Detection of liver metastasis: is diffusion-weighted imaging needed in Gd-EOB-DTPA-enhanced MR imaging for evaluation of colorectal liver metastases?

Purpose

We compared diagnostic ability for detecting hepatic metastases between gadolinium ethoxy benzyl diethylenetriamine pentaacetic acid (Gd-EOB-DTPA)-enhanced magnetic resonance imaging (MRI) and diffusion-weighted imaging (DWI) on a 1.5-T system, and determined whether DWI is necessary in Gd-EOB-DTPA-enhanced MRI for diagnosing colorectal liver metastases.

Materials and methods

We assessed 29 consecutive prospectively enrolled patients with suspected metachronous colorectal liver metastases; all patients underwent surgery and had preoperative Gd-EOB-DTPA-enhanced MRI. Overall detection rate, sensitivity for detecting metastases and benign lesions, positive predictive value, and diagnostic accuracy (Az value) were compared among three image sets [unenhanced MRI (DWI set), Gd-EOB-DTPA-enhanced MRI excluding DWI (EOB set), and combined set].

Results

Gd-EOB-DTPA-enhanced MRI yielded better overall detection rate (77.8?C79.0?%) and sensitivity (87.1?C89.4?%) for detecting metastases than the DWI set (55.9?% and 64.7?%, respectively) for one observer (P?<?0.001). No statistically significant difference was seen between the EOB and combined sets, although several metastases were newly detected on additional DWI.

Conclusions

Gd-EOB-DTPA-enhanced MRI yielded a better overall detection rate and higher sensitivity for detecting metastases compared with unenhanced MRI. Additional DWI may be able to reduce oversight of lesions in Gd-EOB-DTPA-enhanced 1.5-T MRI for detecting colorectal liver metastases.     

Whole-body diffusion-weighted imaging: is it all we need for detecting metastases in melanoma patients?

Objectives

To investigate whether whole-body diffusion-weighted imaging (WB-DWI) alone is adequate for detecting metastases in melanoma patients, or if standard WB contrast-enhanced magnetic resonance imaging (WB-ceMRI) is required.

Methods

Seventy-one WB-DWI studies were performed quarterly along with whole-body MRI including contrast-enhanced sequences (WB-ceMRI) in 19 patients with advanced melanoma. The reference standard was biopsy, other imaging investigations, or changes observed on follow-up. Findings of metastasis in separate WB-DWI and WB-DWI + WB-ceMRI readings were compared using κ statistics. Additionally, the distribution of findings was examined and calculated per body region (brain, neck, chest, abdomen, liver, pelvis, subcutaneous tissues, bones) and diagnostic accuracy (DA), sensitivity, specificity, negative predictive value, and positive predictive value were calculated per patient.

Results

The eight examinations that were positive by the reference standard contained a total of 14 metastatic findings. With almost perfect agreement between techniques (κ?=?85 %, 95 % CI 70–100 %) for detection of examinations with metastatic findings, and complete agreement in extracranial metastasis detection, 10 metastases were detected using WB-DWI and 13 using WB-DWI + WB-ceMRI. WB-DWI and WB-DWI + WB-MRI had equivalent per patient DA (79 %).

Conclusions

WB-DWI without additional WB-ceMRI sequences is promising for the detection of extracranial metastases in melanoma patients, but contrast-enhanced MRI is required for evaluating the brain.

Key Points

? Whole-body (WB) magnetic resonance imaging (MRI) is increasingly used for oncological disease assessment. ? WB diffusion-weighted MRI detects extracranial metastases in melanoma patients. ? Contrast-enhanced MRI is only required for detecting brain metastases. ? WB-DWI is inferior to low-dose CT for detecting lung metastases.     

Fungal versus bacterial brain abscesses: is diffusion-weighted MR imaging a useful tool in the differential diagnosis?

