Diagnostic utility of diffusion-weighted MR imaging and apparent diffusion coefficient value for the diagnosis of adrenal tumors

Diagnostic performance of magnetic resonance imaging features to differentiate adrenal pheochromocytoma from adrenal tumors with positive biochemical testing results

BACKGROUND

It is extremely essential to accurately differentiate pheochromocytoma from Adrenal incidentalomas (AIs) before operation, especially biochemical tests were inconclusive. We aimed to evaluate the value of magnetic resonance imaging (MRI) features to differentiate pheochromocytomas among adrenal tumors, among which the consequences of biochemical screening tests of catecholamines and/or catecholamine metabolites are positive.

METHODS

With institutional review board approval, this study retrospectively compared 35 pheochromocytoma (PHEO) patients with 27 non-pheochromocytoma(non-PHEO) patients between January 2022 to September 2023, among which the consequences of biochemical screening tests of catecholamines and/or catecholamine metabolites are positive. T test was used for the independent continuous data and the chi-square test was used for categorical variables. Univariate and multivariate logistic regression were applied to find the independent variate of the features to differentiate PHEO from non-PHEO and ROC analysis was applied to evaluate the diagnostic value of the independent variate.

RESULTS

We found that the T2-weighted (T2W) signal intensity in patients with pheochromocytoma was higher than other adrenal tumors, with greatly significant (p < 0.001). T2W signal intensity ratio (T2W nodule-to-muscle SI ratio) was an independent risk factor for the differential diagnosis of adrenal PHEOs from non-PHEOs. This feature alone had 91.4% sensitivity and 81.5% specificity to rule out pheochromocytoma based on optimal threshold, with an area under the receiver operating characteristics curve (AUC‑ROC) of 0.910(95% C I: 0.833-0.987).

CONCLUSION

Our study confirms that T2W signal intensity ratio can differentiate PHEO from non-PHEO, among which the consequences of biochemical screening tests of catecholamines and/or catecholamine metabolites are positive.

Optimal and novel imaging of the adrenal glands

PURPOSE OF REVIEW

Adrenal imaging forms an important role in the workup of adrenal masses. The purpose of this review is to briefly review the traditional role of imaging in adrenal diseases and highlight the most recent research and new applications aimed to improve diagnostic accuracy.

RECENT FINDINGS

The current review will focus on new applications of computed tomography (CT), MRI and PET/CT imaging, addressing the implications of artificial intelligence and radiomics in progressing diagnostic accuracy.

SUMMARY

The new applications of adrenal imaging are improving diagnostic accuracy and expanding the role of imaging, particularly with novel PET radiotracers and the use of artificial intelligence.

ACR Appropriateness Criteria® Adrenal Mass Evaluation: 2021 Update

The appropriate evaluation of adrenal masses is strongly dependent on the clinical circumstances in which it is discovered. Adrenal incidentalomas are masses that are discovered on imaging studies that have been obtained for purposes other than adrenal disease. Although the vast majority of adrenal incidentalomas are benign, further radiological and biochemical evaluation of these lesions is important to arrive at a specific diagnosis. Patients with a history of malignancy or symptoms of excess hormone require different imaging evaluations than patients with incidentalomas. This document reviews imaging approaches to adrenal masses and the various modalities utilized in evaluation of adrenal lesions. The American College of Radiology Appropriateness Criteria are evidence-based guidelines for specific clinical conditions that are reviewed annually by a multidisciplinary expert panel. The guideline development and revision include an extensive analysis of current medical literature from peer reviewed journals and the application of well-established methodologies (RAND/UCLA Appropriateness Method and Grading of Recommendations Assessment, Development, and Evaluation or GRADE) to rate the appropriateness of imaging and treatment procedures for specific clinical scenarios. In those instances where evidence is lacking or equivocal, expert opinion may supplement the available evidence to recommend imaging or treatment.

Adrenal pheochromocytoma: is it all or the tip of the iceberg?

Adrenal pheochromocytoma is not always a simple retroperitoneal tumor but may be part of a more complicated condition. It often has a spectrum of complex and variable imaging features, may present as a collision tumor and composite tumor, and is associated with a variety of clinical syndromes. A comprehensive understanding of the clinical, pathological, and variable imaging manifestations of pheochromocytoma can help radiologists make an accurate diagnosis. This article reviews various special imaging features of pheochromocytoma and pheochromocytoma-related diseases.

Multimodality Imaging Review of Multiple Endocrine Neoplasia

OBJECTIVE. The purpose of this article is to review the clinical manifestations, endocrine tumors types, and multimodality diagnostic tools available to physicians involved in the management of patients with multiple endocrine neoplasia (MEN) syndrome, in addition to discussing relevant imaging findings and appropriate imaging follow-up. CONCLUSION. Thorough knowledge of the spectrum of tumors associated with MEN gene mutations aids in the screening, diagnostic workup, and posttreatment monitoring of patients with MEN-related gene mutations.

