Diffusion–Weighted Imaging and Apparent Diffusion Coefficient Values Versus Contrast–Enhanced MR Imaging in the Identification and Characterisation of Acute Pyelonephritis

Objective

To compare contrast-enhanced (CEMR) and diffusion-weighted (DWI) magnetic resonance imaging in diagnosing acute pyelonephritis (APN) and to assess ADC measurement reliability in differentiating among normal renal parenchyma, APN and abscesses.

Methods

Eighty-eight patients (80 women, mean age 36.5 years) with clinical suspicion of APN were retrospectively reviewed. An experienced observer quantified lesions with a score ranging from 0 to 3. DWI and CEMR were compared on the basis of the assigned score, total examination number (88) and on presence (36)/absence (52) of abscesses. ADC values, calculated at the healthy parenchyma, APN and abscessed were compared to each other.

Results

Agreement between CEMR and DWI was 94.3 % (83/88 patients; P?<?0.05). In the APN group, DWI was awarded the highest visibility score compared to CEMR (P?=?0.05), while in the abscess group CEMR had the highest score (P?=?0.04). The difference between ADC values of the APN-healthy parenchyma and abscess-APN groups was significant (P?<?0.05). The area under the ROC curve of ADC values of the APN-healthy and abscess-APN groups were found to be 0.94 (95 % CI; cutoff value?=?2) and 0.78 (95 % CI; cutoff value?=?1.2) respectively.

Conclusions

Diffusion-weighted imaging appears reliable in the diagnosis and follow-up of acute pyelonephritis and could provide a reasonable alternative to contrast-enhanced magnetic resonance imaging.

Key Points

? Acute pyelonephritis (APN) is an inflammatory process that preferentially affects young women ? Contrast-enhanced MRI is the reference investigation for the diagnosis and follow-up of APN ? Diffusion-weighted imaging can help differentiate between APN and abscesses ? This is especially useful when administration of contrast agent is contraindicated.     

The role of diffusion-weighted MR imaging for differentiating benign from malignant bile duct strictures

Objectives

To assess the added value of diffusion-weighted imaging (DWI) to conventional magnetic resonance imaging (MRI) for differentiating benign from malignant bile duct strictures.

Methods

Twenty-seven patients with a benign stricture and 42 patients with a malignant stricture who had undergone gadoxetic acid-enhanced MRI with DWI were enrolled. Qualitative (signal intensity, dynamic enhancement pattern) and quantitative (wall thickness and length) analyses were performed. Two observers independently reviewed a set of conventional MRI and a combined set of conventional MRI and DWI, and receiver operating characteristic (ROC) curve analysis was assessed.

Results

Benign strictures showed isointensity (18.5–70.4 %) and a similar enhancement pattern (22.2 %) to that of normal bile duct more frequently than malignant strictures (0–40.5 % and 0 %) on conventional MRI (P?<?0.05). Malignant strictures (90.5–92.9 %) showed hypervascularity on arterial and portal venous phase images more frequently than benign strictures (37.0–70.4 %) (P?<?0.01) On DWI, all malignant strictures showed hyperintensity compared with benign cases (70.4 %) (P?<?0.001). Malignant strictures were significantly thicker and longer than benign strictures (P?<?0.001). The diagnostic performance of both observers improved significantly after additional review of DWI.

Conclusions

Adding DWI to conventional MRI is more helpful for differentiating benign from malignant bile duct strictures than conventional MRI alone.

Key points

? Accurate diagnosis and exclusion of benign strictures of bile duct are important. ? Diffusion-weighted MRI helps to distinguish benign from malignant bile duct strictures. ? DWI plus conventional MRI provides superior diagnostic accuracy to conventional MRI alone.     

Protocol requirements and diagnostic value of PET/MR imaging for liver metastasis detection

Purpose

To compare the accuracy of PET/MR imaging with that of FDG PET/CT and to determine the MR sequences necessary for the detection of liver metastasis using a trimodality PET/CT/MR set-up.