Introduction The aim of this study was to investigate the appearance of fungal brain abscesses on diffusion-weighted (DW) images, and to evaluate whether the imaging characteristics and apparent diffusion coefficient (ADC) values associated with fungal abscesses were distinct from those of bacterial abscesses. Methods We retrospectively reviewed the MR images from nine patients with fungal brain infections, and 17 patients with pyogenic brain abscesses. All patients underwent conventional MR sequences and DW imaging on 1.5-T clinical MR scanners. ADC values of 20 fungal and 20 bacterial brain abscesses were calculated and compared using a random factor analysis of variance. Results Multiple lesions were present in 6 of 9 patients (67%) with fungal abscesses and in 5 of 17 patients (29%) with bacterial abscesses. On DW images, all but one bacterial brain abscess showed a homogeneous high signal, whereas the appearance of fungal abscesses on DW images was more variable: in five of nine patients with fungal abscesses, the lesions were homogeneously hyperintense, while in the remaining four patients, the lesions were of mixed signal intensity. Mean ADC values were 0.74 × 10⁻³ mm²/s in the fungal group and 0.486 × 10⁻³ mm²/s in the bacterial group (P≤0.05). Conclusion Our results indicate that there is a trend towards higher ADC values in fungal lesions. Additional findings that support fungal rather than bacterial cerebral infection are multiplicity, signal heterogeneity on T2-weighted and DW imaging, and involvement of deep grey-matter nuclei.     

Wernicke's encephalopathy: is diffusion-weighted MRI useful?

We present the clinical and magnetic resonance imaging (MRI) findings of five patients with acute Wernicke's encephalopathy. T2-weighted and fluid-attenuated inversion recovery (FLAIR) images demonstrated symmetrical hyperintense lesions within the dorsomedial thalami, periaqueductal white matter, and the tectum of the midbrain. None of the lesions enhanced with gadolinium. In addition to conventional MRI sequences, we performed diffusion-weighted imaging (DWI). In all patients, DWI showed symmetrical pathologic thalamic and midbrain signal hyperintensities more distinctly than did conventional T2-weighted or FLAIR sequences. The apparent diffusion coefficient (ADC) map images showed slight signal reductions in four patients, suggesting restricted diffusion within these regions. In one patient, the signal intensity within the affected thalami was isointense with the ipsilateral basal ganglia on ADC map images. For enhanced detection of pathology, we conclude that DWI should be included in the imaging protocols of patients suspected to suffer from Wernicke's encephalopathy.     

Liver diffusion-weighted MR imaging: the tower of Babel?

There is a growing amount of literature regarding diffusion-weighted imaging (DWI) of the liver. The apparent diffusion coefficient (ADC) was introduced in 1986 and is used extensively in studies. However, methods for calculating ADC vary considerably and the value of the ADC strongly depends on the b values chosen for its calculation. Indeed, the ADC incorporates the effects of both diffusion and perfusion, which can vary independently. Since signal attenuation as a function of b follows a bi-exponential pattern, other diffusion/perfusion coefficients can be calculated using DWI, and these may provide more meaningful measurements than the ADC. The absence of standardization for both the terminology and the methodology in DWI of the liver makes it difficult for readers to understand the technique used and strongly limits comparisons between studies. Here, we review the main principles of DWI of the liver, the limits of the ADC, and the exciting capabilities of multi-parametric DWI. We also insisted on the need for a common language for DWI of the liver.     

Role of imaging in the evaluation of inflammatory bowel disease: How much is too much?

Inflammatory bowel disease (IBD) is a lifelong condition with waxing and waning disease course that requires reassessment of disease status as well as screening for complications throughout a patient’s lifetime. Laboratory testing, endoscopic assessment, and fecal biomarkers are often used in the initial diagnosis and ongoing monitoring of a patient with IBD. Imaging plays an integral role in the diagnosis and evaluation of IBD. Different imaging modalities can be used over the course of a patient’s lifetime, from the initial screening and diagnosis of IBD, to determining the extent of intestinal involvement, monitoring for disease activity, and evaluating for complications of uncontrolled IBD. The various imaging modalities available to the provider each have a unique set of risks and benefits when considering cost, radiation exposure, need for anesthesia, and image quality. In this article we review the imaging techniques available for the evaluation of IBD including fluoroscopic small bowel follow-through, computed tomography enterography, magnetic resonance enterography, and transabdominal ultrasound with particular focus on the judicious use of imaging and the risks and benefits of each option. We also review the risks of ionizing radiation, strategies to reduce exposure to ionizing radiation, and current imaging guidelines among pediatric and adult patient with IBD.     

What is the optimal b value in diffusion-weighted MR imaging to depict prostate cancer at 3T?

Objective  

To determine an optimal b value to visualise prostate cancer using diffusion-weighted magnetic resonance imaging at 3 T.     

Body diffusion-weighted MR imaging of uterine endometrial cancer: Is it helpful in the detection of cancer in nonenhanced MR imaging?

