Johannes Grueneisen

[ 18 F]FDG PET/MRI vs. PET/CT for whole-body staging in patients with recurrent malignancies of the female pelvis: initial results

PurposeTo evaluate the diagnostic potential of PET/MRI with [18F]FDG in recurrent ovarian and cervical cancer in comparison to PET/CT.MethodsA group of 19 patients with suspected recurrence of pelvic malignancies (ovarian cancer, 11 patients; cervical cancer, 8 patients) scheduled for an [18F]FDG PET/CT were subsequently enrolled for a PET/MRI. The scan protocol comprised: (1) a T1-W axial VIBE after contrast agent adminstration, (2) an axial T2-W HASTE, (3) a coronal TIRM, (4) an axial DWI, and dedicated MR sequences of the female pelvis including (5) a T1-W VIBE before contrast agent adminstration, (6) a sagittal T2-W TSE, and (7) a sagittal T1-W dynamic VIBE. The datasets (PET/CT, PET/MRI) were rated separately by two readers regarding lesion count, lesion localization, lesion conspicuity (four-point scale), lesion characterization (benign/malignant/indeterminate) and diagnostic confidence (three-point scale). All available data (histology, prior examinations, PET/CT, PET/MRI, follow-up examinations) served as standard of reference. Median values were compared using the Wilcoxon rank sum test.ResultsMetastatic lesions were present in 16 of the 19 patients. A total of 78 lesions (malignant, 58; benign, 20) were described. Both PET/CT and PET/MRI allowed correct identification of all malignant lesions and provided equivalent conspicuity (3.86 ± 0.35 for PET/CT, 3.91 ± 0.28 for PET/MRI; p > 0.05). Diagnostic confidence was significantly higher for PET/MRI in malignant (p < 0.01) and benign lesions (p < 0.05).ConclusionBoth PET/CT and PET/MRI offer an equivalently high diagnostic value for recurrent pelvic malignancies. PET/MRI offers higher diagnostic confidence in the discrimination of benign and malignant lesions. Considering the reduced radiation dose and superior lesion discrimination, PET/MRI may serve as a powerful alternative to PET/CT in the future.

Positron Emission Tomography/Magnetic Resonance Imaging for Local Tumor Staging in Patients With Primary Breast Cancer: A Comparison With Positron Emission Tomography/Computed Tomography and Magnetic Resonance Imaging.

ObjectivesThis study aimed to assess the diagnostic performance of integrated positron emission tomography (PET)/magnetic resonance imaging (MRI) of the breast for lesion detection and local tumor staging of patients with primary breast cancer in comparison to PET/computed tomography (CT) and MRI. Materials and MethodsThe study was approved by the local institutional review board. Forty-nine patients with biopsy-proven invasive breast cancer were prospectively enrolled in our study. All patients underwent a PET/CT, and subsequently, a contrast-enhanced PET/MRI of the breast after written informed consent was obtained before each examination. Two radiologists independently evaluated the corresponding data sets (PET/CT, PET/MRI, and MRI) and were instructed to identify primary tumors lesions as well as multifocal/multicentric and bilateral disease. Furthermore, the occurrence of lymph node metastases was assessed, and the T-stage for each patient was determined. Histopathological verification of the local tumor extent and the axillary lymph node status was available for 30 of 49 and 48 of 49 patients, respectively. For the remaining patients, a consensus characterization was performed for the determination of the T-stage and nodal status, taking into account the results of clinical staging, PET/CT, and PET/MRI examinations. Statistical analysis was performed to test for differences in diagnostic performance between the different imaging procedures. P values less than 0.05 were considered to be statistically significant. ResultsPositron emission tomography/MRI and MRI correctly identified 47 (96%) of the 49 patients with primary breast cancer, whereas PET/CT enabled detection of 46 (94%) of 49 breast cancer patients and missed a synchronous carcinoma in the contralateral breast in 1 patient. In a lesion-by-lesion analysis, no significant differences could be obtained between the 3 imaging procedures for the identification of primary breast cancer lesions (P > 0.05). Positron emission tomography/MRI and MRI allowed for a correct identification of multifocal/multicentric disease in 3 additional patients if compared with PET/CT. For the definition of the correct T-stage, PET/MRI and MRI showed identical results and were correct in significantly more cases than PET/CT (PET/MRI and MRI, 82%; PET/CT, 68%; P < 0.05). Furthermore, the calculated sensitivity, specificity, positive predictive value, negative predictive value, and diagnostic accuracy for the detection of nodal positive patients (n = 18) were 78%, 94%, 88%, 88%, and 88% for PET/CT; 67%, 87%, 75%, 82%, and 80% for MRI; and 78%, 90%, 82%, 88%, and 86% for PET/MRI, respectively. Differences between the imaging modalities were not statistically significant (P > 0.05). ConclusionsIntegrated PET/MRI does not provide diagnostic advantages for local tumor staging of breast cancer patients in comparison to MRI alone. Positron emission tomography/MRI and MRI enable an improved determination of the local tumor extent in comparison to PET/CT, whereas all 3 imaging modalities offer a comparable diagnostic performance for the identification of axillary disease.

