration, and quality control procedures for nuclear medicine imaging systems are typically performed using hollow containers filled with radionuclide solutions. This leads to multiple sources of uncertainty, many of which can be overcome by using traceable, sealed, long-lived surrogate sources containing a radionuclide of comparable energies and emission probabilities. This study presents the results of a quantitative SPECT/CT imaging comparison exercise performed within the MRTDosimetry consortium to assess the feasibility of using 133Ba as a surrogate for 131I imaging.
Materials and methods
Two sets of four traceable 133Ba sources were produced at two National Metrology Institutes and encapsulated in 3D-printed cylinders (volume range 1.68–107.4 mL). Corresponding hollow cylinders to be filled with liquid 131I and a mounting baseplate for repeatable positioning within a Jaszczak phantom were also produced. A quantitative SPECT/CT imaging comparison exercise was conducted between seven members of the consortium (eight SPECT/CT systems from two major vendors) based on a standardised protocol. Each site had to perform three measurements with the two sets of 133Ba sources and liquid 131I.
Results
As anticipated, the 131I pseudo-image calibration factors (cps/MBq) were higher than those for 133Ba for all reconstructions and systems. A site-specific cross-calibration reduced the performance differences between both radionuclides with respect to a cross-calibration based on the ratio of emission probabilities from a median of 12–1.5%. The site-specific cross-calibration method also showed agreement between 133Ba and 131I for all cylinder volumes, which highlights the potential use of 133Ba sources to calculate recovery coefficients for partial volume correction.
Conclusion
This comparison exercise demonstrated that traceable solid 133Ba sources can be used as surrogate for liquid 131I imaging. The use of solid surrogate sources could solve the radiation protection problem inherent in the preparation of phantoms with 131I liquid activity solutions as well as reduce the measurement uncertainties in the activity. This is particularly relevant for stability measurements, which have to be carried out at regular intervals.
Purpose
Patient-specific dosimetry is required to ensure the safety of molecular radiotherapy and to predict response. Dosimetry involves several steps, the first of which is the determination of the activity of the radiopharmaceutical taken up by an organ/lesion over time. As uncertainties propagate along each of the subsequent steps (integration of the time–activity curve, absorbed dose calculation), establishing a reliable activity quantification is essential. The MRTDosimetry project was a European initiative to bring together expertise in metrology and nuclear medicine research, with one main goal of standardizing quantitative \(^{177}\)Lu SPECT/CT imaging based on a calibration protocol developed and tested in a multicentre inter-comparison. This study presents the setup and results of this comparison exercise.
Methods
The inter-comparison included nine SPECT/CT systems. Each site performed a set of three measurements with the same setup (system, acquisition and reconstruction): (1) Determination of an image calibration for conversion from counts to activity concentration (large cylinder phantom), (2) determination of recovery coefficients for partial volume correction (IEC NEMA PET body phantom with sphere inserts), (3) validation of the established quantitative imaging setup using a 3D printed two-organ phantom (ICRP110-based kidney and spleen). In contrast to previous efforts, traceability of the activity measurement was required for each participant, and all participants were asked to calculate uncertainties for their SPECT-based activities.
Results
Similar combinations of imaging system and reconstruction lead to similar image calibration factors. The activity ratio results of the anthropomorphic phantom validation demonstrate significant harmonization of quantitative imaging performance between the sites with all sites falling within one standard deviation of the mean values for all inserts. Activity recovery was underestimated for total kidney, spleen, and kidney cortex, while it was overestimated for the medulla.
Conclusion
This international comparison exercise demonstrates that harmonization of quantitative SPECT/CT is feasible when following very specific instructions of a dedicated calibration protocol, as developed within the MRTDosimetry project. While quantitative imaging performance demonstrates significant harmonization, an over- and underestimation of the activity recovery highlights the limitations of any partial volume correction in the presence of spill-in and spill-out between two adjacent volumes of interests.