Objective

In this study, the authors discussed the feasibility and value of diffusion-weighted (DW) MR imaging in the detection of uterine endometrial cancer in addition to conventional nonenhanced MR images.

Methods and materials

DW images of endometrial cancer in 23 patients were examined by using a 1.5-T MR scanner. This study investigated whether or not DW images offer additional incremental value to conventional nonenhanced MR imaging in comparison with histopathological results. Moreover, the apparent diffusion coefficient (ADC) values were measured in the regions of interest within the endometrial cancer and compared with those of normal endometrium and myometrium in 31 volunteers, leiomyoma in 14 patients and adenomyosis in 10 patients. The Wilcoxon rank sum test was used, with a p < 0.05 considered statistically significant.

Results

In 19 of 23 patients, endometrial cancers were detected only on T2-weighted images. In the remaining 4 patients, of whom two had coexisting leiomyoma, no cancer was detected on T2-weighted images. This corresponds to an 83% detection sensitivity for the carcinomas. When DW images and fused DW images/T2-weighted images were used in addition to the T2-weighted images, cancers were identified in 3 of the remaining 4 patients in addition to the 19 patients (overall detection sensitivity of 96%). The mean ADC value of endometrial cancer (n = 22) was (0.97 ± 0.19) × 10⁻³ mm²/s, which was significantly lower than those of the normal endometrium, myometrium, leiomyoma and adenomyosis (p < 0.05).

Conclusion

DW imaging can be helpful in the detection of uterine endometrial cancer in nonenhanced MR imaging.     

Comparison between different imaging techniques in the evaluation of malignant breast lesions: can 3D ultrasound be useful?

Purpose

This study was done to assess the feasibility of three-dimensional ultrasonography (3D-US) for volume calculation of solid breast lesions.

Materials and methods

The volumes of 36 malignant lesions were measured using conventional 2D-US, 3D-US and magnetic resonance imaging (MRI) and compared with that obtained with histology (standard of reference). With 2D Ultrasouns, volume was estimated by measuring three diameters and calculating volume with the mathematical formula for spheres. With 3D-US, stored images were retrieved and boundaries of masses were manually outlined; volume calculation was performed with VOCAL software. For MRI, volume measurements were obtained with special software for 3D reconstructions, after each lesion had been manually outlined. Histology measured the three main diameters and the volume was estimated using the mathematical formula for spheres. Interclass correlation coefficient (ICC) and Bland–Altman plots were used to assess agreement between the volumes measured.

Results

ICC indicated that a good level of concordance was identified between 3D-US and histology (0.79). According to the Bland–Altman analysis, limits of agreement of mean differences of the volumes measured with the three imaging modalities were comparable with histology: ?2÷1.5 cm³ for 3D-US; ?2.3÷1.3 cm³ for 2D-US and ?2.2÷1.6 cm³ for MRI.

Conclusions

3D-US is a reliable method for the volumetric assessment of breast lesions. 3D-US is able to provide valuable information for the preoperative evaluation of lesions.     

Why is cultural safety essential in health care?

The concept of cultural safety involves empowerment of the healthcare practitioner and the patient. The determinants of 'safe' care are defined by the recipient of care. Cultural safety is linked to the principles of New Zealand's founding document, the Treaty of Waitangi. These are participation, protection and partnership. Cultural safety was initially a response to the poor health status of indigenous New Zealanders but has since broadened to encompass a wide range of cultural determinants. Importance is placed on identifying and evaluating one's own beliefs and values and recognising the potential for these to impact on others. Dissemination of cultural safety knowledge and practice outside of New Zealand is growing. This concept provides recognition of the indices of power inherent in any interaction and the potential for disparity and inequality within any relationship. Acknowledgement by the healthcare practitioner that imposition of their own cultural beliefs may disadvantage the recipient of healthcare is fundamental to the delivery of culturally safe care.     

Is diffusion-weighted imaging useful in grading and differentiating histopathological subtypes of meningiomas?

Purpose

Meningiomas are mostly benign, however atypical or malignant subtypes with more aggressive clinical course and higher recurrence rates can also be seen. The purpose of this study was to determine whether histopathological subtypes of meningiomas could be assessed preoperatively using apparent diffusion coefficient (ADC) values.

