Differential Alterations to the Metabolic Connectivity of the Cortical and Subcortical Regions in Rat Brain During Ketamine-Induced Unconsciousness.

BACKGROUND: Ketamine anesthesia increased glucose metabolism in most brain regions compared to another intravenous anesthetic propofol. However, whether the changes in cerebral metabolic networks induced by ketamine share the same mechanism with propofol remains to be explored. The purpose of the present study was to identify specific features of metabolic network in rat brains during ketamine-induced subanesthesia state and anesthesia state compared to awake state. METHODS: We acquired fluorodeoxyglucose positron emission tomography (FDG-PET) images in 20 healthy adult Sprague-Dawley rats that were intravenously administrated saline and ketamine to achieve different conscious states: awake (normal saline), subanesthesia (30 mg kg -1 h -1 ), and anesthesia (160 mg kg -1 h -1 ). Based on the FDG-PET data, the alterations in cerebral glucose metabolism and metabolic topography were investigated by graph-theory analysis. RESULTS: The baseline metabolism in rat brains was found significantly increased during ketamine-induced subanesthesia and anesthesia. The graph-theory analysis manifested a reduction in metabolism connectivity and network global/local efficiency across cortical regions and an increase across subcortical regions during ketamine-induced anesthesia (nonparametric permutation test: global efficiency between awake and anesthesia, cortex: P = .016, subcortex: P = .015; global efficiency between subanesthesia and anesthesia, subcortex: P = .012). CONCLUSIONS: Ketamine broadly increased brain metabolism alongside decreased metabolic connectivity and network efficiency of cortex network. Modulation of these cortical metabolic networks may be a candidate mechanism underlying general anesthesia-induced loss of consciousness.

FDG-PET/CT in intensive care patients with bloodstream infection.

BACKGROUND: 2-Deoxy-2-[18F]fluoro-D-glucose (FDG) positron emission tomography (PET)/computed tomography (CT) is an advanced imaging technique that can be used to examine the whole body for an infection focus in a single examination in patients with bloodstream infection (BSI) of unknown origin. However, literature on the use of this technique in intensive care patients is scarce. The purpose of this study was to evaluate the diagnostic yield of FDG-PET/CT in intensive care patients with BSI. METHODS: In this retrospective cohort study, all intensive care patients from our Dutch university medical center who had culture-proven BSI between 2010 and 2020 and underwent FDG-PET/CT to find the focus of infection were included. Diagnostic performance was calculated and logistic regression analysis was performed to evaluate the association between FDG-PET/CT outcome and C-reactive protein level (CRP), leukocyte count, duration of antibiotic treatment, duration of ICU stay, quality of FDG-PET/CT, and dependency on mechanical ventilation. In addition, the impact of FDG-PET/CT on clinical treatment was evaluated. RESULTS: 30 intensive care patients with BSI were included. In 21 patients, an infection focus was found on FDG-PET/CT which led to changes in clinical management in 14 patients. FDG-PET/CT achieved a sensitivity of 90.9% and specificity of 87.5% for identifying the focus of infection. Poor quality of the FDG-PET images significantly decreased the likelihood of finding an infection focus as compared to reasonable or good image quality (OR 0.16, P = 0.034). No other variables were significantly associated with FDG-PET/CT outcome. No adverse events during the FDG-PET/CT procedure were reported. CONCLUSION: FDG-PET/CT has a high diagnostic yield for detecting the infection focus in patients with BSI admitted to intensive care. Poor PET image quality was significantly associated with a decreased likelihood of finding the infection focus in patients with BSI. This could be improved by adequate dietary preparation and cessation of intravenous glucose and glucose-regulating drugs. Recent advances in PET/CT technology enable higher image quality with shorter imaging time and may contribute to routinely performing FDG-PET/CT in intensive care patients with BSI of unknown origin.

Can surgical adhesives may cause false positivity in follow-up positron emission tomography after lung cancer resection?

