Gd-EOB-DTPA-enhanced 3.0?T MR imaging: quantitative and qualitative comparison of hepatocyte-phase images obtained 10?min and 20?min after injection for the detection of liver metastases from colorectal carcinoma

Objective

To compare quantitatively and qualitatively hepatocyte-phase images obtained 10 and 20?min (Images-10, and Images-20) after injection of gadolinium-ethoxybenzyl-diethylenetriamine-pentaacetic acid (Gd-EOB-DTPA) to detect liver metastases from colorectal carcinoma on 3.0?T MR imaging.

Methods

A total of 48 patients (26 men, 22 women; mean age, 64?years) with 88 histopathologically confirmed liver metastases underwent Gd-EOB-DTPA-enhanced MR imaging. Tumour-to-liver contrast-to-noise ratio (CNR), signal intensity gain (SIG) of liver parenchyma and overall image quality were analysed. Two radiologists independently reviewed two sets of MR images: set 1, unenhanced (T1- and T2-weighted), dynamic images and Images-10; set 2, unenhanced, dynamic and Images-20. Sensitivity and positive predictive value (PPV) to detect liver metastases, and diagnostic performance using the alternative free-response receiver operating characteristics (AFROC) method were calculated.

Results

The mean tumour-to-liver CNR, SIG of liver parenchyma and overall image quality on Images-20 were significantly higher than those on Images-10. The overall image quality of ??fair to excellent?? was achieved on both images in 93.8% of the patients. Sensitivity, PPV and area under the AFROC curve on set 1 were similar to set 2, including lesions <1?cm.

Conclusion

In detecting liver metastases from colorectal carcinoma, Images-10 could replace Images-20 in 3.0?T MR imaging.     

Free-breathing contrast-enhanced T1-weighted gradient-echo imaging with radial k-space sampling for paediatric abdominopelvic MRI

Objective

To compare the image quality of contrast-enhanced abdominopelvic 3D fat-suppressed T1-weighted gradient-echo imaging with radial and conventional Cartesian k-space acquisition schemes in paediatric patients.

Methods

Seventy-three consecutive paediatric patients were imaged at 1.5 T with sequential contrast-enhanced T1-weighted Cartesian (VIBE) and radial gradient echo (GRE) acquisition schemes with matching parameters when possible. Cartesian VIBE was acquired as a breath-hold or as free breathing in patients who could not suspend respiration, followed by free-breathing radial GRE in all patients. Two paediatric radiologists blinded to the acquisition schemes evaluated multiple parameters of image quality on a five-point scale, with higher score indicating a more optimal examination. Lesion presence or absence, conspicuity and edge sharpness were also evaluated. Mixed-model analysis of variance was performed to compare radial GRE and Cartesian VIBE.

Results

Radial GRE had significantly (all P?<?0.001) higher scores for overall image quality, hepatic edge sharpness, hepatic vessel clarity and respiratory motion robustness than Cartesian VIBE. More lesions were detected on radial GRE by both readers than on Cartesian VIBE, with significantly higher scores for lesion conspicuity and edge sharpness (all P?<?0.001).

Conclusion

Radial GRE has better image quality and lesion conspicuity than conventional Cartesian VIBE in paediatric patients undergoing contrast-enhanced abdominopelvic MRI.

Key Points

? Numerous techniques are required to provide optimal MR images in paediatric patients. ? Radial free-breathing contrast-enhanced acquisition demonstrated excellent image quality. ? Image quality and lesion conspicuity were better with radial than Cartesian acquisition. ? More lesions were detected on contrast-enhanced radial than on Cartesian acquisition. ? Radial GRE can be used for performing abdominopelvic MRI in paediatric patients.     

Comparison between gadolinium-enhanced 2D T1-weighted gradient-echo and spin-echo sequences in the detection of active multiple sclerosis lesions on 3.0T MRI

Objectives

To compare the sensitivity of enhancing multiple sclerosis (MS) lesions in gadolinium-enhanced 2D T1-weighted gradient-echo (GRE) and spin-echo (SE) sequences, and to assess the influence of visual conspicuity and laterality on detection of these lesions.

Methods

One hundred MS patients underwent 3.0T brain MRI including gadolinium-enhanced 2D T1-weighted GRE and SE sequences. The two sets of contrast-enhanced scans were evaluated in random fashion by three experienced readers. Lesion conspicuity was assessed by the image contrast ratio (CR) and contrast-to-noise ratio (CNR). The intracranial region was divided into four quadrants and the impact of lesion location on detection was assessed in each slice.

