Molecular Imaging and Biology最新文献

Purpose: Protein synthesis is essential to maintain integrity and function of the human brain, and protein synthesis is associated specifically with the formation of long-term memory. Experimental and clinical observations indicate that this process is disturbed in Alzheimer's dementia and other neurodegenerative diseases. In-vivo investigation with positron emission tomography (PET) using [¹¹C]leucine provides a unique possibility to measure regional cerebral protein synthesis (rCPS) rates in human brain and to determine whether it is altered in Alzheimer's disease (AD), and thus may provide a target for future therapeutic interventions.

Procedures: In this first human study, we measured rCPS by [¹¹C]leucine PET in four patients with AD (age 57-73 years) and compared the results with six healthy controls (three of whom were age matched and the other three were young controls). Quantification of rCPS also required measurement of amino acid (AA) levels and of free and protein-bound [¹¹C]leucine in plasma during the 90 min PET scans conducted following at least six hours of fasting.

Results: Rates of rCPS measured in absolute units of nmol/g/min ranged between 1.81 and 2.53 in AD patients, 2.10 and 2.54 in matched controls, and 2.21 to 2.35 in the young controls. Mean and median values did not show significant differences between the groups. Rates of rCPS also depended upon whether corrections for plasma AA levels were included in the calculations. When considering regional values relative to the corpus callosum as a reference region, there was a tendency towards impairment of rCPS in patients, which was most prominent in the parietal cortex, but did not reach significance. Similar findings were observed with normalisation of rCPS to global cortical mean.

Conclusions: In summary, this first human study assessing regional protein synthesis with [¹¹C]leucine in AD has demonstrated where the sources of variance in measurements of cerebral protein synthesis may arise, along with the potential magnitude of this variance. This study also indicates that there is a tendency towards impairment of rCPS in patients with Alzheimer's disease, which requires further investigation including possible partial volume effects due to atrophy.

Purpose: Oesophaegal cancer patients with a clinical complete response (CR) after neoadjuvant chemoradiotherapy (nCRT) are candidates for an active surveillance strategy. Regrowth rates of 40% after initial clinical CR indicate that identification of a true complete response to nCRT remains challenging. Near-infrared tumour-specific fluorescence endoscopic imaging might help to discriminate patients with a true complete response from patients with residual disease. This study aims to find potential markers to enable molecular imaging in oesophageal cancer and to assess the effect of nCRT on marker expression.

Procedures: Oesophageal cancer tissue slides of diagnostic biopsies (n = 41) (pre-treatment) and paired surgical specimens (n = 31) (post-treatment) were collected. Tissue slides of patients with adenocarcinoma (n = 29) and squamous cell carcinoma (n = 12)) were included. Immunohistochemistry was performed to assess expression of the tumour markers CEA, EpCAM, VEGF-α, EGFR, and c-MET in the tumour and compared to the expression of these markers in surrounding healthy tissue. A total immunostaining score (TIS, range 0-12), which combines the percentage and intensity of stained cells, was calculated. The TIS of pre-treated biopsies were compared with the TIS of the post-treatment surgical specimens to assess the effect of neoadjuvant therapy on the marker expression.

Results: The median TIS of EpCAM in adenocarcinomas was 10, vs. 0 in healthy mucosa (p < 0.001). The median TIS of EGFR in squamous cell carcinoma was 12, vs. 4 in healthy mucosa (p < 0.001). Neoadjuvant therapy did not affect the expression of the markers.

Conclusion: EpCAM and EGFR appear to be the most suitable targets for tumour-specific NIR fluorescence imaging of oesophageal adenocarcinoma and squamous cell carcinoma, respectively. Unaffected expression of all suitable markers by neoadjuvant therapy implies that the diagnostic biopsy can be used to select a patient-specific target for response evaluation by molecular imaging.

Purpose: Type 1 Diabetes (T1D) pathogenesis involves immune cells infiltrating pancreatic Islets of Langerhans, leading to T cell activation, beta cell destruction, and impaired insulin production. However, infiltration has a heterogenic nature that isn't described in detail, as not all islets are infiltrated. The aim of this study was to investigate if the observed heterogeneity is coupled to differences in immune and/or dysfunctional status of islets or exocrine cells, and if specific markers could elucidate mechanistic details of T1D pathogenesis.

