Clinical evaluation of whole-body oncologic PET with time-of-flight and point-spread function for the hybrid PET/MR system

PurposeHybrid positron emission tomography/magnetic resonance (PET/MR) imaging is a new multimodality imaging technology that can provide structural and functional information simultaneously. The aim of this study was to investigate the effects of the time-of-flight (TOF) and point-spread function (PSF) on small lesions observed in PET/MR images from clinical patient image sets.Materials and methodsThis study evaluated 54 small lesions in 14 patients who had undergone ¹⁸F-fluorodeoxyglucose (FDG) PET/MR. Lesions up to 30 mm in diameter were included. The PET data were reconstructed with a baseline ordered-subsets expectation-maximization (OSEM) algorithm, OSEM + PSF, OSEM + TOF and OSEM + TOF + PSF. PET image quality and small lesions were visually evaluated and scored by a 3-point scale. A quantitative analysis was then performed using the mean and maximum standardized uptake value (SUV) of the small lesions (SUV_mean and SUV_max). The lesions were divided into two groups according to the long-axis diameter and the location respectively and evaluated with each reconstruction algorithm. We also evaluated the background signal by analyzing the SUV_liver.ResultsOSEM + TOF + PSF provided the highest value and OSEM + TOF or PSF showed a higher value than OSEM for the visual assessment and quantitative analysis. The combination of TOF and PSF increased the SUV_mean by 26.6% and the SUV_max by 30.0%. The SUV_liverwas not influenced by PSF or TOF. For the OSEM + TOF + PSF model, the change in SUV_mean and SUV_max for lesions <10 mm in diameter was 31.9% and 35.8%, and 24.5% and 27.6% for lesions 10–30 mm in diameter, respectively. The abdominal lesions obtained the higher SUV than those of chest on the images with TOF and/or PSF.ConclusionApplication of TOF and PSF significantly increased the SUV of small lesions in hybrid PET/MR images, potentially improving small lesion detectability.     

Quantification accuracy of neuro-oncology PET data as a function of emission scan duration in PET/MR compared to PET/CT

ObjectivesTo evaluate and compare the effect of reduced acquisition time, as a surrogate of injected activity, on the PET quantification accuracy in PET/CT and PET/MR imaging.MethodsTwenty min ¹⁸F-FDG phantom measurements and 10 min ¹⁸F-FET brain scans were acquired in a Biograph-True-Point-True-View PET/CT (n = 8) and a Biograph mMR PET/MR (n = 16). Listmode data were repeatedly split into frames of 1 min to 10 min length and reconstructed using two different reconstruction settings of a 3D-OSEM algorithm: with post-filtering (“OSEM”), and without post-filtering but with resolution recovery (“PSF”). Recovery coefficients (RC_max, RC_A50) and standard uptake values (SUV_max, SUV_A50) were evaluated.ResultsRC_max (phantom) and SUV_max (patients) increased significantly when reducing the frame duration. Significantly lower deviations were observed for RC_A50 and SUV_A50, respectively, making them more appropriate to compare PET studies at different number of counts. No statistical significant differences were observed when using post-filtering and reducing the frame time to 4 min (RC_A50, reference 20 min, phantom) and to 3 min (SUV_A50, reference 10 min, patients).ConclusionsFor hybrid aminoacid brain imaging, frame duration (or injected activity) can potentially be reduced to 30% of the standard used in clinical routine without significant changes on the quantification accuracy of the PET images if adequate reconstruction settings and quantitative measures are used. Frame times below 4 min in the NEMA phantom are not advisable to obtain quantitative and reproducible measures.     

Assessment of treatment response after lung stereotactic body radiotherapy using diffusion weighted magnetic resonance imaging and positron emission tomography: A pilot study

Background and purposeThere is no early predictor of treatment response after lung stereotactic body radiotherapy (SBRT). We conducted this pilot study to evaluate whether serial diffusion weighted magnetic resonance imaging (DW-MRI) or positron emission tomography (PET) could predict response after SBRT.Material and methodsEarly stage non-small cell lung cancer patients who received SBRT were eligible. DW-MRI and PET were undertaken pretreatment and every 3 months after SBRT in the first year. Patients with <1 year of follow-up were excluded from the analysis. The apparent diffusion coefficient (ADC) value and maximum standardized uptake value (SUV_max) of tumors were measured and compared between groups with or without local recurrence (LR).ResultsFifteen patients were enrolled and the data of 14 patients were analyzed. The median ADC value was significantly lower in patients with LR (n = 3) than in those without LR (n = 11) at 3 and 6 months (1.11 vs. 1.54 and 0.98 vs. 1.69 [×10⁻³ mm²/s]; p = 0.039 and 0.012, respectively) while there was no significant difference pretreatment and at 9 and 12 months after treatment. No significant difference was observed in the SUV_max at any time point.ConclusionsDW-MRI could be an early predictor of treatment response after lung SBRT.     