Results

Six hundred and seven gadolinium-enhancing MS lesions were identified. GRE images were more sensitive for lesion detection (0.828) than SE images (0.767). Lesions showed a higher CR in SE than in GRE images, whereas the CNR was higher in GRE than SE. Most misclassifications occurred in the right posterior quadrant.

Conclusions

The gadolinium-enhanced 2D T1-weighted GRE sequence at 3.0T MRI enables detection of enhancing MS lesions with higher sensitivity and better lesion conspicuity than 2D T1-weighted SE. Hence, we propose the use of gadolinium-enhanced GRE sequences rather than SE sequences for routine scanning of MS patients at 3.0T.

Key Points

? 2D SE and GRE sequences are useful for detecting active MS lesions. ? Which of these sequences is more sensitive at high field remains uncertain. ? GRE sequence showed better sensitivity for detecting active MS lesions than SE. ? We propose GRE sequence for detecting active MS lesions at 3.0T.

     

Myometrial invasion in endometrial cancer: diagnostic performance of diffusion-weighted MR imaging at 1.5-T

Objective

To determine the diagnostic accuracy of diffusion-weighted (DW) magnetic resonance (MR) imaging in the preoperative assessment of myometrial invasion by endometrial cancer.

Materials and methods

In this prospective study, 47 patients with histologically confirmed endometrial cancer underwent preoperative MR imaging and total hysterectomy. The MR protocol included spin-echo multishot T2-weighted, dynamic T1-weighted and DW images acquired with b-values of 0 and 500 s/mm². Myometrial tumour spread was classified as superficial (<50%) or deep (≥50% myometrial thickness). Postoperative histopathological findings served as a reference standard. Indices of diagnostic performance were assessed for each sequence.

Results

At histopathological examination, superficial myometrial invasion was found in 34 patients and deep myometrial invasion in 13. In the assessment of tumour invasion, sensitivity, specificity, positive and negative predictive values of T2-weighted images were 92.3%, 76.5%, 60.0% and 96.3%, respectively. The corresponding values for dynamic images were 69.2%, 61.8%, 40.9% and 84.0%, and for DW images 84.6%, 70.6%, 52.4% and 92.3%. T2-weighted and DW imaging proved to be the most accurate techniques for tumour spread determination.

Conclusion

DW imaging proved to be accurate in assessing myometrial invasion, and it could replace dynamic imaging as an adjunct to routine T2-weighted imaging for preoperative evaluation of endometrial cancer.     

Detection of focal hepatic lesions with 3-T MRI: comparison of two-dimensional and three-dimensional T2-weighted sequences

Purpose

To evaluate whether incorporation of a 3D turbo spin-echo sequence during T2-weighted MR imaging improves the detection of focal hepatic lesions by 3T MR imaging.

Materials and methods

Seventy-nine consecutive patients including 67 patients with 62 malignant and 71 benign lesions and 12 patients having no hepatic lesion underwent respiratory-triggered fat-suppressed axial T2-weighted turbo spin-echo imaging using two-dimensional (2D-TSE) and 3D (3D-TSE) sequences. Coronal multiplanar reformatted images (MPR-3D-TSE) were generated from 3D-TSE images. Breath-hold fat-suppressed 2D axial T2-weighted half-Fourier turbo spin-echo (HF-2D-TSE) images were combined for reading. Two independent radiologists reviewed three imaging sets, (1) 2D-TSE and HF-2D-TSE, (2) 3D-TSE and HF-2D-TSE, and (3) 3D-TSE, HF-2D-TSE and MPR-3D-TSE, for detection of malignant and benign lesions. Lesion-to-liver contrast ratio (CR) and the conspicuity of anatomical boundaries were assessed.

Results

For benign lesions, lesion-to-liver CRs with 3D-TSE (2.77?±?1.91, p?=?.0002) and MPR-3D-TSE (2.47?±?1.42, p?=?.012) were higher than with 2D-TSE (2.13?±?1.80). Sensitivity for lesions of???10-mm was higher with 3D-TSE (86?%, p?=?.0039) and MPR-3D-TSE (84?%, p?=?.0078) than with 2D-TSE (72?%). However, the edge of left lateral lobe was less conspicuous with 3D-TSE (p?< .0001) and MPR-3D-TSE (p?=?.0003) than with 2D-TSE because of susceptibility artifacts.

Conclusion

Incorporation of 3D T2-weighted sequence may incrementally improve the detection of focal hepatic lesions.     

Characterization of Focal Liver Lesions with Superparamagnetic Iron Oxide-Enhanced MR Imaging: Value of Distributional Phase T1-Weighted Imaging

Objective

To determine the potential value of distributional-phase T1-weighted ferumoxides-enhanced magnetic resonance (MR) imaging for tissue characterization of focal liver lesions.

