Pattern of 18F-FDG uptake in the spinal cord in patients with non-central nervous system malignancy

Imaging increased metabolism in the spinal cord in mice after middle cerebral artery occlusion

Emerging evidence indicates crosstalk between the brain and hematopoietic system following cerebral ischemia. Here, we investigated metabolism and oxygenation in the spleen and spinal cord in a transient middle cerebral artery occlusion (tMCAO) model. Sham-operated and tMCAO mice underwent [18F]fluorodeoxyglucose (FDG)-positron emission tomography (PET) to assess glucose metabolism. Naïve, sham-operated and tMCAO mice underwent multispectral optoacoustic tomography (MSOT) assisted by quantitative model-based reconstruction and unmixing algorithms for accurate mapping of oxygenation patterns in peripheral tissues at 24 h after reperfusion. We found increased [18F]FDG uptake and reduced MSOT oxygen saturation, indicating hypoxia in the thoracic spinal cord of tMCAO mice compared with sham-operated mice but not in the spleen. Reduced spleen size was observed in tMCAO mice compared with sham-operated mice ex vivo. tMCAO led to an increase in the numbers of mature T cells in femoral bone marrow tissues, concomitant with a stark reduction in these cell subsets in the spleen and peripheral blood. The combination of quantitative PET and MSOT thus enabled observation of hypoxia and increased metabolic activity in the spinal cord of tMCAO mice at 24 h after occlusion compared to sham-operated mice.

The neurons that restore walking after paralysis

A spinal cord injury interrupts pathways from the brain and brainstem that project to the lumbar spinal cord, leading to paralysis. Here we show that spatiotemporal epidural electrical stimulation (EES) of the lumbar spinal cord1–3 applied during neurorehabilitation4,5 (EESREHAB) restored walking in nine individuals with chronic spinal cord injury. This recovery involved a reduction in neuronal activity in the lumbar spinal cord of humans during walking. We hypothesized that this unexpected reduction reflects activity-dependent selection of specific neuronal subpopulations that become essential for a patient to walk after spinal cord injury. To identify these putative neurons, we modelled the technological and therapeutic features underlying EESREHAB in mice. We applied single-nucleus RNA sequencing6–9 and spatial transcriptomics10,11 to the spinal cords of these mice to chart a spatially resolved molecular atlas of recovery from paralysis. We then employed cell type12,13 and spatial prioritization to identify the neurons involved in the recovery of walking. A single population of excitatory interneurons nested within intermediate laminae emerged. Although these neurons are not required for walking before spinal cord injury, we demonstrate that they are essential for the recovery of walking with EES following spinal cord injury. Augmenting the activity of these neurons phenocopied the recovery of walking enabled by EESREHAB, whereas ablating them prevented the recovery of walking that occurs spontaneously after moderate spinal cord injury. We thus identified a recovery-organizing neuronal subpopulation that is necessary and sufficient to regain walking after paralysis. Moreover, our methodology establishes a framework for using molecular cartography to identify the neurons that produce complex behaviours.

Physiologically intense FDG uptake of distal spinal cord on total-body PET/CT

OBJECTIVE

Physiologically mild-to-moderate FDG uptake of the spinal cord was reported. However, we noticed intense FDG uptake of distal spinal cord in several patients without definite spinal cord lesions on total-body PET/CT. Thus, this study aimed to investigate the frequency, pattern, intensity, and associations of FDG uptake in such cases on total-body PET/CT.

METHODS

The clinical characteristics of age, gender, body mass index (BMI), lower extremity symptom, diabetes, and fasting blood glucose level, and total-body FDG PET/CT metabolic parameters of maximum standard uptake value (SUVmax), SUVmax of lean body mass (SUVlbm), and SUVmax of body surface area (SUVbsa), were retrospectively analyzed in 527 patients without definite spinal cord lesions. Intense FDG uptake was defined as greater than liver glucometabolism on visual analysis, and T5 cord was selected as cord background.

RESULTS

Intense FDG uptake of distal spinal cord was observed in 87 out of 527 patients (16.5%) and involved with 2-3 vertebral segments including T11-T12 in 33 cases (38.0%), T12-L1 in 29 (33.3%), and T11-L1 in 25 (28.7%). No lesions were demonstrated on follow-up physical examinations, MRI or contrast-enhanced CT in these 87 cases with intense FDG accumulation in the distal spinal cord. The median SUVmax, SUVlbm, and SUVbsa of distal spinal cord with intense FDG uptake were 3.8 (2.7-5.5), 2.9 (2.2-4.3), and 1.0 (0.7-1.6), respectively. Significant differences in SUVmax, SUVlbm, and SUVbsa of distal cord and cord background were found between the groups with and without intense FDG uptake (P < 0.05). Moreover, significant differences in ratios of distal spinal cord-to-cord background, to mediastinal blood pool, and to liver were observed between two groups (P < 0.05). Intense FDG uptake of distal cord was associated with age, diabetic status, and blood glucose level.

