Theranostics is an emerging field in medicine that combines diagnostics and therapeutics into a single approach. Overall, theranostics represents a promising paradigm for personalized medicine, as it allows for targeted and precise treatment based on individual patient characteristics. In nuclear medicine, theranostics involves the use of radiopharmaceuticals that have both diagnostic and therapeutic properties. Moreover, theranostics in nuclear medicine offers several advantages over traditional cancer treatments. Unlike radiotherapy, in nuclear medicine the therapy is systemic that targets both primary tumors and metastatic lesions, offering a more comprehensive treatment approach. Additionally, nuclear medicine therapy has been shown to have fewer side effects compared to traditional chemotherapy, making it a more tolerable treatment option for patients. While theranostics in nuclear medicine is still a relatively new field, it has shown promising results in the treatment of neuroendocrine tumors (NETs). One example of a theranostic approach in nuclear medicine is the use of radiolabeled somatostatin analogs for the treatment of NETs. Somatostatin is a hormone that regulates the release of other hormones in the body. It also binds to somatostatin receptors, which are highly expressed in NETs. The first step in theranostics for NETs is the diagnosis and staging of the disease using a radiolabeled somatostatin analog and PET/CT imaging. This allows for the detection of the tumor and assessment of its size and location. Once the tumor has been identified, the same radiolabeled somatostatin analog can be used as a therapeutic agent. The radiopharmaceutical delivers radiation directly to the tumor cells, which destroys them while sparing surrounding healthy tissue. This is known as peptide receptor radionuclide therapy (PRRT). The use of theranostics in NETs also involves the identification of specific somatostatin receptor subtypes that are expressed in the tumor cells. This is important as different somatostatin analogs have varying affinities for different receptor subtypes. By selecting the appropriate radiolabeled somatostatin analog, clinicians can increase the specificity of the therapy, delivering radiation to the tumor cells while minimizing damage to healthy tissue. PRRT has been shown to be effective in treating NETs, particularly those that are resistant to other forms of treatment. It can also be used in combination with other therapies, such as chemotherapy and surgery, to improve outcomes. As research continues, it is likely that theranostics in nuclear medicine will become an increasingly important tool in the fight against cancer, particularly in the context of NETs, offering personalized, targeted treatment options that improve patient outcomes.
Objective: In previous fluorine-18-fluorodeoxyglucose positron emission tomography/computed tomography (18F-FDG PET/CT) studies, tumor segmentation using peritumoral halo layer (PHL; SegPHL) was shown to be reliable and accurate segmentation method in various malignant tumors. We found that the halo layer also was observed on the 99mTc-pertechnetate (99mTcO4) thyroid single photon emission computed tomography (SPECT)/CT. In the present study, we attempted to apply thyroid segmentation using the perithyroidal halo layer (PTHL; SegPTHL) on 99mTcO4 thyroid SPECT/CT and compared SegPTHL with CT-based thyroid segmentation (SegCT).
Subjects and methods: A total of 33 patients (19 females, 14 males; mean age, 46.91±15.7 years old) were enrolled in this study. For SegCT, three-dimensional volume of interest (VOI) of the thyroid was generated via multiple 2-dimensional regions of interest (ROI) along the thyroid margin on transaxial CT images that were manually drawn slice by slice. The PTHL was easily identified by an abrupt increase in layer thickness with minimal or mild distortion of the main thyroid contour, and the thyroid margin for SegPTHL was determined at the innermost portion of PTHL. An automated VOI generation for SegPTHL was performed using the Q. Volumetrix software. The correlation and reliability tests were performed between the quantification parameters of SegPTHL and SegCT.
Results: The PTHL threshold adjusted according to maximal SUV of thyroid were similar to the results of previous SegPHLstudies of 18F-FDG PET/CT. A good correlation was observed between the thyroid volumes of SegCT and SegPTHL (r=0.725; P<0.0001), although the thyroid volume of SegPTHL was slightly larger than that of SegCT (P=0.0017). The % thyroid uptake (TcTU), total lesion activity (TLA), and mean standardized uptake value (SUVmean) of SegPTHL correlated well with those of SegCT (r=0.9877, 0.9883, 0.9875, respectively; P<0.0001). No significant error was observed between the parameters (i.e., TcTU, TLA, and SUVmean) of SegPTHL and SegCT.