Prospective intra-individual comparison of standard dose versus reduced-dose thoracic CT using hybrid and pure iterative reconstruction in a follow-up cohort of pulmonary nodules—Effect of detectability of pulmonary nodules with lowering dose based on nodule size,type and body mass index

ObjectivesTo determine the diagnostic accuracy of lung nodule detection in thoracic CT using 2 reduced dose protocols comparing 3 available CT reconstruction algorithms (filtered back projection-FBP, adaptive statistical reconstruction-ASIR and model-based iterative reconstruction-MBIR) in a western population.Materials and methodsA prospective single-center study recruited 98 patients with written consent. Standard dose (STD) thoracic CT followed by 2 reduced-dose protocols using automatic tube current modulation (RD1) and fixed tube current (RD2) were performed and reconstructed with FBP, ASIR and MBIR with subsequent diagnostic accuracy analysis for nodule detection.Results108 solid nodules, 47 subsolid nodules and 89 purely calcified nodules were analyzed. RD1 was superior to RD2 for assessment of solid nodules ≤4 mm, and subsolid nodules ≤5 mm (p < 0.05). Deterioration of RD2 is correlated to patient’s body mass index and least affected by MBIR. For solid nodules ≤4 mm, MBIR area under curve (AUC) for RD1 was 0.935/0.913 and AUC for RD2 was 0.739/0.739, for rater 1/rater2 respectively. For subsolid nodules ≤5 mm, MBIR AUC for RD1 was 0.971/0.986 and AUC for RD2 was 0.914/0.914, for rater 1/rater2 respectively. For calcified nodules excellent detection accuracy was maintained regardless of reconstruction algorithms with AUC >0.97 for both readers across all dose and reconstruction algorithms.ConclusionsDiagnostic performance of lung nodule is affected by nodule size, protocol, reconstruction algorithm and patient’s body habitus. The protocol in this study showed that RD1 was superior to RD2 for assessment of solid nodules ≤4 mm, and subsolid nodules ≤5 mm and deterioration of RD2 is related to patient’s body mass index.     

Differentiation and diagnosis of benign and malignant testicular lesions using 18F-FDG PET/CT

ObjectivesThe purpose of this study was to evaluate the differential diagnostic value of ¹⁸F-fluorodeoxy glucose positron emission tomography/computed tomography (¹⁸F-FDG PET/CT) for benign and malignant testicular lesions.MethodsThe PET/CT scans of 53 patients with testicular lesions confirmed by biopsy or surgical pathology were retrospectively analyzed. There were 32 cases of malignant tumors and 21 cases of benign lesions. Differences in the maximum standardized uptake value (SUVmax) measurements and the SUVmax lesion/background ratios between benign and malignant lesions were analyzed. The diagnostic value of this PET/CT modality for the differential diagnosis of benign versus malignant testicular lesions was calculated.ResultsThe differences in the SUVmax measurements and the SUVmax lesion/background ratios between benign and malignant lesions were statistically significant (SUVmax: Z = −4.295, p = 0.000; SUVmax lesion/background ratio: Z = −5.219, p = 0.000); specifically, both of these indicators were higher in malignant lesions compared to benign lesions. An SUVmax of 3.75 was the optimal cutoff value to differentiate between benign and malignant testicular lesions. The diagnostic sensitivity, specificity, accuracy, positive predictive value, and negative predictive value of this PET/CT modality in the differential diagnosis of benign versus malignant testicular lesions were 90.6%, 80.9%, 86.8%, 87.9%, and 85.0%, respectively.Conclusions¹⁸F-FDG PET/CT can accurately identify benign and malignant testicular lesions.     

Raw-data-based iterative reconstruction versus filtered back projection: image quality of low-dose chest computed tomography examinations in 87 patients

ObjectiveThe objective was to compare standard-dose chest computed tomography (CT) reconstructed with filtered back projection (FBP) versus low-dose images with FBP and raw-data-based iterative reconstruction.MethodsEighty-seven consecutive patients (46 male; mean age, 54.54±16.12; mean body mass index, 24.58±4.07) referred for initial chest CT with full-dose examinations [mean dose–length product (DLP), 183.37±44.13 mGy·cm] and follow-up chest CT with half-dose examinations (mean DLP, 91.08±23.81 mGy·cm) were included. The full-dose protocol was reconstructed with FBP; the half-dose protocol was reconstructed with FBP and sinogram-affirmed iterative reconstruction (SAFIRE). Noise and signal-to-noise ratio were compared using a paired Student’s t test; subjective image quality and lesion conspicuity were compared using Wilcoxon signed ranks test.ResultsActual radiation dose of follow-up CT was about 50% (49.26%±2.62%) of standard-dose protocol. Compared to full-dose images with FBP, there was no significant difference in half-dose images with SAFIRE in the objective noise (ascending aorta: P= .38, descending aorta: P= .70, trachea on mediastinal images: P= .37) and SNR (ascending aorta: P= .14, descending aorta: P= .72, trachea on mediastinal images: P= .06) on mediastinal images. Noise was significantly lower (P< .001) and SNR was significantly higher (P< .001) in half-dose images with SAFIRE on lung images. Noise was significantly higher (P< .001) and SNR was significantly lower (P< .001) in half-dose images with FBP. Subjective image quality was similar on both mediastinal images (P= .317) and lung images (P= .614) of half-dose SAFIRE images versus full-dose FBP images. Lesion conspicuity was also similar. Subjective image quality was significantly lower on both mediastinal images (P< .001) and lung images (P< .001) of half-dose FBP images versus full-dose FBP images. The conspicuity of some lesions was significantly lower (ground-glass opacity, P< .0001; ill-defined micronodule, P< .0001; lung cyst, P< .0001; emphysematous lesion, P= .003) on half-dose FBP versus full-dose FBP images.ConclusionCompared to full-dose CT images reconstructed with the conventional FBP algorithm, SAFIRE with three iterations could provide similar or better image quality at 50% less dose.     

