Intravoxel incoherent motion diffusion-weighted MR imaging in differentiation of lung cancer from obstructive lung consolidation: comparison and correlation with pharmacokinetic analysis from dynamic contrast-enhanced MR imaging

Objectives

To test whether parameters derived from intravoxel incoherent motion (IVIM) can be used to distinguish lung cancer from obstructive pulmonary consolidation by comparing them with dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI)-derived parameters and to evaluate the correlation between these quantitative parameters.

Methods

A total of 31 lung cancer patients, confirmed by pathology and obstructive consolidations confirmed by positron emission tomography/computed tomography (PET-CT), were recruited. All of them were assessed with structural MRI and IVIM and 17 of them underwent additional DCE-MRI examinations. Parameters derived from IVIM and DCE-MRI in the tumour and consolidation were analysed, and the optimal cut-off values in differential diagnosis were obtained.

Results

ADC_total, D and f values were lower (P?<?0.05), while IAUC₆₀ was higher in lung cancers (P?=?0.013) compared with obstructive pulmonary consolidations. According to the ROC curve, ADC_total outperformed other perfusion and diffusion parameters with the optimal cut-off value of 1.409?×?10^-3 mm²/s (AUC?=?0.95). Poor correlations were found between parameters derived from IVIM and DCE-MRI.

Conclusions

IVIM-MRI is potentially useful in the differentiation of lung cancer and obstructive pulmonary consolidation. ADC_total, D and f may be reliable independent discriminating markers, but D ^* is variable with low diagnostic accuracy.

Key Points

? Lung cancer and consolidation differentiation is essential for treatment decision-making. ? Perfusion and diffusion characteristics of lesions could help differential diagnosis. ? IVIM can separate reflection of tissue diffusivity and microcapillary perfusion. ? The relationship between perfusion quantified by IVIM and DCE-MRI is controversial.     

Intravoxel incoherent motion MR imaging: comparison of diffusion and perfusion characteristics between nasopharyngeal carcinoma and post-chemoradiation fibrosis

Objectives

To compare the intravoxel incoherent motion (IVIM) diffusion and perfusion characteristics of nasopharyngeal carcinoma (NPC) and post-chemoradiation fibrosis to aid in their differentiation.

Methods

Fifty-three (64 %) patients with newly diagnosed NPC and 30 (36 %) patients with biopsy-proven post-chemoradiation fibrosis were recruited into tumour and fibrosis groups respectively. Diffusion-weighted magnetic resonance (MR) imaging was performed using 13 b values (0–1,000 s/mm²). Their respective IVIM parameters (D, pure diffusion; f, perfusion fraction; D*, pseudodiffusion coefficient) were obtained.

Results

D and f were significantly lower in NPC (D?=?0.752?±?0.194?×?10^-3 mm²/s, P <0.001; f?=?0.122?±?0.095, P <0.001) than in fibrosis (D?=?1.423?±?0.364?×?10^-3 mm²/s; f?=?0.190?±?0.120); while D* was significantly higher in NPC (111.366?±?65.528?×?10^-3 mm²/s, P <0.001) than in fibrosis (77.468?±?62.168?×?10^-3 mm²/s). Respective cut-off values with sensitivity, specificity and accuracy were: D?=?1.062?×?10^-3 mm²/s (100 %, 100 %, 100 %); f?=?0.132 (66.0 %, 100 %, 78.3 %); D*?=?85.283?×?10^-3 mm²/s (100 %, 90.7 %, 96.4 %).

Conclusion

NPC and post-chemoradiation fibrosis have distinctive IVIM parameters. IVIM MR imaging is potentially useful in discrimination between NPC and fibrosis.

Key Points

? New MRI techniques offer greater help in the assessment of nasopharyngeal carcinoma. ? Tumour and post-chemoradiation fibrosis have distinctive intravoxel incoherent motion diffusion/perfusion parameters. ? Non-invasive IVIM MRI may help differentiate between tumour and fibrosis. ? Pure diffusion is a robust independent discriminating factor which improves diagnostic confidence.     

Characterization and therapy monitoring of head and neck carcinomas using diffusion-imaging-based intravoxel incoherent motion parameters—preliminary results

Introduction

Using the intravoxel incoherent motion (IVIM) model, diffusion-related coefficient (D) and perfusion-related parameter (f) can be measured. Here, we used IVIM imaging to characterize squamous cell carcinomas of head and neck (HNSCC) and evaluated its application in follow-up after nonsurgical organ preserving therapy.