CONCLUSIONS

Intense FDG uptake of distal spinal cord on total-body PET/CT may be physiological, more common in younger age, patients without diabetes, or lower fasting blood glucose.

Feasibility of imaging synaptic density in the human spinal cord using [11C]UCB-J PET

PURPOSE

Neuronal damage and synapse loss in the spinal cord (SC) have been implicated in spinal cord injury (SCI) and neurodegenerative disorders such as Amyotrophic Lateral Sclerosis (ALS). Current standards of diagnosis for SCI include CT or MRI imaging to evaluate injury severity. The current study explores the use of PET imaging with [11C]UCB-J, which targets the synaptic vesicle protein 2A (SV2A), in the human spinal cord, as a way to visualize synaptic density and integrity in vivo.

RESULTS

First, simulations of baseline and blocking [11C]UCB-J HRRT scans were performed, based on SC dimensions and SV2A distribution to predict VT, VND, and VS values. Next, human baseline and blocking [11C]UCB-J HRRT images were used to estimate these values in the cervical SC (cSC). Simulation results had excellent agreement with observed values of VT, VND, and VS from the real human data, with baseline VT, VND, and VS of 3.07, 2.15, and 0.92 mL/cm3, respectively, with a BPND of 0.43. Lastly, we explored full SC imaging with whole-body images. Using automated SC regions of interest (ROIs) for the full SC, cSC, and thoracic SC (tSC), the distribution volume ratio (DVR) was estimated using the brain gray matter as a reference region to evaluate SC SV2A density relative to the brain. In full body imaging, DVR values of full SC, cSC, and tSC were 0.115, 0.145, and 0.112, respectively. Therefore, measured [11C]UCB-J uptake, and thus SV2A density, is much lower in the SC than in the brain.

CONCLUSIONS

The results presented here provide evidence for the feasibility of SV2A PET imaging in the human SC, however, specific binding of [11C]UCB-J is low. Ongoing and future work include further classification of SV2A distribution in the SC as well as exploring higher-affinity PET radioligands for SC imaging.

[18F]FDG-PET Evaluation of Spinal Pathology in Patients in Oncology: Pearls and Pitfalls for the Neuroradiologist

[¹⁸F]FDG-PET is a widely used technique for specific evaluation of disease and treatment response in oncology. However, the principles behind [¹⁸F]FDG-PET imaging allow a wide-ranging array of benign and malignant pathologies to be identified on both initial and routine surveillance imaging. This is important for clinicians and radiologists, alike, in that effective and accurate evaluation of malignancy and metastatic disease, specifically involving the spine and central nervous system, is crucial. In this article, we review the normal and posttherapy appearance of the spine on [¹⁸F]FDG-PET, the various types and patterns of metastatic disease that involve the spine and spinal cord, and, finally, important spinal pathologies that may mimic malignancy on [¹⁸F]FDG-PET.

Assessing the Utility of 18F-Fluorodeoxyglucose Positron Emission Tomography in the Differential Diagnosis Between Spinal Schwannomas and Meningiomas

Objective

The advantage of 18F-fluorodeoxyglucose-positron emission tomography (FDG-PET) for the differential diagnosis of schwannoma and meningioma remains unclear. The purpose of this study was to compare the maximum standardized uptake value (SUVmax) with computed tomography (CT) and magnetic resonance imaging (MRI) findings and assess its utility in the differential diagnosis of schwannomas and meningiomas.

Methods

This study included 42 patients who underwent surgery and had pathological diagnoses of schwannomas (S group) or meningiomas (M group). Multivariate logistic regression analyses were conducted using meningioma prevalence as the dependent variable, and confounders were selected from those with p-values <0.05, including calcification, dural tail sign, tumor volume, and SUVmax at each spinal level as independent variables.

Results

The SUVmax of the spinal canal type at the level of the cervical vertebrae was significantly higher in the M group (4.6 ± 0.8) than in the S group (2.7 ± 1.4; P = 0.017). Multivariate logistic regression analysis showed that the dural tail sign was significantly associated with differential diagnosis between the S and M groups (odds ratio [OR], 0.851; 95% confidence interval [CI], 0.704-1.031, p<0.001).

Conclusions

The dural tail sign on MRI, but not the SUVmax of FDG-PET, was the most useful for the differential diagnosis between schwannomas and meningiomas.