Implementation of FAST-PET/MRI for whole-body staging of female patients with recurrent pelvic malignancies: A comparison to PET/CT

OBJECTIVES To compare the diagnostic competence of FAST-PET/MRI and PET/CT for whole-body staging of female patients suspect for a recurrence of a pelvic malignancy. METHODS 24 female patients with a suspected tumor recurrence underwent a PET/CT and subsequent PET/MRI examination. For PET/MRI readings a whole-body FAST-protocol was implemented. Two readers separately evaluated the PET/CT and FAST PET/MRI datasets regarding identification of all tumor lesions and qualitative assessment of visual lesion-to-background contrast (4-point ordinal scale). RESULTS Tumor relapse was present in 21 of the 24 patients. Both, PET/CT and PET/MRI allowed for correct identification of tumor recurrence in 20 of 21 cases. Lesion-based sensitivity, specificity, positive predictive value, negative predictive value and diagnostic accuracy for the detection of malignant lesions were 82%, 91%, 97%, 58% and 84% for PET/CT and 85%, 87%, 96%, 63% and 86% for PET/MRI, lacking significant differences. Furthermore, no significant difference for lesion-to-background contrast of malignant and benign lesions was found. CONCLUSION FAST-PET/MRI provides a comparably high diagnostic performance for restaging gynecological cancer patients compared to PET/CT with slightly prolonged scan duration, yet enabling a markedly reduced radiation exposure.

Correlation of Standardized Uptake Value and Apparent Diffusion Coefficient in Integrated Whole-Body PET/MRI of Primary and Recurrent Cervical Cancer

Background To evaluate a potential correlation of the maximum standard uptake value (SUVmax) and the minimum apparent diffusion coefficient (ADCmin) in primary and recurrent cervical cancer based on integrated PET/MRI examinations. Methods 19 consecutive patients (mean age 51.6 years; range 30–72 years) with histopathologically confirmed primary cervical cancer (n = 9) or suspected tumor recurrence (n = 10) were prospectively enrolled for an integrated PET/MRI examination. Two radiologists performed a consensus reading in random order, using a dedicated post-processing software. Polygonal regions of interest (ROI) covering the entire tumor lesions were drawn into PET/MR images to assess SUVmax and into ADC parameter maps to determine ADCmin values. Pearson’s correlation coefficients were calculated to assess a potential correlation between the mean values of ADCmin and SUVmax. Results In 15 out of 19 patients cervical cancer lesions (n = 12) or lymph node metastases (n = 42) were detected. Mean SUVmax (12.5±6.5) and ADCmin (644.5±179.7×10−5 mm2/s) values for all assessed tumor lesions showed a significant but weak inverse correlation (R = −0.342, p<0.05). When subdivided in primary and recurrent tumors, primary tumors and associated primary lymph node metastases revealed a significant and strong inverse correlation between SUVmax and ADCmin (R = −0.692, p<0.001), whereas recurrent cancer lesions did not show a significant correlation. Conclusions These initial results of this emerging hybrid imaging technique demonstrate the high diagnostic potential of simultaneous PET/MR imaging for the assessment of functional biomarkers, revealing a significant and strong correlation of tumor metabolism and higher cellularity in cervical cancer lesions.