Methods

Included in this single-centre IRB-approved study were 55 patients (22 women, age 61?±?11 years) with suspected liver metastases from gastrointestinal cancer. Imaging using a trimodality PET/CT/MR set-up (time-of-flight PET/CT and 3-T whole-body MR imager) comprised PET, low-dose CT, contrast-enhanced (CE) CT of the abdomen, and MR with T1-W/T2-W, diffusion-weighted (DWI), and dynamic CE imaging. Two readers evaluated the following image sets for liver metastasis: PET/CT (set A), PET/CECT (B), PET/MR including T1-W/T2-W (C), T1-W/T2-W with either DWI (D) or CE imaging (E), and a combination (F). The accuracy of each image set was determined by receiver-operating characteristic analysis using image set B as the standard of reference.

Results

Of 120 liver lesions in 21/55 patients (38 %), 79 (66 %) were considered malignant, and 63/79 (80 %) showed abnormal FDG uptake. Accuracies were 0.937 (95 % CI 89.5 – 97.9 %) for image set A, 1.00 (95 % CI 99.9 – 100.0 %) for set C, 0.998 (95 % CI 99.4 – 100.0 %) for set D, 0.997 (95 % CI 99.3 – 100.0 %) for set E, and 0.995 (95 % CI 99.0 – 100.0 %) for set F. Differences were significant for image sets D – F (P?<?0.05) when including lesions without abnormal FDG uptake. As shown by follow-up imaging after 50 – 177 days, the use of image sets D and both sets E and F led to the detection of metastases in one and three patients, respectively, and further metastases in the contralateral lobe in two patients negative on PET/CECT (P?=?0.06).

Conclusion

PET/MR imaging with T1-W/T2-W sequences results in similar diagnostic accuracy for the detection of liver metastases to PET/CECT. To significantly improve the characterization of liver lesions, we recommend the use of dynamic CE imaging sequences. PET/MR imaging has a diagnostic impact on clinical decision making.     

Focal hemodynamic patterns of status epilepticus detected by susceptibility weighted imaging (SWI)

Objective

To investigate pathological findings in the susceptibility weighted imaging (SWI) of patients experiencing convulsive (CSE) or non-convulsive status epilepticus (NCSE) with focal hyperperfusion in the acute setting.

Methods

Twelve patients (six with NCSE confirmed by electroencephalogram (EEG) and six patients with CSE with seizure event clinically diagnosed) underwent MRI in this acute setting (mean time between onset of symptoms and MRI was 3 h 8 min), including SWI, dynamic susceptibility contrast MR imaging (DSC) and diffusion-weighted imaging (DWI). MRI sequences were retrospectively evaluated and compared with EEG findings (10/12 patients), and clinical symptoms.

Results

Twelve out of 12 (100 %) patients showed a focal parenchymal area with pseudo-narrowed cortical veins on SWI, associated with focal hyperperfused areas (increased cerebral blood flow (CBF) and mean transit time (MTT) shortening), and cortical DWI restriction in 6/12 patients (50 %). Additionally, these areas were associated with ictal or postical EEG patterns in 8/10 patients (80 %). Most frequent acute clinical findings were aphasia and/or hemiparesis in eight patients, and all of them showed pseudo-narrowed veins in those parenchymal areas responsible for these symptoms.

Conclusion

In this study series with CSE and NCSE patients, SWI showed focally pseudo-narrowed cortical veins in hyperperfused and ictal parenchymal areas. Therefore, SWI might have the potential to identify an ictal region in CSE/NCSE.

Key Points

? The focal ictal brain regions show hyperperfusion in DSC MR-perfusion imaging. ? SWI shows focally diminished cortical veins in hyperperfused ictal regions. ? SWI has the potential to identify a focal ictal region in CSE/NCSE.     

Diffusion-weighted imaging in acute demyelinating myelopathy

Introduction

Diffusion-weighted imaging (DWI) has become a reference MRI technique for the evaluation of neurological disorders. Few publications have investigated the application of DWI for inflammatory demyelinating lesions. The purpose of the study was to describe diffusion-weighted imaging characteristics of acute, spinal demyelinating lesions.

Methods

Six consecutive patients (two males, four females; aged 28–64?years) with acute spinal cord demyelinating lesions were studied in a prospective case series design from June 2009 to October 2010. We performed magnetic resonance imaging studies from 2 to 14?days from symptom onset on the patients with relapsing remitting multiple sclerosis (n?=?3) or clinically isolated syndrome (n?=?3). Main outcome measures were diffusion-weighted imaging and apparent diffusion coefficient pattern (ADC) of acute spinal cord demyelinating lesions.