Improved clinical workflow for simultaneous whole-body PET/MRI using high-resolution CAIPIRINHA-accelerated MR-based attenuation correction

PurposeTo explore the value and reproducibility of a novel magnetic resonance based attenuation correction (MRAC) using a CAIPIRINHA-accelerated T1-weighted Dixon 3D-VIBE sequence for whole-body PET/MRI compared to the clinical standard.MethodsThe PET raw data of 19 patients from clinical routine were reconstructed with standard MRAC (MRAC_std) and the novel MRAC (MRAC_caipi), a prototype CAIPIRINHA accelerated Dixon 3D-VIBE sequence, both acquired in 19 s/bed position. Volume of interests (VOIs) for liver, lung and all voxels of the total image stack were created to calculate standardized uptake values (SUV_mean) followed by inter-method agreement (Passing-Bablok regression, Bland-Altman analysis). A voxel-wise SUV comparison per patient was performed for intra-individual correlation between MRAC_std and MRAC_caipi. Difference images (MRAC_std-MRAC_caipi) of attenuation maps and SUV images were calculated. The image quality of in/opposed-phase water and fat images obtained from MRAC_caipi was assessed by two readers on a 5-point Likert-scale including intra-class coefficients for inter-reader agreement.ResultsSUV_mean correlations of VOIs demonstrated high linearity (0.95 < Spearman’s rho < 1, p < 0.0001, respectively), substantiated by voxel-wise SUV scatter-plots (1.79 × 10⁸ pixels). Outliers could be explained by different physiological conditions between the scans such as different segmentation of air-containing tissue, lungs, kidneys, metal implants, diaphragm edge or small air bubbles in the gastrointestinal tracts that moved between MRAC acquisitions. Nasal sinuses and the trachea were better segmented in MRAC_caipi. High-resolution T1w Dixon 3D VIBE images were acquired in all cases and could be used for PET/MRI fusion. MRAC_caipi images were of high diagnostic quality (4.2 ± 0.8) with 0.92-0.96 intra-class correlation.ConclusionsThe novel prototype MRAC_caipi extends the value for attenuation correction by providing a high spatial resolution DIXON-based dataset suited for diagnostic assessment towards time-efficient whole-body PET/MRI.     

Effects of pure and hybrid iterative reconstruction algorithms on high-resolution computed tomography in the evaluation of interstitial lung disease

ObjectivesTo compare image quality characteristics of high-resolution computed tomography (HRCT) in the evaluation of interstitial lung disease using three different reconstruction methods: model-based iterative reconstruction (MBIR), adaptive statistical iterative reconstruction (ASIR), and filtered back projection (FBP).MethodsEighty-nine consecutive patients with interstitial lung disease underwent standard-of-care chest CT with 64-row multi-detector CT. HRCT images were reconstructed in 0.625-mm contiguous axial slices using FBP, ASIR, and MBIR. Two radiologists independently assessed the images in a blinded manner for subjective image noise, streak artifacts, and visualization of normal and pathologic structures. Objective image noise was measured in the lung parenchyma. Spatial resolution was assessed by measuring the modulation transfer function (MTF).ResultsMBIR offered significantly lower objective image noise (22.24 ± 4.53, P < 0.01 among all pairs, Student's t-test) compared with ASIR (39.76 ± 7.41) and FBP (51.91 ± 9.71). MTF (spatial resolution) was increased using MBIR compared with ASIR and FBP. MBIR showed improvements in visualization of normal and pathologic structures over ASIR and FBP, while ASIR was rated quite similarly to FBP. MBIR significantly improved subjective image noise (P < 0.01 among all pairs, the sign test), and streak artifacts (P < 0.01 each for MBIR vs. the other 2 image data sets).ConclusionMBIR provides high-quality HRCT images for interstitial lung disease by reducing image noise and streak artifacts and improving spatial resolution compared with ASIR and FBP.     