Simultaneous positron emission tomography/magnetic resonance imaging for whole-body staging in patients with recurrent gynecological malignancies of the pelvis: a comparison to whole-body magnetic resonance imaging alone.

ObjectivesThe objective of this study was to assess the diagnostic value of integrated positron emission tomography/magnetic resonance imaging (PET/MRI) for whole-body staging of patients with recurrent gynecological pelvic malignancies, in comparison to whole-body MRI alone. Materials and MethodsThe study was approved by the local institutional ethics committee. Written informed consent was obtained before each examination. Thirty-four consecutive patients with a suspected recurrence of cervical (n = 18) or ovarian (n = 16) cancer were prospectively enrolled for an integrated PET/MRI examination, which comprised a diagnostic, contrast-enhanced whole-body MRI protocol including dedicated sagittal dynamic imaging of the pelvis. Two radiologists separately evaluated the data sets regarding lesion count, lesion detection, lesion characterization, and diagnostic confidence. Mean and median values were calculated for each rating. Statistical analyses were performed both per-patient and per-lesion bases using a Wilcoxon signed-rank test to indicate potential significant differences among PET/MRI and MRI (alone) data sets. ResultsMalignant lesions were present in 25 of the 34 patients. Positron emission tomography/magnetic resonance imaging offered correct and superior identification of all 25 patients with cancer recurrence, compared with MRI alone (23/25). A total of 118 lesions (malignant, 89; benign, 29) were detected. Positron emission tomography/magnetic resonance imaging correctly identified 88 (98.9%) of 89 malignant lesions, whereas MRI alone allowed for correct identification of 79 (88.8%) of the 89 malignant lesions. In addition, PET/MRI provided significantly higher lesion contrast and diagnostic confidence in the detection of malignant lesions (P < 0.001) compared with MRI alone. ConclusionsThese first results demonstrate the high diagnostic potential of integrated PET/MRI for the assessment of recurrence of female pelvic malignancies compared with MRI alone.

Evaluation of ¹⁸F-FDG PET/MRI, ¹⁸F-FDG PET/CT, MRI, and CT in whole-body staging of recurrent breast cancer.