Methods

Twenty-two patients with locally advanced HNSCC (clinical stage III to IVb) were examined before treatment using eight different b values (b?=?0, 50, 100, 150, 200, 250, 700, 800 s/mm²). All patients were followed for at least 7.5 months after conclusion of therapy. In 16 of these patients, follow-up MRI was available. Using the IVIM approach, f and D were extracted using a bi-exponential fit. For comparison, ADC maps were calculated.

Results

The initial values of f before therapy were located between 5.9 % and 12.9 % (mean: 9.4?±?2.4 %) except for two outliers (f?=?17.9 % and 18.2 %). These two patients exclusively displayed poor initial treatment response. Overall, high initial f (13.1?±?4.1 % vs. 9.1?±?2.4 %) and ADC (1.17?±?0.08?×?10^?3?mm²/s vs. 0.98?±?0.19?×?10^?3?mm²/s) were associated with poor short term outcome (n?=?6) after 7.5 months follow-up. D values before treatment were 0.98?×?10^?3?±?0.18 mm²/s and ADC values were 1.03?×?10^?3?±?0.18 mm²/s. At follow-up, in all primary responders, D (69?±?52 %), f (65?±?46 %), and ADC (68?±?49%) increased.

Conclusions

Our preliminary evaluation indicates that an initial high f may predict poor prognosis in HNSCC. In responders, a significant increase of all IVIM parameters after therapy was demonstrated.     

Nasopharyngeal carcinoma: comparison of diffusion and perfusion characteristics between different tumour stages using intravoxel incoherent motion MR imaging

Objective

To explore intravoxel incoherent motion (IVIM) characteristics of nasopharyngeal carcinoma (NPC) and relationships with different tumour stages.

Methods

We prospectively recruited 80 patients with newly diagnosed undifferentiated NPC. Diffusion-weighted MR imaging was performed and IVIM parameters (D, pure diffusion; f, perfusion fraction; D*, pseudodiffusion coefficient) were calculated. Patients were stratified into low and high tumour stage groups based on American Joint Committee on Cancer (AJCC) and TNM staging for determination of the predictive powers of IVIM parameters using t test, multiple logistic regression and ROC curve analyses.

Results

D, f and D* were all statistically significantly lower in high-stage groups in AJCC, T and N staging. D, f and D* were all independent predictors of AJCC staging, f and D* were independent predictors of T staging, and D was an independent predictor of N staging. D was most powerful for AJCC and N staging, whereas f was most powerful for T staging. Optimal cut-off values (area under the curve, sensitivity, specificity, positive likelihood ratio, negative likelihood ratio) were as follows: AJCC stage, D?=?0.782?×?10^?3 mm²/s (0.915, 93.3 %, 76.2 %, 3.92, 0.09); T staging, f?=?0.133 (0.905, 80.5 %, 92.5 %, 10.73, 0.21); N staging, D?=?0.761?×?10^?3 mm²/s (0.848, 87.5 %, 66.7 %, 2.62, 0.19). Multivariate analysis showed no diagnostic improvement.

Conclusion

Nasopharyngeal carcinoma has distinctive intravoxel incoherent motion characteristics parameters in different tumour staging, potentially helping pretreatment staging.

Key Points

? Magnetic resonance imaging is increasingly used to assess nasopharyngeal carcinoma (NPC). ? NPC has distinctive diffusion/perfusion characteristics at different stages. ? Non-invasive MR imaging may help pretreatment staging prediction. ? Diffusion properties of NPC best correlate with AJCC and N staging. ? Perfusion properties of NPC best correlate with T staging.     

Intravoxel incoherent motion diffusion-weighted MR imaging of gliomas: feasibility of the method and initial results

Introduction

The purpose of this study was to evaluate the feasibility of intravoxel incoherent motion (IVIM) imaging and its value in differentiating the histologic grade among human gliomas.

Methods

The IVIM model generated parametric images for apparent diffusion coefficient ADC, slow diffusion coefficient D (or D _slow), fast diffusion coefficient D* (or D _fast), and fractional perfusion-related volume f in 22 patients with gliomas (WHO grade II–IV) using monopolar Stejskal–Tanner diffusion-weighted imaging (DWI) scheme and 14 b values ranging from 0 s/mm² to a maximum of 1,300 s/mm². A region-of-interest analysis on the tumor as well as in the white matter was conducted. The parameter values were tested for significant differences. The repeatability of the measurements was tested by coefficient of variation and Bland–Altman plots.