Conclusion: Thyroid segmentation PTHL may be a useful method for reliable quantification of thyroid uptake, because the SPECT/CT parameters of SegPTHL were strongly correlated with those of SegCT, as well as the process of SegPTHL is easier and faster than that of SegCT.
Objective: The purpose of the current study was to evaluatethe diagnostic accuracies of fluorine-18-fluorodeoxyglucose (18F-FDG) positron emission tomography (PET) or PET/computed tomography (CT) for diagnosis of myocarditis through and a meta-analysis.
Materials and methods: The PubMed, Cochrane database, and Embase database were searched from inception through November 30, 2022 for studies evaluating diagnostic performance of 18F-FDG PET or PET/CT for diagnosis of acute myocarditis. Based on data extracted from patient-based analysis, we calculated the pooled sensitivity and specificity with the 95% confidence intervals (CI). Also, we calculated positive and negative likelihood ratios (LR+ and LR-), and constructed summary receiver operating characteristic curves.
Results: Across 5 studies (6 results, 264 patients), the pooled sensitivity of 18F-FDG PET or PET/CT was 0.57 (95% CI; 0.26-0.84) and a pooled specificity of 0.89 (95% CI; 0.74-0.96). Likelihood ratio (LR) syntheses gave an overall positive likelihood ratio (LR+) of 5.1 and negative likelihood ratio (LR-) of 0.48. The pooled DOR was 11 (95% CI; 2-47). In meta-regression analysis, no variable was the source of the study heterogeneity.
Conclusion: Fluorine-18-FDG PET or PET/CT showed insufficient sensitivityand moderate specificity for diagnosis of myocarditis. These results indicated that cautious application of 18F-FDG PET or PET/CT should be paid for detection of myocarditis.
Objective: Gallium-68-DOTA-D-Phe1-Try3-Octreotide (68Ga-DOTATOC) is a radiolabeled somatostatin receptor (SSTR) analog that is widely used in the imaging of neuroendocrine tumors (NET). Benign and malignant prostate tumors have been observed to express SSTR. Diffuse symmetric DOTATOC uptake in the prostate is a normal positron emission tomography (PET) finding. The aim of this study was to evaluate the frequency and clinical significance of incidental atypical prostatic uptake in men undergoing 68Ga-DOTATOC PET/computed tomography(CT).
Subjects and methods: A retrospective review of consecutive male patients who underwent 68Ga-DOTATOC PET/CT studies at Aalborg University Hospital, Denmark, from November 2010 to April 2020 was performed. Positron emission tomography/CT reports were searched for text words or phrases indicating incidental atypical prostatic uptake. In the resulting cohort, PET/CT were re-evaluated, and DOTATOC uptake in the prostate gland was categorized as focal, diffuse or mixed. The intensity of the uptake was visually graded using the Krenning visual score. Follow-up was based on all available clinical, biochemical, imaging, and pathology follow-up.
Results: A total of 178 male patients underwent 193 68Ga-DOTATOC PET/CT scans. Incidental atypical uptake of 68Ga-DOTATOC on PET/CT in the prostatic bed was observed in eight patients (4.5%) (mean age 67 years, range 58-85 years). Six patients (75%) had diffuse uptake; two (25%) patients had focal uptake. Four patients out of eight with incidental findings (50%) had uptake less than or equal to that of the liver (Krenning score 2); four patients (50%) had uptake greater than that of the liver (score 3). All patients had measurements of serum prostate-specific antigen and were referred for urological evaluation. Five patients (62%) underwent a transrectal ultrasound, and three required a biopsy of the prostate. No cases of prostate malignancy (including prostatic cancer) were diagnosed.
Conclusion: During a 10-year period, we found that 4.5% of men exhibited prostate incidentalomas on 68Ga-DOTATOC PET/CT. No malignancy was found in the prostate in this population. Our data indicate absent malignancy among incidental 68Ga-DOTATOC findings in the prostate.
18F-FDG PET/CT may facilitate improved diagnosis and treatment in gynecological fields. This method provides pretreatment prognostic information concerning the aggressiveness of tumors which may contribute to optimizing and individualizing patient therapy. Although 18F-FDG PET/CT has a limited role for local staging of primary cancer, it has an important role in staging, as it aids particularly in identifying the involvement of lymph nodes and distant metastases throughout the whole body in a single examination in patients with advanced-stage disease and also in restaging after therapy. Another major indication of the modality is the evaluation of disease recurrence, especially in clinically equivocal patients or in patients in which tumor markers are rising, and conventional imaging studies show negative or equivocal findings.