OBJECTIVES To compare the diagnostic performance of (18)F-fluordesoxyglucose positron emission tomography/magnetic resonance imaging ((18)F-FDG PET/MRI) with (18)F-FDG PET/computed tomography ((18)F-FDG PET/CT), MRI, and CT in whole-body staging of recurrent breast cancer. MATERIAL AND METHODS Twenty-one consecutive patients (age 59.4 ± 11.5 years, range 38.5-76.9 years; 20 female, 1 male) with suspected breast cancer recurrence underwent a clinically indicated (18)F-FDG PET/CT and subsequently a (18)F-FDG PET/MRI examination in a single injection protocol (mean injected activity: 257 ± 44 MBq (18)F-FDG). Each (18)F-FDG PET/MRI, (18)F-FDG PET/CT, as well as the CT component of PET/CT (CTPET/CT) and MR images of PET/MRI (MRIPET/MRI) were separately evaluated by two radiologists regarding lesion count, lesion localization, and lesion categorization (benign/malignant). The reference standard was based on histopathological results as well as prior and follow-up imaging. A Wilcoxon test assessed differences in SUVmax between (18)F-FDG PET/MRI and (18)F-FDG PET/CT. Correlation of SUVmax between (18)F-FDG PET/MRI and (18)F-FDG PET/CT was calculated using Pearsons correlation coefficient. Interobserver agreement on dignity ratings was evaluated using Cohens kappa. RESULTS According to the reference standard, 17 patients had breast cancer recurrence. (18)F-FDG PET/MRI, (18)F-FDG PET/CT, and MRIPET/MRI correctly identified each of the 17 patients, whereas CTPET/CT correctly identified 15 of the 17 patients. A total of 134 lesions were described (116 malignant, 18 benign). (18)F-FDG PET/MRI detected all 134 lesions, of which (18)F-FDG PET/CT, MRIPET/MRI, and CTPET/CT detected 97.0%, 96.2%, and 74.6%, respectively. (18)F-FDG PET/MRI yielded the highest proportion of correctly categorized lesions (98.5%) compared with (18)F-FDG PET/CT (94.8%), MRIPET/MRI (88.1%), and CTPET/CT (57.5%). SUVmax was strongly correlated (r=0.72) but measured significantly higher on (18)F-FDG PET/MRI than on (18)F-FDG PET/CT in corresponding PET-positive lesions (SUVmax: 5.6 ± 2.8 vs. 4.9 ± 1.8; p=0.001). Interobserver agreement on lesion dignity was substantial with (18)F-FDG PET/MRI (k=0.65; p<0.001) and (18)F-FDG PET/CT (k=0.65; p<0.001). With MRIPET/MRI interobserver analysis yielded a moderate agreement (k=0.56; p<0.001), whereas there was only fair agreement evaluating the CTPET/CT datasets (k=0.31; p=0.002). CONCLUSIONS (18)F-FDG PET/MRI offered the highest diagnostic performance compared with (18)F-FDG PET/CT, MRI and CT. Thus, (18)F-FDG PET/MRI should be regarded as a valuable alternative in whole-body staging of recurrent breast cancer.

Comparative Performance of ¹⁸F-FDG PET/MRI and ¹⁸F-FDG PET/CT in Detection and Characterization of Pulmonary Lesions in 121 Oncologic Patients.

Our objective was to compare 18F-FDG PET/MRI (performed using a contrast-enhanced T1-weighted fat-suppressed volume-interpolated breath-hold examination [VIBE]) with 18F-FDG PET/CT for detecting and characterizing lung lesions in oncologic patients. Methods: In 121 oncologic patients with 241 lung lesions, PET/MRI was performed after PET/CT in a single-injection protocol (260 ± 58 MBq of 18F-FDG). The detection rates were computed for MRI, the PET component of PET/CT, and the PET component of PET/MRI in relation to the CT component of PET/CT. Wilcoxon testing was used to assess differences in lesion contrast (4-point scale) and size between morphologic datasets and differences in image quality (4-point scale), SUVmean, SUVmax, and characterization (benign/malignant) between PET/MRI and PET/CT. Correlation was determined using the Pearson coefficient (r) for SUV and size and the Spearman rank coefficient (ρ) for contrast. Results: The detection rates for MRI, the PET component of PET/CT, and the PET component of PET/MRI were 66.8%, 42.7%, and 42.3%, respectively. There was a strong correlation in size (r = 0.98) and SUV (r = 0.91) and a moderate correlation in contrast (ρ = 0.48). Image quality was better for PET/CT than for PET/MRI (P < 0.001). Lesion measurements were smaller for MRI than for CT (P < 0.001). SUVmax and SUVmean were significantly higher for PET/MRI than for PET/CT (P < 0.001 each). There was no significant difference in lesion contrast (P = 0.11) or characterization (P = 0.076). Conclusion: In the detection and characterization of lung lesions 10 mm or larger, 18F-FDG PET/MRI and 18F-FDG PET/CT perform comparably. Lesion size, SUV and characterization correlate strongly between the two modalities. However, the overall detection rate of PET/MRI remains inferior to that of PET/CT because of the limited ability of MRI to detect lesions smaller than 10 mm. Thus, thoracic staging with PET/MRI bears a risk of missing small lung metastases.