Purpose: A new PET radiotracer \(^{18}\)F-AF78 showing great potential for clinical application has been reported recently. It belongs to a new generation of phenethylguanidine-based norepinephrine transporter (NET)-targeting radiotracers. Although many efforts have been made to develop NET inhibitors as antidepressants, systemic investigations of the structure–activity relationships (SARs) of NET-targeting radiotracers have rarely been performed. Methods: Without changing the phenethylguanidine pharmacophore and 3-fluoropropyl moiety that is crucial for easy labeling, six new analogs of \(^{18}\)F-AF78 with different meta-substituents on the benzene-ring were synthesized and evaluated in a competitive cellular uptake assay and in in vivo animal experiments in rats. Computational modeling of these tracers was established to quantitatively rationalize the interaction between the radiotracers and NET. Results: Using non-radiolabeled reference compounds, a competitive cellular uptake assay showed a decrease in NET-transporting affinity from meta-fluorine to iodine (0.42 and 6.51 µM, respectively), with meta-OH being the least active (22.67 µM). Furthermore, in vivo animal studies with radioisotopes showed that heart-to-blood ratios agreed with the cellular experiments, with AF78(F) exhibiting the highest cardiac uptake. This result correlates positively with the electronegativity rather than the atomic radius of the meta-substituent. Computational modeling studies revealed a crucial influence of halogen substituents on the radiotracer–NET interaction, whereby a T-shaped π–π stacking interaction between the benzene-ring of the tracer and the amino acid residues surrounding the NET binding site made major contributions to the different affinities, in accordance with the pharmacological data. Conclusion: The SARs were characterized by in vitro and in vivo evaluation, and computational modeling quantitatively rationalized the interaction between radiotracers and the NET binding site. These findings pave the way for further evaluation in different species and underline the potential of AF78(F) for clinical application, e.g., cardiac innervation imaging or molecular imaging of neuroendocrine tumors.
Das Prostatakarzinom ist der häufigste bösartige Tumor des Mannes in den westlichen Industrieländern und die zweithäufigste tumorassoziierte Todesursache bei Männern weltweit. Für seine Diagnostik ist die Positronenemissionstomographie (PET) klinisch ein zunehmend wichtiges nicht-invasives bildgebendes Verfahren. Dennoch gibt es gegenwärtig noch kein geeignetes Radiopharmakon für die klinische Routineuntersuchung und die Charakterisierung des Prostatakarzinoms mit der PET. In dieser Arbeit wurden die Fettsäuren [18F]Fluorthiapalmitat (FTP) und 13-(4-[124/131I]Iodphenyl)-3-(p-phenylen)tridekansäure (PHIPA) hinsichtlich ihrer Eignung als Radiotracer für die PET zum Nachweis des Prostatakarzinoms in vitro und [18F]Fluorthiapalmitat auch in vivo untersucht. Methode: Für die Zellversuche wurden zwei hormonabhängige Zelllinien, LNCap und 22Rv1, und zwei hormonunabhängige Zelllinien DU145 und PC-3 verwendet. Nach Inkubation mit dem radioaktiven Tracer wurde die Höhe der Aufnahme im zeitlichen Verlauf mit Hilfe einer gamma-Kamera gemessen, sowie Untersuchungen zum Mechanismus der Aufnahme in die Zellen durchgeführt. In einem zweiten Schritt wurde die Aufnahme von [18F]FTP in ein heterotop implantiertes Prostatakarzinom in CD1-nu/nu-Nacktmäusen in vivo am Kleintier-PET bestimmt. Ergebnisse: Es zeigt sich sowohl für [18F]FTP als auch für [124/131I]PHIPA eine zeitabhängige Aufnahme in die Prostatakarzinomzellen mit Erreichen eines Plateaus. Dieses wird von der fluorierten Fettsäure [18F]FTP schneller erreicht als von der jodierten Fettsäure [124/131I]PHIPA. Das Plateau der Aufnahme liegt für [18F]FTP signifikant höher als für [124/131I]PHIPA. Desgleichen ist die maximal erreichte Aufnahme in die beiden hormonabhängigen Zelllinien LNCaP und 22Rv1 höher liegt, als in die hormonunabhängigen Zelllinien DU125 und PC-3. Im Rahmen von kompetitiven Inhibitorexperimenten mit Etomoxir konnte gezeigt werden, dass die Carnitin-Palmitoyltransferase einen wichtigen Aufnahmemechanismus für den Transport von [18F]FTP in die Zellen darstellt. Die Aufnahme von [124/131I]PHIPA in die Prostatakarzinomzellen wird durch Etomoxir nicht beeinflusst. Desgleichen lässt sich die Aufnahme sowohl von [18F]FTP als auch von [124/131I]PHIPA weder durch Koinkubation mit Angiotensin noch mit AICAR hemmen. Die Kleintier-PET-Untersuchungen zeigten eine relativ geringe Aufnahme von [18F]FTP in die Tumoren in vivo im Vergleich zur Akkumulation in Tumorzellen in vitro in der Zellkultur. Die Abgrenzung des Tumors mittels [18F]FTP-PET war zwar möglich, jedoch insgesamt noch nicht zufriedenstellend. Die Diskrepanz zwischen Daten aus Zellexperimenten in vitro und Ergebnissen aus tierexperimentellen Untersuchungen in vivo am Kleintier-PET kann noch nicht erklärt werden. Schlussfolgerung: Insgesamt legen die positiven Ergebnisse der in vitro Experimente mit [18F]FTP und [124/131I]PHIPA einen Grundstein für fortführende in vivo Bewertungen dieser Radiopharmaka mit dem Ziel, das Potential als mögliches Radiopharmakon zur Darstellung des Prostatakarzinoms abschließend klären zu können.