Simultaneous whole-body 18F-FDG PET-MRI in primary staging of breast cancer: A pilot study

PurposeAccurate initial staging in breast carcinoma is important for treatment planning and for establishing the likely prognosis. The purpose of this study was to assess the utility of whole body simultaneous ¹⁸F-FDG PET-MRI in initial staging of breast carcinoma.Methods36 patients with histologically confirmed invasive ductal carcinoma underwent simultaneous whole body ¹⁸F-FDG PET-MRI on integrated 3 T PET-MR scanner (Siemens Biograph mMR) for primary staging. Primary lesion, nodes and metastases were evaluated on PET, MRI and PET-MRI for lesion count and diagnostic confidence (DC). Kappa co relation analysis was done to assess agreement between the satellite, nodal and metastatic lesions detected by PET and MRI. Histopathology, clinical/imaging follow-up served as the reference standard.Results36 patients with 37 histopathologically proven index breast cancer were retrospectively studied. Of 36 patients, 25 patients underwent surgery and 11 patients received systemic therapy. All index cancers were seen on PET and MR. Fused PET-MRI showed highest diagnostic confidence score of 5 as compared to PET (median 4; range 3–5) and MRI (median 4; range 4–5) alone. 2/36 (5.5%) patients were detected to have unsuspected contralateral synchronous cancer. 47 satellite lesions were detected on DCE MRI of which 23 were FDG avid with multifocality and multicentricity in 21 (58%) patients. Kappa co relation analysis revealed fair agreement for satellite lesion detection by the two modalities (κ = 0.303; P = 0.003).The study showed a sensitivity of 60% and 93.3% on PET and MRI respectively for detection of axillary lymph nodes with a specificity of 91% for both and a false negative rate of 6.7% on MRI and 40% on PET. Kappa co relation analysis between PET and MRI for all the lymph nodes detected revealed fair agreement by the two modalities (κ = 0.337; P = 0.000). Combined PET-MRI increased diagnostic confidence for nodal involvement (median DC 5, range 4–5; P < 0.05).Distant metastases were found in 8/36 (22%) patients at the time of diagnosis with a total of 91 metastatic lesions on PET (DC ≥ 4) and 105 on MRI (DC ≥ 4), the difference being statistically significant (P = 0.001) while Kappa co relation analysis showed significant agreement between the two modalities (κ = 0.667; P = 0.000). Overall PET-MRI led to a change in management in 12 (33.3%) patients.ConclusionIn this pilot study, simultaneous ¹⁸F-FDG PET-MR, has been found to be useful in whole-body initial staging of breast cancer patients.     

Dynamic contrast-enhanced perfusion area-detector CT assessed with various mathematical models: Its capability for therapeutic outcome prediction for non-small cell lung cancer patients with chemoradiotherapy as compared with that of FDG-PET/CT

PurposeTo directly compare the capability of dynamic first-pass contrast-enhanced (CE-) perfusion area-detector CT (ADCT) and PET/CT for early prediction of treatment response, disease progression and overall survival of non-small cell carcinoma (NSCLC) patients treated with chemoradiotherapy.Materials and methodsFifty-three consecutive Stage IIIB NSCLC patients who had undergone PET/CT, dynamic first-pass CE-perfusion ADCT, chemoradiotherapy, and follow-up examination were enrolled in this study. They were divided into two groups: 1) complete or partial response (CR + PR) and 2) stable or progressive disease (SD + PD). Pulmonary arterial and systemic arterial perfusions and total perfusion were assessed at targeted lesions with the dual-input maximum slope method, permeability surface and distribution volume with the Patlak plot method, tumor perfusion with the single-input maximum slope method, and SUV_max, and results were averaged to determine final values for each patient. Next, step-wise regression analysis was used to determine which indices were the most useful for predicting therapeutic effect. Finally, overall survival of responders and non-responders assessed by using the indices that had a significant effect on prediction of therapeutic outcome was statistically compared.ResultsThe step-wise regression test showed that therapeutic effect (r² = 0.63, p = 0.01) was significantly affected by the following three factors in order of magnitude of impact: systemic arterial perfusion, total perfusion, and SUV_max. Mean overall survival showed a significant difference for total perfusion (p = 0.003) and systemic arterial perfusion (p = 0.04).ConclusionDynamic first-pass CE-perfusion ADCT as well as PET/CT are useful for treatment response prediction in NSCLC patients treated with chemoradiotherapy.     

Clinical evaluation of PET image reconstruction using a spatial resolution model

Purpose

PET image resolution is variable across the measured field-of-view and described by the point spread function (PSF). When accounting for the PSF during PET image reconstruction image resolution is improved and partial volume effects are reduced. Here, we evaluate the effect of PSF-based reconstruction on lesion quantification in routine clinical whole-body (WB) PET/CT imaging.

Materials and methods

41 oncology patients were referred for a WB-PET/CT examination (Biograph 40 TruePoint). Emission data were acquired at 2.5 min/bed at 1 h pi of 400 MBq [18F]-FDG. Attenuation-corrected PET images were reconstructed on 336 × 336-matrices using: (R1) standard AW-OSEM (4 iter, 8 subsets, 4 mm Gaussian) and (R2) AW-OSEM with PSF (3 iter, 21 subsets, 2 mm). Blinded and randomised reading of R1- and R2-PET images was performed. Individual lesions were located and counted independently on both sets of images. The relative change in PET quantification (SUV_max, SUV_mean, volume) of lesions seen on R1 and R2 is reported as (R2 − R1)/R1. Furthermore, SUV_max and SUV_mean was measured for a 3 cm spherical norm region in the right lobe of the healthy liver for R1 and R2.