Physiological distribution of 18F-FDG in the spinal cord: A systematic review

Context: The importance of physiologic distribution of ¹⁸F-FDG in the spinal cord.Objective: The recognition of the physiologic distribution of ¹⁸F-FDG in the spinal cord is pivotal for accurate PET/CT imaging interpretation, especially in oncologic patients. Therefore, we performed a systematic review to investigate the normal distribution of ¹⁸F-FDG throughout the spinal cord.Methods: Data sources: We carried out a comprehensive search of the literature on the physiologic patterns of ¹⁸F-FDG distribution in the spinal cord. PubMed and Scopus databases were searched using the following keywords: "spinal cord" AND "FDG". Data extraction: Findings of the selected articles were described.Results: Thirteen studies comprising 24,125 patients entered the systematic review. These investigations showed discrepancies in location, size, number, and intensity of ¹⁸F-FDG uptake throughout the spinal cord. However, cumulative results showed that ¹⁸F-FDG uptake was higher in the lower thoracic portion of spinal cord (T11-T12). Moreover, a decreasing trend in ¹⁸F-FDG uptake was observed from cervical to lumbar levels. Low maximal standardized uptake values, female sex, and higher body weight seem to be related to the physiological spinal cord ¹⁸F-FDG uptake.Conclusions: On ¹⁸F-FDG PET/CT imaging, focal hypermetabolism of the spinal cord at the level of lower thoracic and lower cervical vertebrae should be considered physiological until proven otherwise.

Whole-body 18-F-FDG-PET in patients with leptomeningeal disease and correlation with MRI

OBJECTIVE

Studies evaluating leptomeningeal disease on whole-body 18F-FDG PET are lacking. The purpose was to evaluate PET imaging of leptomeningeal disease and investigate the incremental utility of newer PET reconstructions in leptomeningeal disease.

METHODS

PET imaging of 56 patients with leptomeningeal disease detected initially on MRI (n = 53) or cytopathology (n = 35) were retrospectively reviewed. Regular 3-dimensional iterative reconstruction (3D IR, n = 56) and advanced reconstruction (AdvRecon, n = 41) PET images were evaluated by readers blinded to clinical and MRI findings for uptake involving cauda equina, posterior fossa and spinal cord. Spinal cord uptake pattern was classified as normal (uptake < liver), uptake = liver, conus uptake > liver, conus and cervical cord uptake > liver and multifocal/diffuse uptake > liver. SUVmax ratios of conus/liver, conus/left atrium and conus/cervical cord were compared between 3D IR and AdvRecon datasets.

RESULTS

Cauda equina uptake was seen in 64% and 78% on 3D IR and AdvRecon; posterior fossa uptake was seen in 52% and 54% on 3D IR and AdvRecon, respectively. Twelve percent had cauda equina or posterior fossa uptake visible only on AdvRecon. On 3D IR, normal spinal cord uptake was most common (27%); on AdvRecon, conus and cervical cord uptake > liver was most common (32%). Seven of 11 patients with normal spinal cord uptake on 3D IR were upgraded to increased uptake on AdvRecon. AdvRecon showed significantly higher conus/liver, conus/blood pool and conus/cervical cord SUVmax ratios (P < 0.0001).

CONCLUSION

Abnormal uptake in cauda equina, posterior fossa and spinal cord uptake are visible on FDG PET in leptomeningeal disease with increased conspicuity advanced PET reconstructions.

[18F]FDG uptake of the normal spinal cord in PET/MR imaging: comparison with PET/CT imaging

BACKGROUND

The lack of visualization of the spinal cord hinders the evaluation of [¹⁸F]Fluoro-deoxy-glucose (FDG) uptake of the spinal cord in PET/CT. By exploiting the capability of MRI to precisely outline the spinal cord, we performed a retrospective study aimed to define normal pattern of spinal cord [¹⁸F]FDG uptake in PET/MRI.

METHODS

Forty-one patients with lymphoma without clinical or MRI signs of spinal cord or bone marrow involvement underwent simultaneous PET and MRI acquisition using Siemens Biograph mMR after injection of 3.5 MBq/kg body weight of [¹⁸F]FDG for staging purposes. Using a custom-made software, we placed ROIs of 3 and 9 mm in diameter in the spinal cord, lumbar CSF, and vertebral marrow that were identified on MRI at 5 levels (C2, C5, T6, T12, and L3). The SUVmax, SUVmean, and the SUVmax and SUVmean normalized (NSUVmax and NSUVmean) to the liver were measured. For comparison, the same ROIs were placed in PET-CT images obtained immediately before the PET-MRI acquisition following the same tracer injection.