Objective: The objective of this study was to study recurrence in patients with differentiated thyroid carcinoma who after initial therapy consisting of total thyroidectomy and I-131 ablation, were cured defined as a negative TSH-stimulated Tg-levels and a negative I-131 whole body scan (WBS) at the first follow-up after ablation. Methods: Retrospective data for differentiated thyroid carcinoma patients from three university hospitals were pooled. Out of 1993 patients, 526 cured patients were included. All patients received at least one more TSH-stimulated WBS and Tg-measurement within 5 years after initial treatment. Results: 12 patients (2.1%) developed a recurrence after an average interval of 35 months (range: 12-59 months) following administration I-131 ablation. Overall disease-free survival according to the method of Kaplan-Meier was 96.6%. There was no difference in disease-free survival between high- and low-risk patients (p=0.61). Recurrence was first discovered by Tg-measurement during levothyroxin therapy in 7 patients, and by TSH-stimulated Tg-measurement in 5 patients. I-131 WBS did not contribute to the detection of recurrences. Multivariate analysis showed that age TNM-stage (p=0.015) and histology (p=0.032) were independent predictors of disease-free survival. Conclusion: Recurrence is a rare event in patients with DTC who received total thyroidectomy with subsequent I-131 ablation, and who had a negative first follow-up TSH-stimulated I-131 WBS and negative concurrent Tg. In the study population there were no recurrences after more than 5 years of follow-up.
In radiation accidents biological methods are used in dosimetry, if the radiation dose could not be measured by physical methods. The knowledge of individual dose is a prerequisite for planning a medical treatment and for health risk evaluations. In the present work two biodosimetrical assays were calibrated in young patients who were treated with radioiodine for thyroid cancer. Patients were from Belarus. They suffered from radiation induced thyroid cancer as a consequence of the Chernobyl reactor accident. In radioiodine therapy (RIT) bone marrow and lymphatic organs are exposed to ionizing radiation at doses of 0.1 to 0.75 Sv within about 2 days. Since several RIT have to be applied with interval between each of them from 6 months up to approximately 1 year, total dose can be up to 2 Sv within 2 to 3 years. The dose for thyroid tissue is approximately 1000 times higher. The dose-response relationship was measured by the T-cell receptor test (TCR test) in T4 lymphocytes with and without in vitro incubation or by the micronucleus assay in transferrin receptor positive reticulocytes (MN-Tf-Ret test). In all these assays, the frequency of radiation-induced mutants of blood cells is measured using flow cytometry. The TCR test is a cumulative biodosimeter, which measures the total radiation dose within the last 5 to 10 years, whereas the result of the MN-Tf-Ret test reflects the radiation dose of approximately 24 hours interval. It takes 8 hours and 3 days to perform TCR and MN-Tf-Ret tests respectively. Calibration curves based on radioiodine treated patients can be used for dose estimation in humans, if the radiation conditions correspond to those in RIT. This limits their applicability to low dose-rate β- and γ-irradiation and to doses per session not higher than about 0.5 Sv. If higher doses or dose-rates as well as the other types of ionizing radiation are involved, calibration curves in animals are indispensable. In the case MN-Tf-Ret test mouse models are established and may be used. The TCR assay was performed in 72 thyroid cancer patients aged between 14 and 25. T-cell mutant frequency (Mf) reaches its maximum only after half a year following the RIT. Then it declines exponentially. This decline could be described by the 3 parameter single exponential decay function. Based on this equation, the radiation dose could be calculated when the Mf and the time interval since exposure are known. Furthermore, the experimentally measured Mf value, which