INTRODUCTION: Postoperative complications following thoracic procedures are a major cause of morbidity and mortality. Alveolar air leaks and/or bronchopleural fistulas are associated with increased risk of infection, prolonged chest tube, and hospital stay duration and therefore generate economical concern for health care providers. A variety of surgical sealants or adhesives have been introduced to overcome this complication. Since intraoperative BioGlue® application can also cause an inflammatory reaction and mimic tumor recurrence on FDG PET-CT, in the present study we aimed to investigate its potential role in false-positive PET-CT results in patients operated for NSCLC. MATERIALS AND METHODS: Data of six patients who underwent resection for primary NSCLC at our institution (Department of Thoracic Surgery, Hacettepe University Medical Faculty) between January 2015 and December 2018 and had false positivity, due to BioGlue® application, at the bronchial stump in follow-up FDG PET-CT were retrospectively analyzed from a prospectively collected database. RESULT: One of the 6 patients was female and 5 were male. The mean age was 68 years (range, 56-79 years). The average time interval between operation and postoperative FDG-PET imaging was 4.3 months (range, 4-6 months). Follow-up FDG-PET imaging SUVmax values ranged between 3.0 and 9.0 (median: 5.33). All patients have been evaluated by FDG-PET scan following the detection of soft tissue densities at the surgical site suspicious for recurrence at their follow-up chest CT scans. Four patients underwent a bronchoscopic examination, bronchial stumps were examined and multiple biopsies were taken from suspicious nodules or tissues and sent for pathologic examination. Histopathological results revealed inflammation which is compatible with foreign body granuloma, without any suspicion for malignancy, in all cases. Two patients were solely followed-up and subsequent FDG-PET imaging after 3 months revealed complete resolution of FDG uptake. CONCLUSIONS: To avoid unnecessary biopsies or surgical procedures, the possibility of false-positive results due to surgical adhesive product use should be taken into account while interpreting follow-up FDG-PET imaging results and the operative reports should be written in detail, describing which surgical materials used and their exact application sites.

Predictive factors for dental inflammation with exacerbation during cancer therapy with FDG-PET/CT imaging.

PURPOSE: Oral adverse events, such as dental inflammation with exacerbation, are stressful and lead to poor nutrition in patients undergoing cancer therapy. Thus, the prediction of risk factors for dental inflammation with exacerbation is important before cancer therapy is initiated. We hypothesized that, during cancer therapy (DIECT), fluorodeoxyglucose-positron emission tomography/computed tomography (FDG-PET/CT) imaging could be useful to predict dental inflammation with exacerbation. METHODS: We enrolled 124 patients who underwent FDG-PET/CT for diagnostic staging before cancer treatment. We then assessed DIECT outcomes after basic perioperative oral treatment. Moreover, we evaluated clinical parameters, therapeutic strategies, periodontal examination (probing depth (PD) and bleeding on probing (BOP)), dental imaging, and FDG-PET/CT imaging results of patients with and without DIECT. Furthermore, PET/CT images were assessed as per the FDG accumulation of the dental lesion (PAD) grading system. RESULTS: Univariate analysis demonstrated significant differences in age, periodontal examination (PD and BOP), and PAD grade between patients with and without DIECT. Furthermore, multivariate logistic regression analysis identified independent predictive factors for a positive periodontal examination (PD) (odds ratio (OR) 5.9, 95% confidence interval (CI) 1.8-19.7; P = 0.004) and PAD grade (OR 11.6, 95% CI 3.2-41.2; P = 0.0002). In patients with cancer, PAD grade using FDG-PET/CT imaging was an independent and informative risk factor for DIECT. CONCLUSION: Our results suggested that, for patients with DIECT, periodontal examination and PAD grade were independent predictive factors. Hence, regardless of the presence or absence of any lesion on dental imaging, PAD grade might be an additional tool, in addition to periodontal examination that potentially improves oral care management.

Chemistry Considerations for the Clinical Translation of Oncology PET Radiopharmaceuticals.