Results

All spinal lesions showed a restricted diffusion pattern (DWI+/ADC?) with a 24% median ADC signal decrease. A good correlation between clinical presentation and lesion site was observed.

Conclusion

Acute demyelinating spinal cord lesions show a uniform restricted diffusion pattern. Clinicians and neuro-radiologists should be aware that this pattern is not necessarily confirmatory for an ischaemic aetiology.     

Gadoxetate-enhanced versus diffusion-weighted MRI for fused Ga-68-DOTANOC PET/MRI in patients with neuroendocrine tumours of the upper abdomen

Objectives

To compare fused gadoxetate-enhanced Ga-68-DOTANOC PET/MRI and Ga-68-DOTANOC PET/DWI (diffusion-weighted imaging) for the assessment of abdominal neuroendocrine tumours (NETs).

Methods

Eighteen patients with suspected or histologically proven NETs of the abdomen were enrolled in this retrospective study. All patients underwent Ga-68-DOTANOC PET/CT for a primary search, staging, or restaging, and received an additional MRI, including dynamic gadoxetate-enhanced T1-weighted sequences and DWI (b-values 50, 300 and 600). Co-registered gadoxetate-enhanced PET/MRI and PET/DWI were separately analysed for NET lesions by a nuclear medicine physician and a radiologist in consensus. Sensitivity and specificity were calculated on a per-region, per-organ and per-patient basis.

Results

Eighty-seven out of 684 anatomical regions, and 23 out of 270 organs, were NET-positive in 14 out of 18 patients. Region-based sensitivities and specificities were 97.7 % and 99.7 % for gadoxetate-enhanced PET/MRI and 98.9 % and 99.7 % for PET/DWI. Organ-based sensitivities and specificities were 91.3 % and 99.6 % for gadoxetate-enhanced PET/MRI and 95.7 % and 99.6 % for PET/DWI. Finally, patient-based sensitivities and specificities were 100 % and 100 % for gadoxetate-enhanced PET/MRI and 100 % and 75 % for PET/DWI. Sensitivities and specificities of the two methods did not differ significantly.

Conclusions

Gadoxetate-enhanced Ga-68-DOTANOC PET/MRI and Ga-68-DOTANOC PET/DWI are equally useful for the assessment of abdominal NETs.

Key Points

? Positron emission tomography and magnetic resonance imaging can both assess neuroendocrine tumours. ? Fusion of PET/MR imaging provides helpful information. ? Gadoxetate-enhanced Ga-68-DOTANOC PET/MRI and Ga-68-DOTANOC PET/DWI assess neuroendocrine tumours equally well. ? PET/DWI is inherently simpler than gadoxetate-enhanced PET/MRI. ? Only benign hepatic lesions pose a potential diagnostic dilemma for PET/DWI.     

Use of diffusion-weighted imaging (DWI) in PET/MRI for head and neck cancer evaluation

Objective

The purpose of this study was to analyze whether diffusion-weighted imaging (DWI) adds significant information to positron emission tomography/magnetic resonance imaging (PET/MRI) on lesion detection and characterization in head and neck cancers.

Methods

Seventy patients with different head and neck cancers were enrolled in this prospective study. All patients underwent sequential contrast-enhanced (ce) PET/computed tomography (CT) and cePET/MRI using a tri-modality PET/CT-MR setup either for staging or re-staging. First, the DWI alone was evaluated, followed by the PET/MRI with conventional sequences, and in a third step, the PET/MRI with DWI was evaluated. McNemar’s test was used to evaluate differences in the accuracy of PET/MRI with and without DWI compared to the standard of reference.

Results

One hundred eighty-eight (188) lesions were found, and of those, 118 (62.8 %) were malignant and 70 (37.2 %) were benign. PET/MRI without DWI had a higher accuracy in detecting malignant lesions than DWI alone (86.8 % vs. 60.6 %, p?Conclusion The use of DWI as part of PET/MRI to evaluate head and neck cancers does not provide remarkable information. Thus, the use of DWI might not be needed in clinical PET/MRI protocols for the staging or restaging of head and neck cancers.     