significantly exceeds the corresponding calculated Mf value would indicate an individual with higher radiosensitivity. However, among our patients there were none. The reticulocytes micronuclei test (MN-Tf-Ret) was performed in 46 radioiodine treated patients. When measuring the MN frequency (f(MN-Tf-Ret)) the measured cell fraction should be limited only to the youngest cohort of reticulocytes, because all the micronucleated erythrocytes are quickly removed from the peripheral blood by spleen. Thus, the MN test was performed only in CD71 positive (having transferring receptor) reticulocytes. These reticulocytes just entered the peripheral blood flow from red marrow. The MN frequency was measured before the therapy and then every day after the irradiation until day 7. MN frequency curve has typical shape with latent period for days 0 to 3. Then there is a sharp increase in MN frequency which lasts for 24 hours and could start between days 3 and 4. In the following days the MN frequency is dropping to its base level that equals the one before the treatment. The decay of MN frequency is depending on the half-life of radioiodine in the patient organism. If the half-life is low, then the increased f(MN-Tf-Ret) lasts shorter and vice versa. It was shown that the MN frequency curve could be described by the model where all the micronuclei arise only through the last mitosis of erythroblasts in the red marrow and the MN frequency is proportional to the radiation dose in the last cell cycle. The shape of this curve depends on the cell kinetics of erythropoiesis on one side and the exponential decay of radioiodine activity on the other. To the best of our knowledge, the MN-Tf-Ret test was applied in the present study for the first time in biological dosimetry.
11C-Methionin (11C-MET) ist ein alternatives Radiopharmakon für die Positronen-Emissions-Tomographie (PET) zur Beurteilung der Krankheitsaktivität bei Patient/-innen mit Multiplem Myelom (MM). Frühe Daten legen eine höhere Sensitivität und Spezifität als bei dem bisherigen Standardtracer 18F-Fluordesoxyglucose (18F-FDG) nahe. Es fehlen bislang jedoch Untersuchungen, welche die neuen, aus PET-Daten abgeleiteten Parameter „metabolic tumor volume“ (MTV) und „total lesion glycolysis / total lesion methionin uptake“ (TLG/TLMU) in diesen Vergleich miteinbeziehen. In früheren Studien konnte bereits eine prognostische Aussagekraft dieser neuen Imaging Parameter für die 18F-FDG-PET/CT gezeigt werden. Das Ziel dieser bizentrischen Studie war es, die sich im Rahmen bisheriger Studienergebnisse andeutende Überlegenheit von 11C-MET für das Staging des MM zu überprüfen und seine Eignung für die Bewertung von metabolischen Imaging Parametern im Vergleich zu 18F-FDG zu untersuchen.
Zweiundzwanzig Patient/-innen mit neu diagnostiziertem unbehandelten MM, davon 15 Patient/-innen des Universitätsklinikums Würzburg und sieben Patient/-innen der Clinica Universidad de Navarra in Pamplona, die eine doppelte PET/CT-Bildgebung unter Verwendung der beiden Tracer 11C-MET und 18F-FDG innerhalb eines Zeitraums von maximal 14 Tagen erhalten hatten, wurden retrospektiv durch den Doktoranden (Oliver Viering) sowie eine nuklearmedizinische Assistenzärztin (Maria I. Morales-Lozano) und im Anschluss durch je eine PET/CT-Expert/-in des Universitätsklinikums Würzburg (Constantin Lapa) und der Clinica Universidad de Navarra (Maria J. Garcia-Velloso) untersucht.
Hierfür wurden die 18F-FDG- und 11C-MET-PET/CT-Aufnahmen einer dreidimensionalen Analyse mit Hilfe des "PET/CT-Viewer Beth Israel for FIJI" unterzogen. Diese open source Software ermöglichte die Berechnung von SUVmean, SUVmax und SUVpeak sowie der neuen Imaging Biomarker MTV und TLG/TLMU. Die genannten PET-Parameter wurden mit klinischen und laborchemischen Parametern (Hämoglobin, Calcium, Kreatinin, CRP, β2-Mikroglobulin, Albumin, M-Gradient/M-Protein, Knochenmarkinfiltration, LDH, freier Leichtketten-quotient, R-ISS, zytogenetisches Risiko) korreliert, welche in früheren Studien als prognostisch relevante Parameter der Myelom-Erkrankung identifiziert worden waren.