Positron emission tomography (PET) has proven to be an invaluable tool in the staging and management of disease in oncology; however, [18F]fluorodeoxyglucose ([18F]FDG) remains the most widely used PET radiopharmaceutical despite the large financial investment in novel radiotracer development. We report our perspective and experience of translating radiopharmaceuticals into clinical studies, discussing the PET development pipeline from a chemistry perspective. We hope that, by identifying potential points of attrition along the pipeline and suggesting solutions to these problems, we may help others take their preclinical radiotracers into human studies. This review focuses primarily on the development of fluorine-18 radiopharmaceuticals, although the broader field of radiometal chemistry is considered where the translation journey is similar.

Hyperglycemia and 18F-FDG PET/CT, issues and problem solving: a literature review.

Positron emission tomography/computed tomography (PET/CT) is a standard procedure for imaging cancer commonly used in the clinical practice for several diseases, in particular for cancer staging, restaging, treatment monitoring and radiation therapy planning. Despite the availability of many radiotracers, 18F-fluoro-2-deoxy-2-D-glucose ([18F]FDG) is the most used. International PET/CT guidelines propose protocols for patients' correct preparation before [18F]FDG injection, in particular with the regard of diabetic patients and therapy management. Hyperglycemic conditions and oral or insulin medication showed advantages and disadvantages on PET/CT scan accuracy: A correct knowledge of effects of these conditions on glucose metabolism assumes a fundamental role on patients management before [18F]FDG PET/CT scan.

Development of Simple Methods to Reduce the Exposure of the Public to Radiation from Patients Who Have Undergone 18F-FDG PET/CT.

At a time when reducing the radiation dose to patients and the public has become a major focus, we assessed the radiation exposure rate from patients after an 18F-FDG PET/CT scan and evaluated different interventions to reduce it. Methods: We enrolled 100 patients, divided into 2 groups. For both groups, the radiation dose rate was measured with an ionization survey meter immediately after the scan. For group 1, the patients then voided and their dose rate was measured again. For group 2, the patients waited 30 min before voiding, and we measured the dose rate before (group 2A) and after (group 2B) they voided. Results: In total, 74 of the 100 patients exceeded the 20 µSv/h (2 mR/h) threshold immediately after the scan. In group 1, the mean dose rate decreased by 20.0% from the postscan measurement, with 12 of 36 remaining at or above 20 µSv/h. In group 2A, the mean dose rate decreased by 23% from the postscan measurement, with 9 of 38 remaining at or above 20 µSv/h. In group 2B, the mean dose rate decreased by 35% from the postscan measurement, with 1 of 38 remaining at 20 µSv/h. Conclusion: Nearly 75% of patients undergoing an 18F-FDG PET/CT scan exceed 20 µSv/h when leaving the imaging facility. The most effective method to reduce radiation exposure was to have the patient void 30 min after the examination.

DNA damage in human whole blood caused by radiopharmaceuticals evaluated by the comet assay.

Radiopharmaceuticals used for diagnosis or therapy induce DNA strand breaks, which may be detectable by single-cell gel electrophoresis (called comet assay). Blood was taken from patients before and at different time points after treatment with radiopharmaceuticals; blood cells were investigated by the comet assay using the percentage of DNA in the tail as the critical parameter. Whereas [225Ac]Ac-prostate-specific membrane antigen (PSMA)-617 alpha therapy showed no difference relative to the blood sample taken before treatment, beta therapy with [177Lu]Lu-PSMA-617 3 h post-injection revealed a small but significant increase in DNA strand breaks. In blood of patients who underwent positron emission tomography (PET) with either [18F]2-fluor-2-deoxy-D-glucose (FDG) or [68Ga]Ga-PSMA-11, an increase of DNA migration determined by the comet assay was not found when analysed at different time points (2-70 min) after intravenous tracer injection. Human whole blood was incubated with the targeted clinically relevant therapeutic radiopharmaceuticals [225Ac]Ac-PSMA-617, [177Lu]Lu-PSMA-617 and [90Y]Y-DOTA(0)-Phe(1)-Tyr(3)-octreotide (DOTA-TOC) at different activity concentrations (kBq/ml) for 5 days and then analysed by the comet assay. DNA damage increased with higher concentrations of all radiolabeled compounds tested. [177Lu]Lu-PSMA-617 caused higher blood cell radiotoxicity than equal activity concentrations of [90Y]Y-DOTA-TOC. Likewise, whole human blood was exposed to the positron emitters [18F]FDG and [68Ga]Ga-PSMA-11 in vitro for 24 h with activity concentrations ranging between 5 and 40 MBq/ml. The same activity concentration dependent elevated DNA migration was observed for both compounds although decay energies are different. This study demonstrated that the amount of DNA damage detected by the comet assay in whole human blood is similar among different positron emitters and divergent by a factor of 200 between alpha particles and beta radiation.