RESULTS

On PET/MRI using the 3 mm ROI, the following average (all level excluding L3) spinal cord median (1st and 3rd quartile) values were measured: SUVmean, 1.68 (1.39 and 1.83); SUVmax, 1.92 (1.60 and 2.14); NSUVmean, 1.18 (0.93 and 1.36); and NSUVmax, 1.27 (1.01 and 1.33). Using the 9 mm ROI, the corresponding values were SUVmean, 1.41 (1.25-1.55); SUVmax, 2.41 (2.08 and 2.61); NSUVmean, 0.93 (0.79 and 1.04); and NSUVmax, 1.28 (1.02 and 1.39). Using the 3 mm ROI, the highest values of PET-MRI SUVmax, SUVmean, NSUVmax, and NSUVmean were consistently observed at C5 and the lowest at T6. Using a 9 mm ROI, the highest values were consistently observed at C5 and the lowest at T12 or T6. The spinal cord [¹⁸F]FDG-uptake values correlated with the bone marrow uptake at the same level, especially in case of NSUVmax. Comparison with PET-CT data revealed that the average SUVmax and SUVmean of the spinal cord were similar in PET-MRI and PET-CT. However, the average NSUVmax and NSUVmean of the spinal cord were higher (range 21-47%) in PET-MRI than in PET-CT.

CONCLUSIONS

Using a whole-body protocol, we defined the maximum and mean [¹⁸F]FDG uptake of the normal spinal cord in PET/MRI. While the observed values show the expected longitudinal distribution, they appear to be higher than those measured in PET/CT. Normalization of the SUVmax and SUVmean of the spinal cord to the liver radiotracer uptake could help in multi-institutional comparisons and studies.

Physiological fluorodeoxyglucose uptake of spinal cord in adults

OBJECTIVE

Physiological fluorodeoxyglucose (FDG) uptake of spinal cord needs to be correctly recognized during evaluation of whole-body PET scans, especially for oncological cases. Our aim was to analyze physiological cord FDG uptake and its relation to gender, age, body weight, environmental temperature and time to imaging.

MATERIALS AND METHODS

PET scans of 254 patients in a single year, one patient for every working day were retrospectively selected. Temperature data were obtained from meteorology recordings. Maximum standard uptake value (SUVmax) of spinal cord at cervical and lower thoracic levels were noted. Spinal canal at L5 level, cerebellum and liver were used for normalization. Correlations with age, body weight, time to imaging and environmental temperature were analyzed.

RESULTS

Cervical SUV was higher than thoracic SUV (2.5-2.3). Cervical and lower thoracic SUV's were strongly correlated, highest when corrected with L5 level vertebral canal and liver (corr coeff 0.84 and 0.75) and lowest with cerebellum (corr coeff 0.4). Cervical spinal cord FDG uptake was higher for females than males (2.6 to 2.4). Temperature and age did not change spinal cord uptake. There were weak positive correlations with body weight (corr coeff 0.16 and 0.28, cervical and thoracic). There was weak negative correlation of cervical uptake with time to imaging (corr coeff -0.17).

CONCLUSION

Spinal cord FDG uptake at cervical and lower thoracic levels are strongly correlated. Females have slightly higher cervical SUV. Age and temperature does not change spinal cord FDG uptake in adults. Cord SUV's slightly increased with body weight.

Flourine-18 fluorodeoxyglucose positron emission tomography imaging exhibits increased SUVmax at the level of the spinal intumescence in normal dogs

Positron emission tomography (PET) imaging utilizing fluorine-18 labeled fluorodeoxyglucose is a relatively new imaging modality in veterinary medicine that is becoming more common for oncological staging and for musculoskeletal imaging. Thus, it is important to identify the normal variations on PET imaging that may be mistaken for pathology. Variation in standardized uptake values (SUVmax) have been anecdotally identified in the spinal cord of dogs undergoing fluorodeoxyglucose (FDG) PET-CT examinations for oncological staging, with notable increase in SUVmax values identified in the region of the cervical and lumbar spinal intumescences. The aim of this retrospective, analytical study was to compare the SUVmax values at four different locations throughout the spinal cord (C3, C5-T1, T13, and L3-S1) of a group of dogs with no evidence of neurologic disease and compare those findings to histologic specimens from dogs euthanized for unrelated disease. SUVmax values were significantly higher at the cervical and lumbar intumescences in comparison to the control regions (P < .0001 and P < .0001, respectively). Neuronal count and spinal cord gray matter area were also significantly greater at the cervical and lumbar intumescences (neuronal count P = .0025 and P = .0001; area P = .0004 and P = .0009, respectively) while overall neuronal density was lower (P = .003 and P = .028, respectively). We presume the increased SUVmax values at the spinal cord intumescences are the result of overall increased neuron count, increased proportion of gray matter, and increased spinal cord gray matter area. These findings will aid in the interpretation of future PET-CT studies and hopefully prevent the misdiagnosis of spinal cord disease in normal canines.