Diffusion Weighted Imaging in Unilateral Adrenal Infarction: A Case of Colicky Right Upper Quadrant Pain in a Pregnant Female

Diffusion weighted imaging (DWI) is a magnetic resonance imaging (MRI) non-contrast sequence that can indicate tissue ischemia or infarction. Adrenal infarct may present similarly to biliary or gallbladder pathologies, and the differential diagnosis during emergency work-up can be narrowed utilizing DWI sequences. In this paper, we describe the usefulness of DWI for urgent diagnosis in a case of non-hemorrhagic adrenal infarct of a pregnant female presenting with right upper quadrant pain. Although uncommon, adrenal infarct may occur in patients with hypercoagulability and localizing pain that is unexplained by other imaging modalities. We outline the imaging features of DWI in evaluating adrenal infarct as a safe and time effective application for patients with contraindications to imaging with ionizing radiation.

Validity of diffusion-weighted magnetic resonance imaging in the evaluation of acute pyelonephritis in comparison with contrast-enhanced computed tomography

Purpose

Applications of diffusion-weighted magnetic resonance imaging outside the brain have gained increasing importance in recent years, and recent studies have shown the usage of diffusion-weighted (DW) imaging in diagnosing pyelonephritis based on renal cortical and medullary apparent diffusion coefficient (ADC) values. The aim of this study was to assess the validity of DW magnetic resonance (MR) imaging in comparison with contrast-enhanced computed tomography (CECT) in diagnosing pyelonephritis.

Material and methods

A cross-sectional observational study was conducted for a period of six months in a tertiary hospital in Coimbatore. All patients with clinical and laboratory diagnosis of acute pyelonephritis, who were referred for radiological imaging (CECT), were taken into the study. Out of 112 patients with a clinical and laboratorial diagnosis of acute pyelonephritis (APN), who underwent both DW MR and CECT, diagnosis of APN was made in 100 patients based on CECT, while in 12 cases the investigation (CECT) was negative. Finally, these 100 patients were included in the study. The validity of DW MR imaging in diagnosing APN was assessed by deriving sensitivity, specificity, and positive and negative predictive value in comparison with CECT findings.

Results

The validity report of DW MR imaging in the detection of APN showed a very high sensitivity (96-100%) and specificity (86-90%) and very low false positives (6-10%) and negatives (< 5%), and it also showed that in the areas of affected renal parenchyma ADC values were consistently lower compared to unaffected renal parenchyma.

Conclusion

Based on the generated hypothesis, DW MR imaging of the kidneys seems to be highly sensitive and specific for the detection of focal or diffuse infections within the kidney in comparison with CECT.

Magnetic resonance imaging of adrenal gland: state of the art

Detection of adrenal lesions, because of the widespread use of imaging and especially high-resolution imaging procedures, is increased. Because of the importance to characterize those findings, magnetic resonance imaging (MRI), in particular chemical shift imaging (CSI), is useful to distinguish whether a lesion is benignant or malignant and to avoid further diagnostic or surgical procedures. It represents the first choice of imaging in patient like children or pregnant women, and a valid complement to other imaging techniques like CT or PET/CT. In this review we analyze the role and characteristic of MRI and the imaging features of most common benignant (adenoma, hyperplasia, pheochromocytoma, hemorrhage, cyst, myelolipoma, teratoma, ganglioneuroma, cystic lymphangioma, hemangioma) and malignant [neuroblastoma, adrenocortical carcinoma (ACC), metastases, lymphoma] adrenal lesions.

Bilateral adrenal abnormalities: imaging review of different entities

Bilateral adrenal abnormalities are not infrequently encountered during routine daily radiology practice. The differential diagnoses of bilateral adrenal abnormalities include neoplastic and non-neoplastic entities. The bilateral adrenal tumors include metastasis, lymphoma, neuroblastoma, pheochromocytoma, adenoma, and myelolipoma. Non-neoplastic bilateral adrenal masses include infectious processes and haematomas. There are different diffuse bilateral adrenal changes such as adrenal atrophy, adrenal enlargement, adrenal calcifications, and altered adrenal enhancement. In this pictorial review article, we will discuss the imaging features of these entities with emphasis on their clinical implications.

