Comparing diffusion-weighted imaging and positron emission tomography for pulmonary nodules measuring from 1 to 3 cm in size

Diagnostic performance of diffusion-weighted imaging versus 18F-FDG PET/CT in differentiating pulmonary lesions: an updated meta-analysis of comparative studies

OBJECTIVE

To compare the diagnostic accuracy of diffusion-weighted imaging (DWI) and 18F-fluorodeoxyglucose positron emission tomography/computed tomography (18F-FDG PET/CT) for differentiating pulmonary nodules and masses.

METHODS

We systematically searched six databases, including PubMed, EMBASE, the Cochrane Library, and three Chinese databases, to identify studies that used both DWI and PET/CT to differentiate pulmonary nodules. The diagnostic performance of DWI and PET/CT was compared and pooled sensitivity and specificity were calculated along with 95% confidence intervals (CIs). The Quality Assessment of Diagnostic Accuracy Studies 2 was used to assess the quality of the included studies, and STATA 16.0 software was utilized to perform statistical analysis.

RESULTS

Overall, 10 studies that enrolled a total of 871 patients with 948 pulmonary nodules were included in this meta-analysis. DWI had greater pooled sensitivity (0.85 [95% CI 0.77-0.90]) and specificity (0.91 [95% CI 0.82-0.96]) than PET/CT (sensitivity, 0.82 [95% CI 0.70-0.90]); specificity, (0.81, [95% CI 0.72-0.87]). The area under the curve of DWI and PET/CT were 0.94 (95% CI 0.91-0.96) and 0.87 (95% CI 0.84-0.90) (Z = 1.58, P > 0.05), respectively. The diagnostic odds ratio of DWI (54.46, [95% CI 17.98-164.99]) was superior to that of PET/CT (15.77, [95% CI 8.19-30.37]). The Deeks' funnel plot asymmetry test showed no publication bias. The Spearman correlation coefficient test revealed no significant threshold effect. Lesion diameter and reference standard could be potential causes for the heterogeneity of both DWI and PET/CT studies, and quantitative or semi-quantitative parameters used would be a potential source of bias for PET/CT studies.

CONCLUSION

As a radiation-free technique, DWI may have similar performance compare with PET/CT in differentiating malignant pulmonary nodules or masses from benign ones.

State of the Art: Lung Cancer Staging Using Updated Imaging Modalities

Lung cancer is among the most common mortality causes worldwide. This scientific article is a comprehensive review of current knowledge regarding screening, subtyping, imaging, staging, and management of treatment response for lung cancer. The traditional imaging modality for screening and initial lung cancer diagnosis is computed tomography (CT). Recently, a dual-energy CT was proven to enhance the categorization of variable pulmonary lesions. The National Comprehensive Cancer Network (NCCN) recommends usage of fluorodeoxyglucose positron emission tomography (FDG PET) in concert with CT to properly stage lung cancer and to prevent fruitless thoracotomies. Diffusion MR is an alternative to FDG PET/CT that is radiation-free and has a comparable diagnostic performance. For response evaluation after treatment, FDG PET/CT is a potent modality which predicts survival better than CT. Updated knowledge of lung cancer genomic abnormalities and treatment regimens helps to improve the radiologists’ skills. Incorporating the radiologic experience is crucial for precise diagnosis, therapy planning, and surveillance of lung cancer.

Whole-Lesion DCE-MRI Intensity Histogram Analysis for Diagnosis in Patients with Suspected Lung Cancer

RATIONALE AND OBJECTIVES

To explore the diagnostic value of dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI) intensity histogram metrics, relative to time intensity curve (TIC)-derived metrics, in patients with suspected lung cancer.