Diffusion-weighted magnetic resonance imaging: new perspectives in the diagnostic pathway of non-complicated acute pyelonephritis

Objectives

The diagnosis of acute pyelonephritis (APN) requires demonstration of parenchymal involvement. When no predisposing conditions are found, non-complicated APN is suspected and CT or MRI should be performed. Diffusion-weighted (DW) MRI might be useful, quicker and cheaper than the standard gadolinium-enhanced (GE) MRI. The aim of this study is to compare DW-MRI with GE-MRI to test its diagnostic accuracy in APN.

Methods

Of 318 consecutive patients hospitalised for APN, 279 underwent MRI. Four hundred and fourteen MR studies (first test and follow-up examinations) were gathered and data were processed using Diffusion Analysis software. DW-MRI has been compared with GE-MRI for evaluating diagnostic agreement.

Results

Two hundred and forty-four patients were diagnosed as having APN; 35 were negative. One hundred and sixty-three APN cases were considered non-complicated and selected for the study. Among the 414 MR examinations, comparing DW-MRI with GE-MRI, positive correlation was found in 258 cases, negative in 133. There were 14 false-negatives and 9 false-positives. DW-MRI achieved sensitivity 95.2 %, specificity 94.9 %, positive predictive value 96.9 %, negative predictive value 92.3 % and accuracy 94.6 %.

Conclusions

DW-MRI is reliable for diagnosing non-complicated APN. The high diagnostic agreement between DW-MRI and GE-MRI offers new perspectives in diagnostic management, enabling diagnosis of non-complicated APN without using ionising radiation or contrast media.

Key Points

? The diagnosis of acute pyelonephritis (APN) requires demonstration of renal involvement. ? Hitherto magnetic resonance imaging required gadolinium enhancement (GE-MRI) to establish this diagnosis. ? But diagnostic agreement between diffusion-weighted and GE-MRI offers new diagnostic opportunities. ? Quantification of ADC values can help diagnose and monitor APN. ? DW-MRI avoids ionising radiation and paramagnetic contrast medium administration.     

Multishot diffusion-weighted MR imaging features in acute trauma of spinal cord

Objectives

To analyse diffusion-weighted MRI of acute spinal cord trauma and evaluate its diagnostic value.

Methods

Conventional MRI and multishot, navigator-corrected DWI were performed in 20 patients with acute spinal cord trauma using 1.5-T MR within 72 h after the onset of trauma.

Results

Twenty cases were classified into four categories according to the characteristics of DWI: (1) Oedema type: ten cases presented with variable hyperintense areas within the spinal cord. There were significant differences in the apparent diffusion coefficients (ADCs) between lesions and unaffected regions (t?=?-7.621, P?<?0.01). ADC values of lesions were markedly lower than those of normal areas. (2) Mixed type: six cases showed heterogeneously hyperintense areas due to a mixture of haemorrhage and oedema. (3) Haemorrhage type: two cases showed lesions as marked hypointensity due to intramedullary haemorrhage. (4) Compressed type (by epidural haemorrhage): one of the two cases showed an area of mild hyperintensity in the markedly compressed cord due to epidural haematoma.

Conclusions

Muti-shot DWI of the spinal cord can help visualise and evaluate the injured spinal cord in the early stage, especially in distinguishing the cytotoxic oedema from vasogenic oedema. It can assist in detecting intramedullary haemorrhage and may have a potential role in the evaluation of compressed spinal cord.

Key Points

? Multishot, navigator-corrected diffusion-weighted MRI is helpful when evaluating spinal cord injury (SCI). ? Four types of SCI may be classified according to the DWI characteristics. ? DWI differentiates cytotoxic from vasogenic oedema, thereby determining the centre of SCI. ? DWI can assist in detecting intramedullary haemorrhage. ? DWI can help evaluate the degree of compressed spinal cord.     

MRI-only lesions: application of diffusion-weighted imaging obviates unnecessary MR-guided breast biopsies

Objective

To assess if the application of diffusion-weighted imaging (DWI) obviates unnecessary MR-guided biopsies in suspicious breast lesions visible only on contrast-enhanced MRI (CE-MRI).