Materials and Methods

Ferumoxides-enhanced MR imaging was performed using a 1.5-T system in 46 patients referred for evaluation of known or suspected hepatic malignancies. Seventy-three focal liver lesions (30 hepatocellular carcinomas [HCC], 12 metastases, 15 cysts, 13 hemangiomas, and three cholangiocarcinomas) were evaluated. MR imaging included T1-weighted double-echo gradient-echo (TR/TE: 150/4.2 and 2.1 msec), T2*-weighted gradient-echo (TR/TE: 180/12 msec), and T2-weighted turbo spin-echo MR imaging at 1.5 T before and after intravenous administration of ferumoxides (15 mmol/kg body weight). Postcontrast T1-weighted imaging was performed within eight minutes of infusion of the contrast medium (distributional phase). Both qualitative and quantitative analysis was performed.

Results

During the distributional phase after infusion of ferumoxides, unique enhancement patterns of focal liver lesions were observed for hemangiomas, metastases, and hepatocellular carcinomas. On T1-weighted GRE images obtained during the distributional phase, hemangiomas showed a typical positive enhancement pattern of increased signal; metastases showed ring enhancement; and hepatocellar carcinomas showed slight enhancement. Quantitatively, the signal-to-noise ratio of hemangiomas was much higher than that of other tumors (p < .05) and was similar to that of intrahepatic vessels. This finding permitted more effective differentiation between hemangiomas and other malignant tumors.

Conclusion

T1-weighted double-echo FLASH images obtained soon after the infusion of ferumoxides, show characteristic enhancement patterns and improved the differentiation of focal liver lesions.     

Hepatic metastases: diffusion-weighted sensitivity-encoding versus SPIO-enhanced MR imaging

PURPOSE: To retrospectively compare accuracy of diffusion-weighted (DW) single-shot echo-planar imaging with sensitivity encoding (SENSE) with that of superparamagnetic iron oxide (SPIO)-enhanced magnetic resonance (MR) imaging in the evaluation of hepatic metastases due to extrahepatic malignancies. MATERIALS AND METHODS: Patients provided informed consent; ethics committee approval was not required. The data of 24 patients (16 men, eight women; age range, 41-68 years; mean age, 61.9 years) with 40 resected hepatic metastases were retrospectively reviewed. Before SPIO administration, DW SENSE imaging and T2-weighted fast spin-echo (SE) and T1-weighted dual-echo fast field-echo (FFE) MR imaging were performed. After SPIO administration, T2-weighted fast SE, T1-weighted dual-echo, and T2*-weighted FFE MR examinations were performed. Images were divided into two sets: The SPIO-enhanced MR image set consisted of pre- and postcontrast T2-weighted fast SE and dual-echo T1-weighted FFE images and postcontrast T2*-weighted FFE images. The DW SENSE image set included DW SENSE images and precontrast T2-weighted fast SE and dual-echo T1-weighted FFE images. Three radiologists individually interpreted these images and sorted the confidence levels for presence of hepatic metastasis in each section into five grades. Area under the receiver operating characteristic (ROC) curve (A(z)) was calculated for each image set. RESULTS: Hepatic metastases showed higher signal intensity on DW SENSE images than on T2-weighted fast SE images. Conversely, signals from vessels and cysts were suppressed with DW SENSE imaging. ROC analysis showed higher A(z) values when the DW SENSE image set was interpreted (0.90) than when the SPIO-enhanced MR image set was interpreted (0.81). The sensitivity and specificity, respectively, of total cases were 0.66 and 0.90, for the SPIO-enhanced MR image set and 0.82 and 0.94 for the DW SENSE image set. During SPIO-enhanced MR image interpretation, lesions 1 cm in diameter or smaller showed significantly lower sensitivity than lesions larger than 1 cm in diameter. During both interpretation sessions, left lobe lesions showed significantly lower sensitivity than right lobe lesions. CONCLUSION: Combined reading of DW SENSE images and T2-weighted fast SE and dual-echo T1-weighted FFE MR images showed higher accuracy in the detection of hepatic metastases than did reading of SPIO-enhanced MR images.     

Kontrastmittelunterstützte MR „Magnetization-transfer-Technik”

Aims

To improve tumor conspicuity and delineation on contrast-enhanced T1-weighted MR images with and without magnetization transfer (MT) contrast as a strategy to improve the macroscopic boost volume definition in the planning process of radiosurgery in patients with high grade gliomas or metastatic brain lesions.