Evaluation of the Outcome of Lung Nodules Missed on 18F-FDG PET/MRI Compared with 18F-FDG PET/CT in Patients with Known Malignancies

The lower detection rate of 18F-FDG PET/MRI than 18F-FDG PET/CT regarding small lung nodules should be considered in the staging of malignant tumors. The purpose of this study was to evaluate the outcome of these small lung nodules missed by 18F-FDG PET/MRI. Methods: Fifty-one oncologic patients (mean age ± SD, 56.6 ± 14.0 y; 29 women, 22 men; tumor stages, I [n = 7], II [n = 7], III [n = 9], IV [n = 28]) who underwent 18F-FDG PET/CT and subsequent 18F-FDG PET/MRI on the same day were retrospectively enrolled. Images were analyzed by 2 interpreters in random order and separate sessions with a minimum of 4 wk apart. A maximum of 10 lung nodules was identified for each patient on baseline imaging. The presence, size, and presence of focal tracer uptake was noted for each lung nodule detected on 18F-FDG PET/CT and 18F-FDG PET/MRI using a postcontrast T1-weighted 3-dimensional gradient echo volume-interpolated breath-hold examination sequence with fat suppression as morphologic dataset. Follow-up CT or 18F-FDG PET/CT (mean time to follow-up, 11 mo; range, 3–35 mo) was used as a reference standard to define each missed nodule as benign or malignant based on changes in size and potential new tracer uptake. Nodule-to-nodule comparison between baseline and follow-up was performed using descriptive statistics. Results: Out of 134 lung nodules found on 18F-FDG PET/CT, 18F-FDG PET/MRI detected 92 nodules. Accordingly, 42 lung nodules (average size ± SD, 3.9 ± 1.3 mm; range, 2–7 mm) were missed by 18F-FDG PET/MRI. None of the missed lung nodules presented with focal tracer uptake on baseline imaging or follow-up 18F-FDG PET/CT. Thirty-three out of 42 missed lung nodules (78.6%) in 26 patients were rated benign, whereas 9 nodules (21.4%) in 4 patients were rated malignant. As a result, 1 patient required upstaging from tumor stage I to IV. Conclusion: Although most small lung nodules missed on 18F-FDG PET/MRI were found to be benign, there was a relevant number of undetected metastases. However, in patients with advanced tumor stages the clinical impact remains controversial as upstaging is usually more relevant in lower stages.

Evaluation of a Fast Protocol for Staging Lymphoma Patients with Integrated PET/MRI