3'-Deoxy-3'-18F-Fluorothymidine and 18F-Fluorodeoxyglucose positron emission tomography for the early prediction of response to Regorafenib in patients with metastatic colorectal cancer refractory to all standard therapies.

PURPOSE: The purpose of this study was to evaluate the value of 3'-deoxy-3'-18F-fluorothymidine (18F-FLT) and 18F-fluorodeoxyglucose (18F-FDG) positron emission tomography/computed tomography (PET/CT) for early prediction of standard anatomic response and survival outcomes in patients with metastatic colorectal cancer (mCRC) receiving Regorafenib. METHODS: Sixty-eight patients with mCRC refractory to standard cytotoxic chemotherapy were enrolled and received Regorafenib (160 mg/day on days 1-21, following a 7-day break). Standard anatomical response was evaluated every 8 weeks. Both scans were performed before and on day 21 of Regorafenib. RESULTS: Of the 61 patients included in per-protocol analysis, complete response was not observed, but partial response was observed in 8.2% (n = 5), stable disease in 67.2% (n = 41), and progressive disease in 24.6% (n = 15). The objective response rate was 8.2% and disease control rate 75.4%. Five responders (8.2%) and 13 non-responders (21.3%) met the CT and 18F-FLT PET/CT criteria (maximum standardized uptake value decrease ≥ 10.6% for responders). Forty-three (70.5%) exhibited discordant responses on CT and 18F-FLT PET/CT (McNemar test, P < 0.001). At a median follow-up of 8.9 months, median progression-free survival (PFS) and median overall survival (OS) were 3.6 months (95% confidence interval [CI], 3.34-3.80 months) and 8.5 months (95% CI, 6.95-10.10 months), respectively. Comparison of PFS and OS according to 18F-FLT PET/CT response revealed slightly longer PFS (P = 0.015) in responders, but the correlation with OS was not significant. The PET Response Criteria in Solid Tumours (PERCIST) of 18F-FDG PET/CT revealed differences in PFS and OS between partial metabolic response (PMR) and non-PMR (P = 0.048 and P = 0.014, respectively), and between progressive metabolic disease (PMD) and non-PMD (P = 0.189 and P = 0.007, respectively). CONCLUSIONS: Survival outcome was significantly associated with PERCIST using 18F-FDG PET/CT but the change of 18F-FLT uptake was only slightly associated with PFS. 18F-FDG PET/CT can be used as imaging biomarker to predict clinical outcomes early in patients with mCRC receiving Regorafenib.

OCCUPATIONAL RADIATION DOSE TO NUCLEAR MEDICINE STAFF DUE TO TC99M, F18-FDG PET AND THERAPEUTIC I-131 BASED EXAMINATIONS.

The aim was to track the exposure to radiation workers in six nuclear medicine examinations. A number of 180 patients were recruited and external exposure was measured. Patients had undergone cardiac stress and rest, bone scan, I-131 therapy, Gallium-67 and FDG PET/CT imaging. The average dose received due to cardiac stress and rest were 20.4 ± 5.0 and 16.0 ± 3.8 µSv per patient, respectively, whereas for bone scan, Ga-67, FDG and I-131 therapy, the average dose was 6.1 ± 2.5, 6.0 ± 1.4, 11.1 ± 2.2 and 4.1 ± 2.6 µSv per patient. The patient-to-staff dose coefficients were on average 0.051 ± 0.009, 0.042 ± 0.010, 0.034 ± 0.016, 0.039 ± 0.021, 0.052 ± 0.012, 0.094 ± 0.021 µSv m2/MBq h for stress, rest, bone, I-131, Ga-67 and FDG reported post-administration, respectively. Patient injection and setup for imaging represent a high percentage of the total dose received by staff. The information revealed is able to revise local measures, safety standards, and could help further in dose optimization and minimal exposure to occupationally exposed worker in nuclear medicine laboratories.