Tumor to cervical spinal cord standardized uptake ratio (SUR) improves the reproducibility of 18F-FDG-PET based tumor segmentation in head and neck squamous cell carcinoma in a multicenter setting

BACKGROUND

In quantitative FDG-PET data analysis, normalization of the standardized uptake value (SUV) with an internal image-derived standard improves its reproducibility. In this study, the cervical spinal cord is proposed as an internal standard that is within the field of view of the radiotherapy planning PET/CT-scan in head and neck cancer. The aim is to evaluate if the tumor to cervical spinal cord standardized uptake ratio (SUR) can improve the reproducibility of a model to determine the metabolic tumor volume (MTV) on FDG-PET/CT in a multicenter setting.

MATERIALS AND METHODS

Ninety-five radiotherapy planning FDG-PET/CT-scans of patients with head and neck cancer were analyzed using the Bland-Altman method to evaluate differences in FDG-uptake in the cervical spinal cord and the mediastinal blood pool. Non-linear regression analysis was used to determine the optimal MTV using the gross tumor volume (GTV) as ground truth and a spatial overlap-index as statistical validation metric. Reproducibility was evaluated using the Bland-Altman method and external validation was performed in an independent dataset consisting of 62 patients.

RESULTS

Bland-Altman's analyses demonstrated equivalence of FDG-uptake in the mediastinal blood pool and the cervical spinal cord. Reproducibility of the models improved when using SUR instead of SUV. These results were confirmed in the validation cohort.

CONCLUSION

The use of the tumor to cervical spinal cord SUR instead of SUV improves the reproducibility of a model to determine the MTV on FDG-PET/CT in a multicenter setting. This study indicates that SUR may be preferred over SUV based approaches.

Clinical Significance of Incidental Focal 18F-FDG Uptake in the Spinal Cord of Patients with Cancer

PURPOSE

We investigated the incidence, location, and clinical significance of focal ¹⁸F-FDG uptake of the spinal cord in patients with cancer.

METHODS

We reviewed the medical records of 22,937 consecutive adult patients with known or suspicious malignancy who underwent ¹⁸F-FDG PET/CT. PET/CT scans with incidental focal spinal cord uptake were selected and retrospectively reviewed to determine the presence, location, number, and maximum standardized uptake value (SUV_max) of any focal hypermetabolic lesions of the spinal cord. In subjects with focal spinal uptake, clinical characteristics and clinical follow-up results, including follow-up PET/CT, were reviewed.

RESULTS

Incidental focal spinal cord uptake was observed in 69 of 22,937 adult patients (incidence = 0.3%; M:F = 31:38; age, 55.8 ± 14.7 years). Seventy-eight focal hypermetabolic lesions on spinal cord in the PET/CT scans of the 69 study subjects were analyzed. The most common sites of focal spinal cord uptake were the T12 vertebra (47/78; 60.3%) and L1 vertebra (20/78; 25.6%). Multifocal cord uptake was found in 8 of 69 patients (11.6%). The average SUV_max for cord uptake was 2.5 ± 0.5 (range, 1.4∼3.9). There was no clinical or imaging evidence of abnormalities in the spinal cord, both at the time of PET/CT and during clinical follow-up.

CONCLUSIONS

Although incidental focal ¹⁸F-FDG uptake of the spinal cord is rare in patients with cancer, it may be physiological or benign, but it should not be considered as malignant involvement. Common sites for the uptake were in the T12 and L1 spine levels.

A Large Cohort Study of 18F Fluoro-Deoxy-Glucose Uptake in Normal Spinal Cord: Quantitative Assessment of the Contamination From Adjacent Vertebral Marrow Uptake and Validity of Normalizing the Cord Uptake Against the Lumbar Thecal Sac

PURPOSE

This study aimed (1) to assess the influence of age, sex, blood glucose, and body mass index on the F fluoro-deoxy-glucose (F-FDG) uptake in normal spinal cord; (2) to quantitatively evaluate contamination of the spinal cord SUVmax by the adjacent vertebral marrow activity; and (3) to investigate the validity of normalizing spinal cord SUVmax against lumbar thecal sac SUVmax.

METHODS

Two hundred positron emission tomography-computed tomography examinations of subjects with normal spinal cord were retrospectively reviewed. SUVmax of spinal cord and vertebral body was obtained at C2, C5, T6, T12, and L3 levels. Pearson correlation coefficients (r) were obtained at each level between spinal cord SUVmax and vertebral marrow SUVmax, age, body mass index, and blood glucose. Cord to background ratio (CTB) was calculated as the ratio between SUVmax of spinal cord and SUVmax of L3 thecal sac. The coefficient of variation (CV) of spinal cord SUVmax was compared with the CV of CTB.