Methods

This institutional review board (IRB)-approved, retrospective, single-centre study included 101 patients (mean age, 49.5; SD 13.9 years) who underwent additional DWI at 1.5 T prior to MRI-guided biopsy of 104 lesions classified as suspicious for malignancy and visible on CE-MRI only. An experienced radiologist, blinded to histopathologic and follow-up results, measured apparent diffusion coefficient (ADC) values obtained from DWI. Diagnostic accuracy was investigated using receiver operating characteristics (ROC) analysis.

Results

Histopathology revealed 20 malignant and 84 benign lesions. Lesions were masses in 61 (15 malignant, 24.6 %) and non-masses in 43 cases (five malignant, 11.6 %). Mean ADC values were 1.53?±?0.38?×?10^?3 mm²/s in benign lesions and 1.06?±?0.27?×?10^?3 mm²/s in malignant lesions. ROC analysis revealed exclusively benign lesions if ADC values were greater than 1.58?×?10^?3 mm²/s. As a consequence, 29 false-positive biopsies (34.5 %) could have been avoided without any false-negative findings. Both in mass and in non-mass lesions, rule-in and rule-out criteria were identified using flexible ADC thresholds based on ROC analysis.

Conclusion

Additional application of DWI in breast lesions visible only on MRI can avoid false-positive, MR-guided biopsies. Thus, DWI should be an integral part of breast MRI protocols.

Key Points

? DWI measurements are a fast and helpful technique for improved breast lesion diagnosis ? DWI application in breast lesions visible only on MRI obviates false-positive, MR-guided biopsies ? Flexible ADC thresholds provide rule-in and rule-out criteria for breast lesion malignancy     

Staging of colorectal liver metastases after preoperative chemotherapy. Diffusion-weighted imaging in combination with Gd-EOB-DTPA MRI sequences increases sensitivity and diagnostic accuracy

Objectives

To compare the diagnostic accuracy and sensitivity of Gd-EOB-DTPA MRI and diffusion-weighted (DWI) imaging alone and in combination for detecting colorectal liver metastases in patients who had undergone preoperative chemotherapy.

Methods

Thirty-two consecutive patients with a total of 166 liver lesions were retrospectively enrolled. Of the lesions, 144 (86.8 %) were metastatic at pathology. Three image sets (1, Gd-EOB-DTPA; 2, DWI; 3, combined Gd-EOB-DTPA and DWI) were independently reviewed by two observers. Statistical analysis was performed on a per-lesion basis.

Results

Evaluation of image set 1 correctly identified 127/166 lesions (accuracy 76.5 %; 95 % CI 69.3–82.7) and 106/144 metastases (sensitivity 73.6 %, 95 % CI 65.6–80.6). Evaluation of image set 2 correctly identified 108/166 (accuracy 65.1 %, 95 % CI 57.3–72.3) and 87/144 metastases (sensitivity of 60.4 %, 95 % CI 51.9–68.5). Evaluation of image set 3 correctly identified 148/166 (accuracy 89.2 %, 95 % CI 83.4–93.4) and 131/144 metastases (sensitivity 91 %, 95 % CI 85.1–95.1). Differences were statistically significant (P?<?0.001). Notably, similar results were obtained analysing only small lesions (<1 cm).

Conclusions

The combination of DWI with Gd-EOB-DTPA-enhanced MRI imaging significantly increases the diagnostic accuracy and sensitivity in patients with colorectal liver metastases treated with preoperative chemotherapy, and it is particularly effective in the detection of small lesions.

Key Points

? Accurate detection of colorectal liver metastases is essential to determine resectability. ? Almost 80 % of patients are candidates for neoadjuvant chemotherapic treatment at diagnosis. After chemotherapy, metastases usually decrease, and drug-induced liver steatosis may be present. ? The sensitivity of imaging is significantly inferior to that in chemotherapy-naïve patients. ? DWI combined with Gd-EOB-DTPA increases sensitivity in detecting small metastases after chemotherapy.     

Prostate cancer recurrence after radical prostatectomy: the role of 3-T diffusion imaging in multi-parametric magnetic resonance imaging

Objectives

To validate the role of 3-T diffusion-weighted imaging (DWI) in the detection of local prostate cancer recurrence after radical prostatectomy (RP).

