Diagnostic significance of MRI versus CT using identical PET data in patients with recurrent differentiated thyroid cancer: A PET/MRI study.

In this retrospective study we compared magnet resonance imaging (MRI) and computed tomography (CT) each combined with identical 2-deoxy-2-[18F] fluoro-D-glucose or 2-[18F] F-18 fluorodeoxyglucose (FDG) positron emission tomography (PET) data in patients with recurrent differentiated thyroid cancer (DTC). In total 42 patients with DTC were examined. All patients underwent FDG PET/MRI and CT, the latter originating from one of the following examinations: I-131 single photon emission computed tomography/CT (32/42), low dose FDG PET/CT (5/42) or diagnostic FDG PET/CT (5/42). Two readers assessed FDG PET/MRI as well as FDG PET/CT, with the latter CT coming from one of the above examinations performed at a maximum temporal interval of 5 days from PET/MRI. Local recurrence, cervical lymph node - and pulmonary metastases were assessed in a consensus read. Lesions rated with a high malignancy score (score 4 or 5) were further analyzed. Every malignant lesion was verified if it was identified by one of both or by both modalities. In 20 of 42 patients altogether 100 malignant lesions were present. In 11/20 patients in total 15 local recurrences (15 in MRI/ 9 in CT: 9 CT/MRI, 6 MRI only, 0 CT only; P = .04) were found with a statistically significant better performance of MRI. Regarding lymph node metastases, in total 13 lesions (12 in MRI/ 8 in CT: 7 CT/MRI, 5 MRI only, 1 CT only; P = .22) in 8/20 patients were found with no significant difference between both modalities. Furthermore, in 9/20 patients in total 72 lung lesions (40 in MRI/ 63 in CT: 31 CT/MRI, 9 MRI only, 32 CT only; P = .001) were found with a statistically significant better performance of CT. In 33/42 patients follow up was available and supported the observations. In patients with recurrent DTC, PET/MRI showed superiority compared to PET/CT in evaluation of the neck region. PET/MRI was inferior to PET/CT in evaluation of the lung. PET/MRI in combination with a low dose CT of the lung may thus represent the ideal staging tool in patients with recurrent DTC.

18F-FDG PET/MRI compared with clinical and serological markers for monitoring disease activity in patients with aortitis and chronic periaortitis.

OBJECTIVES: We compared the diagnostic value of fully integrated 18F-FDG PET/MRI to that of clinical and serological markers for monitoring disease activity in patients with aortitis/chronic periaortitis (A/CPA) during immunosuppressive therapy. METHODS: Patients positive for A/CPA at the initial and at least 2 consecutive PET/MRI studies were included for retrospective analysis. Imaging (qualitative and quantitative analysis), clinical, and serologic (C-reactive protein, erythrocyte sedimentation rate) assessments were determined at each visit, and their findings compared. Differences in various PET/MRI parameters, clinical symptoms, and serologic markers during therapy between first and second visits were tested for statistical significance. Spearman's rank correlation coefficient was calculated to relate imaging to serologic marker changes between the first 2 visits. RESULTS: Serial assessments were performed in 12 patients with A/CPA, over 34 visits. PET/MRI suggested active disease in 22/34 (64.7%) studies, whereas clinical assessment and serological analysis were positive in only 18/34 (52.9%) and 17/34 (50%) cases, respectively. Disease activity assessment differed between PET/MRI, and clinical and serological markers, in 8/34 (23.5%) and 9/34 (26.5%) cases, respectively. Imaging and serologic parameters (p < 0.009) and clinical symptoms (p = 0.063) predominantly improved at the second visit. Changes from the first to the second visit were not correlated between PET/MRI and serologic markers. CONCLUSIONS: Fully integrated 18F-FDG PET/MRI provides a comprehensive imaging approach with data on vascular/perivascular inflammation that is complementary to clinical and laboratory assessments. This highlights the potential value of imaging-based disease activity monitoring, which might have a crucial impact on clinical management in patients with A/CPA.

11C-choline PET/CT and whole-body MRI including diffusion-weighted imaging for patients with recurrent prostate cancer.