RESULTS

Spinal cord SUVmax was highest at C2 (mean, 1.76) and lowest at T6 (mean, 1.37) with SD of 0.32 to 0.36 SUV. Sex (P > 0.45), age (r: -0.25 to -0.06), body mass index (r: 0.19 to 0.27), and blood glucose (r: -0.17 to 0.22) had no impact on the spinal cord SUVmax. A moderate to strong positive correlation (r: 0.66-0.80) was found between spinal cord SUVmax and the corresponding vertebral marrow SUVmax. The CV of CTB was greater (0.28-0.32) than the CV of spinal cord SUVmax (0.19-0.25) across all levels.

CONCLUSIONS

Of the variables studied, only contamination from adjacent vertebral marrow activity significantly affected the SUVmax of spinal cord. This contamination should be corrected for when reporting spinal cord FDG uptake. Lumbar thecal sac is not a valid reference for normalizing spinal cord FDG uptake.

Association between 18F-FDG PET/CT and MRI appearance of spinal leptomeningeal disease before and after treatment at a tertiary referral center

OBJECTIVE

Leptomeningeal disease (LMD), the presence of metastasis in the subarachnoid space, has devastating implications if left untreated. The gold standard for LMD diagnosis is cytologic analysis of cerebrospinal fluid (CSF); MRI is also used to evaluate suspected LMD. The purpose of this study was to compare the appearance of LMD in the spinal canal on 18F-FDG PET/CT imaging with the appearance of LMD on MRI and with CSF cytology.

METHODS

In twenty-one patients with cytologically-proven spinal LMD, findings on 18F-FDG PET/CT, MRI, and CSF cytology at diagnosis of LMD and after the initiation of treatment for LMD were retrospectively reviewed.

RESULTS

At diagnosis of LMD, abnormal 18F-FDG avidity was demonstrated in the spinal canal in six patients, and the anatomic distribution of 18F-FDG activity corresponded to the sites of LMD on MRI. All six of these patients were then treated with intrathecal chemotherapy. Follow-up 18F-FDG PET/CT and MRI were obtained in four of the six cases. In all four cases, normalization of 18F-FDG activity in the spinal canal and reduction of enhancement on MRI corresponded to the cytologic response to treatment, as determined by CSF analysis.

CONCLUSION

18F-FDG avidity in the spinal canal greater than the normal contents of the canal can suggest spinal LMD. This abnormal avidity may be detected before the diagnosis of LMD has been established with MRI or CSF cytology. The spinal canal should be routinely evaluated on 18F-FDG PET/CT in patients with suspected LMD so that appropriate treatment is initiated.

(18)F-FDG uptake of the spinal cord was decreased after conventional dose radiotherapy in esophageal cancer patients

OBJECTIVE

We retrospectively investigated changes of (18)F-fluorodeocyglucose ((18)F-FDG) uptake in the spinal cord, inside and outside the radiation fields, in patients with esophageal cancer before and after conventional dose radiotherapy.

METHODS

A total of 17 consecutive patients with esophageal cancer (16 males, one female; age 50-83 years, mean 67.0 years), who underwent conventional dose radiotherapy and (18)F-FDG PET/CT before and 5.1 months (range 1.6-8.6 months) after the radiotherapy, were retrospectively evaluated. Sixteen patients had esophageal cancer and one patient had esophageal metastasis from thyroid cancer. Mean standardized uptake values (SUVmean) of the cervical, thoracic (inside and outside the radiation fields) and lumbar spinal cord were measured.

RESULTS

SUVmean of the thoracic spinal cord inside the radiation field was decreased significantly after radiotherapy compared to those before radiotherapy (p < 0.001). SUVmean of the cervical spinal cord showed the same trend but it was not statistically significant (p = 0.051). SUVmean of the thoracic spinal cord outside the radiation field and the lumbar spinal cord did not differ significantly before and after the radiotherapy (p = 0.146 and p = 0.701, respectively).

CONCLUSIONS

The results suggest that glucose metabolism of the spinal cord is decreased in esophageal cancer patients after conventional dose radiotherapy.

