Our purpose was to investigate differences between PET/MRI and PET/CT in lesion detection and classification in oncologic whole-body examinations and to investigate radiation exposure differences ...between the 2 modalities.
In this observational single-center study, 1,003 oncologic examinations (918 patients; mean age, 57.8 ± 14.4 y) were included. Patients underwent PET/CT and subsequent PET/MRI (149.8 ± 49.7 min after tracer administration). Examinations were reviewed by radiologists and nuclear medicine physicians in consensus. Additional findings, characterization of indeterminate findings on PET/CT, and missed findings on PET/MRI, including their clinical relevance and effective dose of both modalities, were investigated. The McNemar test was used to compare lesion detection between the 2 hybrid imaging modalities (
< 0.001, indicating statistical significance).
Additional information on PET/MRI was reported for 26.3% (264/1,003) of examinations, compared with PET/CT (
< 0.001). Of these, additional malignant findings were detected in 5.3% (53/1,003), leading to a change in TNM staging in 2.9% (29/1,003) due to PET/MRI. Definite lesion classification of indeterminate PET/CT findings was possible in 11.1% (111/1,003) with PET/MRI. In 2.9% (29/1,003), lesions detected on PET/CT were not visible on PET/MRI. Malignant lesions were missed in 1.2% (12/1,003) on PET/MRI, leading to a change in TNM staging in 0.5% (5/1,003). The estimated mean effective dose for whole-body PET/CT amounted to 17.6 ± 8.7 mSv, in comparison to 3.6 ± 1.4 mSv for PET/MRI, resulting in a potential dose reduction of 79.6% (
< 0.001).
PET/MRI facilitates staging comparable to that of PET/CT and improves lesion detectability in selected cancers, potentially helping to promote fast, efficient local and whole-body staging in 1 step, when additional MRI is recommended. Furthermore, younger patients may benefit from the reduced radiation exposure of PET/MRI.
Recently, radiomics has emerged as a non-invasive, imaging-based tissue characterization method in multiple cancer types. One limitation for robust and reproducible analysis lies in the inter-reader ...variability of the tumor annotations, which can potentially cause differences in the extracted feature sets and results. In this study, the diagnostic potential of a rapid and clinically feasible VOI (Volume of Interest)-based approach to radiomics is investigated to assess MR-derived parameters for predicting molecular subtype, hormonal receptor status, Ki67- and HER2-Expression, metastasis of lymph nodes and lymph vessel involvement as well as grading in patients with breast cancer.
A total of 98 treatment-naïve patients (mean 59.7 years, range 28.0-89.4) with BI-RADS 5 and 6 lesions who underwent a dedicated breast MRI prior to therapy were retrospectively included in this study. The imaging protocol comprised dynamic contrast-enhanced T1-weighted imaging and T2-weighted imaging. Tumor annotations were obtained by drawing VOIs around the primary tumor lesions followed by thresholding. From each segmentation, 13.118 quantitative imaging features were extracted and analyzed with machine learning methods. Validation was performed by 5-fold cross-validation with 25 repeats.
Predictions for molecular subtypes obtained AUCs of 0.75 (HER2-enriched), 0.73 (triple-negative), 0.65 (luminal A) and 0.69 (luminal B). Differentiating subtypes from one another was highest for HER2-enriched vs triple-negative (AUC 0.97), followed by luminal B vs triple-negative (0.86). Receptor status predictions for Estrogen Receptor (ER), Progesterone Receptor (PR) and Hormone receptor positivity yielded AUCs of 0.67, 0.69 and 0.69, while Ki67 and HER2 Expressions achieved 0.81 and 0.62. Involvement of the lymph vessels could be predicted with an AUC of 0.8, while lymph node metastasis yielded an AUC of 0.71. Models for grading performed similar with an AUC of 0.71 for Elston-Ellis grading and 0.74 for the histological grading.
Our preliminary results of a rapid approach to VOI-based tumor-annotations for radiomics provides comparable results to current publications with the perks of clinical suitability, enabling a comprehensive non-invasive platform for breast tumor decoding and phenotyping.
Clinical Use of PET/MR in Oncology: An Update Seifert, Robert; Kersting, David; Rischpler, Christoph ...
Seminars in nuclear medicine,
20/May , Volume:
52, Issue:
3
Journal Article
Peer reviewed
The combination of PET and MRI is one of the recent advances of hybrid imaging. Yet to date, the adoption rate of PET/MRI systems has been rather slow. This seems to be partially caused by the high ...costs of PET/MRI systems and the need to verify an incremental benefit over PET/CT or sequential PET/CT and MRI.
