Clinical utility of texture analysis of 18F-FDG PET/CT in patients with Stage I lung cancer treated with stereotactic body radiotherapy

We evaluated the reproducibility and predictive value of texture parameters and existing parameters of 18F-FDG PET/CT images in Stage I non-small-cell lung cancer (NSCLC) patients treated with stereotactic body radiotherapy (SBRT). Twenty-six patients with Stage I NSCLC (T1-2N0M0) were retrospectively analyzed. All of the patients underwent an 18F-FDG PET/CT scan before treatment and were treated with SBRT. Each tumor was delineated using PET Edge (MIM Software Inc., Cleveland, OH), and texture parameters were calculated using open-source code CGITA. From 18F-FDG PET/CT images, three conventional parameters, including maximum standardized uptake value (SUV), metabolic tumor volume (MTV) and total lesion glycolysis (TLG), and four texture parameters, including entropy and dissimilarity (derived from a co-occurrence matrix) and high-intensity large-area emphasis (HILAE) and zone percentage (derived from a size-zone matrix) were analyzed. Reproducibility was evaluated using two independent delineations conducted by two observers. The ability to predict local control (LC), progression-free survival (PFS) and overall survival (OS) was tested for each parameter. All of the seven parameters except zone percentage showed good reproducibility, with intraclass correlation coefficient values >0.8. In univariate analysis, only HILAE was a significant predictor for LC. Histology, dose fractionation, and maximum SUV were associated with PFS, and histology and dose fractionation were associated with OS. We showed that texture parameters derived from 18F-FDG PET/CT were reproducible and potentially beneficial for predicting LC in Stage I lung cancer patients treated with SBRT.

Pancreatic solitary fibrous tumor causing ectopic adrenocorticotropic hormone syndrome

Solitary fibrous tumors occasionally present with hypoglycemia because of the excessive release of insulin-like growth factor II. We report the first case of pancreatic solitary fibrous tumor causing ectopic adrenocorticotropic hormone syndrome. An 82-year-old Japanese man presented with lower limb edema, uncontrolled hypertension, hypokalemia, and baseline hypercortisolism. Distal pancreatectomy was performed after the clinical diagnosis of a neuroendocrine tumor with ectopic secretion of adrenocorticotropic hormone. On histological examination, the tumor showed spindle cells in a fascicular arrangement. The diagnosis of the solitary fibrous tumor was confirmed by the identification of the NAB2-STAT6 fusion gene and positive immuno-histochemical staining for STAT6 and CD34. Using quantitative real-time polymerase chain reaction, mRNA that encoded proopiomelanocortin, precursor of adrenocorticotropic hormone, was detected. Proopiomelanocortin production through the demethylation of the promoter region Domain IV was detected. Pancreatic solitary fibrous tumors represent a new cause of ectopic adrenocorticotropic hormone syndrome.

Pitfalls of voxel-based amyloid PET analyses for diagnosis of Alzheimer's disease: artifacts due to non-specific uptake in the white matter and the skull

Two methods are commonly used in brain image voxel-based analyses widely used for dementia work-ups: 3-dimensional stereotactic surface projections (3D-SSP) and statistical parametric mapping (SPM). The methods calculate the Z-scores of the cortical voxels that represent the significance of differences compared to a database of brain images with normal findings, and visualize them as surface brain maps. The methods are considered useful in amyloid positron emission tomography (PET) analyses to detect small amounts of amyloid-β deposits in early-stage Alzheimer's disease (AD), but are not fully validated. We analyzed the (11)C-labeled 2-(2-[2-dimethylaminothiazol-5-yl]ethenyl)-6-(2-[fluoro]ethoxy)benzoxazole (BF-227) amyloid PET imaging of 56 subjects (20 individuals with mild cognitive impairment [MCI], 19 AD patients, and 17 non-demented [ND] volunteers) with 3D-SSP and the easy Z-score imaging system (eZIS) that is an SPM-based method. To clarify these methods' limitations, we visually compared Z-score maps output from the two methods and investigated the causes of discrepancies between them. Discrepancies were found in 27 subjects (9 MCI, 13 AD, and 5 ND). Relatively high white matter uptake was considered to cause higher Z-scores on 3D-SSP in 4 subjects (1 MCI and 3 ND). Meanwhile, in 17 subjects (6 MCI, 9 AD, and 2 ND), Z-score overestimation on eZIS corresponded with high skull uptake and disappeared after removing the skull uptake ("scalping"). Our results suggest that non-specific uptakes in the white matter and skull account for errors in voxel-based amyloid PET analyses. Thus, diagnoses based on 3D-SSP data require checking white matter uptake, and "scalping" is recommended before eZIS analysis.