18F-FDG PET/CT scanning: Biological effects on patients: Entrance surface dose, DNA damage, and chromosome aberrations in lymphocytes.

Positron Emission Tomography/Computed Tomography (PET/CT), a combination of PET and CT, is used in tumor staging, therapy planning, and treatment response monitoring. During PET imaging, patients receive low doses of radiation, which can induce an adaptive response and necessitate higher doses for therapeutic efficacy. Higher doses may augment toxicity to normal cells. We are examining the effects of short-term, low-dose exposures to ionizing radiation. Entrance Surface Dose (ESD) to head, shoulders, and pelvis regions were measured using Li2B4O7: Mn thermoluminescent dosimeters. Induced DNA damage in lymphocytes was measured using γ-H2AX, p53Ser-15, chromosome aberrations, and micronucleus formation in subjects (n = 25) who underwent 18F-FDG PET/CT. The mean ESD ± SD value obtained were 32.40 ± 16.86, 32.58 ± 14.22, 32.02 ± 15.42, 43.55 ± 18.25 and 42.80 ± 24.67 mGy for the head, right shoulder, left shoulder, right pelvic, and left pelvic regions, respectively. The effective doses of PET and CT ranged from 4.01 to 6.61 and 16.40-72.18 mSv, respectively, and the obtained Dose Length Product (DLP) varied from 1093 to 4812 mGy*cm. There was no correlation between DLP and ESD (r2 = 0.1). The chromosome aberration assay showed a significant increase (p < 0.05), post-scanning vs. pre-scanning; the γ-H2AX, p53Ser-15, and micronucleus assays did not show significant increases. Induced DNA damage showed inter-individual variation among the study subjects. Our results imply that the patients received a biologically significant dose during 18F-PET/CT scanning and precautions may be needed to reduce any long-term risk of exposure.

Relationship Between Clinicopathological Characteristics and PET/CT Uptake in Esophageal Squamous Cell Carcinoma: [18F]Alfatide versus [18F]FDG.

PURPOSE: To assess a novel radiotracer aluminum [18F]fluoride-1,4,7-triazacyclononane-triacetic acid-pegylated dimeric RGD ([18F]ALF-NOTA-PRGD2, denoted as [18F]Alfatide) for positron emission tomography (PET)/X-ray computed tomography (CT) and explore the relationships between clinicopathological characteristics and maximum standard uptake values in primary (SUVP) and metastatic lymph nodes (SUVLN) of patients with esophageal squamous cell carcinoma (ESCC), as verified by pathologic examination and compared with those obtained with 2-deoxy-2-[18F]fluoro-D-glucose ([18F]DG) PET. PROCEDURES: We prospectively enrolled patients with newly diagnosed ESCC who agreed to undergo [18F]Alfatide PET/CT or [18F]FDG PET/CT scans before surgery at Shandong Cancer Hospital from May 2011 to July 2017. SUVs and the pathological tumor-node-metastasis (pTNM) stages of primary tumors and metastatic lymph nodes (LNs) were measured and confirmed pathologically. Immunohistochemical (IHC) staining for integrin αvß3 was performed on tumor samples (both primary tumors and metastatic LNs) collected from nine patients. RESULTS: Of 61 patients who underwent PET/CT scans, 46 then underwent curative surgery and were included in our analysis (n = 21 for [18F]Alfatide PET/CT and n = 25 for [18F]FDG PET/CT). No significant differences in the SUVP on [18F]Alfatide PET/CT or [18F]FDG PET/CT were observed among the cohorts according to gender, pathological stage, T stage, status of LNs, and differentiation (all P > 0.05). The SUVLN differed significantly between the pathological stages and status of LNs both on [18F]Alfatide PET/CT (P = 0.03, 0.003) and [18F]FDG PET/CT (P = 0.001. < 0.001), but not according to gender (P = 0.128, 0.129), T stage (P = 0.791, 0.727), or tumor differentiation (P = 0.049, 0.053). Significant positive correlations were observed between the SUVLN on [18F]Alfatide PET/CT and [18F]FDG PET/CT, and pathological stage (r = 0.52, P = 0.016; r = 0.503, P = 0.01), LN status (r = 0.73, P < 0.001; r = 0.649, P < 0.001), and differentiation (r = 0.509, P < 0.019; r = 0.459, P = 0.021) were observed. No significant differences were found between the relationships of SUVP with SUVLN, length, age, gender, pathological stage, T stage, status of LN, or differentiation, or of SUVLN with length, age, gender, or T stage both on [18F]Alfatide PET/CT and [18F]FDG PET/CT (all P > 0.05). The quantitated expression levels of αvß3 in primary tumors and metastatic LNs were 1.67 ± 1.12 and 3.42 ± 2.93, respectively (P = 0.031). CONCLUSIONS: Our results suggest that SUVLN is influenced by pathological stage, LN status, and differentiation. SUVLN may therefore serve as a new parameter for risk stratification of with ESCC patients. Moreover, [18F]Alfatide PET can provide complementary molecular information about ESCC metastasis.