Methods

T2-weighted imaging, DWI and dynamic contrast-enhanced MRI (DCE-MRI) were performed with a 3-T magnet in 262 patients after RP. Twenty out of 262 patients evaluated were excluded. MRI results were validated by prostate-specific antigen (PSA) reduction after external beam radiotherapy in group A (126 patients, local recurrence size range 4–8 mm) and by transrectal ultrasound biopsy in group B (116 patients, local recurrence size range 9–15 mm).

Results

In group A combined T2-weighted and DCE-MRI (T2+DCE) shows 98 % sensitivity, 94 % specificity and 93 % accuracy in identifying local recurrence; combined T2-weighted and DWI with a b value of 3,000 s/mm² (T2+DW3) displays 97 % sensitivity, 95 % specificity and 92 % accuracy, while with a b value of 1,000 s/mm² (T2+DW1) affords 93 % sensitivity, 89 % specificity and 88 % accuracy. In group B T2+DCE shows 100 % sensitivity, 97 % specificity and 91 % accuracy in detecting local cancer recurrence; T2+DW3 displays 98 % sensitivity, 96 % specificity and 89 % accuracy; T2+DW1 has 94 % sensitivity, 92 % specificity and 86 % accuracy.

Conclusion

DCE-MRI is the most reliable technique in detecting local prostate cancer recurrence after RP, though DWI can be proposed as a reliable alternative.

Key Points

? Diffusion-weighted magnetic resonance imaging (DWI-MRI) is being increasingly used in oncology. ? PSA analysis does not distinguish prostate cancer recurrence from distant metastasis. ? DWI-MR can diagnose local prostate cancer recurrence after radical prostatectomy. ? DWI-MR is almost comparable to DCE-MRI in detecting local recurrence.     

Differentiation of malignant from benign soft tissue tumours: use of additive qualitative and quantitative diffusion-weighted MR imaging to standard MR imaging at 3.0 T

Objectives

To determine the added value of diffusion-weighted imaging (DWI) to standard magnetic resonance imaging (MRI) to differentiate malignant from benign soft tissue tumours at 3.0 T.

Methods

3.0 T MR images including DWI in 63 patients who underwent surgery for soft tissue tumours were retrospectively analyzed. Two readers independently interpreted MRI for the presence of malignancy in two steps: standard MRI alone, standard MRI and DWI with qualitative and quantitative analysis combined.

Results

There were 34 malignant and 29 non-malignant soft tissue tumours. In qualitative analysis, hyperintensity relative to skeletal muscle was more frequent in malignant than benign tumours on DWI (P=0.003). In quantitative analysis, ADCs of malignant tumours were significantly lower than those of non-malignant tumours (P≤0.002): 759±385 vs. 1188±423 μm²/sec minimum ADC value, 941±440 vs. 1310±440 μm²/sec average ADC value. The mean sensitivity, specificity and accuracy of both readers were 96 %, 72 %, and 85 % on standard MRI alone and 97 %, 90 %, and 94 % on standard MRI with DWI.

Conclusions

The addition of DWI to standard MRI improves the diagnostic accuracy for differentiation of malignant from benign soft tissue tumours at 3.0 T.

Key Points

? DWI has added value for differentiating malignant from benign soft tissue tumours. ? Addition of DWI to standard MRI at 3.0 T improves the diagnostic accuracy. ? Measurements of both ADC _min within solid portion and ADC _av are helpful.

     

The value of diffusion-weighted imaging in the detection of prostate cancer: a meta-analysis

Objectives

To evaluate the diagnostic performance of diffusion-weighted imaging (DWI) as a single non-invasive method in detecting prostate cancer (PCa) and to deduce its clinical utility.

Methods

A systematic literature search was performed to identify relevant original studies. Quality of included studies was assessed by QUADAS-2 (Quality Assessment of Diagnostic Accuracy Studies). Data were extracted to calculate sensitivity and specificity as well as running the test of heterogeneity and threshold effect. The summary receiver operating characteristic (SROC) curve was drawn and area under SROC curve (AUC) served as a determination of the diagnostic performance of DWI for the detection of PCa.

Results

A total of 21 studies were included, with 27 subsets of data available for analysis. The pooled sensitivity and specificity with corresponding 95 % confidence interval (CI) were 0.62 (95 % CI 0.61–0.64) and 0.90 (95 % CI 0.89–0.90), respectively. Pooled positive likelihood ratio and negative likelihood ratio were 5.83 (95 % CI 4.61–7.37) and 0.30 (95 % CI 0.23–0.39), respectively. The AUC was 0.8991. Significant heterogeneity was observed. There was no notable publication bias.