Assessment of myocardial metabolic disorder associated with mediastinal radiotherapy for esophageal cancer -a pilot study

Background

To evaluate the dose-effect relations for myocardial metabolic disorders after mediastinal radiotherapy (RT) by performing iodine-123 β-methyl-iodophenyl pentadecanoic acid (I-123 BMIPP) scintigraphy.

Methods

Between 2011 and 2012, we performed I-123 BMIPP scintigraphy for patients with esophageal cancer before and six months after curative mediastinal RT. Single photon emission computed tomography (SPECT) images of pre-RT and post-RT were registered into RT dose distributions. The myocardium was contoured, and the regional RT dose was calculated. Normalization is required to compare pre- and post-RT SPECT images because the uptake pattern is changed due to the breathing level. Normalization was applied on the mean of SPECT counts in regions of the myocardium receiving less than 5 Gy. Relative values in each dose region (interval of 5 Gy) were calculated on the basis of this normalization for each patient. The reduction in the percent of relative values was calculated.

Results

Five patients were enrolled in this study. None of the patients had a past history of cardiac disease. The left ventricle was partially involved in RT fields in all patients. The patients received RT with median total doses of 60-66 Gy for the primary tumor and metastatic lymph nodes. Concomitant chemotherapy consisting of cisplatin or nedaplatin and 5-fluorouracil with RT was performed in 4 patients. All patients had reduced uptake corresponding to RT fields. Dose-effect relations for reduced uptake tended to be observed at 6 months after RT with mean decreases of 8.96% in regions at 10-15 Gy, 12.6% in regions at 20-25 Gy, 15.6% in regions at 30-35 Gy, 19.0% in regions at 40-45 Gy and 16.0% in regions at 50-55 Gy.

Conclusions

Dose-effect relations for myocardial metabolic disorders tended to be observed. We may need to make an effort to reduce high-dose mediastinal RT to the myocardium in RT planning.

Case report: adrenal oncocytoma associated with markedly increased FDG uptake and immunohistochemically positive for GLUT1

Usually, benign tumors are not associated with an increased F-18 fluorodeoxyglucose (F-18 FDG) uptake on positron emission tomography (PET), although some exceptions have been reported in adrenal neoplasms. We present a rare case of adrenocortical oncocytoma associated with markedly increased FDG uptake, demonstrating a maximum standardized uptake value of 46.8. Histological examination demonstrated diffuse proliferation of tumor cells with eosinophilic and granular cytoplasm that were diffusely immunopositive for mitochondria and glucose transport protein 1, with focal and weak immunopositivity for 3β-hydroxysteroid dehydrogenase. Ultrastructural examination also revealed abundant mitochondria in the tumor cells. The tumor was diagnosed as adrenocortical oncocytoma and was considered benign according to Lin-Weiss-Bisceglia criteria. Diagnosis of adrenocortical oncocytoma can pose difficulties during both preoperative radiological and postoperative histopathological investigations.

MRI findings of radiation-induced myocardial damage in patients with oesophageal cancer

AIM

To evaluate radiation-induced myocardial damage after mediastinal radiotherapy using MRI.

MATERIALS AND METHODS

Between May 2010 and April 2011, delayed contrast-enhanced MRI was performed for patients who had maintained a complete response to curative radiotherapy for oesophageal cancer for more than 6 months. The patients received radiotherapy with a median total dose of 66 Gy (60-70 Gy) for the primary tumour and metastatic lymph nodes. Images of MRI were analysed by a 17-segment method recommended by the American Heart Association. A segment included mainly in the 40 Gy dose line was defined as Segment 40 Gy, a segment included mainly in the 60 Gy dose line as Segment 60 Gy, and a segment out of the radiation fields as Segment OUT. The percentage of late gadolinium enhancement (LGE) was examined in those categories. The layer in which LGE was predominantly distributed was evaluated for each patient.

RESULTS

Four hundred and eight segments in 24 patients were analysed. The median interval from completion of radiotherapy to MRI was 23.5 months (range 6-88 months). LGE was detected in 12 of the 24 patients. LGE was detected in 15.38% of Segment 40 Gy cases, 21.21% of Segment 60 Gy cases, and 0% of Segment OUT cases. LGE in mid-myocardial and subendocardial layers was detected in 11 patients and one patient, respectively.

CONCLUSION

LGE suggesting radiation induced myocardial fibrosis was observed by performing delayed contrast-enhanced MRI. Care should be taken when planning radiotherapy to avoid late cardiac damage.