Procedures: The GeoMx platform was used to spatially quantify protein levels in pancreatic islets and exocrine tissue in Non-Obese Diabetic (NOD) mice. The protein panel included 17 immune activity markers and nine dysfunction markers. Immunohistochemical (IHC) staining and digital image analysis was used to analyze select marker proteins.

Results: Use of the GeoMx platform to investigate T1D was shown to be possible, as Granzyme B protein levels were found to be lower in distal islet areas when compared to proximal areas. Smooth Muscle Actin protein levels were higher in exocrine areas proximal to immune-infiltrated islets, when compared to distally located exocrine areas. Findings from GeoMx were however not observed in IHC-stained sections.

Conclusions: This study demonstrates that investigating T1D is possible with spatial proteomics, as the assays revealed presence of heterogenic islet areas in NOD mice, which may play a role in T1D progression and escape from immune recognition. This study highlights the potential of spatial technologies for elucidating T1D pathogenesis and future treatment strategies.

Purpose: Metabolic dysfunction-associated steatotic liver disease (MASLD) comprises simple steatosis (SS), which has a low risk of mortality, and metabolic dysfunction-associated steatohepatitis (MASH), which can progress to liver cirrhosis and hepatocellular carcinoma. Because differentiation between MASH and SS is the most important issue in the diagnosis of MASLD, the establishment of noninvasive diagnostic methods is urgently needed. In this study, we evaluated the potential of [¹²³I]IIMU, a thymidine phosphorylase (TYMP) targeted SPECT imaging probe, for differential diagnosis of MASLD in a preclinical animal model.

Procedures: SS and MASH mice were prepared by feeding db/db mice with a standard diet and a methionine/choline-deficient diet, respectively. Control mice were prepared by feeding m/m mice with a standard diet. TYMP expression in the liver was evaluated by RT-PCR, western blotting, and immunohistochemistry. The biodistribution of [¹²⁵I]IIMU in the three model mice was evaluated at 30 min post-injection. SPECT/CT imaging studies of the three model mice were performed 30 min after injection of [¹²³I]IIMU.

Results: Hepatic TYMP expression level was the highest in the SS mice and the lowest in the MASH mice at both mRNA and protein levels. The immunohistochemistry experiment showed a patchy distribution of TYMP only in the liver of MASH mice. In the biodistribution study, the hepatic accumulation of [¹²⁵I]IIMU was the highest in the SS mice and the lowest in the MASH mice. The SPECT/CT imaging study showed similar results to the biodistribution experiment.

Conclusion: Hepatic TYMP expression level may serve as a promising imaging biomarker for differential diagnosis of SS and MASH. SPECT imaging using [¹²³I]IIMU potentially provides a novel noninvasive diagnostic method to differentiate MASH and SS.

Purpose: Preclinical models of cutaneous wound healing can be useful for improving clinical wound care. Oxygen Enhanced Photoacoustic imaging (OE PAI) can measure oxygenation, and Dynamic Contrast Enhanced (DCE) PAI can measure vascular perfusion. We investigated how a combined OE-DCE PAI protocol can measure vascular oxygenation and perfusion to a cutaneous healing model.

Procedures: We developed a cutaneous "punch" wound model and photographed the wounds to track healing for 9 days. We performed OE-DCE PAI on Day 0, 3, 6, and 9. OE PAI was performed with 21% O₂ and 100% O₂ breathing gases to measure oxyhemoglobin (HbO₂), deoxyhemoglobin (Hb), total hemoglobin (HbT), and oxygen saturation (%sO₂), along with changes in these parameters caused by a change in breathing gas (ΔHb, ΔHbO₂, ΔHbT, ΔsO₂). To perform DCE PAI, indocyanine green (ICG) was administered intravenously while monitoring the PAI signal for 10 min as the agent washed through the wound area, which was used to evaluate the wash-out rate.