Lung metastases from benign uterine leiomyoma: does 18-FDG-PET/CT have a role to play?

Uterine leiomyomas are the most common benign gynaecological tumours. However, 0.13 to 6% of them have malignant potential (Robboy et al. Environ Health Perspect 108(Suppl 5):779-784, 2000). Uterine smooth muscle tumours with unusual growth patterns include a spectrum of lesions such as intravenous leiomyomatosis, benign metastasizing leiomyoma and disseminated peritoneal leiomyomatosis (Vaquero et al. J Minim Invasive Gynecol 16:263-268, 2009). Benign metastasizing leiomyoma (BML) is a very rare condition with around 100 cases reported to date. BML is a cytologically bland, mitotically inactive smooth muscle tumour in extra uterine sites, occurring in conjunction with similarly appearing or previously removed uterine leiomyomas (Beck et al. Hong Kong Med J = Xianggang yi xue za zhi 18:153-155, 2012). Pulmonary metastases are the most common sites of metastases, but other sites include skin, bladder, liver, lymph nodes, oesophagus, skeletal muscles, heart, bones and central nervous system (Jo et al. Korean J Int Med 21:199-201, 2006; Arai et al. Chest 117:921-922, 2000; Kwon et al. Korean J Int Med 21:173-177, 2006; Rivera et al. J Clin Endocrinol Metab 89:3183-3188, 2004; Jautzke et al. Pathol Res Pract 192:215-223, 1996; Goyle et al. Am J Clin Oncol 26:473-476, 2003; Schneider et al. Der Chirurg; Zeitschrift fur alle Gebiete der operativen Medizen 72:308-311, 2001; Andrade et al. Pathol Oncol Res: POR 4:44-47, 1998; Abramson et al. AJR Am J Roentgenol 176:1409-1413, 2001; Yoon et al. Cancer Res Treat 43:131-133, 2011; Egberts et al. Arch Gynecol Obstet 274:319-322, 2006). The condition is more common in late childbearing age, mean age of diagnosis is 43 years (Kwon et al. Korean J Int Med 21:173-177, 2006), suggesting that it is hormone related. Lung metastases in BML are usually an incidental finding during the preoperative assessment; however, on rare occasions, patients are symptomatic with cough, chest pain, haemoptysis or dyspnoea. The differential diagnosis includes pulmonary metastases from leiomyosarcoma, intravenous leiomyomatosis or metastasis from other malignancies. Lung biopsy is the only way to confirm the benign nature of these lesions. Recently, positron emission tomography (PET) scan showed promise in differentiating these benign lesions from malignant lung lesion (Sawai et al. Oncol Lett 14:3641-3646, 2017). We present three cases with pulmonary metastases from BML and discuss the pathogenesis and management of this rare condition.