Patients and Methods

Thirty-two patients (mean age 47 years) with histologically proven or suspected high grade glioma (n=12) or metastatic brain lesions (n=20) were prospectively examined by MR imaging. After the administration of gadolinium dimeglumine (0.1 mmol/kg body weight) the lesions were imaged with a T1-weighted MT-fast low angle shot (FLASH) pulse sequence and with a conventional T1-weighted SE sequence without MT saturation.

Results

The mean CNR of enhancing lesions on T1-weighted MT-FLASH was 15±5 compared to 14±4 on SE images, representing a significant (p<.01) improvement. The mean tumor diameter of malignant gliomas was significantly (p<.01) larger measured on T1-weighted MT-FLASH images compared to those obtained from T1-weighted SE images and were comparable for metastatic lesions. Lesion conspicuity and delineation were improved in 50% of patients with high grade gliomas and in 35% of patients with brain metastases. Lesion conspicuity was markedly improved in the posterior fossa. Additional contrast enhancing lesions were detected in 10% of patients with metastases on MT-FLASH images.

Conclusions

It is concluded that contrast-enhanced MT-FLASH images may improve lesion detection and delineation in the planning process of radiosurgery in patients with intracranial high grade gliomas or metastases or even alter the treatment approach.     

Comparison of gadolinium-EOB-DTPA-enhanced and diffusion-weighted liver MRI for detection of small hepatic metastases

Objective

To compare the accuracy of gadolinium ethoxybenzyl-diethylenetriamine pentaacetic acid (Gd-EOB-DTPA)-enhanced MRI with that of diffusion-weighted MRI (DWI) in the detection of small hepatic metastases (2 cm or smaller).

Methods

Forty-five patients underwent abdominal MRI at 3 T, including T1-weighted imaging (T1WI), T2-weighted imaging (T2WI), heavily T2WI (HASTE), DWI with a b-value of 500 s/mm² and contrast-enhanced MRI with Gd-EOB-DTPA. Two groups were assigned and compared: group A (T1WI, T2WI, HASTE and contrast-enhanced study with Gd-EOB-DTPA), and group B (T1WI, T2WI, HASTE and DWI). Two observers independently interpreted the images obtained in a random order. For all hepatic metastases, the diagnostic performance using each imaging set was evaluated by receiver-operating characteristic (ROC) curve analysis.

Results

A total of 51 hepatic metastases were confirmed. The area under the ROC curve (Az) of group A was larger than that of group B, and the difference in the mean Az values between the two image sets was statistically significant, whereas, there were three metastases that lay near thin vessels or among multiple cysts and were better visualised in group B than in group A.

Conclusion

Gd-EOB-DTPA-enhanced MRI showed higher accuracy in the detection of small metastases than DWI.     

Isolated cerebral susceptibility artefacts in patients with malignant melanoma: metastasis or not?

Objective

While staging patients with malignant melanoma, cerebral susceptibility artefacts on T2*-weighted/susceptibility-weighted imaging (SWI) sequences without a correlate on contrast-enhanced T1-weighted images can be confusing. Without intravenous contrast enhancement, cavernomas, microhaemorrhages and melanin-containing metastases represent possible differential diagnoses for these findings. The purpose of this study was to find out, how often such lesions correspond to metastases.

Methods

Brain MR images (1.5 T) of 408 patients with malignant melanoma but without cerebral metastases in the initial staging by MRI were reviewed retrospectively. Eighteen patients (5 female, 13 male) with malignant melanoma and signal intensity loss on T2*/SWI were included in our study. The average observation period was 19.6 months (6–46 months, 2006–2009).

Results

In each of these 18 patients between one and seven hypointense lesions on T2*/SWI were found. None of these lesions developed into metastasis.

Conclusion

Focal areas of susceptibility artefacts in the brain parenchyma without corresponding abnormalities in contrast-enhanced T1 weighted images are unlikely to represent brain metastases.

Key Points

? In melanoma patients early diagnosis of metastatic brain lesions is mandatory. ? Melanin content and haemorrhage are potential reasons for MRI characteristics of melanoma metastases. ? Susceptibility-weighted MRI visualises melanin and blood products. ? Isolated cerebral susceptibility artefacts do not convert into melanoma metastases. ? SWI/T2* sequences cannot replace Gd-enhanced sequences.     

MR-guided radiofrequency ablation using a wide-bore 1.5-T MR system: clinical results of 213 treated liver lesions

Objective

To evaluate the technical effectiveness, technical success and patient safety of MR-guided radiofrequency (RF) ablation of liver malignancies using a wide-bore 1.5-T MR system.