Results

D, D*, and f in the high-grade gliomas demonstrated significant differences compared to the healthy white matter. D* and f showed a significant difference between low- and high-grade gliomas. D tended to be slightly lower in the WHO grade II compared to WHO grade III–IV tumors. f and D* demonstrated higher coefficients of variation than the ADC and D in tumor. The Bland–Altman plots demonstrated satisfactory results without any outliers outside the mean?±?1.96 standard deviation.

Conclusion

The IVIM-fitted post-processing of DWI-signal decay in human gliomas could show significantly different values of fractional perfusion-related volume and fast diffusion coefficient between low- and high-grade tumors, which might enable a noninvasive WHO grading in vivo.     

Diffusion weighted imaging of the normal breast: reproducibility of apparent diffusion coefficient measurements and variation with menstrual cycle and menopausal status

Objectives

To establish the reproducibility of apparent diffusion coefficient (ADC) measurements in normal fibroglandular breast tissue and to assess variation in ADC values with phase of the menstrual cycle and menopausal status.

Methods

Thirty-one volunteers (13 premenopausal, 18 postmenopausal) underwent magnetic resonance twice (interval 11–22?days) using diffusion-weighted MRI. ADC_total and a perfusion-insensitive ADC_high (omitting b?=?0) were calculated. Reproducibility and inter-observer variability of mean ADC values were assessed. The difference in mean ADC values between the two phases of the menstrual cycle and the postmenopausal breast were evaluated.

Results

ADC_total and ADC_high showed good reproducibility (r%?=?17.6, 22.4). ADC_high showed very good inter-observer agreement (kappa?=?0.83). The intraclass correlation coefficients (ICC) were 0.93 and 0.91. Mean ADC values were significantly lower in the postmenopausal breast (ADC_total 1.46?±?0.3?×?10^-3?mm²/s, ADC_high 1.33?±?0.3?×?10^-3?mm²/s) compared with the premenopausal breast (ADC_total 1.84?±?0.26?×?10^-3?mm²/s, ADC_high 1.77?±?0.26?×?10^-3?mm²/s; both P?total P?=?0.2, ADC_high P?=?0.24) or between postmenopausal women taking or not taking oestrogen supplements (ADC_total P?=?0.6, ADC_high P?=?0.46).

Conclusions

ADC values in fibroglandular breast tissue are reproducible. Lower ADC values within the postmenopausal breast may reduce diffusion-weighted contrast and have implications for accurately detecting tumours.

Key Points

? ADC values from fibroglandular breast tissue are measured reproducibly by multiple observers. ? Mean ADC values were significantly lower in postmenopausal than premenopausal breast tissue. ? Mean ADC values did not vary significantly with menstrual cycle. ? Low postmenopausal ADC values may hinder tumour detection on DW-MRI.     

Diffusion-weighted imaging with acquisition of three b-values for response evaluation of neuroendocrine liver metastases undergoing selective internal radiotherapy

Objectives

To evaluate diffusion-weighted MRI with acquisition of three b-values and calculation of fractioned ADCs for response evaluation of neuroendocrine liver metastases undergoing selective internal radiotherapy (SIRT).

Methods

Ten consecutive patients with neuroendocrine liver metastases underwent MRI before and following SIRT. Diffusion-weighted imaging included acquisition of the b-values 0, 50 and 800 s/mm² and calculation of ADC_(50,800), ADC_(0,50) and ADC_(0,800) maps. According to therapy response, lesions were categorised into group A [≥20 % reduction of the longest diameter (LD) in comparison to baseline MRI] and group B (<20 % reduction of the LD).

Results

Twelve out of 31 metastases were categorised as group A and 19 out of 31 metastases were categorised as group B. Pretherapeutic values of ADC_(0,800) and ADC_(50,800) did not differ significantly between the two groups; however, ADC_(0,50) was 32 % lower in group A (P?=?0.049). ADC_(0,800) and ADC_(50,800) increased significantly after therapy in both groups, however, group differences were not statistically significant. Conversely, the increase in ADC_(0,50) was about a factor of 7 larger in group A than in group B (P?=?0.023).

Conclusions

Our study showed that the ADC_(0,50) is a promising biomarker for response assessment of neuroendocrine liver metastases following SIRT.

Key Points

? Diffusion-weighted MRI offers new information about neuroendocrine hepatic metastases. ? Evaluation of perfusion and diffusion components requires fractioned apparent diffusion coefficients (ADCs). ? Perfusion effects represented by ADC (0.50) can be observed in neuroendocrine metastases. ? Pretherapeutic ADC (0.50) was significantly lower in metastases with a response ≥20 %. ? Such biomarkers may help evaluate liver metastases in patients undergoing therapy.     