Results: The average wound size was significantly smaller only by Day 6. For comparison, OE PAI measured a significant increase in HbO₂, Hb, HbT, and %sO₂ immediately after creating the wound, which significantly decreased by Day 3 and continued to decrease towards values for normal tissue by Day 9. The vascular wash-out rate significantly increased by Day 3, and continued to increase during the healing process. Notably, the wash-out rate can be assessed at a single PAI absorbance wavelength and by simply comparing signal amplitudes without advanced analysis, which may facilitate clinical translation.

Conclusions: OE-DCE PAI can monitor significant changes in vascular perfusion and oxygenation prior to significant changes in cutaneous wound size. These results establish OE-DCE PAI as a tool for future pre-clinical wound healing studies and eventual clinical translation.

Purpose: In humans, 2-deoxy-2-[¹⁸F]fluoro-D-glucose ([¹⁸F]FDG) tumour-to-background contrast continues to increase long after a typical uptake period of 45 - 60 min. Similar studies have not been performed in mice and the static imaging time point for most studies is arbitrarily set at 30 - 60 min post-injection of [¹⁸F]FDG. Ideally, static PET imaging should be performed after the initial period of rapid uptake but this period has not been defined in mice, with previous dynamic studies in mice being limited to 60 min. This study aimed to define the kinetics of [¹⁸F]FDG biodistribution over periods of 3 - 4 h in different murine tumour models, both subcutaneous and autochthonous, and to further refine fasting and warming protocols used prior to imaging.

Procedures: Dynamic [¹⁸F]FDG PET-CT scans lasting 3 or 4 h were performed with C57BL/6 J and Balb/c nude mice bearing subcutaneous EL4 murine T-cell lymphoma and Colo205 human colorectal tumours, respectively, and with transgenic Eμ-Myc lymphoma mice. Prior to [¹⁸F]FDG injection, four combinations of different animal handling conditions were used: warming for 1 h at 31 °C; maintenance at room temperature (20 - 24 °C), fasting for 6 - 10 h and a fed state.

Results: Tumour mean standardised uptake value (SUV_mean) peaked at 147 ± 48 min post injection in subcutaneous tumours and 74 ± 31 min in autochthonous Eμ-Myc lymphomas. The tumour-to-blood ratio (TBR) peaked at 171 ± 57 and 83 ± 33 min in subcutaneous and autochthonous Eμ-Myc tumours, respectively. Fasting increased tumour [¹⁸F]FDG uptake and suppressed myocardial uptake in EL4 tumour-bearing mice. There was a good correlation between tumour SUV_mean and K_i calculated using an input function (IDIF) derived from the inferior vena cava.

Conclusions: Delayed static [¹⁸F]FDG-PET imaging (> 60 min) in both autochthonous and subcutaneous tumours in improved tumour-to-background contrast and increased reproducibility.

Purpose: This study evaluates the semi-quantitative single-photon emission computed tomography (SPECT) parameters of prone SPECT using [^99mTc]Tc-sestamibi and compares them with Molecular Breast Imaging (MBI)-derived semi-quantitative parameters for the potential use of response prediction in women with locally advanced breast cancer (LABC).

Procedures: Patients with proven LABC with a tumor ≥ 2 cm on mammography and an indication for MBI using [^99mTc]Tc-sestamibi were prospectively enrolled. All patients underwent a prone SPECT/CT at 5 min (early exam) and an additional scan at 90 min (delayed exam) after injection of 600 MBq [^99mTc]Tc-sestamibi to compose wash-out rates (WOR). All patients underwent MBI after early SPECT/CT. Volumes of interest of the primary tumor were drawn semi-automatically on early and delayed SPECT images. Semi-quantitative analysis included maximum and mean standardized uptake values (SUV_max, SUV_mean,), functional tumor volume (FTV_SPECT), total lesion mitochondrial uptake (TLMU), tumor-to-background ratios (TBR_max and TBR_mean), WOR and coefficient of variation (COV_SPECT). Subsequently, the FTV_SPECT, TBR_SPECT and COV_SPECT were compared to FTV_MBI, TBR_MBI and COV_MBI.

Results: Eighteen patients were included. Early SUV_max, and TBR_max showed significantly higher interquartile range (IQR) compared to SUV_mean and TBR_mean, respectively 2.22 (2.33) g/mL, 6.86 (8.69), 1.29 (1.39) g/mL and 3.99 (5.07) (median (IQR), p < 0.05). WOR showed a large IQR (62.28), indicating that there is WOR variation among the LABC patients. FTV showed no difference between MBI and early SPECT semi-quantitative parameter (p = 0.46).