Methods

In 110 patients, 56 primary liver lesions and 157 liver metastases were treated in 157 sessions using percutaneous RF ablation. Mean lesion diameter was 20?mm (range 4–54?mm). All planning, procedural and post-interventional control MR investigations were carried out using a wide-bore 1.5-T MR system. Technical success was assessed by a contrast-enhanced MR liver examination immediately after the intervention. Technique effectiveness was assessed by dynamic hepatic MR study 1?month post ablation; mean follow-up period was 24.2?months (range 5–44).

Results

Technical success and technique effectiveness were achieved in 210/213 lesions (98.6?%). In 18/210 lesions (8.6?%), local tumour progression occurred 4–28?months after therapy. Seven of these 18 lesions were treated in a second session achieving complete ablation, 6 other lesions were referred to surgery. Overall RF effectiveness rate was 199/213 (93.4?%); overall therapy success (including surgery) was 205/213 (96.2?%). Two major complications (1.3?%) (bleeding and infected biloma) and 14 (8.9?%) minor complications occurred subsequent to 157 interventions.

Conclusion

Wide-bore MR-guided RF ablation is a safe and effective treatment option for liver lesions.

Key Points

? Magnetic resonance-guided radiofrequency ablation offers various options for monitoring therapy. ? All steps of RF ablation carried out in 1.5-T wide-bore system. ? Therapeutic decisions were based on T1-weighted imaging. ? Technical success and technical effectiveness were high. ? Local tumour progression rate was 8.6?% over a 24-month mean follow-up.     

Diffusion-weighted and T2-weighted MR imaging for colorectal liver metastases detection in a rat model at 7 T: a comparative study using histological examination as reference

Objectives

To compare diffusion-weighted (DW) and T2-weighted MR imaging in detecting colorectal liver metastases in a rat model, using histological examination as a reference method.

Methods

Eighteen rats had four liver injections of colon cancer cells. MR examinations at 7 T included FSE-T2-weighted imaging and SE-DW MR imaging (b?=?0, 20 and 150 s/mm²) and were analysed by two independent readers. Histological examination was performed on 0.4-mm slices. McNemar’s test was used to compare the sensitivities and the Wilcoxon matched pairs test to compare the average number of false-positives per rat.

Results

One hundred and sixty-six liver metastases were identified on histological examination. The sensitivity in detecting liver metastases was significantly higher on DW MR than on T2-weighted images (99/166 (60 %) (reader 1) and 92/166 (55 %) (reader 2) versus 77/166 (46 %), P?≤?0.001), without an increase in false-positives per rat (P?=?0.773/P?=?0.850). After stratification according to metastasis diameter, DW MR imaging had a significantly higher sensitivity than T2-weighted imaging only for metastases with a diameter (0.6–1.2 mm) similar to that of the spatial resolution of MR imaging in the current study.

Conclusions

This MR study with histological correlations shows the higher sensitivity of DW relative to T2-weighted imaging at 7 T for detecting liver metastases, especially small ones.

Key Points

? Diffusion weighted (DW) sequences are increasingly used in magnetic resonance imaging (MRI). ? DW has higher sensitivity for liver metastases than T2-weighted imaging at 7 T. ? This increase in sensitivity is especially marked for small liver metastasis detection. ? This higher sensitivity is confirmed in an animal model with histological correlation. ? DW imaging has the potential for earlier diagnosis of small liver metastases.     

Uterine cervical carcinoma: a comparison of two- and three-dimensional T2-weighted turbo spin-echo MR imaging at 3.0 T for image quality and local-regional staging

Objective

To compare three-dimensional (3D) T2-weighted turbo spin-echo (TSE) with multiplanar two-dimensional (2D) T2-weighted TSE for the evaluation of invasive cervical carcinoma.

Methods

Seventy-five patients with cervical carcinoma underwent MRI of the pelvis at 3.0 T, using both 5-mm-thick multiplanar 2D (total acquisition time?=?12 min 25 s) and 1-mm-thick coronal 3D T2-weighted TSE sequences (7 min 20 s). Quantitative analysis of signal-to-noise ratio (SNR) and qualitative analysis of image quality were performed. Local-regional staging was performed in 45 patients who underwent radical hysterectomy.

Results

The estimated SNR of cervical carcinoma and the relative tumour contrast were significantly higher on 3D imaging (P?<?0.0001). Tumour conspicuity was better with the 3D sequence, but the sharpness of tumour margin was better with the 2D sequence. No significant difference in overall image quality was noted between the two sequences (P?=?0.38). There were no significant differences in terms of the diagnostic accuracy, sensitivity, and specificity of parametrial invasion, vaginal invasion, and lymph node metastases.

Conclusion

Multiplanar reconstruction 3D T2-weighted imaging is largely equivalent to 2D T2-weighted imaging for overall image quality and staging accuracy of cervical carcinoma with a shorter MR data acquisition, but has limitations with regard to the sharpness of the tumour margin.