Results

Clinical reading revealed 91 and 103 positive lesions for R1 and R2, respectively. For all lesions SUV_max (R2) was higher than SUV_max (R1). Regression analysis indicated that the relative increase in SUV_max (and SUV_mean) decreased with lesion size, whilst it increased with increasing radial distance from the centre of the field of view (FOV). There was no significant difference in SUV_mean in homogenous liver tissue between R1 and R2.

Conclusion

In whole-body FDG-PET/CT using routine clinical protocols, PSF-based PET reconstruction increases lesion detection and affects SUV_max measurements compared to standard AW-OSEM PET reconstruction.     

PET quantification with a histogram derived total activity metric: Superior quantitative consistency compared to total lesion glycolysis with absolute or relative SUV thresholds in phantoms and lung cancer patients

IntroductionThe increasing use of molecular imaging probes as biomarkers in oncology emphasizes the need for robust and stable methods for quantifying tracer uptake in PET imaging. The primary motivation for this research was to find an accurate method to quantify the total tumor uptake. Therefore we developed a histogram-based method to calculate the background subtracted lesion (BSL) activity and validated BSL by comparing the quantitative consistency with the total lesion glycolysis (TLG) in phantom and patient studies.MethodsA thorax phantom and a PET-ACR quality assurance phantom were scanned with increasing FDG concentrations. Volumes of interest (VOIs) were placed over each chamber. TLG was calculated with a fixed threshold at SUV 2.5 (TLG_2.5) and a relative threshold at 42% of SUV_max (TLG_42%). The histogram for each VOI was built and BSL was calculated. Comparison with the total injected FDG activity (TIA) was performed using concordance correlation coefficients (CCC) and the slope (a). Fifty consecutive patients with FDG-avid lung tumors were selected under an IRB waiver. TLG_42%, TLG_2.5 and BSL were compared to the reference standard calculating CCC and the slope.ResultsIn both phantoms, the CCC for lesions with a TIA ≤ 50 ml*SUV between TIA and BSL was higher and the slope closer to 1 (CCC = 0.933, a = 1.189), than for TLG_42% (CCC = 0.350, a = 0.731) or TLG_2.5 (CCC = 0.761, a = 0.727). In 50 lung lesions BSL had a slope closer to 1 compared to the reference activity than TLG_42% (a = 1.084 vs 0.618 – for high activity lesions) and also closer to 1 than TLG_2.5 (a = 1.117 vs 0.548 – for low activity lesions).ConclusionThe histogram based BSL correlated better with TIA in both phantom studies than TLG_2.5 or TLG_42%. Also in lung tumors, the BSL activity is overall more accurate in quantifying the lesion activity compared to the two most commonly applied TLG quantification methods.     

18F-FDG PET/CT and contrast-enhanced CT findings of pulmonary cryptococcosis

PurposePulmonary cryptococcosis is an uncommon cause of pulmonary nodules in non-AIDS patients. This study reports the ¹⁸F-fluorodeoxyglucose-positron emission tomography (¹⁸F-FDG PET/CT) and contrast-enhanced CT (CE-CT) findings of 42 patients with pulmonary cryptococcosis.Materials and methodsA retrospective review of the ¹⁸F-FDG PET/CT and CE-CT findings of 42 patients with histologically proven pulmonary cryptococcosis was conducted. All patients underwent PET/CT and CE-CT in the same session. The CT diagnosis was based on the location, morphological features, and enhancement of lesions. The PET/CT findings were recorded, and clinical data and surgical and histopathological findings were collected.ResultsThe results of the PET scans revealed that 37 (88%) of 42 patients showed higher FDG uptake, and 5 (12%) patients demonstrated lower FDG uptake than the mediastinal blood pool. The maximum standardized uptake value (SUV) of pulmonary cryptococcosis ranged from 1.4 to 13.0 (average: 5.7 ± 3.3, median 4.9). A single nodular pattern was the most prevalent pattern observed and was found in 29 (69%) patients. This pattern was followed by scattered nodular (n = 4, 10%), clustered nodular (n = 3, 7%), mass-like (n = 3, 7%), and bronchopneumonic (n = 3, 7%) patterns. The most frequent pattern of immunocompetent patients was the single nodular pattern (29 of 33, 88%). Immunocompromised patients most frequently pattern exhibited mass-like (3 of 9, 33%) and bronchopneumonic (3 of 9, 33%) patterns.ConclusionPulmonary cryptococcosis most commonly appears as single nodules in immunocompetent patients. Mass-like and bronchopneumonic patterns were common in immunocompromised patients. In 88% of patients, lung lesions showed high FDG uptake, thus mimicking a possible malignant condition.     