Practical Approach to Adrenal Imaging

Various pathologies can affect the adrenal gland. Noninvasive cross-sectional imaging is used for evaluating adrenal masses. Accurate diagnosis of adrenal lesions is critical, especially in cancer patients; the presence of adrenal metastasis changes prognosis and treatment. Characterization of adrenal lesions predominantly relies on morphologic and physiologic features to enable correct diagnosis and management. Key diagnostic features to differentiate benign and malignant adrenal lesions include presence/absence of intracytoplasmic lipid, fat cells, hemorrhage, calcification, or necrosis and locoregional and distant disease; enhancement pattern and washout values; and lesion size and stability. This article reviews a spectrum of adrenal pathologies.

Current diagnostic imaging of pheochromocytomas and implications for therapeutic strategy

The topic of pheochromocytomas is becoming increasingly popular as a result of major advances in different medical fields, including laboratory diagnosis, genetics, therapy, and particularly in novel advances in imaging techniques. The present review article discusses current clinical, biochemical, genetic and histopathological aspects of the diagnosis of pheochromocytomas and planning of pre-surgical preparation and subsequent surgical treatment options. The main part of the paper is focused on the role of morphological imaging methods (primarily computed tomography and magnetic resonance imaging) and functional imaging (scintigraphy and positron emission tomography) in the diagnosis and staging of pheochromocytomas.

Adrenocortical neoplasms in adulthood and childhood: distinct presentation. Review of the clinical, pathological and imaging characteristics

Adrenocortical tumors (ACT) in adulthood and childhood vary in clinical, histopathological, molecular, prognostic, and imaging aspects. ACT are relatively common in adults, as adenomas are often found incidentally on imaging. ACT are rare in children, though they have a significantly higher prevalence in the south and southeast regions of Brazil. In clinical manifestation, adults with ACT present more frequently with glucocorticoid overproduction (Cushing syndrome), mineralocorticoid syndromes (Conn syndrome), or the excess of androgens in women. Subclinical tumors are frequently diagnosed late, associated with compression symptoms of abdominal mass. In children, the usual presentation is the virilizing syndrome or virilizing association and hypercortisolism. Histopathological grading and ACT classification in malignant and benign lesions are different for adults and children. In adults, the described criteria are the Hough, Weiss, modified Weiss, and Van Slooten. These scores are not valid for children; there are other criteria, such as proposed by Wieneke and colleagues. In molecular terms, there is also a difference related to genetic alterations found in these two populations. This review discusses the imaging findings of ACT, aiming to characterize the present differences between ACT found in adults and children. We listed several differences between magnetic resonance imaging (MRI), computed tomography (CT), and positron emission tomography-computed (PET-CT) and also performed a literature review, which focuses on studied age groups of published articles in the last 10 years regarding cortical neoplasm and imaging techniques. Published studies on ACT imaging in children are rare. It is important to stress that the majority of publications related to the differentiation of malignant and benign tumors are based almost exclusively on studies in adults. A minority of articles, however, studied adults and children together, which may not be appropriate.

Diffusion tensor imaging in abdominal organs

Initially, diffusion tensor imaging (DTI) was mainly applied in studies of the human brain to analyse white matter tracts. As DTI is outstanding for the analysis of tissue´s microstructure, the interest in DTI for the assessment of abdominal tissues has increased continuously in recent years. Tissue characteristics of abdominal organs differ substantially from those of the human brain. Further peculiarities such as respiratory motion and heterogenic tissue composition lead to difficult conditions that have to be overcome in DTI measurements. Thus MR measurement parameters have to be adapted for DTI in abdominal organs. This review article provides information on the technical background of DTI with a focus on abdominal imaging, as well as an overview of clinical studies and application of DTI in different abdominal regions. Copyright © 2015 John Wiley & Sons, Ltd.

Apparent diffusion coefficient of normal adrenal glands

Objective

To assess the feasibility and reliability of apparent diffusion coefficient (ADC) measurements of normal adrenal glands.

Materials and methods

This was a retrospective study involving 32 healthy subjects, divided into two groups: prepubertal (PreP, n = 12), aged from 2 months to 12.5 years (4 males; 8 females); and postpubertal (PostP, n = 20), aged from 11.9 to 61 years (5 males; 15 females). Diffusion-weighted magnetic resonance imaging (DW-MRI) sequences were acquired at a 1.5 T scanner using b values of 0, 20, 500, and 1000 s/mm². Two radiologists evaluated the images. ADC values were measured pixel-by-pixel on DW-MRI scans, and automatic co-registration with the ADC map was obtained.

Results

Mean ADC values for the right adrenal glands were 1.44 × 10^-3 mm²/s for the PreP group and 1.23 × 10^-3 mm²/s for the PostP group, whereas they were 1.58 × 10^-3 mm²/s and 1.32 × 10^-3 mm²/s, respectively, for the left glands. ADC values were higher in the PreP group than in the PostP group (p < 0.05). Agreement between readers was almost perfect (intraclass correlation coefficient, 0.84-0.94; p < 0.05).