PURPOSE: To compare the detection efficacy of 11C-choline positron emission tomography and computed tomography (PET/CT) with whole-body magnetic resonance imaging (MRI) including diffusion-weighted imaging (DWI) in patients with suspected recurrent prostate cancer. MATERIALS AND METHODS: Fifty-seven patients (mean age 68, range 54-80 years) underwent 11C-choline PET/CT and MRI using T1-weighted (T1w), short-tau inversion recovery (STIR), and DWI. Two readers visually rated suspicious lesions on a 5-point scale in 20 different regions. Clinical follow-up and histopathology served as the standard of reference (SOR). RESULTS: Fifty patients (mean PSA 29.9, range 1.0-670 ng/mL) had at least one positive lesion according to the SOR. Twenty-four patients had local recurrence (LR), 27 had lymph node (LN) involvement, and 22 had bone metastases. The overall detection rates for PET/CT and MRI on a patient basis were 94% and 88%, respectively (p = 0.07). The PSA level (>2 ng/mL vs ≤2 ng/mL) significantly influenced the overall performance of PET/CT (p = 0.003) and MRI (p = 0.03). PET/CT was significantly superior to MRI in detecting LR (p = 0.03) and bone metastasis (p = 0.02). We found no difference with respect to the detection of LN metastasis (p = 0.65). CONCLUSION: 11C-choline PET/CT was superior in the detection of local recurrence and bone metastasis on a regional basis. Whole-body MRI including DWI showed similar diagnostic accuracy only for detecting lymph node metastases. Compared with 11C-choline PET/CT, therefore, whole-body MRI including DWI cannot serve as alternative imaging modality for restaging prostate cancer.

68Ga-PSMA PET/MR Showing Intense PSMA Uptake in Nodular Fasciitis Mimicking Prostate Cancer Metastasis.

The recently introduced PSMA PET has developed as a powerful imaging tool for staging of prostate cancer. This case showed an intense uptake of Ga-PSMA in a soft-tissue mass of the rectus femoris muscle. Histopathology revealed the diagnosis of fasciitis nodularis. Therefore, it advises caution particularly in patients with solitary and atypical located lesions as they might not be indicative for metastatic prostate cancer, but eventually be caused by different conditions.

Textural Parameters of Tumor Heterogeneity in ¹8F-FDG PET/CT for Therapy Response Assessment and Prognosis in Patients with Locally Advanced Rectal Cancer.

UNLABELLED: (18)F-FDG PET/CT is effective in the assessment of therapy response. Changes in glucose uptake or tumor size are used as a measure. Tumor heterogeneity was found to be a promising predictive and prognostic factor. We investigated textural parameters for their predictive and prognostic capability in patients with rectal cancer using histopathology as the gold standard. In addition, a comparison to clinical outcome was performed. METHODS: Twenty-seven patients with rectal cancer underwent (18)F-FDG PET/CT before, 2 wk after the start, and 4 wk after the completion of neoadjuvant chemoradiotherapy. In all PET/CT scans, conventional parameters (tumor volume, diameter, maximum and mean standardized uptake values, and total lesion glycolysis [TLG]) and textural parameters (coefficient of variation [COV], skewness, and kurtosis) were determined to assess tumor heterogeneity. Values on pretherapeutic PET/CT as well as changes early in the course of therapy and after therapy were compared with histopathologic response. In addition, the prognostic value was assessed by correlation with time to progression and survival time. RESULTS: The COV showed a statistically significant capability to assess histopathologic response early in therapy (sensitivity, 68%; specificity, 88%) and after therapy (79% and 88%, respectively). Thereby, the COV had a higher area under the curve in receiver-operating-characteristic analysis than did any analyzed conventional parameter for early and late response assessment. The COV showed a statistically significant capability to evaluate disease progression and to predict survival, although the latter was not statistically significant. CONCLUSION: Tumor heterogeneity assessed by the COV, being superior to the investigated conventional parameters, is an important predictive factor in patients with rectal cancer. Furthermore, it can provide prognostic information. Therefore, its application is an important step for personalized treatment of rectal cancer.

Evaluation of a method for improving the detection of hepatocellular carcinoma.