Evaluation of radiation-induced myocardial damage using iodine-123 β-methyl-iodophenyl pentadecanoic acid scintigraphy

We evaluated radiation-induced myocardial damage using iodine-123 β-methyl-iodophenyl pentadecanoic acid (I-123 BMIPP) scintigraphy. Between May 2010 and April 2011 we performed I-123 BMIPP scintigraphy for patients who had maintained complete response to curative radiotherapy (RT) for esophageal cancer for more than six months. We compared the area of the myocardium in the RT fields with that of reduced I-123 BMIPP uptake using a 15-segment model that is based on axial computed tomography (CT) images. We classified the segments into three categories: segments receiving 40 Gy (Segment 40 Gy), segments receiving 60 Gy (Segment 60 Gy) and segments out of the radiation fields (Segment 0 Gy). A segment with reduced uptake in the RT fields was defined as positive. A total of 510 segments in 34 patients were used for analysis. The median interval from completion of RT to I-123 BMIPP scintigraphy was 22 months (range, 6-103 months). The numbers of Segment 0 Gy, Segment 40 Gy and Segment 60 Gy were 324, 133 and 53, respectively. Reduced uptake was detected in 42.9% (57/133) of Segment 40 Gy, 67.9% (36/53) of Segment 60 Gy and 13.3% (43/324) of Segment 0 Gy. The odds ratios of 40 Gy and 60 Gy compared with regions out of the RT fields were 5.2 (95% confidence interval [CI]: 3.7-7.4) and 15.4 (95% CI: 6.9-34.6), respectively. Reduced myocardial I-123 BMIPP uptake in RT fields, suggesting RT-induced myocardial damage, was frequently observed. I-123 BMIPP myocardial scintigraphy may be useful for identifying RT-induced myocardial damage.

Intraductal papillary mucininous neoplasm of the bile ducts: multimodality assessment with pathologic correlation

Mucin-producing intraductal papillary neoplasm (adenocarcinoma/adenoma) in the bile duct is becoming recognized as a specific type of neoplasm. Since, it bears a striking similarity to intraductal papillary mucinous neoplasms of the pancreas with regard to its histopathologic features, the term "intraductal papillary mucinous neoplasms of the bile duct" (IPMN-B) is frequently used, although no definite terminology or definition has been decided by World Health Organization. This neoplasm lacks ovarian-like stroma and communicates with the bile ducts, unlike biliary mucinous cystic neoplasm (MCN). On the other hand, malignant IPMN-B is categorized as an intraductal-growth type of intrahepatic cholangiocarcinoma (ICC). In comparison to other types of ICC, such as the mass-forming type and periductal-infiltrating type that have poor resectability and an unfavorable prognosis, malignant IPMN-B can be resected and demonstrates a more favorable prognosis. Meanwhile, unlike biliary MCN that is usually confined in a closed cyst, IPMN-B can spread along the mucosal surface of the bile ducts, and it should be widely resected. Therefore, multimodality assessment is needed to ensure the correct diagnosis of IPMN-B. We herein review the imaging findings of IPMN-B with pathologic correlation.

Additional value of FDG PET/CT to contrast-enhanced CT in the differentiation between benign and malignant intraductal papillary mucinous neoplasms of the pancreas with mural nodules

OBJECTIVES

This study aimed at determining the additional value of FDG PET/CT to contrast-enhanced CT in the differentiation between benign and malignant intraductal papillary mucinous neoplasms (IPMNs) of the pancreas with mural nodules.

METHODS

This retrospective review of medical records was approved by our institutional review board. The preoperative PET/CT images of 16 non-diabetic patients with surgically proven IPMN, where mural nodules of 3 mm or larger were shown by preoperative contrast-enhanced CT, were retrospectively evaluated. The 16 patients were divided into two groups: 7 patients with benign IPMN [adenoma (n = 1) and borderline tumor (n = 6)] and 9 patients with malignant IPMN [carcinoma in situ (CIS) (n = 8) and invasive carcinoma (n = 1)]. Nuclear medicine physician blinded to the pathologic assessment of malignancy of IPMN set a spherical volume of interest (VOI) over the mural nodules on PET/CT images and recorded the peak standardized uptake value (SUV(max)) in the VOI, referring the contrast-enhanced CT images. Statistical differences in the size of mural nodule, the diameter of main pancreatic duct (MPD), and SUV(max) of the tumors between benign IPMNs and malignant IPMNs were compared using the Mann-Whitney U test. Statistical significance was set at p < 0.05. Additionally, the diagnostic accuracy of FDG PET for the detection of malignancy was calculated.