Materials and methods

Conventional magnetic resonance (MR) and diffusion-weighted (DW) imaging of 177 adult patients with pathologically proven meningiomas were retrospectively evaluated. Tumor size and the degree of associated edema were noted. The signal intensity of the lesions on DW imaging was evaluated and graded. Mean ADC values were obtained as the mean of measurements from three regions of interests within the mass. ADC ratios of meningioma/contralateral normal appearing subcortical parietal white matter were also calculated.

Results

The histopathological analysis revealed 135 benign, 37 atypical and 5 malignant lesions. With classification according to the subtype, the mean ADC values and ratios of benign meningiomas were as 0.99 ± 0.12 × 10⁻³ mm²/s and 1.22 ± 0.07, respectively. ADC values for atypical and malignant groups were both 0.84 ± 0.1 × 10⁻³ mm²/s. The ADC ratios were 1.05 ± 0.1 and 0.96 ± 0.2 for atypical and malignant subtypes, respectively. There was no statistically significant difference between the mean ADC ratios of the three subtypes (ANOVA test; P ≥ 0.05). Gender, age of the patients and tumor size showed no statistically significant difference between the different histological groups.

Conclusion

DW MR imaging was not found to have any additional value in determining histological behaviour nor in differentiating histopathological subtypes of meningiomas.     

Lacrimal gland lesions: Can addition of diffusion-weighted MR imaging improve diagnostic accuracy in characterization?

The aim of the work

To evaluate the diagnostic value of apparent diffusion coefficient (ADC) maps in the characterization of lacrimal gland lesions.

Material and methods

A retrospective study was conducted on 40 patients (26 female and 14 male subjects aged 13–74 years) with lacrimal gland mass. They underwent echo-planar diffusion-weighted magnetic resonance imaging (MRI) of the orbit with a b-factor of 0500 and 1000 s/mm² at 3-Tesla magnetic resonance (MR) unit. ADC maps were reconstructed and the ADC of each mass lesion was calculated. Lesion diagnosis was confirmed by the clinical follow-up or the results of histopathology analysis depending on the specific disease to identify the specificity, sensitivity and accuracy of diffusion-weighted imaging (DWI) in the differentiation between benign and malignant lacrimal lesions.

Results

Forty-two lesions were detected in the examined 40 patients included in this study. Thirty-one were benign and 11 were malignant. The mean ADC value of the malignant lacrimal tumors (0.76 ± 0.14 × 10⁻³ mm²/s) was significantly (P = 0.001) lower than that of the benign lacrimal lesions (1.17 ± 0.22 × 10⁻³ mm²/s). A statistically significant (P = 0.001) difference is identified between the subjects with lacrimal adenitis and those with idiopathic orbital inflammatory syndrome (orbital pseudotumor). Lacrimal lymphoma has the lowest ADCs among a wide range of lacrimal masses. The selection of an ADC value of 0.90 × 10⁻³ mm²/s as a threshold value for differentiating malignant tumors from benign lacrimal lesions has an accuracy of 90%, a sensitivity of 90%, and specificity of 89%.

Conclusion

ADC offers a useful reliable safe non-invasive imaging parameter that can be used for the differentiation of malignant tumors from benign lacrimal lesions with high sensitivity and specificity. The absence of contrast media in DWI reduces the cost of the examination and leads to an increase in the overall accuracy of MRI, hence reducing the number of false positive results and consequently reducing the number of unnecessary biopsies.     

Short communication: imaging pulmonary embolism in pregnancy: what is the most appropriate imaging protocol?

Pulmonary embolism is the leading cause of death in pregnancy. Despite the difficulties in clinical diagnosis and the concerns regarding radiation of the fetus, the British Thoracic Society guidelines for imaging pulmonary embolism do not specifically address the issue of imaging for pulmonary embolism in this group. This communication discusses the difficulties of diagnosis and imaging pulmonary embolism in pregnancy and proposes a suitable imaging protocol. Clinical exclusion of patients from further imaging is recommended if the patient has a low pre-test probability of pulmonary embolism and a normal d-dimer. It is advised that all remaining patients undergo bilateral leg Doppler assessment. If this test is positive, the patient should be treated for pulmonary embolism; if negative, all patients should be referred for CT pulmonary angiography. Ideally, informed consent should be obtained prior to CT scanning. All neonates exposed to iodinated contrast in utero should have their thyroid function tested in the first week of life due to the theoretical risk of contrast induced hypothyroidism.