Intravoxel incoherent motion MRI: emerging applications for nasopharyngeal carcinoma at the primary site

Objectives

We compared pure molecular diffusion (D), perfusion-related diffusion (D*), perfusion fraction (f) and apparent diffusion coefficient (ADC) based on intravoxel incoherent motion (IVIM) theory in patients with nasopharyngeal carcinoma (NPC).

Methods

Sixty-five consecutive patients (48 men) with suspected NPC were examined using a 3.0-T MR system. Diffusion-weighted imaging (DWI) was performed with 13 b values (range, 0–800 s/mm²). We regarded the result of endoscopy and biopsy as the gold standard for detection. D, D* and f were compared between patients with primary NPC and enlarged adenoids.

Results

IVIM DWI was successful in 37 of 40 NPC and 23 of 25 enlarged adenoids cases. D (P?=?0.001) and f (P?<?0.0001) were significantly lower in patients with NPC than in patients with enlarged adenoids, whereas D* was significantly higher (P?<?0.0001). However, the ADC was not significantly different between the two groups (P?>?0.05). The area under the ROC curve (AUC) for D was 0.849 and was significantly larger than that for ADC (P?<?0.05).

Conclusions

IVIM DWI is a feasible technique for investigating primary NPC. D was significantly decreased in primary NPC, and increased D* reflected increased blood vessel generation and parenchymal perfusion in primary NPC.

Key Points

? Intravoxel incoherent motion (IVIM) analysis permits separate quantification of diffusion and perfusion. ? IVIM DWI is a feasible technique for investigating primary NPC. ? IVIM suggests that primary NPC tissue voxels exhibit both perfusion and diffusion.     

Head and neck tumours: combined MRI assessment based on IVIM and TIC analyses for the differentiation of tumors of different histological types

Objectives

We evaluated the combined use of intravoxel incoherent motion (IVIM) and time-signal intensity curve (TIC) analyses to diagnose head and neck tumours.

Methods

We compared perfusion-related parameters (PP) and molecular diffusion values (D) determined from IVIM theory and TIC profiles among 92 tumours with different histologies.

Results

IVIM parameters (f and D values) and TIC profiles in combination were distinct among the different types of head and neck tumours, including squamous cell carcinomas (SCCs), lymphomas, malignant salivary gland tumours, Warthin’s tumours, pleomorphic adenomas and schwannomas. A multiparametric approach using both IVIM parameters and TIC profiles differentiated between benign and malignant tumours with 97 % accuracy and diagnosed different tumour types with 89 % accuracy.

Conclusions

Combined use of IVIM parameters and TIC profiles has high efficacy in diagnosing head and neck tumours.

Key points

? Head and neck tumours have wide MR perfusion/diffusion properties. ? Dynamic contrast-enhanced (DCE) MR imaging can characterise tumour perfusion (TIC analysis). ? Intravoxel incoherent motion (IVIM) imaging can provide diffusion and perfusion properties. ? However, IVIM or DCE imaging alone is insufficient for diagnosing head/neck tumours. ? Multiparametric approach using both IVIM and TIC profiles can facilitate the diagnosis.     

Perfusion and diffusion characteristics of cervical cancer based on intraxovel incoherent motion MR imaging-a pilot study

Objectives

To investigate the tissue characteristics of cervical cancer based on the intravoxel incoherent motion (IVIM) model and to assess the IVIM parameters in tissue differentiation in the female pelvis.

Methods

Sixteen treatment-naïve cervical cancer and 17 age-matched healthy subjects were prospectively recruited for diffusion-weighted (b?=?0–1,000 s/mm²) and standard pelvic MRI. Bi-exponential analysis was performed to derive the perfusion parameters f (perfusion fraction) and D* (pseudodiffusion coefficient) as well as the diffusion parameter D (true molecular diffusion coefficient) in cervical cancer (n?=?16), normal cervix (n?=?17), myometrium (n?=?33) and leiomyoma (n?=?14). Apparent diffusion coefficient (ADC) was calculated. Kruskal–Wallis test and receiver operating characteristics (ROC) curves were used.