Analysis of decrease in lung perfusion blood volume with occlusive and non-occlusive pulmonary embolisms

PurposeThe aim of this study was to determine if lung perfusion blood volume (lung PBV) with non-occlusive pulmonary embolism (PE) differs quantitatively and visually from that with occlusive PE and to investigate if lung PBV with non-occlusive PE remains the same as that without PE.Materials and methodsTotally, 108 patients suspected of having acute PE underwent pulmonary dual-energy computed tomography angiography (DECTA) between April 2011 and January 2012. Presence of PE on DECTA was evaluated by one radiologist. Two radiologists visually evaluated the PE distribution (segmental or subsegmental) and its nature (occlusive or non-occlusive) on DECTA and classified perfusion in lung PBV as “decreased,” “slightly decreased,” and “preserved”. Two radiologists used a lung PBV application to set a region of interest (ROI) in the center of the lesion and measured HU values of an iodine map. In the same slice as the ROI of the lesion and close to the lesion, another ROI was set in the normal perfusion area without PE, and HUs were measured. The proportion of lesions was compared between the occlusive and non-occlusive groups. HUs were compared among the occlusive, non-occlusive, and corresponding normal groups.ResultsTwenty-five patients had 80 segmental or subsegmental lesions. There were 37 and 43 lesions in the occlusive and non-occlusive groups, respectively. The proportion of decreased lesions was 73.0% (27/37) in the occlusive group, while that of preserved lesions in the non-occlusive group was 76.7% (33/43). There was a significant difference in the proportion of lesions (P < 0.001) between the two groups. HUs of the iodine map were significantly higher in the non-occlusive group than in the occlusive group (33.8 ± 8.2 HU vs. 11.9 ± 6.1 HU, P < 0.001). There was no significant difference in HUs for the entire lesion between the non-occlusive (33.8 ± 8.2 HU) and corresponding normal group (34.5 ± 6.8 HU; P = 0.294).ConclusionIodine perfusion tended to be visually and quantitatively preserved in lungs with nonocclusive PE. Lung PBV is required to evaluate pulmonary blood flow.     

Volumetric parameters of 2-deoxy-2-[18F]fluoro-d-glucose positron emission tomography/computed tomography can predict histopathologic treatment response after neoadjuvant chemoradiotherapy in pancreatic adenocarcinoma

PurposeThe purpose of this study was to investigate the clinical potential of 2-deoxy-2-[18F]fluoro-d-glucose positron emission tomography/computed tomography (FDG PET/CT) to evaluate histopathologic effects of preoperative chemoradiotherapy (CRT) in pancreatic adenocarcinoma, with particular focus on volumetric PET/CT parameters.Material and methodsThis study included 25 patients with pancreatic adenocarcinoma who underwent radical surgery after gemcitabine- and S-1-based preoperative-CRT. The extent of residual tumor was graded using the Evans grading systems, and patients with more than 50% destruction of tumor cells were defined as responder. Peak SUV corrected for lean body mass (SUL_peak), metabolic tumor volume (MTV) with a threshold of SUV = 2.0, total lesion glycolysis (TLG) of pre- and post-CRT, and reduction rates of SUL_peak in those parameters were assessed by PET/CT. These parameters were compared using the student's t-test between responder and non-responder. The treatment effect was also assessed by contingency table analysis divided with median value of each parameter using chi-square tests.ResultsEight patients (32%) showed histopathologic poor response (Evans grade I), 11 cases (44%) had mild response (Evans grade IIa), and six cases (24%) had moderate response (Evans grade IIb); therefore, six cases (24%) were assigned to responders and others 19 cases (76%) were non-responders. With regards to volumetric PET parameters, post-CRT SUL_peak of responders was significantly lower than that of non-responders (p = 0.013). Post-CRT MTV and TLG were negative for all six cases of responders. There were significant differences between responder and non-responder on the contingency table analysis of post-CRT MTV and TLG status (p = 0.014 for both).ConclusionsThis study demonstrated that the volumetric PET/CT parameters, higher post-treatment SUL_peak and positive MTV/TLG could predict the unfavorable histopathological effects of CRT in patients with pancreatic adenocarcinoma.     

Diagnostic performance of diffusion-weighted MR imaging in differentiation of diabetic osteoarthropathy and osteomyelitis in diabetic foot