Conclusion

Our results demonstrate the feasibility and reliability of performing DW-MRI measurements of normal adrenal glands. They could also support the feasibility of ADC measurements of small structures.

Practical Approach to Adrenal Imaging

Various pathologies can affect the adrenal gland. Noninvasive cross-sectional imaging is used for evaluating adrenal masses. Accurate diagnosis of adrenal lesions is critical, especially in cancer patients; the presence of adrenal metastasis changes prognosis and treatment. Characterization of adrenal lesions predominantly relies on morphologic and physiologic features to enable correct diagnosis and management. Key diagnostic features to differentiate benign and malignant adrenal lesions include presence/absence of intracytoplasmic lipid, fat cells, hemorrhage, calcification, or necrosis and locoregional and distant disease; enhancement pattern and washout values; and lesion size and stability. This article reviews a spectrum of adrenal pathologies.

ADC histogram analysis for adrenal tumor histogram analysis of apparent diffusion coefficient in differentiating adrenal adenoma from pheochromocytoma

PURPOSE

To determine the diagnostic performance of apparent diffusion coefficient (ADC) histogram analysis in diffusion-weighted (DW) magnetic resonance imaging (MRI) for differentiating adrenal adenoma from pheochromocytoma.

MATERIALS AND METHODS

We retrospectively evaluated 52 adrenal tumors (39 adenomas and 13 pheochromocytomas) in 47 patients (21 men, 26 women; mean age, 59.3 years; range, 16-86 years) who underwent DW 3.0T MRI. Histogram parameters of ADC (b-values of 0 and 200 [ADC₂₀₀ ], 0 and 400 [ADC₄₀₀ ], and 0 and 800 s/mm² [ADC₈₀₀ ])-mean, variance, coefficient of variation (CV), kurtosis, skewness, and entropy-were compared between adrenal adenomas and pheochromocytomas, using the Mann-Whitney U-test. Receiver operating characteristic (ROC) curves for the histogram parameters were generated to differentiate adrenal adenomas from pheochromocytomas. Sensitivity and specificity were calculated by using a threshold criterion that would maximize the average of sensitivity and specificity.

RESULTS

Variance and CV of ADC₈₀₀ were significantly higher in pheochromocytomas than in adrenal adenomas (P < 0.001 and P = 0.001, respectively). With all b-value combinations, the entropy of ADC was significantly higher in pheochromocytomas than in adrenal adenomas (all P ≤ 0.001), and showed the highest area under the ROC curve among the ADC histogram parameters for diagnosing adrenal adenomas (ADC₂₀₀ , 0.82; ADC₄₀₀ , 0.87; and ADC₈₀₀ , 0.92), with sensitivity of 84.6% and specificity of 84.6% (cutoff, ≤2.82) with ADC₂₀₀ ; sensitivity of 89.7% and specificity of 84.6% (cutoff, ≤2.77) with ADC₄₀₀ ; and sensitivity of 94.9% and specificity of 92.3% (cutoff, ≤2.67) with ADC₈₀₀ .

CONCLUSION

ADC histogram analysis of DW MRI can help differentiate adrenal adenoma from pheochromocytoma.

LEVEL OF EVIDENCE

3 J. Magn. Reson. Imaging 2017;45:1195-1203.

Images of pheochromocytoma in adrenal glands

Pheochromocytomas are relatively rare tumors of the adrenal medulla. A wide spectrum of imaging findings has been described. The aim of this article is to describe the multimodality imaging features of pheochromocytomas including diagnostic pearls that can help differentiate them from other adrenal lesions and pitfalls to avoid.

[Adrenal tumors: principles of imaging and differential diagnostics]

CLINICAL/METHODICAL ISSUE

Adrenal masses are very common and are usually detected incidentally. Less frequently, imaging is performed for the localization of the underlying lesion in the case of endocrine disease. The differentiation between adenomas and non-adenomas is fundamental.

METHODICAL INNOVATIONS

Adenomas show a low density on unenhanced computed tomography (CT) and a rapid washout of contrast agents. In magnetic resonance imaging (MRI) adenomas are characterized by a low signal in opposed phase imaging as compared to in phase imaging.

PERFORMANCE

According to the literature a density of less than 10 HU in an adrenal mass has a specificity of 98% and a sensitivity of 71% for the presence of an adenoma and MRI is slightly more sensitive. Some adrenal lesions, e.g. cysts or myelolipomas can be diagnosed with high accuracy due to pathognomonic findings.