Background The aim of this study was to assess the applicability of a fast MR-protocol for whole-body staging of lymphoma patients using an integrated PET/MR system. Methods A total of 48 consecutive lymphoma patients underwent 52 clinically indicated PET/CT and subsequent PET/MRI examinations with the use of 18F-FDG. For PET/MR imaging, a fast whole-body MR-protocol was implemented. A radiologist and a nuclear medicine physician interpreted MRI and PET/MRI datasets in consensus and were instructed to identify manifestations of lymphoma on a site-specific analysis. The accuracy for the identification of active lymphoma disease was calculated and the tumor stage for each examination was determined. Furthermore, radiation doses derived from administered tracer activities and CT protocol parameters were estimated and the mean scan duration of PET/CT and PET/MR imaging was determined. Statistical analysis was performed to compare the diagnostic performance of PET/MRI and MRI alone. The results of PET/CT imaging, all available histopathological samples as well as results of prior examinations and follow-up imaging were used for the determination of the reference standard. Results Active lymphoma disease was present in 28/52 examinations. PET/MRI revealed higher values of diagnostic accuracy for the identification of active lymphoma disease in those 52 examinations in comparison to MRI, however, results of the two ratings did not differ significantly. On a site specific analysis, PET/MRI showed a significantly higher accuracy for the identification of nodal manifestation of lymphoma (p<0.05) if compared to MRI, whereas ratings for extranodal regions did not reveal a significant difference. In addition, PET/MRI enabled correct identification of lymphoma stage in a higher percentage of patients than MRI (94% vs. 83%). Furthermore, SUVs derived from PET/MRI were significantly higher than in PET/CT, however, there was a strong positive correlation between SUVmax and SUVmean of the two imaging modalities (R = 0.91 p<0.001 and R = 0.87, p<0.001). Average scan duration of whole-body PET/CT and PET/MRI examinations amounted to 17.3±1.9 min and 27.8±3.7 min, respectively. Estimated mean effective-dose for whole-body PET/CT scans were 64.4% higher than for PET/MRI. Conclusions Our results demonstrate the usefulness of 18F-FDG PET data as a valuable additive to MRI for a more accurate evaluation of patients with lymphomas. With regard to patient comfort related to scan duration and a markedly reduced radiation exposure, fast PET/MRI may serve as a powerful alternative to PET/CT for a diagnostic workup of lymphoma patients.

Hybrid imaging for detection of carcinoma of unknown primary: A preliminary comparison trial of whole-body PET/MRI versus PET/CT

PURPOSE The aim of this study is to evaluate and compare the diagnostic potential of integrated whole-body [18F]FDG-PET/MRI to [18F]FDG-PET/CT for detection of a potential primary cancer and metastases in patients suspected for cancer of unknown primary (CUP). METHODS A total of 20 patients (15 male, 5 female, age 53±13 years) suspect for CUP underwent a dedicated head and neck & whole-body [18F]FDG-PET/CT (Biograph mCT 128, Siemens Healthcare) and a subsequent simultaneous [18F]FDG-PET/MRI examination (Biograph mMR, Siemens Healthcare). Two readers rated the datasets (PET/CT; PET/MRI) regarding the detection of the primary cancer and metastases, lesion conspicuity (4-point ordinal scale) and diagnostic confidence (3-point ordinal scale). PET analysis comprised the assessment of maximum standardized uptake values (SUVmax) of all PET-positive lesions using volume of interest (VOI) analysis derived from the PET/CT and PET/MR datasets. All available data considering histology and imaging including prior and clinical follow-up examinations served as reference standard. Statistical analysis included comparison of mean values using Mann-Whitney U test and correlation of SUVmax using Pearsons correlation. RESULTS In 14 out of 20 patients 49 malignant lesions were present. The primary cancer could be correctly identified in 11/20 patients with both PET/CT and PET/MRI. PET/CT enabled the detection of a total 38 metastases, PET/MR respectively of 37 metastases (one lung metastasis <5mm was missed). PET/CT and PET/MRI showed comparably high lesion conspicuity (2.6±0.6 each), with superior assessment of cervical lesions in PET/MRI and an indicated superior assessment of pulmonary lesions in PET/CT. Diagnostic confidence was rated comparably high in PET/CT and PET/MRI (2.7±0.5 each). The mean values of SUVmax of all PET-positive lesions (PET/MRT 7.9±4.2 vs. PET/CT 7.2±3.5) showed a strong positive correlation between the SUVs derived from both hybrid imaging systems (Pearsons correlation r=0.927). CONCLUSIONS Both hybrid imaging techniques provide a comparable diagnostic ability for detection of primary cancer and metastases in patients with CUP, with comparably high lesion conspicuity and diagnostic confidence, offering superior assessment of cervical lesions in PET/MRI and potentially of pulmonary lesions in PET/CT. Furthermore, due to the significantly lower dose of ionizing radiation, PET/MRI may serve as a powerful alternative to PET/CT, particularly for therapy monitoring and/or surveillance considering the long-term cumulative dose.