The increasing success of recent nuclear medicine therapies, which followed the NETTER-1 and VISION trials, has boosted the interest for setting up and operating theragnostic centers. EANM, SNMMI and IAEA have recently published a joint guideline in order to assist nuclear medicine centers towards that path. The present paper will focus on the main points of these guidelines, with reference to the Greek radiation protection legislation.
The experience gained through the practice of radioembolization (SIRT) results in improvement of clinical outcomes. Improved outcomes are a prerequisite for the clinicians to reffer patients for SIRT. In recent years there are some critical changes in the concept and practice of SIRT that also contribute to the improvement of clinical outcomes, beyond the experience of the center performing SIRT. Two of them are dosimetry and a trend toward more focused therapies in the form of radiation lobectomy or segmentectomy.
Objective: With single photon emission computed tomography (SPECT)/computed tomography (CT) quantitative examinations, CT-based attenuation correction (CTAC) is considered necessary, though its effect on the quantitative values of an examined area close to the body surface, such as the jawbone, has not been elucidated. We performed an investigation to determine whether quantitative evaluation using a bone SPECT standalone device without CT is possible.
Subjects and methods: The calculated indices were maximum standardized uptake value (SUVmax) and SUVpeak. Grouping was performed based on the presence or absence of CTAC. The CTAC group underwent CTAC, while the noAC group did not.Validation was performed using clinical data of patients who underwent a jawbone SPECT/CT examination. Becquerel calibration factor (BCF) is required for calculation of SUV, and was determined with values obtained with both phantom and syringe methods. The index for the uptake areas in each group was assessed using a paired t-test.
Results: Using BCF obtained with the phantom method, both SUVmax and SUVpeak were higher in the noAC group. In contrast, BCF obtained with the syringe method showed no significant difference between the CTAC and noAC groups in regard to SUVmax and SUVpeak. This tendency was found regardless of the device used. Also, a high correlation was observed between the groups for both devices (r=0.95 and 0.93).
Conclusion: Our findings show that BCF obtained with a syringe method should be used when performing quantitative evaluation without CTAC. They also indicate that quantitative evaluation using a SPECT standalone device may be possible for jawbone SPECT/CT examinations.
Objective: To construct a novel targeted drug delivery nanoprobe: iodine-131-arginine-glycine-aspartate-tyrosine-cysteine peptide-polyethylene glycol-fifth generation polyamide-amine-docetaxel (131I-RGDyC-PEG-PAMAM-DTX) and to investigate its physicochemical properties and biological activity.
Materials and methods: Docetaxel was wrapped by solvent volatilization method, and the regression curve of DTX was constructed by high-performance liquid chromatography to determine its drug loading. The particle size of RGDyC-PEG-PAMAM-DTX was detected by dynamic light scattering. The 131I labeling was performed by a chloramine-T method and purified by Sephadex-G50 column chromatography, and it is in vitro stability and lipid-water partition coefficient was investigated. The cytotoxicity of RGDyC-PEG-PAMAM-DTX and 131I-RGDyC-PEG-PAMAM-DTX on A549 cells in vitro was detected by Cell Counting Kit-8 assay.
Results: Arginine-glycine-aspartate-tyrosine-cysteine peptide-PEG-PAMAM-DTX was successfully prepared by solvent volatilization with a loading capacity of about 44μg/mg. The average particle size of RGDyC-PEG-PAMAM-DTX was 57.8nm; the labeling rate of 131I-RGDyC-PEG-PAMAM-DTX by the chloramine-T method was 74.09%-76.09%, and the radiochemical purity was 88.9%-92.6% after purification. The in vitro stability showed that the radiochemical purity was above 80% after 72h in fetal bovine serum and PBS buffer (25oC and 37oC).CCK-8 assay showed that RGDyC-PEG-PAMAM-DTX and 131I-RGDyC-PEG-PAMAM-DTX had more pronounced cytotoxic effects than free DTX and 131I.
Conclusion: Iodine-131-RGDyC-PEG-PAMAM-DTX has good physicochemical properties and apparent cytotoxic effectsandis expected to be used in treating tumors.
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