Key Points

? 3D T2-weighted MR sequence is equivalent to 2D for cervical carcinoma staging. ? Coronal 3D acquisitions can reduce the examination time. ? SNR and relative tumour conspicuity were significantly higher on 3D sequences. ? Reformatted 3D T2-weighted imaging had limitations in sharpness of tumour margin.     

Axial 3D gradient-echo imaging for improved multiple sclerosis lesion detection in the cervical spinal cord at 3T

Introduction

In multiple sclerosis (MS), spinal cord imaging can help in diagnosis and follow-up evaluation. However, spinal cord magnetic resonance imaging (MRI) is technically challenging, and image quality, particularly in the axial plane, is typically poor compared to brain MRI. Because gradient-recalled echo (GRE) images might offer improved contrast resolution within the spinal cord at high magnetic field strength, both without and with a magnetization transfer prepulse, we compared them to T2-weighted fast-spin-echo (T2-FSE) images for the detection of MS lesions in the cervical cord at 3T.

Methods

On a clinical 3T MRI scanner, we studied 62 MS cases and 19 healthy volunteers. Axial 3D GRE sequences were performed without and with off-resonance radiofrequency irradiation. To mimic clinical practice, all images were evaluated in conjunction with linked images from a sagittal short tau inversion recovery scan, which is considered the gold standard for lesion detection in MS. Two experienced observers recorded image quality, location and size of focal lesions, atrophy, swelling, and diffuse signal abnormality independently at first and then in consensus.

Results

The number and volume of lesions detected with high confidence was more than three times as high on both GRE sequences compared to T2-FSE (p?<?0.0001). Approximately 5 % of GRE scans were affected by artifacts that interfered with image interpretation, not significantly different from T2W-FSE.

Conclusions

Axial 3D GRE sequences are useful for MS lesion detection when compared to 2D T2-FSE sequences in the cervical spinal cord at 3T and should be considered when examining intramedullary spinal cord lesions.     

MR characterisation of dysplastic nodules and hepatocarcinoma in the cirrhotic liver with hepatospecific superparamagnetic contrast agents: pathological correlation in explanted livers

Purpose

The authors sought to evaluate the potential of magnetic resonance (MR) imaging with superparamagnetic iron oxide (SPIO) contrast material for identifying, characterising and differentiating dysplastic nodules (DN) and hepatocellular carcinoma (HCC) in the cirrhotic liver by correlating the results with pathological findings on the explanted liver.

Material and methods

MR imaging was used to study the liver of 400 cirrhotic patients awaiting liver transplantation, 31 of whom were selected to receive a liver. Of these 31 patients, we included in the study 22 patients (mean age 53 years; range 46–57 years) who underwent liver transplantation within 12–24 h after MR examination. Patients were studied with a 1.5-T device, and scans were acquired before and after the administration of paramagnetic contrast material. For every lesion, we recorded signal intensity on unenhanced baseline T1- and T2-weighted images and enhancement pattern after SPIO administration. Histological examination of the entire liver provided the definitive diagnosis of the lesions.

Results

Histological examination identified 59 lesions: 14 HCC, 4 HCC-DN, 39 DN, and 2 cystoadenomas. Among the 14 HCC, three were well differentiated, eight were moderately differentiated and three were poorly differentiated. Of the 39 DN, 28 were low-grade and 11 high-grade lesions. Unenhanced baseline MR imaging correctly identified and characterised 20 lesions, equal to 33.90% of all lesions: 6 HCC, 12 DN and 2 DN with a subfocus of HCC. SPIO-enhanced MR imaging showed greater sensitivity detecting and characterising 45 lesions, equal to 76.27% of all lesions identified at histology: 14 HCC, 27 DN and 4 DN with subfocus of HCC. SPIO administration improved the sensitivity of MR imaging in lesion detection and characterisation by 42.37%. False negative results with SPIO-enhanced MR imaging occurred in 12 DN (31%), which histological examination revealed to be low-grade DN with a diameter <1 cm.

Conclusions

SPIO-enhanced MR imaging proved to be of value in detecting and characterising lesions in the cirrhotic liver, allowing differentiation of DN from HCC and providing an early diagnosis of neoplastic degeneration of DN.     

Efficacy of magnetic resonance imaging at 3 T compared with 1.5 T in small pituitary tumors for stereotactic radiosurgery planning

Purpose

The objective of this study was to determine the value of high-field magnetic resonance imaging and to clarify the characteristics of each image among three-dimensional gradient echo (3D-GRE), two-dimensional spin echo (2D-SE) and inversion recovery (2D-IR) sequences used as contrast-enhanced T1-weighted images for stereotactic irradiation treatment planning of sellar lesions.