ACHIEVEMENTS

In the majority of cases the synopsis of imaging along with clinical and laboratory findings is necessary for a reliable diagnosis.

PRACTICAL RECOMMENDATIONS

For the evaluation of an adrenal mass the CT examination should begin with an unenhanced scan, if necessary followed by a washout examination. In the case of MRI in phase and opposed phase imaging are essential components of the examination.

Apparent diffusion coefficient characteristics of various adrenal tumors

PURPOSE

Using pathologically proven tumors and 3 methods of apparent diffusion coefficient (ADC) measurement, we examined the potential of diffusion-weighted imaging (DWI) to differentiate adrenal tumors.

METHODS

We evaluated adrenal tumors of 52 patients who underwent magnetic resonance (MR) examination including DWI and adrenal resection or biopsy between July 2006 and August 2011. Tumors included 25 cortical adenomas, 14 pheochromocytomas, 6 adrenal metastases, and seven others. We defined the tumor's "solid" region as an enhancing area on contrast-enhanced MR or computed tomography (CT) and measured the ADC of the tumor's "entire" and "solid" regions within a region of interest (ROI) placed on an ADC map ("entire" and "solid" ADCs). We obtained a "minimum" ADC by placing an ROI in an area showing the lowest ADC within the "solid" region. We also calculated the ratio of "non-solid" area to "entire" tumor and compared the average "entire," "solid," and "minimum" ADCs and the ratio of "non-solid" area to "entire" tumor between benign and malignant groups.

RESULTS

The average "entire" ADC was significantly higher for the benign (1.35 ± 0.38 × 10(-3) mm2/s) than malignant group (1.01 ± 0.17 × 10(-3) mm2/s), and the average "solid" and "minimum" ADC and the ratio of "non-solid" area to "entire" tumor did not differ significantly between the benign and malignant groups.

CONCLUSION

The higher "entire" ADC value of the benign group, which might be obtained incidentally, can be considered dependent on the condition of necrosis, hemorrhage, and degeneration. ADC measurement of a tumor's "solid" region was not useful for differentiating pathologically proven adrenal tumors.

The role of diffusion weighted magnetic resonance imaging in oncologic settings

There is growing interest in the applications of diffusion-weighted-imaging (DWI) in oncologic area for last ten years. DWI has important advantages as do not require contrast medium, very quick technique and it provides qualitative and quantitative information that can be helpful for tumor assessment. In this article, we present oncologic applications of DWI in the parts of the body. DWI has been applied to the evaluation of central nervous system (CNS) pathologies. Some technologic advances lead to using of DWI in the extracranial sites such as abdomen and pelvis. As well as tumor detection and characterization, DWI has been widely used for predicting and monitoring response to therapy. One of the most prominent contributions of DWI is differentiation of between malignant and benign tumoral process. Apparent-diffusion-coefficient (ADC) value is quantitative parameter of DWI which reflects diffusion movements of water molecules in various tissues. Most of the studies suggested that malignant tumors had lower ADC values than benign ones. DWI may be a routine sequence in oncologic settings and it provides much useful information about tumoral tissue. We think it can be added to conventional magnetic resonance imaging (MRI) sequences.

Cross-sectional imaging work-up of adrenal masses

Advances in medical imaging with current cross-section modalities enable non-invasive characterization of adrenal lesions. Computed tomography (CT) provides characterization with its non-contrast and wash-out features. Magnetic resonance imaging (MRI) is helpful in further characterization using chemical shift imaging (CSI) and MR spectroscopy. For differentiating between benign and malignant masses, positron emission tomography (PET) imaging is useful with its qualitative analysis, as well as its ability to detect the presence of extra-adrenal metastases in cancer patients. The work-up for an indeterminate adrenal mass includes evaluation with a non-contrast CT. If a lesion is less than 10 Hounsfield Units on a non-contrast CT, it is a benign lipid-rich adenoma and no further work-up is required. For the indeterminate adrenal masses, a lipid-poor adenoma can be differentiated from a metastasis utilizing CT wash-out features. Also, MRI is beneficial with CSI and MR spectroscopy. If a mass remains indeterminate, PET imaging may be of use, in which benign lesions demonstrate low or no fluorodeoxyglucose activity. In the few cases in which adrenal lesions remain indeterminate, surgical sampling such as percutaneous biopsy can be performed.