MATERIALS AND METHODS

This retrospective study enrolled 49 patients with suspected lung cancer on routine CT imaging who underwent DCE-MRI scans and had final histopathologic diagnosis. Three TIC-derived metrics (maximum enhancement ratio, peak time [T_max] and slope) and eight intensity histogram metrics (volume, integral, maximum, minimum, median, coefficient of variation [CoV], skewness, and kurtosis) were extracted from DCE-MRI images. TIC-derived and intensity histogram metrics were compared between benignity versus malignancy using the Wilcoxon rank-sum test. Associations between imaging metrics and malignancy risk were assessed by univariate and multivariate logistic regression odds ratios (ORs).

RESULTS

There were 33 malignant lesions and 16 benign lesions based on histopathology. Lower CoV (OR = 0.2 per 1-SD increase, p = 0.0006), lower T_max (OR = 0.4 per 1-SD increase, p = 0.005), and steeper slope (OR = 2.4 per 1-SD increase, p = 0.010) were significantly associated with increased risk of malignancy. Under multivariate analysis, CoV was significantly independently associated with malignancy likelihood after accounting for either T_max (OR = 0.3 per 1-SD increase, p = 0.007) or slope (OR = 0.3 per 1-SD increase, p = 0.011).

CONCLUSION

This initial study found that DCE-MRI CoV was independently associated with malignancy in patients with suspected lung cancer. CoV has the potential to help diagnose indeterminate pulmonary lesions and may complement TIC-derived DCE-MRI metrics. Further studies are warranted to validate the diagnostic value of DCE-MRI intensity histogram analysis.

Quantitative Assessment of Bone Marrow Edema in Adolescent Athletes with Lumbar Spondylolysis Using Contrast Ratio on Magnetic Resonance Imaging

STUDY DESIGN

Prospective cohort study.

PURPOSE

To quantitatively evaluate bone marrow edema (BME) in the pedicle on magnetic resonance imaging (MRI) for adolescent athlete patients with spondylolysis.

OVERVIEW OF LITERATURE

Spondylolysis, a stress fracture of the pars interarticularis, is a common occurrence in adolescent athletes with low back pain. T2-weighed fat-saturated MRI is reportedly useful for the detection of BME in the pedicle in the early stage of spondylolysis; however, to our knowledge, the quantitative assessment of BME in spondylolysis has not been reported.

METHODS

Adolescent athletes with spondylolysis, including those with symptoms of low back pain, were enrolled. The sporting activity of the patients was restricted, and a hard brace was attached to the spine. The BME range of interest was taken on T2-weighed fat-saturated MRI, and the signal intensity (SI) of the BME (SIedema) was measured. The contrast ratio (CR) between the SI of the BME and SI of the spinal cord (SIcord) was calculated per the following formulae: CRedema=(SIedema-SIcord)/(SIedema+SIcord). The CR of the normal pedicle was measured as a control per the following formulae: CRcontrol=(SIcontrol-SIcord)/(SIcontrol+SIcord).

RESULTS

The study enrolled 32 men and one woman; the mean patient age was 15.2 years (range, 12-18 years). The average CR of the edema and normal pedicle at the first visit was 0.506 (range, 0.097-0.804) and 0.137 (range, -0.741 to 0.572), respectively. The CR of the edema was significantly higher as compared to that of the normal pedicle (p<0.01). MRI that was performed 1 month after the first visit showed that the CR of the edema had decreased to 0.204 (range, -0.152 to 0.517). The CR of the edema 1 month thereafter was significantly lower than that at the first visit (p<0.01).

CONCLUSIONS

Quantitative assessment of BME using CR on MRI is useful in the evaluation of the healing process of spondylolysis.

Role of Various DW MRI and DCE MRI Parameters as Predictors of Malignancy in Solid Pulmonary Lesions

PURPOSE

We aimed to evaluate various diffusion and dynamic contrast-enhanced magnetic resonance imaging (DCE MRI) parameters in differentiating malignant from benign pulmonary lesions.