Bei elf der 22 Patient/-innen (50 %) wurden mithilfe von 11C-MET mehr fokale Läsionen als mit 18F-FDG nachgewiesen (p < 0,01), daneben konnte bei einer größeren Zahl von Patient/-innen eine diffuse Knochenmarkinfiltration durch die malignen Plasmazellen identifiziert werden (11C-MET: 19, 18F-FDG: 12). Sowohl die SUV-Parameter (SUVmean, SUVmax und SUVpeak) als auch die neuen Imaging Parameter (TMTV und TLG/TLMU) waren bei der 11C-MET- signifikant höher als bei der 18F-FDG-PET/CT (p < 0,05).
In Bezug auf die neuen Imaging Parameter zeigten sich für 11C-MET häufiger signifikante Korrelationen mit den prognostisch relevanten klinischen und laborchemischen Parametern als für 18F-FDG. Bei TMTV konnten für die 11C-MET-PET/CT signifikante Korrelationen für β2-Mikroglobulin (p = 0,006), die M-Komponente (p = 0,003), den Grad der Knochenmarkinfiltration (p = 0,007) und das Serum-Hämoglobin (p = 0,016) gefunden werden, wohingegen sich bei 18F-FDG lediglich eine signifikante Korrelation für β2-Mikroglobulin (p = 0,044) zeigte. In Bezug auf die TLG/TLMU konnten bei 18F-FDG keine signifikanten Korrelationen zwischen TLG und den klinischen und laborchemischen Parametern nachgewiesen werden. Bei 11C-MET zeigten sich hingegen signifikante Korrelationen zwischen dem TLMU und der Kalzium-Konzentration im Serum (p = 0,028), dem β2-Mikroglobulin (p = 0,047), der M-Komponente (p = 0,033) und dem Grad der Knochenmarkinfiltration (p = 0,041).
Trotz zahlreicher Limitationen dieser Arbeit, wie etwa der geringen Patientenzahl und des retrospektiven Charakters der Auswertung bekräftigt auch diese Studie in Übereinstimmung mit den bisherigen Studienergebnissen, dass 11C-MET im Vergleich zu 18F-FDG ein sensitiverer Marker für die Beurteilung der Myelom-Tumorlast sein könnte. Eine Untersuchung der prognostischen Aussagekraft von 11C-MET in Bezug auf progressionsfreies- und Gesamtüberleben im Zuge der primären Bildgebung der Erkrankung war aufgrund der kurzen Nachbeobachtungszeit und der Heterogenität der Behandlung, welche die Patient/-innen im Anschluss an die Staging-Untersuchungen erhalten hatten, nicht möglich und muss im Rahmen zukünftiger, insbesondere prospektiver Studien weiter untersucht werden.
In dieser Studie wurden zwei Immunoassays zur Bestimmung von TG- und TPO-Antikörpern hinsichtlich diagnostischer Trennschärfe sowie klinischer Relevanz in der Diagnostik der chronischen lymphozytären Thyreoiditis-Hashimoto (CLT) untersucht. Im Rahmen der vorliegenden Studie wurden zwei Patientengruppen erfasst: ein Kollektiv mit der Diagnose CLT (n=203) und das sogenannte Normalkollektiv, das 205 Probanden umfasste. Die diagnostischen Kriterien zur Diagnosestellung CLT ergaben sich aus dem Zusammenspiel von klinischem Befund, Ultraschalluntersuchung und Antikörpertiter. Verglichen wurden der an der Klinik und Poliklinik für Nuklearmedizin der Universität Würzburg für die Routinediagnostik eingesetzte manuelle VarELISA TG und TPO Antibodies Assay, PHARMACIA Diagnostics mit dem automatisierten BRAHMS anti-TGn bzw. anti-TPOn KRYPTOR Assay. Die Bestimmung der Ergebnisse bei TPO-AK zeigte, dass die von KRYPTOR gemessenen Werte im Mittel um 2670,51 U/ml höher lagen als bei VarELISA. Bei TG-AK wurden die Konzentrationen auf der Plattform KRYPTOR allerdings um 325,07 U/ml niedriger gemessen als bei VarELISA; es zeigte sich bei TG-AK somit ein umgekehrtes Verhältnis. Des Weiteren wurde eine relativ gute Übereinstimmung zwischen beiden Assays (Kappa-Koeffizient nach Cohen = 0,63) bei der Bestimmung der TPO-Antikörper festgestellt; 86,8% der Seren wurden als konkordant bewertet. Demgegenüber stehen 