RESULTS

The SUV(max) of the malignant IPMNs with mural nodules of 3 mm or larger was higher than that of benign IPMNs (2.7 ± 0.6 vs. 1.9 ± 0.3, p < 0.01). Meanwhile, there was no significant difference in mural nodule diameter and MPD diameter between the two groups. FDG PET/CT showed an excellent diagnostic accuracy for the differentiation between malignant and benign IPMNs with mural nodules: the sensitivity, specificity, PPV, NPV, and accuracy in malignant IPMN with mural nodule of FDG PET/CT were 77.8, 100, 100, 77.8, and 87.5 for the cutoff value of 2.3; and 100, 57.1, 75.0, 100, and 81.3 for the cutoff value of 2.0, respectively.

CONCLUSIONS

The result of this study indicates that FDG PET/CT can provide additional information for the differentiation between benign and malignant IPMNs of the pancreas with mural nodules.

Positive correlations between tumor uptake on FDG PET and energy expenditure of patients with esophageal cancer

PURPOSE

Cancer patients are prone to clinical malnutrition; moreover, the energy expenditure in patients with certain cancers is higher than that in healthy individuals, rendering their nutritional management a challenging issue. We hypothesized that 2-deoxy-2-[(18)F]fluoro-D: -glucose (FDG) uptake on positron emission tomography (PET) may be related to the energy expenditure and analyzed the FDG uptake and energy expenditure in esophageal cancer patients to clarify this.

METHODS

Esophageal cancer patients [n = 13, 10 males and 3 females, age 66.5 ± 8.9 (51-82) years] were evaluated for FDG uptake using PET. The resting energy expenditure (REE) and basal energy expenditure (BEE) were calculated using indirect calorimetry and the Harris-Benedict formula, respectively. Regression analyses were performed to compare the parameters of imaging and energy expenditure.

RESULTS

Positive correlations were found between tumor uptake on FDG PET and the parameters of energy expenditure. Among them, the correlations between SUV(max) and the ratio of REE to BEE (REE/BEE, r = 0.59; p = 0.035) and between SUV(max) and the difference between REE and BEE (REE - BEE, r = 0.58; p = 0.036) were moderate and statistically significant. Further, the correlation between tumor uptake expressed as a percentage (%TU) and REE/BEE was mild (r = 0.51) but not significant (p = 0.07), while that between %TU and REE-BEE was weak (r = 0.42) and not significant (p = 0.15).

CONCLUSION

Significant positive correlations between SUV(max) on FDG PET and energy expenditure were noted in our study; we consider that these results may aid in determining the nutritional management for esophageal cancer patients.

Imaging of hypoxic lesions in patients with gliomas by using positron emission tomography with 1-(2-[18F] fluoro-1-[hydroxymethyl]ethoxy)methyl-2-nitroimidazole, a new 18F-labeled 2-nitroimidazole analog

OBJECT

Assessment of hypoxic conditions in brain tumors is important for predicting tumor aggressiveness and treatment response. A new hypoxia imaging agent, 1-(2-[(18)F]fluoro-1-[hydroxymethyl]ethoxy)methyl-2-nitroimidazole (FRP-170), with higher image contrast and faster clearance than preexisting hypoxia tracers for PET, was used to visualize hypoxic tissues in 8 patients with glioma.

METHODS

The FRP-170 was injected and PET imaging was performed 2 hours later in 8 patients, including 3 with glioblastoma multiforme, 2 with oligodendroglioma, and 1 each with diffuse astrocytoma, anaplastic ganglioglioma, and recurrent anaplastic astrocytoma. All 8 patients also underwent MR imaging, and some patients underwent [(11)C]methionine or [(18)F]fluorodeoxyglucose PET, and proton MR spectroscopy for comparison. Tissues obtained at biopsy or radical resection were immunostained with hypoxia-inducible factor-1alpha (HIF-1alpha) antibody for the confirmation of hypoxia, except in the patient with recurrent anaplastic astrocytoma who was treated using Gamma Knife surgery.

RESULTS

The FRP-170 PET images showed marked uptake with upregulation of HIF-1alpha in the 3 glioblastomas multiforme, and moderate uptake in the recurrent anaplastic astrocytoma and one oligodendroglioma, but no uptake in the other tumors. The FRP-170 PET images showed positive correlation with HIF-1alpha immunoreactivity and some correlation with FDG PET and MR imaging enhancement, but no correlation with [(11)C]methionine PET. Imaging with FRP-170 PET seemed to be more sensitive for detecting hypoxia than identifying the lactate peak on proton MR spectroscopy.