In analogy to PET/CT, the MRI part of PET/MRI was primarily used for anatomical imaging. Though this can be advantageous, for example in diseases where the superior soft tissue contrast of MRI is highly appreciated, the sole use of MRI for anatomical orientation lessens the potential of PET/MRI. Consequently, more recent studies focused on its multiparametric potential and employed diffusion weighted sequences and other functional imaging sequences in PET/MRI. This integration puts the focus on a more wholesome approach to PET/MR imaging, in terms of releasing its full potential for local primary staging based on multiparametric imaging and an included one-stop shop approach for whole-body staging. This approach as well as the implementation of computational analysis, in terms of radiomics analysis, has been shown valuable in several oncological diseases, as will be discussed in this review article.
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.
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.
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.
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.
Purpose
To assess and compare the diagnostic accuracy of PET/MRI and MRI alone for the detection of local recurrences of soft tissue sarcomas (STS) after initial surgical resection of the primary ...tumors.
Material and methods
A total of 41 patients with clinically suspected tumor relapse of STS underwent an
18
F–FDG-PET/MRI examination for assessment of local recurrence. Two experienced physicians interpreted the MRI data and subsequently the PET/MRI datasets in two separate reading sessions and were instructed to identify potential local tumor recurrences. Additionally, the diagnostic confidence in each reading for the identification of malignant lesions was determined. A McNemar test was applied to test for differences of both ratings and a Wilcoxon signed-rank test was used to identify differences of the confidence levels. Histopathological verification and follow-up imaging were applied for standard of reference.
Results
Tumor relapse was present in 27/41 patients. Calculated sensitivity, specificity, positive predictive value, negative predictive value and diagnostic accuracy for the detection of local tumor recurrence was 82%, 86%, 92%, 71% and 83% for MRI, and 96%, 79%, 90%, 92% and 90% for PET/MRI (
p
> 0.05). Furthermore, PET/MRI showed significantly higher confidence levels (
p
< 0.05) for the determination of malignant lesions.
Conclusion
Our results endorse
18
F–FDG PET/MRI to be an excellent imaging method in the evaluation of recurrent STS after surgical excision, yielding superior tumor detection when compared to MRI alone.
Abstract Objectives To investigate the diagnostic value of different MR sequences and 18F-FDG PET data for whole-body restaging of breast cancer patients utilizing PET/MRI. Methods A total of 36 ...patients with suspected tumor recurrence of breast cancer based on clinical follow-up or abnormal findings in follow-up examinations (e.g. CT, MRI) were prospectively enrolled in this study. All patients underwent a PET/CT and subsequently an additional PET/MR scan. Two readers were instructed to identify the occurrence of a tumor relapse in subsequent MR and PET/MR readings, utilizing different MR sequence constellations for each session. The diagnostic confidence for the determination of a malignant or benign lesion was qualitatively rated (3-point ordinal scale) for each lesion in the different reading sessions and the lesion conspicuity (4-point ordinal scale) for the three different MR sequences was additionally evaluated. Results Tumor recurrence was present in 25/36 (69%) patients. All three PET/MRI readings showed a significantly higher accuracy as well as higher confidence levels for the detection of recurrent breast cancer lesions when compared to MRI alone (p < 0.05). Furthermore, all three PET/MR sequence constellations showed comparable diagnostic accuracy for the identification of a breast cancer recurrence (p > 0.05), yet the highest confidence levels were obtained, when all three MR sequences were used for image interpretation. Moreover, contrast-enhanced T1-weighted VIBE imaging showed significantly higher values for the delineation of malignant and benign lesions when compared to T2 w HASTE and diffusion-weighted imaging. Conclusion Integrated PET/MRI provides superior restaging of breast cancer patients over MRI alone. Facing the need for appropriate and efficient whole-body PET/MR protocols, our results show the feasibility of fast and morphologically adequate PET/MR protocols. However, considering an equivalent accuracy for the detection of breast cancer recurrences in the three PET/MR readings, the application of contrast-agent and the inclusion of DWI in the study protocol seems to be debatable.
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.
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.
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.
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.
To compare the apparent diffusion coefficient (ADC) in lymph node metastases of non-small cell lung cancer (NSCLC) patients with standardized uptake values (SUV) derived from combined ...18F-fluoro-deoxy-glucose-positron emission tomography/magnetic resonance imaging (18F-FDG PET/MRI).