Materials and methods

Pulse sequences of 2D-SE and 3D-spoiled gradient recalled acquisition in the steady state (3D-SPGR) using GRE at 1.5 T and 2D-IR and 3D-fast SPGR (3D-FSPGR) at 3 T after injection of contrast material were acquired for 14 small pituitary tumors. As quantitative methods, signal-to-noise ratios (SNR) and contrast-to-noise ratios (CNR) were evaluated using a region-of-interest analysis.

Results

There was no significant difference in SNR between 1.5-T SPGR and 3-T FSPGR, while 3-T IR was superior to 1.5-T SE. The 2D-SE and -IR provided significantly better CNR than 3D-GRE between tumor and normal structures.

Conclusions

Three Tesla was found to be superior to 1.5 T in distinguishing tumors from the normal sellar structure. Optimal dose planning will utilize each advantage of imaging; 3D-GRE allows high-resolution acquisition and 2D-SE and -IR can offer better tissue contrast.     

Non-hyperfunctioning neuroendocrine tumours of the pancreas: MR imaging appearance and correlation with their biological behaviour

Objective

To describe MR imaging features of non-hyperfunctioning neuroendocrine pancreatic tumours by comparing them to histopathology and to determine the accuracy of MR imaging in predicting biological behaviour.

Materials and Methods

After institutional review board approval, we retrospectively reviewed 45 patients with pathologically proven NF-NET of the pancreas and ≥1 preoperative MR/MRCP examinations. Of the NF-NETS, 29/45 (64.4 %) were G1 and 16/45 (35.5 %) were G2. Image analysis included the lesion maximum diameter, vascular encasement, extrapancreatic spread, signal intensity on T1- and T2-weighted, contrast enhancement features, and presence of metastases. Tumour vessel density was calculated on the histological specimen using a grid.

Results

The median maximum diameter of NF-NETs was 20 mm (range 5–200 mm). Eighty per cent of the NF-NETs were hypointense on T1-weighted images, 82.2 % were hyperintense on T2-weighted images, and 75.6 % were hypervascular. Overall MRI accuracy showed a mean AUC of 0.86 compared to pathology. Lesions with a maximum diameter of 30 mm irregular margins, absence of a cleavage plane with the main pancreatic duct, vascular encasement, extrapancreatic spread and abdominal metastases were significantly associated with malignant NF-NETs. No correlation was found between the tumour vessel density and contrast-enhanced MR imaging pattern.

Conclusions

Hyperintensity on T2-weighted images and iso-/hypervascularity occurred in 27/45 (60.0 %) of NF-NETs. MRI identifies malignant NF-NETs with a sensitivity of 93.3 % and a specificity of 76.9 % (AUC?=?0.85).

Key Points

? Non-hyperfunctioning neuroendocrine pancreatic tumours (NF-NET) pose a difficult diagnostic challenge. ? On T2-weighted MRI, 82.2 % of neuroendocrine tumours appeared hyperintense. ? MR imaging showed 0.94 sensitivity and 0.77 specificity in predicting biological behaviour. ? The hyper-/isointensity during dynamic MRI did not correlate with vessel density at pathology.     

Locally advanced rectal cancer: diffusion-weighted MR tumour volumetry and the apparent diffusion coefficient for evaluating complete remission after preoperative chemoradiation therapy

Objective

To evaluate DW MR tumour volumetry and post-CRT ADC in rectal cancer as predicting factors of CR using high b values to eliminate perfusion effects.

Methods

One hundred rectal cancer patients who underwent 1.5-T rectal MR and DW imaging using three b factors (0, 150, and 1,000 s/mm²) were enrolled. The tumour volumes of T2-weighted MR and DW images and pre- and post-CRT ADC_150–1000 were measured. The diagnostic accuracy of post-CRT ADC, T2-weighted MR, and DW tumour volumetry was compared using ROC analysis.

Results

DW MR tumour volumetry was superior to T2-weighted MR volumetry comparing the CR and non-CR groups (P?<?0.001). Post-CRT ADC showed a significant difference between the CR and non-CR groups (P?=?0.001). The accuracy of DW tumour volumetry (A_z?=?0.910) was superior to that of T2-weighed MR tumour volumetry (A_z?=?0.792) and post-CRT ADC (A_z?=?0.705) in determining CR (P?=?0.015). Using a cutoff value for the tumour volume reduction rate of more than 86.8 % on DW MR images, the sensitivity and specificity for predicting CR were 91.4 % and 80 %, respectively.