Conclusions

DWI is an informative MRI modality in detecting PCa and shows moderately high diagnostic accuracy. General clinical application was limited because of the absence of standardized DW-MRI techniques.

Key points

? DWI provides incremental information for the detection and evaluation of PCa ? DWI has moderately high diagnostic accuracy in detecting PCa ? Patient condition, imaging protocols and study design positively influence diagnostic performance ? General clinical application requires optimization of image acquisition and interpretation     

Simple measurements on diffusion-weighted MR imaging for assessment of complete response to neoadjuvant chemoradiotherapy in locally advanced rectal cancer

Purpose

To determine diagnostic performance of simple measurements on diffusion-weighted MR imaging (DWI) for assessment of complete tumour response (CR) after neoadjuvant chemoradiotherapy (CRT) in patients with locally advanced rectal cancer (LARC) by signal intensity (SI) and apparent diffusion coefficient (ADC) measurements.

Materials and methods

Sixty-five patients with LARC who underwent neoadjuvant CRT and subsequent surgery were included. Patients underwent pre-CRT and post-CRT 3.0 T MRI. Regions of interest of the highest brightness SI were included in the tumour volume on post-CRT DWI to calculate the SI_lesion, rSI, ADC_lesion and rADC; diagnostic performance was compared by using the receiver operating characteristic (ROC) curves. In order to validate the accuracy and reproducibility of the current strategy, the same procedure was reproduced in 80 patients with LARC at 1.5 T MRI.

Results

Areas under the ROC curve for identification of a CR, based on SI_lesion, rSI, ADC_lesion, and rADC, respectively, were 0.86, 0.94, 0.66, and 0.71 at 3.0 T MRI, and 0.92, 0.91, 0.64, and 0.61 at 1.5 T MRI.

Conclusion

Post-CRT DWI SI_lesion and rSI provided high diagnostic performance in assessing CR and were significantly more accurate than ADC_lesion, and rADC at 3.0 T MRI and 1.5 T MRI.

Key Points

? Signal intensity (SI _lesion ) and rSI are accurate for assessment of complete response. ? rSI seems to be superior to SI _lesion at 3.0 T MRI. ? ADC or rADC measurements are not accurate for assessment of complete response.     

Diffusion-weighted MR imaging of fetal lung maturation in sheep: effect of prenatal cortisone administration on ADC values

Objective

To assess changes in diffusion properties in the fetal lung after cortisone administration with diffusion-weighted imaging (DWI) in fetal sheep.

Methods

DWI was performed on 11 pregnant sheep with singleton pregnancies on a 1.5-T MRI scanner. Four animals received cortisone injections before baseline imaging. Seven animals served as controls. Apparent diffusion coefficient (ADC) was measured on DWI in the fetal lungs by two independent readers. The Pearson test was used to correlate ADC and gestational age. A t-test was performed to compare differences in ADC values at the baseline and follow-up images within and between groups. Inter-rater reliability was calculated.

Results

In the cortisone group, ADC values increased about 10 % between the baseline and follow-up images (P?=?0.039). Comparing the cortisone and control groups, ADC values of the baseline images did not differ; whereas in the follow-up imaging, ADC values were significantly higher in the cortisone group (P?=?0.024). Lung ADC values did not correlate with gestational age (P?=?0.970). Inter-rater reliability was high (0.970, P?=?0.000).

Conclusion

In this experimental model, MR-DWI can detect cortisone-induced changes in diffusion properties of the fetal lung.

Key Points

? Corticosteroids are frequently administered antenatally to prevent fetal lung immaturity at birth ? DWI can detect changes in the fetal lung after corticosteroid administration ? Changes can be detected as early as 5 days after treatment ? Fetal MRI may offer a non-invasive method of monitoring lung maturation     

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.     

Diffusion-weighted imaging of patients with neonatal bilirubin encephalopathy

Purpose

The aim of the study is to evaluate neonatal bilirubin encephalopathy in the acute period by the DWI.