Results

Cervical cancer had the lowest f (14.9?±?2.6 %) and was significantly different from normal cervix and leiomyoma (p?<?0.05). The D (0.86?±?0.16 x 10^-3 mm2/s) was lowest in cervical cancer and was significantly different from normal cervix and myometrium (p?<?0.05) but not leiomyoma. No difference was observed in D*. D was consistently lower than ADC in all tissues. ROC curves indicated that f < 16.38 %, D < 1.04?×?10^-3 mm²/s and ADC < 1.13?×?10^-3 mm²/s could differentiate cervical cancer from non-malignant tissues (AUC 0.773–0.908).

Conclusions

Cervical cancer has low perfusion and diffusion IVIM characteristics with promising potential for tissue differentiation.

Key Points

? Diffusion-weighted MRI is increasingly applied in evaluation of cervical cancer. ? Cervical cancer has distinctive perfusion and diffusion characteristics. ? Intravoxel incoherent motion characteristics can differentiate cervical cancer from non-malignant uterine tissues.     

Assessing response in bone metastases in prostate cancer with diffusion weighted MRI

Objectives

To determine whether changes in ADC of bone metastases secondary to prostate carcinoma are significantly different in responders compared with progressors on chemotherapy.

Methods

Twenty-six patients with known bone metastases secondary to prostate carcinoma underwent diffusion-weighted MRI of the lumbar spine and pelvis at baseline and 12 weeks following chemotherapy. RECIST assessment of staging CT and PSA taken at the same time points were used to classify patients as responders, progressors or stable. ADC (from b?=?0,50,100,250,500,750 smm^?2) and ADC_slow (from b?=?100,250,500,750 smm^?2) were calculated for up to 5 lesions per patient.

Results

Mean ADC/ADC_slow in lesions from responders and progressors showed a significant increase. Although the majority of lesions demonstrated an ADC/ADC_slow rise, some lesions in both responders and progressors demonstrated a fall in ADC beyond the limits of reproducibility.

Conclusions

Mean ADC is not an appropriate measure of response in bone metastases. The heterogeneity of changes in ADC is likely to be related to the composition of bone marrow with changes that have opposing effects on ADC.     

Intravoxel incoherent motion perfusion imaging in acute stroke: initial clinical experience

Introduction

Intravoxel incoherent motion (IVIM) imaging is an MRI perfusion technique that uses a diffusion-weighted sequence with multiple b values and a bi-compartmental signal model to measure the so-called pseudo-diffusion of blood caused by its passage through the microvascular network. The goal of the current study was to assess the feasibility of IVIM perfusion fraction imaging in patients with acute stroke.

Methods

Images were collected in 17 patients with acute stroke. Exclusion criteria were onset of symptoms to imaging >5 days, hemorrhagic transformation, infratentorial lesions, small lesions <0.5 cm in minimal diameter and hemodynamic instability. IVIM imaging was performed at 3 T, using a standard spin-echo Stejskal-Tanner pulsed gradients diffusion-weighted sequence, using 16 b values from 0 to 900 s/mm². Image quality was assessed by two radiologists, and quantitative analysis was performed in regions of interest placed in the stroke area, defined by thresholding the apparent diffusion coefficient maps, as well as in the contralateral region.

Results

IVIM perfusion fraction maps showed an area of decreased perfusion fraction f in the region of decreased apparent diffusion coefficient. Quantitative analysis showed a statistically significant decrease in both IVIM perfusion fraction f (0.026?±?0.019 vs. 0.056?±?0.025, p?=?2.2?·?10^?6) and diffusion coefficient D compared with the contralateral side (3.9?±?0.79?·?10^?4 vs. 7.5?±?0.86?·?10^?4 mm²/s, p?=?1.3?·?10^?20).

Conclusion

IVIM perfusion fraction imaging is feasible in acute stroke. IVIM perfusion fraction is significantly reduced in the visible infarct. Further studies should evaluate the potential for IVIM to predict clinical outcome and treatment response.     

Evaluation of true diffusion, perfusion factor, and apparent diffusion coefficient in non-necrotic liver metastases and uncomplicated liver hemangiomas using black-blood echo planar imaging

Purpose

To assess the added value of true diffusion (D), perfusion factor (f) and apparent diffusion coefficient at low b-values (ADC_low) for differentiation between liver metastases and hemangiomas based on respiratory-triggered high-resolution Black-Blood Single-Shot SpinEcho Echo Planar Imaging (BB SS SE-EPI).

Materials and methods

Twenty-five patients suspected for malignant colorectal liver lesions were included in this study. A total of 106 lesions were examined. Different b-value images were compared for lesion conspicuity, image quality and artifacts using rank order statistic (RIDIT) and Student's t-test. D, f, and ADC_low values were calculated. Pearson correlation coefficient is used for comparison of interobserver variability.