PurposeTo study the diagnostic performance of diffusion weighted MR imaging in differentiation of diabetic osteoarthropathy and osteomyelitis in diabetic foot.Patients and methodsThis prospective study was carried out on 41 patients with diabetic foot, 22 males and 19 females with mean age of 51 years. They underwent diffusion-weighted MR imaging of the foot. The apparent diffusion coefficient (ADC) values of the bony lesions were calculated by two reviewers and correlated with the surgical findings or biopsy. The kappa statistic (k) was used to estimate the proportion of inter-observer agreement of two reviewers.ResultsThe mean ADC of acute diabetic osteoarthropathy was 1.27 ± 0.19 × 10⁻³ mm²/s for reviewer 1 and 1.26 ± 0.21 × 10⁻³ mm²/s for reviewer 2. The mean ADC value in diabetic osteomyelitis was 0.86 ± 0.11 × 10⁻³ mm²/s for reviewer 1 and 0.85 ± 0.12 × 10⁻³ mm²/s for reviewer 2. There was excellent inter-observer agreement of ADC value of bony lesions in diabetic foot by both reviewers (K = 0.93). There was statistically significant difference in the ADC values of both groups (P = 0.001). The cut-off point of ADC value of both reviewers used in differentiating acute diabetic osteoarthropathy and osteomyelitis were 0.98 × 10⁻³ mm²/s and 1.04 × 10⁻³ mm²/s with an accuracy of 94% and 93% and area under the curve of 0.94 and 0.93 respectively.ConclusionWe conclude that the ADC value is a non-invasive imaging parameter that can help in differentiation of diabetic osteoarthropathy from osteomyelitis with excellent inter-observer agreement.     

Dual energy CT of peripheral arteries: Effect of automatic bone and plaque removal on image quality and grading of stenoses

PurposeTo evaluate the effect of automatic bone and plaque removal on image quality and grading of steno-occlusive lesions in patients undergoing dual energy CT angiography (CTA) of lower extremity.Materials and methodsDual energy (DE) runoff CTA was performed in 50 patients using the following parameters: collimation 2 × 32 × 0.6; tube potentials, 80 kV and 140 kV; reconstructed slice thickness 1 mm. 100 mL iomeprol 400 and 50 mL saline were injected at 4 mL/s. Separate datasets were calculated for each of the two tubes and used to generate automatically bone-subtracted images (ABS) as well as bone and plaque subtracted images (ABPS). Residual bone in the ABS dataset was removed manually (=ABS-B dataset). In addition, a weighted average dataset from both dual energy acquisitions resembling a routine 120 kV CT acquisition was used for standard manual bone subtraction (MBS). Operator time for bone removal was measured. Effectiveness of bone subtraction and presence of vessel erosions was assessed by two readers in consensus. Stenosis grading in plaque subtracted and unsubtracted images was assessed and correlated.ResultsResidual bone fragments (ribs: 46%, patella: 25%, spine: 4%, pelvis: 2%, tibia 2% of patients) were only observed with ABS. The time needed to manually remove these residual bones was 2.1 ± 1.1 min and was significantly lower than the duration of manual bone removal (6.8 ± 2.0 min, p < 0.0001, paired t-test). A total of 1159 arteries were analyzed. Compromising vessel erosions were observed less frequently in the ABS-B dataset (10.6%) than in the MBS dataset (15.2%, p < 0.001, wilcoxon’s signed rank test). A total of 817 steno-occlusive lesions were assessed. While the agreement of grading of steno-occlusive lesions was good at the levels of the aorta and the pelvic arteries (κ = 0.70 in both, Cohen’s kappa statistics), it was moderate at the level of the thigh arteries (κ = 0.57) and poor at the level of the calf (κ = 0.16).ConclusionDE CTA has substantial advantages over conventional CTA. Automatic bone subtraction is more time efficient and reliable. Automatic plaque subtraction for the first time provides a true CTA-luminogram which is easy to interpret and reduces the need for further post-processing. DE CTA provides best results in arteries of the thigh; below the knee, plaque subtraction is less accurate.     

Emphysema quantification and lung volumetry in chest X-ray equivalent ultralow dose CT – Intra-individual comparison with standard dose CT

ObjectivesTo determine whether ultralow dose chest CT with tin filtration can be used for emphysema quantification and lung volumetry and to assess differences in emphysema measurements and lung volume between standard dose and ultralow dose CT scans using advanced modeled iterative reconstruction (ADMIRE).Methods84 consecutive patients from a prospective, IRB-approved single-center study were included and underwent clinically indicated standard dose chest CT (1.7 ± 0.6 mSv) and additional single-energy ultralow dose CT (0.14 ± 0.01 mSv) at 100 kV and fixed tube current at 70 mAs with tin filtration in the same session. Forty of the 84 patients (48%) had no emphysema, 44 (52%) had emphysema. One radiologist performed fully automated software-based pulmonary emphysema quantification and lung volumetry of standard and ultralow dose CT with different levels of ADMIRE. Friedman test and Wilcoxon rank sum test were used for multiple comparison of emphysema and lung volume. Lung volumes were compared using the concordance correlation coefficient.ResultsThe median low-attenuation areas (LAA) using filtered back projection (FBP) in standard dose was 4.4% and decreased to 2.6%, 2.1% and 1.8% using ADMIRE 3, 4, and 5, respectively. The median values of LAA in ultralow dose CT were 5.7%, 4.1% and 2.4% for ADMIRE 3, 4, and 5, respectively. There was no statistically significant difference between LAA in standard dose CT using FBP and ultralow dose using ADMIRE 4 (p = 0.358) as well as in standard dose CT using ADMIRE 3 and ultralow dose using ADMIRE 5 (p = 0.966). In comparison with standard dose FBP the concordance correlation coefficients of lung volumetry were 1.000, 0.999, and 0.999 for ADMIRE 3, 4, and 5 in standard dose, and 0.972 for ADMIRE 3, 4 and 5 in ultralow dose CT.ConclusionsUltralow dose CT at chest X-ray equivalent dose levels allows for lung volumetry as well as detection and quantification of emphysema. However, longitudinal emphysema analyses should be performed with the same scan protocol and reconstruction algorithms for reproducibility.     