Materials and methods

Thirty newborn babies with hyperbilirubinemia at the gestational age of 38–40 weeks, diagnosed with acute neonatal bilirubin encephalopathy as a result of clinical findings were included in the study, and a further 24 newborn babies, whose ages, weights and gestational ages were equalized, were regarded as a control group. DWI was performed on both patient and control groups.

Results

When DWI apparent diffusion coefficients (ADC) of both neonatal bilirubin encephalopathy patients and the control group were compared, ACD values of neonatal bilirubin encephalopathy patients were found to be statistically significantly highly compared to that of the control group (p < 0.001). There was a significant correlation between bilirubin values and DWI findings (r = 0.41, p < 0.05).

Conclusion

The ADC measurement could be a promising parameter in detecting neonatal bilirubin encephalopathy.     

Patterns in early diffusion-weighted MRI in children with haemolytic uraemic syndrome and CNS involvement

Objectives

Diffusion-weighted imaging (DWI) in children with diarrhoea associated haemolytic uraemic syndrome (D+HUS) and cerebral involvement was evaluated retrospectively.

Methods

DWI within 24?h of onset of neurological symptoms. The apparent diffusion coefficient (ADC) was measured in grey/white matter and correlated with clinical and laboratory findings.

Results

DWI was abnormal in all. Abnormal ADC was detected in the supratentorial white matter (6/12) and cortex (1/12), the basal ganglia (5/12), the thalami (4/12), and the cerebellum (1/12). ADC was reduced in 5/12, increased in 4/12, and both in 3/12. Mean serum sodium was lower in patients with DWI abnormalities affecting the white matter (6/12), than in those with basal ganglia/thalamic involvement (6/12). Neurological outcome was normal in 4/11 and abnormal in 7/11, and 1 patient died, outcome did not correlate to either localisation or type of DWI abnormality.

Conclusions

In D+HUS with neurological symptoms, early DWI may reveal abnormal ADC not only in the basal ganglia/thalami, but also in the white matter/cortex. Besides thrombotic microangiopathy, toxic effects of shiga toxin, azotaemia and hyponatraemia / hypoosmolality may be involved in cerebral involvement in children with D+HUS. Findings on early MRI seem not to predict clinical course or outcome.

Key Points

? DWI MR imaging may detect early CNS involvement in haemolytic uraemic syndrome ? Different pathogenetical mechanisms may contribute to the CNS disease in HUS ? Early MRI findings do not seem to allow prediction of clinical outcome     

Magnetic resonance imaging with diffusion-weighted imaging in the evaluation of thyroid-associated orbitopathy: getting below the tip of the iceberg

Objectives

To compare extraocular muscles (EOMs) T2, post-contrast T1 (T1Gad) signal intensity ratios (SIRs) and normalized-apparent diffusion coefficient (n-ADC) values in patients with thyroid-associated orbitopathy (TAO) at different phases of activity and severity and correlate MRI modifications to clinical evolution during follow-up.

Methods

A total of 74 TAO patients were classified as active or inactive on the basis of the clinical activity score (CAS). Severity of EOM impairment was evaluated by assigning a functional score to each rectus. T2, T1Gad SIRs and n-ADC of EOMs were compared in patients with active inflammation, those with inactive disease and 26 healthy controls, and correlated with clinical scores. MRI parameter variation was correlated with clinical modifications during follow-up.

Results

All MRI parameters in TAO EOMs were significantly higher than in healthy subjects and correlated with muscle dysfunction and CAS. EOMs of active patients showed higher T2 and T1Gad SIRs than those with inactive disease. The T2 SIR and n-ADC of normally functioning TAO EOMs were higher than those of healthy controls. SIRs decreased in clinically improved and clinically stable EOMs after therapy.

Conclusions

T2 SIR, T1Gad SIR and n-ADC are objective measures of activity and severity of EOMs in TAO patients. MRI shows clinically silent muscle involvement and modifications.

Key Points

? MRI and DWI measures are objective, quantitative parameters of TAO activity and severity ? MRI and DWI measures significantly correlate with clinical scores in TAO patients ? MRI and DWI can identify clinically silent inflammation of deep orbital structures ? MRI and DWI can depict subclinical modifications during follow-up ? MRI and DWI may aid clinicians in choosing the most appropriate treatment