Results

Best lesion conspicuity (p < 0.05) was achieved with BB SS SE-EPI (b = 0 and 10 s/mm²); best image quality (p < 0.05) with b = 10 s/mm². Image artifacts were lowest (p < 0.05) with b = 0 s/mm². Over the whole sample, D in metastases (D_met) was significantly (p < 0.05) lower than D in hemangiomas (D_hem); f and ADC_low of metastases (f_met, respectively, ADC_low met) were significantly (p < 0.05) higher than f and ADC_low of hemangiomas (f_hem, respectively, ADC_low hem). All Pearson correlations were statistically significant at a 0.01 level.

Conclusions

This preliminary study shows the potential of BB SS SE-EPI as a useful technique to aid in differentiating between liver metastasis and hemangioma. The calculation of D, f and ADC_low provides useful additional information for differentiating metastases from hemangiomas.     

Initial experience of correlating parameters of intravoxel incoherent motion and dynamic contrast-enhanced magnetic resonance imaging at 3.0 T in nasopharyngeal carcinoma

Purpose

To determine the correlation between intravoxel incoherent motion (IVIM) and dynamic contrast-enhanced (DCE) magnetic resonance imaging (MRI) parameters.

Methods

Thirty-eight newly diagnosed NPC patients were prospectively enrolled. Diffusion-weighted images (DWI) at 13 b-values were acquired using a 3.0-T MRI system. IVIM parameters including the pure molecular diffusion (D), perfusion-related diffusion (D*), perfusion fraction (f), DCE-MRI parameters including maximum slope of increase (MSI), enhancement amplitude (EA) and enhancement ratio (ER) were calculated by two investigators independently. Intra- and interobserver agreement were evaluated using the intraclass correlation coefficient (ICC) and Bland-Altman analysis. Relationships between IVIM and DCE-MRI parameters were evaluated by calculation of Spearman’s correlation coefficient.

Results

Intra- and interobserver reproducibility were excellent to relatively good (ICC?=?0.887-0.997; narrow width of 95 % limits of agreement). The highest correlation was observed between f and EA (r?=?0.633, P?f and MSI (r?=?0.598, P?=?0.001). No correlation was observed between f and ER (r?=?-0.162; P?=?0.421) or D* and DCE parameters (r?=?0.125–0.307; P?>?0.119).

Conclusion

This study suggests IVIM perfusion imaging using 3.0-T MRI is feasible in NPC, and f correlates significantly with EA and MSI.

Key Points

? Assessment of tumour perfusion is important in nasopharyngeal carcinoma. ? DCE-MRI provided perfusion information with the use of intravenous contrast media. ? Perfusion information could be provided by non-invasive IVIM MRI. ? IVIM parameter f correlated with DCE-MRI parameters.     

Quantitative evaluation of bone metastases from prostate cancer with simultaneous [18F] choline PET/MRI: combined SUV and ADC analysis

Objective

To quantitatively analyze bone metastases from prostate cancer and correlate the apparent diffusion coefficients (ADCs) and standardized uptake values (SUVs).

Methods

Fifty-five patients with biopsy-proven prostate cancer or suspected recurrent prostate cancer were examined with simultaneous [¹⁸F] choline Positron emission tomography (PET)/MRI at 3 T. In 11 patients, thirty-two PET-positive bone lesions could be identified that were located in the field-of-view of the Diffusion weighted imaging-sequence. Region-of-interest and volume-of-interest analyses were performed to measure the mean and minimal ADCs and to assess maximum and mean SUVs of every bone lesion. Correlations between maximum and mean SUVs and mean and minimal ADCs were calculated.

Results

The SUV_max of all lesions was 5.5 ± 3.1 (mean ± SD). The SUV_mean was 1.8 ± 0.9. The mean ADC (ADC_mean) of all lesions was 0.67 ± 0.13 × 10^?3 mm²/s. The minimal ADC (ADC_min) of all lesions was 0.56 ± 0.14 × 10^?3 mm²/s. There was a moderate but significant inverse correlation of SUV_max vs. ADC_mean with a correlation coefficient of ?0.4 (p = 0.02). There was also a significant inverse correlation of SUV_max vs. ADC_min with r = ?0.41 (p = 0.02).

Conclusion

Our initial results demonstrate a moderate but significant inverse correlation between increased choline metabolism and ADC values of bone metastases from prostate cancer. Further research on a multimodality approach using simultaneous PET/MRI in bone metastasis of prostate cancer seems to be justified.     