Abdominal applications of diffusion-weighted magnetic resonance imaging: Where do we stand

Diffusion-weighted imaging (DWI) is one of the magnetic resonance imaging (MRI) sequences providing qualitative as well as quantitative information at a cellular level. It has been widely used for various applications in the central nervous system. Over the past decade, various extracranial applications of DWI have been increasingly explored, as it may detect changes even before signal alterations or morphological abnormalities become apparent on other pulse sequences. Initial results from abdominal MRI applications are promising, particularly in oncological settings and for the detection of abscesses. The purpose of this article is to describe the clinically relevant basic concepts of DWI, techniques to perform abdominal DWI, its analysis and applications in abdominal visceral MR imaging, in addition to a brief overview of whole body DWI MRI.

Comparative utility of MRI perfusion with MSIDR and DWIBS for the characterization of breast tumors

BACKGROUND

In recent years, breast magnetic resonance imaging (MRI) has been used to evaluate the morphology and functional markers of breast lesions, which might influence local staging and surgical planning.

PURPOSE

To evaluate the feasibility of a one stop MRI protocol combined with diffusion-weighted imaging with background body signal suppression (DWIBS), T2*-weighted perfusion imaging (T2*-PWI) and delayed contrast-enhanced T1-weighted MRI (T1W-C+).

MATERIAL AND METHODS

All experiments were conducted with a 3-T clinical MRI scanner. The apparent diffusion coefficient (ADC) and detectability of lesions in DWIBS, the maximal signal intensity drop rate (MSIDR) in T2*-PWI and the intensity increasing rate (IIR) on T1W-C+ were compared between breast malignancies (n = 29) and benign lesions (n = 31). The time-signal curves in the T2*-PWI sequences were classified into two subtypes (a and b) according to the end of the curve. The ADC, MSIDR, the first maximal signal intensity decrease time (MSIDT), and IIR between the malignant and benign lesions were statistically analyzed by unpaired t-tests.

RESULTS

Overall, 90% of the lesions were detected by DWIBS. There were significant differences in ADC, MSIDR, and IIR between the carcinomas and benign lesions. The Ib subtype in T2*-PWI demonstrated a specificity of 66.7% in differentiating between carcinomas and benign lesions. At a fixed specificity of 93.5%, the MSIDR, IIR, and ADC differentiated breast carcinomas from benign lesions with sensitivities of 82.8%, 44.8%, and 86.2%, respectively.

CONCLUSION

DWIBS might be a compensation sequence for detecting breast lesions in pre-contrast sequences. MSIDR from T2*-PWI had the best specificity index, and the two subtypes in the T2*-PWI curve were helpful in the differential diagnosis of carcinomas from benign lesions.

Apparent diffusion coefficient measurements in the differentiation between benign and malignant lesions: a systematic review

Objectives

To systematically review the value of apparent diffusion coefficient (ADC) measurement in the differentiation between benign and malignant lesions.

Methods

A systematic search of the Medline/Pubmed and Embase databases revealed 109 relevant studies. Quality of these articles was assessed using the Quality Assessment of the Studies of Diagnostic Accuracy Included in Systematic Reviews (QUADAS) criteria. Reported ADC values of benign and malignant lesions were compared per organ.

Results

The mean quality score of the reviewed articles was 50%. Comparison of ADC values showed marked variation among studies and between benign and malignant lesions in various organs. In several organs, such as breast, liver, and uterus, ADC values discriminated well between benign and malignant lesions. In other organs, such as the salivary glands, thyroid, and pancreas, ADCs were not significantly different between benign and malignant lesions.

Conclusion

The potential utility of ADC measurement for the characterisation of tumours differs per organ. Future well-designed studies are required before ADC measurements can be recommended for the differentiation of benign and malignant lesions. These future studies should use standardised acquisition protocols and provide complete reporting of study methods, to facilitate comparison of results and clinical implementation of ADC measurement for tumour characterisation.

Electronic supplementary material

The online version of this article (doi:10.1007/s13244-012-0175-y) contains supplementary material, which is available to authorized users.

Adrenal imaging: a comprehensive review

The discovery of an incidental adrenal mass (adrenal incidentaloma) continues to rise with the increasing use of cross-sectional imaging. Although most adrenal lesions are benign and asymptomatic, radiologists should guide evaluation of these lesions, whether benign or malignant. This article reviews the various imaging techniques used to evaluate adrenal masses and their relative strengths and weaknesses. It focuses on the most prevalent adrenal pathologies and their typical imaging characteristics, and concludes with a brief discussion of developing techniques, including diffusion-weighted imaging and dual-energy CT.

Oncologic applications of diffusion-weighted MRI in the body

Diffusion-weighted MRI (DWI) allows the detection of malignancies in the abdomen and pelvis. Lesion detection and characterization using DWI largely depends on the increased cellularity of solid or cystic lesions compared with the surrounding tissue. This increased cellularity leads results in restricted diffusion as indicated by reduction in the apparent diffusion coefficient (ADC). Low pretreatment ADC values of several malignancies have been shown to be predictive of better outcome. DWI can assess response to systemic or regional treatment of cancer at a cellular level and will therefore detect successful treatment earlier than anatomical measures. In this review, we provide a brief technical overview of DWI, discuss quantitative image analysis approaches, and review studies which have used DWI for the purpose of detection and characterization of malignancies as well as the early prediction of treatment response.