METHODS

We enrolled 31 (22 males) patients who had solid pulmonary lesion(s) >2 cm in our cross sectional study. Of these, 23 (74.2%) were found to be malignant on histopathology. Dynamic contrast-enhanced MRI was performed using 36 dynamic measurements (volumetric interpolated breath-hold examination). Diffusion-weighted MRI (DW MRI) performed at b value of 800 s/mm². We measured different diffusion and perfusion parameters, for example, diffusion-weighted imaging (DWI) SI, mean apparent diffusion coefficient (ADC), minimum ADC, lesion-to-spinal cord ratio, DWI score, T2 score, K^trans, K_ep, and V_e. We stratified values of each parameter as high if it was >median of values observed in our data set and low if it was ≤median. Normally distributed data were compared by unpaired t test, whereas non-normal continuous data were compared by Kruskal Wallis-H test. We applied Wilson score method to calculate sensitivity, specificity, and predictive values of parameters that were statistically significant by type of lesion with reference to histopathological examination as gold standard.

RESULTS

Diffusion-weighted imaging SI, mean ADC, minimum ADC, DWI score and K^trans values were found to be significantly different (P value < .05) by type of lesion. K^trans was found to have the highest diagnostic accuracy (74.2%) among these parameters.

CONCLUSION

K^trans and mean ADC had similar sensitivity of 65.2%. However, K^trans had highest diagnostic accuracy among various DWI and DCE MRI parameters in predicting malignancy in solid pulmonary lesions. In our study, we found a cutoff value 0.251 min^-1 for K^trans as 100% specific.

Diagnostic performance of diffusion-weighted magnetic resonance imaging in pulmonary malignant lesions: a meta-analysis

Background

Overuse or misuse of positron emission tomography/computed tomography (PET/CT) should be avoided for its ionizing-radiation. Diffusion-weighted magnetic resonance imaging (DW-MRI), characterized by no radiation, may be regarded as an alternative in differentiating pulmonary nodules. We aim to estimate the diagnostic accuracy of DW-MRI in diagnosing of pulmonary lesions.

Methods

Relevant studies were searched through PubMed and Embase with no language restriction from inception to March 8, 2019. We selected studies reporting sensitivity and specificity of DW-MRI for differentiating pulmonary nodules. A summary estimates of sensitivity, specificity and area under curve (AUC) of receiver operating characteristic (ROC) of DW-MRI were analyzed with a random effects model.

Results

We included data from 37 studies, which altogether included 2,311 pulmonary lesions. The pooled sensitivity and specificity were 0.86 (95% CI, 0.82-0.89) and 0.79 (95% CI, 0.72-0.85), and AUC was 0.90 (95% CI, 0.87-0.92). Subsequent subgroup analysis showed the higher sensitivity of DW-MRI in pulmonary lesion >2 cm in comparison to lesions ≤2 cm, however, higher specificity was observed in smaller lesions.

Conclusions

Radiation-free DW-MRI showed a favorable balance between sensitivity and specificity in diagnosing pulmonary malignancies especially in lesion size ≤2 cm. Existing evidence indicated that DW-MRI may be considered as an independent substitute in diagnosis of lung lesions, which might help to prevent long-term side-effects from radiographic diagnosing and evaluating procedures.

Chest Magnetic Resonance Imaging Decreases Inter-observer Variability of Gross Target Volume for Lung Tumors

Purpose: PET/CT is a standard medical imaging used in the delineation of gross tumor volume (GTV) in case of radiation therapy for lung tumors. However, PET/CT could present some limitations such as resolution and standardized uptake value threshold. Moreover, chest MRI has shown good potential in diagnosis for thoracic oncology. Therefore, we investigated the influence of chest MRI on inter-observer variability of GTV delineation.

Methods and Materials: Five observers contoured the GTV on CT for 14 poorly defined lung tumors during three contouring phases based on true daily clinical routine and acquisition: CT phase, with only CT images; PET phase, with PET/CT; and MRI phase, with both PET/CT and MRI. Observers waited at least 1 week between each phases to decrease memory bias. Contours were compared using descriptive statistics of volume, coefficient of variation (COV), and Dice similarity coefficient (DSC).