38 patients with histopathologically proven NSCLC (mean age 60.1 ± 9.5 y) received whole-body PET/CT (Siemens mCT™) 60 min after injection of a mean dose of 280 ± 50 MBq 18F-FDG and subsequent PET/MRI (mean time after tracer injection: 139 ± 26 min, Siemens Biograph mMR). During PET acquisition, simultaneous diffusion-weighted imaging (DWI, b values: 0, 500, 1000 s/mm²) was performed. A maximum of 10 lymph nodes per patient suspicious for malignancy were analyzed. Regions of interest (ROI) were drawn covering the entire lymph node on the attenuation-corrected PET-image and the monoexponential ADC-map. According to histopathology or radiological follow-up, lymph nodes were classified as benign or malignant. Pearson's correlation coefficients were calculated for all lymph node metastases correlating SUVmax and SUVmean with ADCmean.
A total of 146 suspicious lymph nodes were found in 25 patients. One hundred lymph nodes were eligible for final analysis. Ninety-one lymph nodes were classified as malignant and 9 as benign according to the reference standard. In malignant lesions, mean SUVmax was 9.1 ± 3.8 and mean SUVmean was 6.0 ± 2.5 while mean ADCmean was 877.0 ± 128.6 x10(-5) mm²/s in PET/MRI. For all malignant lymph nodes, a weak, inverse correlation between SUVmax and ADCmean as well as SUVmean and ADCmean (r = -0.30, p<0.05 and r = -0.36, p<0.05) existed.
The present data show a weak inverse correlation between increased glucose-metabolism and cellularity in lymph node metastases of NSCLC patients. 18F-FDG-PET and DWI thus may offer complementary information for the evaluation of treatment response in lymph node metastases of NSCLC.
Background: The aim of this study was to assess whether multiparametric 18F-FDG PET/MRI-based radiomics analysis is able to predict pathological complete response in breast cancer patients and hence ...potentially enhance pretherapeutic patient stratification. Methods: A total of 73 female patients (mean age 49 years; range 27–77 years) with newly diagnosed, therapy-naive breast cancer underwent simultaneous 18F-FDG PET/MRI and were included in this retrospective study. All PET/MRI datasets were imported to dedicated software (ITK-SNAP v. 3.6.0) for lesion annotation using a semi-automated method. Pretreatment biopsy specimens were used to determine tumor histology, tumor and nuclear grades, and immunohistochemical status. Histopathological results from surgical tumor specimens were used as the reference standard to distinguish between complete pathological response (pCR) and noncomplete pathological response. An elastic net was employed to select the most important radiomic features prior to model development. Sensitivity, specificity, positive predictive value, negative predictive value, and accuracy were calculated for each model. Results: The best results in terms of AUCs and NPV for predicting complete pathological response in the entire cohort were obtained by the combination of all MR sequences and PET (0.8 and 79.5%, respectively), and no significant differences from the other models were observed. In further subgroup analyses, combining all MR and PET data, the best AUC (0.94) for predicting complete pathologic response was obtained in the HR+/HER2− group. No difference between results with/without the inclusion of PET characteristics was observed in the TN/HER2+ group, each leading to an AUC of 0.92 for all MR and all MR + PET datasets. Conclusion: 18F-FDG PET/MRI enables comprehensive high-quality radiomics analysis for the prediction of pCR in breast cancer patients, especially in those with HR+/HER2− receptor status.
To assess the response to initial treatment strategies of cervical cancer using multiparametric-PET/MRI.
PET/MR-derived morphological (tumor size), functional (DWI, DCE-MRI) and metabolic (18F-FDG ...PET) parameters were acquired in pre- and posttreatment examinations of 8 patients. Besides RECIST- and PERCIST-criteria, functional quantitative parameters were used to assess therapeutic response.
RECIST- and PERCIST-response criteria demonstrated high correlations for the differentiation between therapy-responders and non-responders, which was additionally reflected by functional (DWI, DCE-MRI) quantitative imaging parameters.
Multiparametric-PET/MRI bears the potential of a more comprehensive response assessment of initial treatment strategies in cervical cancer patients.
•Integrated PET/MRI acquires morphologic, metabolic (e.g. 18F-FDG PET) and functional (e.g. DWI) parameters in one examination.•Within one PET/MRI examination different facets of the underlying tumor biology are reflected.•Quantitative multiparametric PET/MRI bears the potential of a more comprehensive evaluation of the primary cervical tumor.•PET/MRI may function as a useful diagnostic tool for monitoring initial treatment strategies in cervical cancer patients.
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