Radiological evaluation of adrenal incidentalomas: current methods and future prospects

Incidental adrenal lesions are very common. Computed tomography (CT), magnetic resonance imaging (MRI) and positron emission tomography (PET) all have a role to play in characterizing adrenal lesions. The purpose of this review is to discuss the rationale behind both established and emerging imaging techniques. We also discuss how to follow up incidentally found lesions.

Update on imaging of the adrenal cortex

PURPOSE OF REVIEW

To explain the rationale behind and findings on both established and newer techniques in adrenal cortical imaging. We also discuss management of incidentally found adrenal lesions.

RECENT FINDINGS

Computed tomography, MRI and PET all have a role to play in imaging of adrenal lesions.

SUMMARY

The role of adrenal imaging is to differentiate benign 'leave-alone' lesions from those that warrant further management.

Diffusion-weighted magnetic resonance imaging in the upper abdomen: technical issues and clinical applications

Recent technological achievements have enabled the transposition of diffusion-weighted imaging (DWI) with good diagnostic quality into other body regions, especially the abdomen and pelvis. Many emerging and established applications are now being evaluated on the upper abdomen, the liver being the most studied organ. This article discusses imaging strategies for DWI on the upper abdomen, describes the clinical protocol, and reviews the most common clinical applications of DWI on solid abdominal organs.

Incidental and metastatic adrenal masses

In the last decades discoveries of adrenal masses incidentally during the course of diagnostic procedures for unrelated disorders (incidentalomas) have become progressively more frequent. The clinician in this position must answer two main questions: Is the mass benign or malignant?, and To what extent is the adrenal secretion altered? To come to a clinical decision, several diagnostic tools need to be engaged, starting with an accurate and correct radiological evaluation and a hormonal assessment of the adrenal function. When necessary, other diagnostic procedures such as functional imaging and fine-needle biopsy (FNB) can be considered in selected cases. Surgical removal is recommended for clinically relevant hypersecretory masses, as well as for masses suspected to be malignant. Most frequently, adrenal incidentalomas (AIs) are represented by benign cortical adenomas, a subset of which causes a mild hypercortisolism, known as subclinical Cushing's syndrome (SCS). The criteria to define this syndrome, as well as its treatment, are still debated and controversial. AIs that are not surgically removed should be re-examined in time to exclude a supervening increase in size or function. Follow-up criteria have not been established. Laparoscopic surgery is the recommended procedure to remove benign masses. The surgical procedure for adrenal malignancies is still debated.

Adrenal imaging

OBJECTIVE

Adrenal nodules are frequently encountered on current high-resolution imaging, and accurate characterization of such lesions is critical for appropriate patient care. Our article highlights how imaging techniques such as CT densitometry, CT washout characteristics, chemical shift MRI, PET, and PET/CT help characterize most adrenal lesions. We focus on these techniques as well as specifically, because of space constraints, the varied imaging appearances of adrenocortical carcinoma, pheochromocytoma, and lymphoma on these techniques.

CONCLUSION

The imaging characterization of adrenal lesions has continued to advance over the past decade as new technologies have evolved. CT, MRI, PET, and PET/CT are now established clinical techniques capable of differentiating benign from malignant adrenal lesions.

Abdominal magnetic resonance imaging at 3 T: oncological applications

The gain in signal-to-noise ratio at 3 T magnetic resonance (MR) imaging produces many benefits for abdominal imaging applications, including the capability to reduce acquisition times and/or improve spatial resolution for a variety of pulse sequences, the potential for broader application of parallel imaging techniques, and an increased sensitivity to gadolinium-based contrast media. These advances have the potential of improving the accuracy of MR imaging in the detection, staging, treatment planning, and follow-up of patients with abdominal tumors. At the same time, because certain high-field-strength-related drawbacks could not be compensated for, abdominal 3 T MR imaging should be clinically implemented with caution in some patients (eg, patients with massive ascites).

Magnetic resonance imaging in the analysis of pediatric orbital tumors: utility of diffusion-weighted imaging

PURPOSE

To identify common radiographic features of pediatric orbital tumors by the use of magnetic resonance imaging (MRI) techniques, diffusion-weighted imaging (DWI), fat saturated T2, and pre- and postgadolinium T1. DWI is hypothesized to help identify and predict the malignancy of specific brain tumors. To our knowledge, a similar analysis in which the authors have used this combination of MRI techniques has not been performed with orbital tumors.