Results: MRI phase volumes (median 4.8 cm³) were significantly smaller than PET phase volumes (median 6.4 cm³, p = 0.015), but not different from CT phase volumes (median 5.7 cm³, p = 0.30). The mean COV was improved for the MRI phase (0.38) compared to the CT (0.58, p = 0.024) and PET (0.53, p = 0.060) phases. The mean DSC of the MRI phase (0.67) was superior to those of the CT and PET phases (0.56 and 0.60, respectively; p < 0.001 for both).

Conclusions: The addition of chest MRI seems to decrease inter-observer variability of GTV delineation for poorly defined lung tumors compared to PET/CT alone and should be explored in further prospective studies.

Fluorine 18-FDG PET/CT and Diffusion-weighted MRI for Malignant versus Benign Pulmonary Lesions: A Meta-Analysis

Purpose To perform a meta-analysis of the literature to compare the diagnostic performance of fluorine 18 fluorodeoxyglucose PET/CT and diffusion-weighted (DW) MRI in the differentiation of malignant and benign pulmonary nodules and masses. Materials and Methods Published English-language studies on the diagnostic accuracy of PET/CT and/or DW MRI in the characterization of pulmonary lesions were searched in relevant databases through December 2017. The primary focus was on studies in which joint DW MRI and PET/CT were performed in the entire study population, to reduce interstudy heterogeneity. For DW MRI, lesion-to-spinal cord signal intensity ratio and apparent diffusion coefficient were evaluated; for PET/CT, maximum standard uptake value was evaluated. The pooled sensitivities, specificities, diagnostic odds ratios, and areas under the receiver operating characteristic curve (AUCs) for PET/CT and DW MRI were determined along with 95% confidence intervals (CIs). Results Thirty-seven studies met the inclusion criteria, with a total of 4224 participants and 4463 lesions (3090 malignant lesions [69.2%]). In the primary analysis of joint DW MRI and PET/CT studies (n = 6), DW MRI had a pooled sensitivity and specificity of 83% (95% CI: 75%, 89%) and 91% (95% CI: 80%, 96%), respectively, compared with 78% (95% CI: 70%, 84%) (P = .01 vs DW MRI) and 81% (95% CI: 72%, 88%) (P = .056 vs DW MRI) for PET/CT. DW MRI yielded an AUC of 0.93 (95% CI: 0.90, 0.95), versus 0.86 (95% CI: 0.83, 0.89) for PET/CT (P = .001). The diagnostic odds ratio of DW MRI (50 [95% CI: 19, 132]) was superior to that of PET/CT (15 [95% CI: 7, 32]) (P = .006). Conclusion The diagnostic performance of diffusion-weighted MRI is comparable or superior to that of fluorine 18 fluorodeoxyglucose PET/CT in the differentiation of malignant and benign pulmonary lesions. © RSNA, 2018 Online supplemental material is available for this article. See also the editorial by Schiebler in this issue.

Restriction spectrum imaging: An evolving imaging biomarker in prostate MRI

Restriction spectrum imaging (RSI) is a novel diffusion-weighted MRI technique that uses the mathematically distinct behavior of water diffusion in separable microscopic tissue compartments to highlight key aspects of the tissue microarchitecture with high conspicuity. RSI can be acquired in less than 5 min on modern scanners using a surface coil. Multiple field gradients and high b-values in combination with postprocessing techniques allow the simultaneous resolution of length-scale and geometric information, as well as compartmental and nuclear volume fraction filtering. RSI also uses a distortion correction technique and can thus be fused to high resolution T2-weighted images for detailed localization, which improves delineation of disease extension into critical anatomic structures. In this review, we discuss the acquisition, postprocessing, and interpretation of RSI for prostate MRI. We also summarize existing data demonstrating the applicability of RSI for prostate cancer detection, in vivo characterization, localization, and targeting.

LEVEL OF EVIDENCE

5 J. Magn. Reson. Imaging 2017;45:323-336.