Qualitative analysis of spinal intramedullary lesions using PET/CT

OBJECT Although the usefulness of PET for brain lesions has been established, few reports have examined the use of PET for spinal intramedullary lesions. This study investigated the diagnostic utility of PET/CT for spinal intramedullary lesions. METHODS l-[methyl-¹¹C]-methionine (MET)- or [¹⁸F]-fluorodeoxyglucose (FDG)-PET/CT was performed in 26 patients with spinal intramedullary lesions. The region of interest (ROI) within the spinal cord parenchyma was placed manually in the axial plane. Maximum pixel counts in the ROIs were normalized to the maximum standardized uptake value (SUV_max) using subject body weight. For FDG-PET the SUV_max was corrected for lean body mass (SUL_max) to exclude any influence of the patient's body shape. Each SUV was analyzed based on histopathological results after surgery. The diagnostic validity of the SUV was further compared with the tumor proliferation index using the MIB-1 monoclonal antibody (MIB-1 index). RESULTS A total of 16 patients underwent both FDG-PET and MET-PET, and the remaining 10 patients underwent either FDG-PET or MET-PET. Pathological diagnoses included high-grade malignancy such as glioblastoma multiforme, anaplastic astrocytoma, or anaplastic ependymoma in 5 patients; low-grade malignancy such as hemangioblastoma, diffuse astrocytoma, or ependymoma in 12 patients; and nonneoplastic lesion including cavernous malformation in 9 patients. Both FDG and MET accumulated significantly in high-grade malignancy, and the SUL_max and SUV_max correlated with the tumor proliferation index. Therapeutic response after chemotherapy or radiation in high-grade malignancy was well monitored. However, a significant difference in SUL_max and SUV_max for FDG-PET and MET-PET was not evident between low-grade malignancy and nonneoplastic lesions. CONCLUSIONS Spinal PET/CT using FDG or MET for spinal intramedullary lesions appears useful and practical, particularly for tumors with high-grade malignancy. Differentiation of tumors with low-grade malignancy from nonneoplastic lesions may still prove difficult. Further technological refinement, including the selection of radiotracer or analysis evaluation methods, is needed.

Physiological Activity of Spinal Cord in Children: An 18F-FDG PET-CT Study

STUDY DESIGN

Retrospective study.

OBJECTIVE

To evaluate, in a pediatric population, F-Fluoro-deoxy-glucose (F-FDG) metabolic activity of normal spinal cord and to assess the correlation with demographic, clinical, and environmental variables.

SUMMARY OF BACKGROUND DATA

F-FDG uptake of normal spinal cord is variable in children. The knowledge of physiological metabolism of spinal cord is essential to distinguish normal from pathological findings by positron emission tomography-computed tomography (PET-CT).

METHODS

We retrospectively evaluated F-FDG positron emission tomography-computed tomography scans from a total of 167 pediatric patients (97 males; 3.9-18.9 yr) divided into 4 age groups (0-4.9 yr, 5-9.9 yr, 10-14.9 yr, and 15-18.9 yr), excluding those submitted to previous or recent therapeutic procedures influencing spinal cord metabolism or with central nervous system diseases. Spinal cord was divided into 3 levels (C1-C7; D1-D6; and D7-L1), and maximum standardized uptake value (SUVmax) of each cord level was measured. Correlations between SUVmax and spinal cord level, age, body weight, sex, type of disease, and season were statistically assessed.

RESULTS

Median SUVmax was similar and significantly (P < 0.01) higher at C1-C7 and D7-L1 levels than at D1-D6 level and it significantly (P < 0.01) increased with age in all spinal cord levels. A positive and significant association between SUVmax and body weight, female sex, and Hodgkin lymphoma was found. No significant association with season was observed. By multivariate analysis, only weight and female sex remained significant.

CONCLUSION

Knowledge of physiological F-FDG spinal cord activity in children is essential for a correct interpretation of positron emission tomography-computed tomography, especially in oncologic pediatric patients to avoid potential pitfalls.

LEVEL OF EVIDENCE

N/A.

Postradiation changes in tissues: evaluation by imaging studies with emphasis on fluorodeoxyglucose-PET/computed tomography and correlation with histopathologic findings

Efforts have been made to minimize the damage to adjacent normal tissues during radiotherapy, primarily by shifting from the use of conventional radiotherapy to more advanced techniques. Reviewing the overall pattern on combined anatomic and functional imaging can enhance diagnostic accuracy. Several radiotracers can be used; [(18)F]fluorodeoxyglucose is the most common. Familiarity with the type and timing of previous radiation therapy, the spectrum of imaging findings after radiation injury, and the appropriate use of the different radiotracers can be crucial. This article summarizes postradiation histologic findings and multimodality imaging findings, with emphasis on PET/computed tomography.

[(18)F]-fluorodeoxyglucose-positron emission tomography in patients with active myelopathy

OBJECTIVE

To report and compare spinal cord [(18)F]-fluorodeoxyglucose-positron emission tomography (FDG-PET) metabolism in 51 patients with active myelopathy.

PATIENTS AND METHODS

We retrospectively identified patients from January 1, 2001, through December 31, 2011, with active myelopathy in whom FDG-PET was performed. Inclusion criteria were (1) intramedullary myelopathy, (2) neoplastic/inflammatory etiology, and (3) FDG-PET performed after myelopathy onset. Exclusion criteria were (1) extramedullary myelopathy, (2) radiation-associated myelopathy, (3) no pathological confirmation of neoplasm, and (4) inactive myelopathy. Diagnostic categories of nonsarcoid inflammatory, neoplastic, and neurosarcoid were based on their final myelopathic diagnosis. Two radiologists who independently assessed FDG-PET for spinal cord hypermetabolism and maximum standardized uptake value (SUVmax) were blinded to the underlying etiology.