Analysis of radiation measurement of FDG radiopharmaceuticals and the development of medical image processing techniques.

This paper based on the theory of radiopharmaceuticals and the theory of radiation risk prediction, the author mainly studies the dose distribution of F-FDG and its radiation risk. Through the assessment of the risk of radiation carcinogenesis, the effective dose range was 4.61mSv to 8.97mSv, and the range of radiation carcinogenic risk was 1.57 ×10-3-3.14×10-3. Also, we reviewed the development trend of medical image processing techniques, and the development of medical imaging processing in three-dimensional (3D) medical imaging visualization and PACS-based medical imaging compression is introduced.

Evaluation and optimization of occupational eye lens dosimetry during positron emission tomography (PET) procedures.

The last recommendations of the International Commission on Radiological Protection for eye lens dose suggest an important reduction on the radiation limits associated with early and late tissue reactions. The aim of this work is to quantify and optimize the eye lens dose associated to nurse staff during positron emission tomography (PET) procedures. PET is one of the most important diagnostic methods of oncological and neurological cancer disease involving an important number of workers exposed to the high energy isotope F-18. We characterize the relevant stages as preparation and administration of monodose syringes in terms of occupational dose. A direct reading silicon dosimeter was used to measure the lens dose to staff. The highest dose of radiation was observed during preparation of the fluorodesoxyglucose (FDG) syringes. By optimizing a suitable vials' distribution of FDG we find an important reduction in occupational doses. Extrapolation of our data to other clinical scenarios indicates that, depending on the work load and/or syringes activity, safety limits of the dose might be exceeded.

Does Delayed-Time-Point Imaging Improve 18F-FDG-PET in Patients With MALT Lymphoma?: Observations in a Series of 13 Patients.

PURPOSE: To determine whether in patients with extranodal marginal zone B-cell lymphoma of the mucosa-associated lymphoid tissue lymphoma (MALT), delayed-time-point 2-F-fluoro-2-deoxy-d-glucose-positron emission tomography (F-FDG-PET) performs better than standard-time-point F-FDG-PET. MATERIALS AND METHODS: Patients with untreated histologically verified MALT lymphoma, who were undergoing pretherapeutic F-FDG-PET/computed tomography (CT) and consecutive F-FDG-PET/magnetic resonance imaging (MRI), using a single F-FDG injection, in the course of a larger-scale prospective trial, were included. Region-based sensitivity and specificity, and patient-based sensitivity of the respective F-FDG-PET scans at time points 1 (45-60 minutes after tracer injection, TP1) and 2 (100-150 minutes after tracer injection, TP2), relative to the reference standard, were calculated. Lesion-to-liver and lesion-to-blood SUVmax (maximum standardized uptake values) ratios were also assessed. RESULTS: F-FDG-PET at TP1 was true positive in 15 o f 23 involved regions, and F-FDG-PET at TP2 was true-positive in 20 of 23 involved regions; no false-positive regions were noted. Accordingly, region-based sensitivities and specificities were 65.2% (confidence interval [CI], 45.73%-84.67%) and 100% (CI, 100%-100%) for F-FDG-PET at TP1; and 87.0% (CI, 73.26%-100%) and 100% (CI, 100%-100%) for F-FDG-PET at TP2, respectively. FDG-PET at TP1 detected lymphoma in at least one nodal or extranodal region in 7 of 13 patients, and F-FDG-PET at TP2 in 10 of 13 patients; accordingly, patient-based sensitivity was 53.8% (CI, 26.7%-80.9%) for F-FDG-PET at TP1, and 76.9% (CI, 54.0%-99.8%) for F-FDG-PET at TP2. Lesion-to-liver and lesion-to-blood maximum standardized uptake value ratios were significantly lower at TP1 (ratios, 1.05 ± 0.40 and 1.52 ± 0.62) than at TP2 (ratios, 1.67 ± 0.74 and 2.56 ± 1.10; P = 0.003 and P = 0.001). CONCLUSIONS: Delayed-time-point imaging may improve F-FDG-PET in MALT lymphoma.