Intravoxel incoherent motion MR imaging measurements of the bilateral parotid glands at 3.0-T MR: effect of age,gender and laterality in healthy adults

Objective:

To investigate the effect of age, gender and laterality on the intravoxel incoherent motion (IVIM) MR imaging measurements of parotid glands in healthy participants at 3.0-T MRI.

Methods:

A total of 108 healthy participants were prospectively recruited. IVIM MRI scan was performed using a 3.0-T MR scanner, and corresponding parameters (perfusion fraction, f; pseudodiffusion coefficient, D*; tissue diffusivity, D) were derived from biexponential fitting of IVIM data. Pearson correlation analysis was performed to determine the association between the IVIM MRI parameters and age. The parameter difference between male and female participants or between left and right parotid glands was compared using unpaired or paired t test, respectively.

Results:

Excellent interreader and intrareader agreements on the measurements of IVIM MRI parameters were achieved. Both D and f values correlated inversely with the age in both left and right parotid glands (p < 0.05) while D* value did not (p > 0.05). Male participants had higher IVIM MRI parameters than the female participants in both left and right glands (p < 0.05). No significant differences were found in the IVIM MRI parameters between left and right glands in both male and female participants (p > 0.05).

Conclusion:

The IVIM MRI parameters are age and gender dependent, but not laterality dependent. Age- and gender-related effect should be taken into consideration in future IVIM MRI studies for parotid glands.

Advances in knowledge:

(1) Both D and f values correlated inversely with the age in healthy parotid glands, while D* value did not. (2) The parotid glands of males showed higher IVIM MRI parameters than that of females. (3) There were no significant differences on the IVIM MRI parameters between the left and right glands. (4) Age- and gender-related effect should be taken into consideration in future IVIM MRI studies for parotid glands.     

Diffusion-weighted MR imaging in primary rectal cancer staging demonstrates but does not characterise lymph nodes

Objectives

To evaluate the performance of diffusion-weighted MRI (DWI) for the detection of lymph nodes and for differentiating between benign and metastatic nodes during primary rectal cancer staging.

Methods

Twenty-one patients underwent 1.5-T MRI followed by surgery (± preoperative 5?×?5 Gy). Imaging consisted of T2-weighted MRI, DWI (b0, 500, 1000), and 3DT1-weighted MRI with 1-mm isotropic voxels. The latter was used for accurate detection and per lesion histological validation of nodes. Two independent readers analysed the signal intensity on DWI and measured the mean apparent diffusion coefficient (ADC) for each node (ADC_node) and the ADC of each node relative to the mean tumour ADC (ADC_rel).

Results

DWI detected 6 % more nodes than T2W-MRI. The signal on DWI was not accurate for the differentiation of metastatic nodes (AUC 0.45–0.50). Interobserver reproducibility for the nodal ADC measurements was excellent (ICC 0.93). Mean ADC_node was higher for benign than for malignant nodes (1.15?±?0.24 vs. 1.04?±?0.22 *10^-3 mm²/s), though not statistically significant (P?=?0.10). Area under the ROC curve/sensitivity/specificity for the assessment of metastatic nodes were 0.64/67 %/60 % for ADC_node and 0.67/75 %/61 % for ADC_rel.

Conclusions

DWI can facilitate lymph node detection, but alone it is not reliable for differentiating between benign and malignant lymph nodes.

Key Points

? Diffusion-weighted (DW) magnetic resonance imaging (MRI) offers new information in rectal cancer. ? DW MRI demonstrates more lymph nodes than standard T2-weighted MRI. ? Visual DWI assessment does not discriminate between benign and metastatic nodes. ? Apparent diffusion coefficients do not discriminate between benign and metastatic nodes.     

Multiple antiplatelet therapy contributes to the reversible high signal spots on diffusion-weighted imaging in elective coiling of unruptured cerebral aneurysm

Introduction

Our aim was to systematically investigate radiographic characteristics and outcome of diffusion-weighted imaging (DWI) changes in the elective coiling of unruptured cerebral aneurysm with analyzing the correlation of antiplatelet therapy (APT).

Methods

In a total of 34 consecutive patients with unruptured cerebral aneurysms initially treated by coiling without stent assist, 26 (76.5 %) had DWI changes with 91 high signal spots within 24–48 h after the procedure. We recorded DWI parameters (location, volume, mean, and minimum values of the apparent diffusion coefficient: expressed as ADC_AVE and ADC_MIN) for each lesion, and evaluated its radiographic outcome on conventional MRI at follow-up (interval, 58.4?±?37.2 days) in the modes of APT.