65,4% in ihrem subjektiven Urteil übereinstimmende Ergebnisse bei der TG-Antikörper Bestimmung, was für eine schwache Übereinstimmung der TG-AK-Werte spricht (Kappa-Koeffizient nach Cohen = 0,31). Zudem ist die diagnostische Trennschärfe bei TPO-AK höher (Area under Curve = 0,929) als bei TG-AK (Area under Curve = 0,805); somit unterscheidet KRYPTOR bei der Bestimmung der TPO-AK besser zwischen „gesunden“ und „erkrankten“ Patienten als VarELISA. Bei der Messung der TPO-AK auf der Plattform KRYPTOR zeigte sich bei dem dem Cut-Off (vom Hersteller auf 60 U/ml festgelegt) am nächsten liegenden Wert (59,9 U/ml) sowohl eine hohe Sensitivität (81,4%) als auch Spezifität (97,6%). Bei der TG-AK Messung lag bei dem Cut-Off Wert von 59,8 U/ml bei hoher Spezifität (99,5%) die Sensitivität sehr niedrig (43,6%), d.h. viele Patienten wurden als falsch negativ eingestuft. Aus der Auswertung geht ein optimaler Schwellenwert von 67,2 U/ml für TPO-AK und 40,7 U/ml für TG-AK hervor, wobei der vom Hersteller angegebene Cut-Off Wert für beide AK 60 U/ml beträgt. Mittels neu ermitteltem Cut-Off Wert (67,2 U/ml) konnte bei TPO-AK eine Steigerung der Spezifität auf 99,5% bei unveränderter Sensitivität erreicht werden. Dementsprechend erbrachte der Cut-Off Wert von 40,7 U/ml eine Steigerung der Sensitivät auf 50% bei gleich bleibender Spezifität bei TG-AK. Die Bestimmung des Antikörperprofils in den beiden Testsystemen zeigte somit, insbesondere bei TG-AK, häufig diskrepante Ergebnisse. Dies belegt erneut die bekannte Problematik bei der Labordiagnostik der CLT. Ursächlich sind Affinitätsunterschiede und unterschiedliche Kalibrierungen der verwendeten Tests sowie das Fehlen einer Standardisierung zu diskutieren. Darüber hinaus bestätigen die Ergebnisse die Notwendigkeit einer Definition eines institutionellen Cut-Offs.
Purpose
For somatostatin receptor (SSTR)-positron emission tomography/computed tomography (PET/CT), a standardized framework termed SSTR-reporting and data system (RADS) has been proposed. We aimed to elucidate the impact of a RADS-focused training on reader’s anxiety to report on SSTR-PET/CT, the motivational beliefs in learning such a system, whether it increases reader’s confidence, and its implementation in clinical routine.
Procedures
A 3-day training course focusing on SSTR-RADS was conducted. Self-report questionnaires were handed out prior to the course (Pre) and thereafter (Post). The impact of the training on the following categories was evaluated: (1) test anxiety to report on SSTR-PET/CT, (2) motivational beliefs, (3) increase in reader’s confidence, and (4) clinical implementation. To assess the effect size of the course, Cohen’s d was calculated (small, d = 0.20; large effect, d = 0.80).
Results
Of 22 participants, Pre and Post were returned by 21/22 (95.5%). In total, 14/21 (66.7%) were considered inexperienced (IR, < 1 year experience in reading SSTR-PET/CTs) and 7/21 (33.3%) as experienced readers (ER, > 1 year). Applying SSTR-RADS, a large decrease in anxiety to report on SSTR-PET/CT was noted for IR (d = − 0.74, P = 0.02), but not for ER (d = 0.11, P = 0.78). For the other three categories motivational beliefs, reader’s confidence, and clinical implementation, agreement rates were already high prior to the training and persisted throughout the course (P ≥ 0.21).
Conclusions
A framework-focused reader training can reduce anxiety to report on SSTR-PET/CTs, in particular for inexperienced readers. This may allow for a more widespread adoption of this system, e.g., in multicenter trials for better intra- and interindividual comparison of scan results.