Conclusion

DW MR tumour volumetry after CRT showed significant superiority in predicting CR compared with T2-weighted MR images and post-CRT ADC.

Key Points

? Diffusion-weighted MR (DWMR) imaging offers new information about rectal cancer. ? DWMR helps to predict complete remission after chemoradiotherapy in patients with advanced rectal cancer. ? DWMR provides more accurate diagnostic information than T2-weighted MRI. ? Apparent diffusion coefficients can predict CR, but they have certain clinical limitations.     

Characterization of focal hepatic lesions with ferumoxides-enhanced MR imaging: utility of T1-weighted spoiled gradient recalled echo images using different echo times

PURPOSE: To evaluate the different signal characteristics of focal hepatic lesions on ferumoxides-enhanced MR imaging, including T1-weighted spoiled gradient recalled echo (GRE) images using different echo times (TE) and T2- and T2*-weighted images. MATERIALS AND METHODS: Ferumoxides-enhanced MR imaging was performed using a 1.5-T system in 46 patients who were referred for evaluation of known or suspected hepatic malignancies. One hundred and seven lesions (42 hepatocellular carcinomas [HCC], 40 metastases, 13 cysts, eight hemangiomas, three focal nodular hyperplasias [FNHs], and one cholangiocarcinoma) were evaluated. Postcontrast MR imaging included 1) T2-weighted FSE; 2) T2*-weighted GRE; 3) T1-weighted spoiled GRE using moderate (TE = 4.2-4.4 msec) TE; and 4) minimum (TE = 1.8-2.1 msec) TE. Signal intensities of the focal lesions were rated by two radiologists in conference as follows: hypointense, isointense or invisible, hyperintense, and markedly hyperintense. Lesion-to-liver contrast-to-noise ratio (C/N) was measured by one radiologist for a quantitative assessment. RESULTS: On ferumoxides-enhanced FSE images, 92% of cysts were "markedly hyperintense" and most of the other lesions were "hyperintense", and the mean C/N of cysts was significantly higher than that of other focal lesions. T2*-weighted GRE images showed most lesions with similar hyperintensities and the mean C/N was not significantly different between any two types of lesion. T1-weighted GRE images using moderate TE showed all FNHsand hemangiomas, 29 (69%) HCCs and eight (20%) metastases as "hyperintense". On T1-weighted GRE images using minimum TE, however, all HCCs and metastasis except one were iso- or hypointense, while all of the FNHs and hemangiomas were hyperintense. Ring enhancement was highly suggestive of malignant lesions, and was more commonly seen on the minimum TE images than on the moderate TE images. CONCLUSION: Addition of T1-weighted GRE images using minimum and moderate TE is helpful for characterizing focal lesions in ferumoxides-enhanced MR imaging.     

Colorectal hepatic metastases: detection with SPIO-enhanced breath-hold MR imaging--comparison of optimized sequences

PURPOSE: To compare the accuracy of four breath-hold magnetic resonance (MR) imaging sequences to establish the most effective superparamagnetic iron oxide (SPIO)-enhanced sequence for detection of colorectal hepatic metastases. MATERIALS AND METHODS: Thirty-one patients with colorectal hepatic metastases underwent T1-weighted gradient-echo (GRE) and T2-weighted fast spin-echo (FSE) MR imaging before and after SPIO enhancement. Four sequences were optimized for lesion detection: T2-weighted FSE, multiecho data image combination (MEDIC), T2-weighted GRE with an 11-msec echo time (TE), and T2-weighted GRE with a 15-msec TE. Images were reviewed independently by three blinded observers. The accuracy of each sequence was measured by using alternative free-response receiver operating characteristic analysis. All results were correlated with findings at surgery, intraoperative ultrasonography, or histopathologic examination. Differences between the mean results of the three observers were measured by using the Student t test. RESULTS: Postcontrast T2-weighted GRE sequences were the most accurate and were significantly superior to postcontrast T2-weighted FSE and unenhanced sequences alone (P <.05). For all lesions that were malignant or smaller than 1 cm, respectively, mean accuracies of postcontrast sequences were 0.082 and 0.64 for T2-weighted FSE, 0.90 and 0.78 for MEDIC, 0.92 and 0.80 for GRE with an 11-msec TE, 0.93 and 0.82 for GRE with a 15-msec TE, and 0.81 and 0.62 for unenhanced sequences. CONCLUSION: Optimized SPIO-enhanced T2-weighted GRE combined with unenhanced T2-weighted FSE MR sequences were the most sensitive. Breath-hold FSE postcontrast sequences offer no improvement in sensitivity compared with unenhanced sequences alone.