Conclusions: In LABC patients it is feasible to obtain semi-quantitative parameters from prone SPECT/CT. The FTV derived from early prone SPECT/CT is comparable with MBI-based FTV. Studies with comprehensive clinical parameters are needed to establish the clinical relevance of these semi-quantitative parameters, including WOR, for response prediction before its use in clinical routine.

Purpose: Esophageal squamous cell carcinoma (ESCC) frequently exhibits skip metastasis to lymph nodes; however, non-invasive imaging techniques capable of directly visualizing metastatic lymph nodes (MLN) are still lacking. Although biopsy is the clinical standard method, it is invasive and poses risks to patient health. This study aims to detect MLN in an intralymphatic tumor metastasis model of ESCC using the CXCR4-targeted tracer [⁶⁴Cu]Cu-NOTA-CP01.

Procedures: The CXCR4 expression in ESCC cell lines was assessed using Western blot and immunofluorescence. An intralymphatic tumor metastasis model was established and monitored using bioluminescence imaging (BLI). Small animal PET studies and biodistribution studies were performed to evaluate the specificity of [⁶⁴Cu]Cu-NOTA-CP01 for MLN. Histopathology evaluation was employed to check for the presence of metastatic tumor cells and to assess CXCR4 expression levels in the metastatic lymph nodes.

Results: The intralymphatic tumor metastasis model was successfully established using the EC109/Luc cell line, which exhibited high CXCR4 expression, as verified by BLI. PET/CT imaging showed that the MLN uptakes in the baseline group were significantly inhibited in the blocking group. The ratios of MLN/muscle and MLN/blood were also significantly higher in the baseline group than in the blocking group. Ex vivo PET/CT imaging of MLN corroborated the in vivo data. Biodistribution studies further supported the PET imaging studies, showing rapid clearance of the tracer from the blood and major organs, with significantly higher MLN/muscle and MLN/blood ratios in the baseline group compared to the blocking group. Histopathological staining verified positive CXCR4 expression in these lymph nodes containing metastatic tumor cells.

Conclusions: Targeting CXCR4 with [⁶⁴Cu]Cu-NOTA-CP01 for PET imaging of lymph nodes metastasis represents a promising approach that warrants further investigation. These findings have the potential to enhance diagnostic and therapeutic strategies for individuals with lymph nodes metastasis of ESCC.

Purpose: Bacterial infection causes significant mortality and morbidity worldwide despite the availability of antibiotics. Differentiation between responders and non-responders early on during antibiotic treatment will be informative to patients and healthcare providers. Our objective was to investigate whether PET imaging with ¹⁸F-Fluorodeoxysorbitol (¹⁸F-FDS) or ¹⁸F-FDG can be used to differentiate responders from non-responders to antibiotic treatment.

Procedures: NTUH-K2044 was used for infection in Albino C57 female mice. Each mouse was inoculated intratracheally with NTUH-K2044 to induce lung infection (n = 8). For treatment studies, two bacterial doses for animal inoculation and two treatment starting times were compared to optimize treatment profiles. ¹⁸F-FDS or ⁸F-FDG /PET imaging was performed to monitor treatment progression.

Results: Our results demonstrated that the treatment profiles for mice infected with 25 CFU hvKp and antibiotic treatment starting at 24 p.i. were not ideal due to no evidence of lung infection and lack of treatment efficacy. The optimal scheme is to use 250 CUF for infection and start antibiotic treatment at 24 h p.i. to monitor antimicrobial efficacy. 75% of the mice were classified as responders to antibiotic treatment. 25% of the mice were classified as non-responders. ¹⁸F-FDG was used to compare with ¹⁸F-FDS, but all mice showed increased lung uptake of ¹⁸F-FDG during 3-day treatments.

Conclusions: ¹⁸F-FDS is a promising PET tracer to image bacterial infection. It can be used to monitor response to treatment, and differentiate responders from non-responders to antibiotic treatment, but ¹⁸F-FDG cannot, probably due to the presence of high degree of inflammation before and after treatment.