OBJECTIVE: To improve the detection of liver lesions in patients with hepatocellular carcinoma (HCC) via an iodine contrast enhancement tool. METHODS: Thirty-two patients with clinically proven HCCs underwent imaging with a three-phase protocol on a 256-slice MDCT. The contrast enhancement in the reconstructed slices was improved via a post-processing tool. Mean image noise was measured in four different regions: liver lesion, healthy liver, subcutaneous fat and bone. For each image set the image noise and contrast-to-noise ratio (CNR) were assessed. For subjective image assessment, four experienced radiologists evaluated the diagnostic quality. RESULTS: While employing the post-processing algorithm, CNR between the liver lesion and healthy liver tissue improves significantly by a factor of 1.78 (CNRwithout vC = 2.30 ± 1.92/CNRwith vC = 4.11 ± 3.05) (P* = 0.01). All results could be achieved without a strengthening of artefacts; mean HU values of subcutaneous fat and bone did not significantly change. Subjective image analysis illustrated a significant improvement when employing post-processing for clinically relevant criteria such as diagnostic confidence. CONCLUSION: With post-processing we see a significantly improved detection of arterial uptake in hepatic lesions compared with non-processed data. The improvement in CNR was confirmed by subjective image assessment for small lesions and for lesions with limited uptake. KEY POINTS: • Enhancement with iodine-based contrast agents is an essential part of CT. • A new post-processing tool significantly improves the diagnostics of hepatocellular carcinoma. • It also improves detection of small lesions with limited iodine uptake.

Evaluation of an iterative model-based reconstruction algorithm for low-tube-voltage (80 kVp) computed tomography angiography.

The objective of this study was to investigate the improvement in diagnostic quality of an iterative model-based reconstruction (IMBR) algorithm for low-tube-voltage (80-kVp) and low-tube-current in abdominal computed tomography angiography (CTA). A total of 11 patients were imaged on a 256-slice multidetector computed tomography for visualization of the aorta. For all patients, three different reconstructions from the low-tube-voltage data are generated: filtered backprojection (FBP), IMBR, and a mixture of both [Formula: see text]. To determine the diagnostic value of IMBR-based reconstructions, the image quality was assessed. With IMBR-based reconstructions, image noise could be significantly reduced, which was confirmed by a highly improved contrast-to-noise ratio. In the image quality assessment, radiologists were able to reliably detect more third-order and higher aortic branches in the IMBR reconstructions compared to FBP reconstructions. The effective dose level was, on average, 3.0 mSv for 80-kVp acquisitions. Low-tube-voltage CTAs significantly improve vascular contrast as presented by others; however, this effect in combination with IMBR enabled yet another substantial improvement of diagnostic quality. For IMBR, a significant improvement of image quality and a decreased radiation dose at low-tube-voltage can be reported.

Molecular imaging for early prediction of response to Sorafenib treatment in sarcoma.

The role of [(18)F]fluorodeoxyglucose ([(18)F]FDG) PET in staging of sarcoma is well established. The aim of this preclinical study was to compare [(18)F]fluorothymidine ([(18)F]FLT) PET to [(18)F]FDG PET regarding early metabolic changes of sarcoma in the course of targeted cancer therapy. SCID mice bearing sarcoma A673 xenotransplants were used for investigation of tumor response after treatment with the multikinase inhibitor Sorafenib. [(18)F]FLT and/or [(18)F]FDG-PET were performed prior to and early after initiation of treatment. Tumoral uptake (% Injected Dose per gram (%ID/g) of [(18)F]FLT-PET was compared to [(18)F]FDG-PET. Results were correlated with histopathology and in vitro data including cellular uptake, cell cycle-related protein expression, cell cycle distribution and apoptosis. In vitro experiments showed that A673 cells were sensitive to Sorafenib. In vivo, tumor growth was inhibited in comparison to a 4-fold increase of the tumor volume in control mice. Using [(18)F]FDG as tracer, a moderate reduction in tracer uptake (n=15, mean relative %ID/g 74%, range 35%-121%, p=0.03) was observed. The decrease in %ID/g using [(18)F]FLT-PET was significantly higher (p=0.003). The mean relative %ID/g in [(18)F]FLT uptake on day + 5 was significantly reduced to 54% compared to baseline (n=15, range 24%-125%, SD=29%). The PET analysis 24 hr after therapy showed a significant reduction of the mean [(18)F]FLT-%ID/g (p=0.04). The reduction of %ID/g on day + 1 in [(18)F]FDG-PET was not statistically significant (p=0.99). In conclusion, both [(18)F]FDG- and [(18)F]FLT-PET were able to predict response to Sorafenib treatment. In contrast to [(18)F]FDG-PET, [(18)F]FLT-PET was more predictive for very early response to treatment.