Results

All patients with DWI high spots had no clinical symptoms. There was a strong correlation between ADC_AVE and ADC_MIN (r?=?0.82, p?<?0.0001). The mean ADC_AVE and rADC_AVE were 0.74?±?0.14?×?10^?3?mm²/s and 87?±?10 %. DWI high spots were small with a mean volume of 0.13?±?0.12 cm³, ranging from 0.04 to 0.86 cm³. A negative correlation was observed between the volume and values of ADC_AVE (r?=??0.48, p?<?0.0001). The DWI volume was significantly larger in single APT than in multiple (0.15?±?0.14 versus 0.10?±?0.07 cm³, p?=?0.0091). The permanent signal change was more observed in single APT than in multiple (24.5 % versus 5.2 %, p?=?0.02).

Conclusion

DWI high spots after elective coiling were small without significant decrease of ADC, and do not correspond to brain infarction. Periprocedural use of multiple antiplatelet agents is expected to reduce the volume of thromboembolism and permanent tissue damages.     

Diffusion-weighted MR imaging in liver metastases of colorectal cancer: reproducibility and biological validation

Objectives

Before diffusion-weighted imaging (DWI) can be implemented in standard clinical practice for response monitoring, data on reproducibility are needed to assess which differences outside the range of normal variation can be detected in an individual patient. In this study we assessed the reproducibility of the apparent diffusion coefficient (ADC) values in colorectal liver metastases. To provide a biological basis for these values, their relation with histopathology was assessed.

Methods

DWI was performed twice in 1 week in patients scheduled for metastasectomy of colorectal liver metastases. Correlation between ADC values and apoptosis marker p53, anti-apoptotic protein BCL-2, proliferation marker Ki67 and serum vascular endothelial growth factor (VEGF) concentration were assessed.

Results

A good reproducibility coefficient of the mean ADC (coefficient of reproducibility 0.20 × 10^?3?mm²/s) was observed in colorectal liver metastases (n?=?21). The ADC value was related to the proliferation index and BCL-2 expression of the metastases. Furthermore, in metastases recently treated with systemic therapy, the ADC was significantly higher (1.27 × 10^?3?mm²/s vs 1.05 × 10^?3?mm²/s, P?=?0.02).

Conclusions

The good reproducibility, correlation with histopathology and implied sensitivity for systemic treatment-induced anti-tumour effects suggest that DWI might be an excellent tool to monitor response in metastatic colorectal cancer.

Key Points

? ADC values are becoming important oncological biomarkers ? DWI provides reproducibile ADC values in colorectal liver metastases ? The coefficient of reproducibility of the mean ADC is 0.20 × 10 ^?3 ? mm ² /s ? ADC values correlate with proliferation index and are related to BCL-2 expression     

IVIM-DWI of transplanted kidneys: Reduced diffusion and perfusion dependent on cold ischemia time

Purpose

To evaluate the effect of cold ischemia time (CIT) of renal allografts on diffusion and perfusion using intravoxel incoherent motion (IVIM) derived parameters.

Material and methods

A total of 37 patients with renal allografts (CIT: 27 <15 h, 10 ≥15 h) and 30 individuals with healthy kidneys were examined at 1.5 T using a single-shot echo-planar diffusion-weighted pulse sequence with nine b-values ranging from 0 to 800 s/mm². ADC, perfusion fraction f, and the diffusion coefficient D were calculated using the IVIM model. Parameters of allografts stratified by CIT were compared with healthy kidney groups using the Mann–Whitney U test for unpaired data. We computed the Spearman correlation coefficient for correlation with creatinine values.

Results

ADC, D, and f of transplanted kidneys were significantly lower than in the healthy controls. The long-CIT group showed significantly lower diffusion parameters compared with the short-CIT group [mean ± SD]: ADC: 1.63 ± 0.14 μm²/ms, f: 11.90 ± 5.22%, D: 1.55 ± 0.25 μm²/ms versus ADC: 1.79 ± 0.13 μm²/ms, f: 16.12  ± 3.43%, D: 1.73 ± 0.14 μm²/ms, P_ADC, _f, _D < 0.05.

Conclusion

Our results suggest that diffusion parameters, especially the ADC, depend on the CIT of the kidney allograft. Potentially, this stands for functional changes in renal allografts. Diffusion-weighted imaging could be used for follow-up examinations. Thus, diffusion parameters may help guide therapy in patients with delayed graft function.