RESULTS

Fifty-one patients (53% women) with a median age of 60 years (range, 20-82 years) were included. Inflammatory myelopathic diagnoses (n=24) were as follows: paraneoplastic (n=13), autoimmune/other (n=5), inflammatory demyelinating (n=4), and transverse myelitis (n=2). Neoplastic diagnoses (n=21) were as follows: intramedullary metastases (n=12), intramedullary lymphoma/leukemia (n=7), and primary intramedullary neoplasm (n=2). Six patients had neurosarcoid myelopathy. Spinal cord hypermetabolism was more common with neoplastic myelopathy than with nonsarcoid inflammatory myelopathy (17 of 21 [81%] vs 6 of 24 [25%]; P<.001). Agreement between radiologist's assessments was excellent (κ=0.88). Median SUVmax was greater in neoplastic than in nonsarcoid inflammatory causes of myelopathy (3.3 g/mL vs 1.9 g/mL; P<.001). The FDG-PET hypermetabolism was seen in 3 of the 6 patients (50%) with neurosarcoid myelopathy (median SUVmax, 2.6 g/mL; range, 1.8-12.2 g/mL).

CONCLUSION

Spinal cord FDG-PET hypermetabolism in patients with active myelopathy may be reliably detected and was more common in neoplastic than in inflammatory myelopathies in this study. Future investigation of spinal cord FDG-PET is indicated to assess its potential contributions in evaluating active myelopathies.

Completing the Pain Circuit: Recent Advances in Imaging Pain and Inflammation beyond the Central Nervous System

This review describes some of the recent developments in imaging aspects of pain in the periphery. It is now possible to image nerves in the cornea non-invasively, to image receptor level expression and inflammatory processes in injured tissue, to image nerves and alterations in nerve properties, to image astrocyte and glial roles in neuroinflammatory processes, and to image pain conduction functionally in the trigeminal ganglion. These advances will ultimately allow us to describe the pain pathway, from injury site to behavioral consequence, in a quantitative manner. Such a development could lead to diagnostics determining the source of pain (peripheral or central), objective monitoring of treatment progression, and, hopefully, objective biomarkers of pain.

Clinical value of 2-deoxy-[18F]fluoro-d-glucose positron emission tomography in patients with cervical spondylotic myelopathy

Cervical spondylotic myelopathy (CSM) is one of the most common spinal cord disorders in the elderly. It is usually diagnosed by MRI, but in a significant number of patients the clinical course of CSM does not correlate with the extent of the spinal cord compression. Recent studies have suggested that a distinct metabolic pattern of the cervical cord, as assessed by PET with 2-deoxy-[18F]fluoro-d-glucose (18F-FDG) may predict a patient's clinical outcome after decompressive surgery for cervical spine stenosis. The authors provide an overview of the recent literature regarding the value of PET with 18F-FDG of the cervical cord in patients with CSM, paying attention to prognostic aspects and the potential role of inflammatory processes in the acute phase of the disease.

Changes in (18)f-fluorodeoxyglucose uptake in the spinal cord in a healthy population on serial positron emission tomography/computed tomography

We aimed to determine the changes in ¹⁸F-fluorodeoxyglucose (FDG) uptake in the spinal cord on two serial positron emission tomography/computed tomography (PET/CT) scans in a healthy population. We retrospectively enrolled healthy people who underwent PET/CT twice for cancer screening. We excluded those who had degenerative vertebral disease, neurologic disease, or a history of a vertebral operation. The standardized uptake value (SUVmax) of the spinal cord of each mid-vertebral body was obtained by drawing a region of interest on an axial image of PET/CT. For analysis, the cord-to-background ratio (CTB) was used (CTB=SUVmax of each level/SUVmax of L5 level). Differences in pattern, sex, age, and intervals of the two serial PET/CT scans were analyzed. A total of 60 PET/CT images of 30 people were analyzed. The mean interval between the two PET/CT imaging studies was 2.80±0.94 years. On the follow-up PET/CT, significant change was shown only at the level of the C6 and T10 vertebrae (p<0.005). Mean CTB showed a decreasing pattern from cervical to lumbar vertebrae. There were two peaks at the lower cervical level (C4-6) and at the lower thoracic level (T12). Neither sex nor age significantly affected CTB. The FDG uptake of the spinal cord changed significantly on follow-up PET/CT only at the level of the C6 and T10 vertebrae. This finding is valuable as a baseline reference in the follow-up of metabolic changes in the spinal cord.