Impact of fibroglandular tissue and background parenchymal enhancement on diffusion weighted imaging of breast lesions

PurposeTo evaluate the influence of the amount of fibroglandular breast tissue (FGT) and background-parenchymal enhancement (BPE) on lesion detection, quantitative analysis of normal breast tissue and of breast lesions on DWI.Materials and methodsIRB approved this retrospective study on focal findings at contrast-enhanced (CE) breast MR and DWI performed during July–December 2011. Patients with cysts, previous irradiation, silicone implants and current chemotherapy were excluded. DWI with fat suppression was acquired before dynamic acquisition (b factors: 0.1000 s/mm²) using 1.5 and 3 T scanners. Using correlation with dynamic and T2 images, ROIs were drawn free-hand within the borders of any visible lesion and in contralateral normal breast. Fisher's exact test to evaluate visibility and Wilcoxon-rank-sum test for comparison of ADC values were used. The amount of FGT and BPE was visually assessed by concurrent MRI. Analysis was stratified by menopausal status.Results25/127 (20%) lesions were excluded for technical reasons. 65/102 (64%) lesions were visible on DWI (median diameter: 1.85 cm). Mass lesions (M) were more visible (43/60 = 72%) than non-mass enhancement (NME) (22/42 = 52%) and malignant lesions were more visible (55/72 = 76%) than benign (10/30 = 33%). BPE and FGT did not influence visibility of M (p = 0.35 and p = 0.57 respectively) as well as of NME (p = 0.54 and p = 0.10). BPE and FGT did not influence visibility of malignant (p = 0.96 and p = 1.0) and benign lesions (p = 1.0 and p = 0.10). Results were confirmed adjusting for menopausal status. The ADC value of normal breast tissue was not influenced by BPE, while it was lower in predominantly fatty breasts compared to dense ones (p = 0.002).ConclusionsFGT affects the quantitative evaluation of ADC in normal breast tissue whereas BPE does not. Furthermore, both BPE and FGT do not influence visibility of benign or malignant findings, including both mass lesions and non-mass enhancement, on DWI.     

Comparison of trans-1-amino-3-[18 F]fluorocyclobutanecarboxylic acid (anti-[18 F]FACBC) accumulation in lymph node prostate cancer metastasis and lymphadenitis in rats

IntroductionTrans-1-amino-3-[¹⁸ F]fluorocyclobutanecarboxylic acid (anti-[¹⁸ F]FACBC) is a positron emission tomography (PET) tracer used to visualize prostate cancer (PCa). In this study, we investigated the differences in anti-[¹⁸ F]FACBC accumulation between metastatic and inflamed lymph node (LN) lesions.MethodsA PCa LN metastasis (PLM) model was developed by inoculating a rat PCa cell line, MAT-Ly-Lu-B2, into popliteal LNs of Copenhagen rats. Acute lymphadenitis (AL) was induced by injecting concanavalin A (Con A) into the hind footpad, and chronic lymphadenitis (CL) was induced by daily injection of Con A into the tissues surrounding the popliteal LNs for 2 weeks. Main lesions of all animal models were established in lumbar and/or inguinal LNs. Biodistribution and dynamic PET imaging data were acquired after tracer injection. T2-weighted magnetic resonance (MR) images were registered with PET images.ResultsIn the biodistribution study, the uptake ratios of PLM-to-lymphadenitis in lesional lumbar and inguinal LNs were 0.97 − 1.57 and 1.47 − 2.08 at 15 and 60 min post-anti-[¹⁸ F]FACBC injection respectively. In PET imaging, the lesional lumbar LNs of CL and PLM, but not of AL, were visualized on anti-[¹⁸ F]FACBC-PET/MR fusion images without disturbance from radioactivity from urine, and the rank order of anti-[¹⁸ F]FACBC accumulation at 50 − 60 post-injection in lesional lumbar LNs was PLM > CL > AL.ConclusionsAnti-[¹⁸ F]FACBC accumulation in LNs with PLM was higher than that in inflamed LNs.Advances in knowledgeThe study showed that although low but significant levels of anti-[¹⁸ F]FACBC uptake by chronic inflamed lesions might cause false-positives in anti-[¹⁸ F]FACBC-PET in some PCa patients, uptake of the tracer at acutely inflamed sites was minimal.Implications for patient careThe findings of this study suggest the potential of Anti-[¹⁸ F]FACBC for distinguishing between tumors and acute inflammation in clinical practice.