METHODS

We performed a retrospective chart review of all patients younger than 18 years of age, each diagnosed with an orbital mass lesion, imaged by MRI from 2005 to 2008. The MR images were analyzed by use of the aforementioned techniques.

RESULTS

Mass lesions identified in the chart review included rhabdomyosarcoma (n = 4), myofibroma (n = 2), hemangioma (n = 4), lymphangioma (n = 2), neurofibroma (n = 4), Langerhans histiocytosis (n = 2), and one of each of the following: giant cell tumor, meningioma, lymphoid hyperplasia of the lacrimal gland (chronic sclerosing sialadenitis), optic nerve glioma, lipodermoid, and dermoid. DWI was used to differentiate tumors into those with increased diffusion, restricted diffusion, and a mixed diffusion pattern. Capillary hemangiomas and rhabdomyosarcomas 2 tumors with potentially overlapping appearances with traditional MRI techniques had contrasting appearances with DNI.

CONCLUSIONS

DWI can help to distinguish among certain pediatric orbital tumors when combined with traditional MRI techniques. This technique may thus be considered an additional tool to help, refine the differential diagnosis of orbital tumors in children.

Utility of diffusion-weighted MRI in characterization of adrenal lesions

OBJECTIVE

The purpose of our study was to evaluate the utility of apparent diffusion coefficient (ADC) values for characterizing adrenal lesions and determine if diffusion-weighted imaging (DWI) can distinguish lipid-rich from lipid-poor adenomas.

MATERIALS AND METHODS

We retrospectively evaluated 160 adrenal lesions in 156 patients (96 women and 60 men; mean age, 63 years). ADCs and signal intensity (SI) decrease on chemical shift imaging were measured in adrenal lesions with a wide variety of pathologies. Lipid-rich and lipid-poor adenomas were identified by unenhanced CT. The overall predictive power of ADC, SI decrease, and lesion size were determined by receiver operating characteristic (ROC) analysis. Areas under the ROC curve (AUC) were compared for equivalence using nonparametric methods. Sensitivity, specificity, and positive and negative predictive values were calculated. Correlation coefficients were used to assess ADCs versus percentage SI decrease and ADCs versus CT attenuation.

RESULTS

ADCs of adrenal malignancies (median, 1.67 x 10(-3) mm(2)/s; interquartile range, 1.41-1.84 x 10(-3) mm(2)/s) were not different compared with those of benign lesions (1.61 x 10(-3) mm(2)/s; 1.27-1.96 x 10(-3) mm(2)/s; p > 0.05). Cysts (2.93 x 10(-3) mm(2)/s; 2.70-3.09 x 10(-3) mm(2)/s) showed higher ADCs than the remaining adrenal lesions (p < 0.05). The median ADCs of lipid-rich adenomas did not differ from those of lipid-poor ones (p > 0.05). The CT attenuation had no negative or positive correlation with the ADCs of adrenal adenomas (r = -0.05, p = 0.97).

CONCLUSION

Unlike lesion size and percentage decrease in SI, the ADCs were not useful in distinguishing benign from malignant adrenal lesions. Lipid-poor adenomas could not be distinguished from lipid-rich adenomas and all other nonfatty lesions of the adrenal gland with DWI.

Characterization of genitourinary lesions with diffusion-weighted imaging

Diffusion-weighted imaging has been widely accepted as a powerful imaging technique in neuroradiology. Until recently, the inclusion of diffusion-weighted sequences in body imaging protocols has been hindered by technical limitations. However, with advances in magnetic resonance (MR) imaging technology and technique, these limitations are being overcome. The addition of diffusion-weighted sequences to routine abdominopelvic MR imaging protocols has been found to yield diagnostically useful information with only a minimal increase in imaging time. More specifically, the use of diffusion-weighted imaging in the genitourinary system can facilitate the detection and characterization of genitourinary tract lesions that demonstrate equivocal signal intensity characteristics with routine MR imaging sequences. Diffusion-weighted imaging is not only helpful in differentiating benign from malignant processes, but it can also be used to assess meta-static lesions, possible tumor recurrence, and treatment response. Because it does not require injection of a gadolinium-based contrast agent, diffusion-weighted imaging can be used in patients with renal insufficiency or contrast material allergy. Most of the body diffusion-weighted imaging studies reported in the literature to date have been conducted with 1.5-T magnets. However, the feasibility of body diffusion-weighted imaging at 3.0 T is currently under investigation in an effort to determine the efficacy of the routine inclusion of diffusion-weighted imaging sequences in 3.0-T body MR imaging protocols.