CONCLUSIONS

Imaging with FRP-170 PET can visualize hypoxic lesions in patients with glioma, as confirmed by histological examination. This new method can assess tumor hypoxia preoperatively and noninvasively.

Steroid receptor signalling in the brain--lessons learned from molecular imaging

Studies with green fluorescent protein (GFP) have revealed the subcellular distribution of many steroid hormone receptors to be much more dynamic than previously thought. Fluorescence resonance energy transfer (FRET) and fluorescence recovery after photobleaching (FRAP) are powerful techniques with which to examine protein-protein interaction and the mobility of tagged proteins, respectively. FRET analysis revealed that steroid treatment (with corticosterone or testosterone) induces direct interaction of the glucocorticoid receptor (GR) and importin alpha in the cytoplasm and that, shortly after nuclear entry, the GR detaches from importin alpha. The mineralocorticoid receptor (MR) and androgen receptor (AR) show the same trafficking. Upon oestradiol treatment, ERalpha and ERbeta in the same cell are relocalised to form a discrete pattern and are localised in the same discrete cluster (subnuclear foci). FRAP analysis showed that nuclear ERalpha and ERbeta are most dynamic and mobile in the absence of the ligand, and that mobility decreases slightly after ligand treatment. Genomic as well as non-genomic actions of steroid hormones influence the cellular function of target tissues spacio-temporally.

Validation of the use of calibration factors between the iodine concentration and the computed tomography number measured outside the objects for estimation of iodine concentration inside the objects: phantom experiment

PURPOSE

The aim of this study was to validate the use of a calibration factor measured outside the object for estimating the iodine concentration inside the object to improve the accuracy of the quantitative contrast-enhanced computed tomography (CT).

MATERIALS AND METHODS

Several known concentrations (0, 6, 9, and 12 mg I/ml) of iodine contrast material (CM) samples were placed inside and outside cylindrical acrylic phantoms of two sizes and were imaged under various combinations of the tube voltages and currents (kV/mAs-80/200, 100/200, 120/200, 140/200) to obtain K factors. The K factors were compared between the phantoms and among the tube voltages. Each CM concentration was estimated from the CT number using the K factor measured outside the phantom.

RESULTS

The K factors varied between the phantoms or among the tube voltages (P < 0.05). Although there were statistically significant variations in K factors among the different regions in a phantom, the mean variation coefficient was 3%-4%. The mean error of the estimated concentration was -5.5%.

CONCLUSION

The CM concentration should be accurately estimated at the region within a patient's body using the K factor measured at the surface of the body regardless of body size and tube voltage.

Intense FDG Uptake in the Ovary With Painless Torsion

We report a case demonstrating intense FDG uptake in the ovary, which was diagnosed to be a hemorrhage and congestion due to painless torsion. An asymptomatic retropelvic mass was detected in a 51-year-old female by echography. FDG-PET demonstrated intense uptake in the mass, thus suggesting an ovarian tumor. A resection of the tumor was performed, and histopathological examination revealed hemorrhage and congestion in the ovary due to ovarian torsion. An ovarian hemorrhage due to painless torsion should be considered in the differential diagnosis of intrapelvic masses demonstrating high FDG uptake, even in asymptomatic patients.

High-density materials do not always induce artifacts on PET/CT: What is responsible for the difference?

OBJECTIVE

PET/CT often show increased uptake at sites of high-density materials. However, some materials seldom demonstrate increased uptake on PET/CT, such as the materials used in hip prostheses. We hypothesized that the motion of materials may be crucial for such artifacts. Here, we present representative cases, and validate our hypothesis based on the results of phantom studies.

METHODS

A standard cylinder, 20 cm in diameter, was filled with approximately 37 MBq of 18F-based activity, and a pacemaker was attached to the side of the cylinder. This phantom was placed on the bed with the pacemaker side facing the scanner. PET scans were performed using a Biograph LSO DUO. CT scans were performed first for transmission scans, followed by acquisition of emission scans. The phantom was first scanned (protocol 1). The phantom was then moved about 2 cm closer to the distal edge of the bed just after transmission CT scan, and the emission scan was performed (protocol 2).

RESULTS

Homogenous uptake was seen in the cylinder in protocol 1, and there was no visible uptake at the site of the pacemaker. In contrast, a clear hotspot was seen at the site of the pacemaker in protocol 2. The uptake in the cylinder was inhomogeneous; that on the pacemaker side of the cylinder was low, while that on the opposite side was high.

CONCLUSIONS

High-density materials do not show false increased uptake without motion on PET/CT. Motion of these materials surrounded by radioactive organs may play an important role in inducing false increased uptake on PET/CT.