The value of 15-minute delayed contrast-enhanced CT to differentiate hyperattenuating adrenal masses compared with chemical shift MR imaging

Objectives

To investigate the diagnostic performance of 15-min delayed contrast-enhanced computed tomography (15-DECT) compared with that of chemical shift magnetic resonance (CSMR) imaging in differentiating hyperattenuating adrenal masses and to perform subgroup analysis in underlying malignancy and non-malignancy.

Methods

This study included 478 adrenal masses in 453 patients examined with 15-DECT and 235 masses in 217 patients examined with CSMR. Relative percentage washout (RPW) and absolute percentage washout (APW) on 15-DECT, and signal intensity index (SII) and adrenal-to-spleen ratio (ASR) on CSMR were measured. Sensitivity, specificity and accuracy of 15-DECT and CSMR were analysed for characterisation of adrenal adenoma. Subgroup analyses were performed in patients with and without underlying malignancy. Attenuation and size of the masses on unenhanced CT correlated with the risk of non-adenoma.

Results

RPW calculated from 15-DECT showed the highest diagnostic performance for characterising hyperattenuating adrenal masses regardless of underlying malignancy, and the sensitivity, specificity and accuracy were 91.7 %, 74.8 % and 88.1 %, respectively in all patients. The risk of non-adenoma increased approximately threefold as mass size increased 1 cm or as its attenuation value increased by 10 Hounsfield units.

Conclusions

15-DECT was more accurate than CSMR in characterising hyperattenuating adrenal masses regardless of underlying malignancy.

Key Points

? Delayed contrast-enhanced CT and chemical shift magnetic resonance (CSMR) characterise adrenal lesions. ? 15-min DECT is more accurate than CSMR in characterising hyperattenuating adrenal masses. ? Sensitivity of CSMR decreases as the CT attenuation of adenomas increases. ? Risk of non-adenoma is increased 2.9-fold as size increased by 1 cm. ? Risk of non-adenoma is increased 2.9-fold as attenuation increased by 10 HU.     

Can single-phase dual-energy CT reliably identify adrenal adenomas?

Purpose

To evaluate whether single-phase dual-energy-CT-based attenuation measurements can reliably differentiate lipid-rich adrenal adenomas from malignant adrenal lesions.

Materials and methods

We retrospectively identified 51 patients with adrenal masses who had undergone contrast-enhanced dual-energy-CT (140/100 or 140/80 kVp). Virtual non-contrast and colour-coded iodine images were generated, allowing for measurement of pre- and post-contrast density on a single-phase acquisition. Adrenal adenoma was diagnosed if density on virtual non-contrast images was ≤10 HU. Clinical follow-up, true non-contrast CT, PET/CT, in- and opposed-phase MRI, and histopathology served as the standard of reference.

Results

Based on the standard of reference, 46/57 (80.7 %) adrenal masses were characterised as adenomas or other benign lesions; 9 malignant lesions were detected. Based on a cutoff value of 10 HU, virtual non-contrast images allowed for correct identification of adrenal adenomas in 33 of 46 (71 %), whereas 13/46 (28 %) adrenal adenomas were lipid poor with a density ≥10 HU. Based on the threshold of 10 HU on the virtual non-contrast images, the sensitivity, specificity, and accuracy for detection of benign adrenal lesions was 73 %, 100 %, and 81 % respectively.

Conclusion

Virtual non-contrast images derived from dual-energy-CT allow for accurate characterisation of lipid-rich adrenal adenomas and can help to avoid additional follow-up imaging.

Key Points

? Adrenal adenomas are a common lesion of the adrenal glands. ? Differentiation of benign adrenal adenomas from malignant adrenal lesions is important. ? Dual-energy based virtual non-contrast images help to evaluate patients with adrenal adenomas.     

Role of quantitative chemical shift magnetic resonance imaging and chemical shift subtraction technique in discriminating adenomatous from non adenomatous adrenal solid lesions

Purpose

To evaluate role of quantitative assessment of chemical shift MR imaging and chemical shift subtraction technique in differentiating adenomatous from non-adenomatous adrenal lesions with comparison of accuracy level of each technique.

Dynamic perfusion CT parameters and delayed contrast washout CT in characterization of adrenal tumors: A comparative study

Purpose

The study aims to compare the accuracy of washout and perfusion CT techniques in diagnosis of adrenal tumors.

Incidental adrenal lesions detected on enhanced abdominal dual-energy CT: Can the diagnostic workup be shortened by the implementation of virtual unenhanced images?

Objective

To determine whether post-processing of the data from portal-phase enhanced dual-energy CT (DECT), with or without the addition of a late enhanced phase acquisition, may enable characterization of adrenal lesions without the need for acquisition of pre-contrast images.

Materials and methods

Twenty-two patients with 24 adrenal lesions underwent unenhanced, venous and delayed phase DECT. Of these lesions, 20 were found to be adrenal adenomas, on the basis of histopathology, unenhanced attenuation values between 0 and −10 HU, or stability over at least 6 months.For all 24 lesions, true and virtual unenhanced attenuation values were measured based on the data of the portal (VNCp) and the delayed (VNCd) DECT acquisition. The absolute washout values based on the true non-contrast (TNC) and the VNCp and VNCd image series were also measured. The washout was also calculated based on the iodine concentration measured from both contrast-enhanced acquisitions.

Results

Mean virtual unenhanced attenuation values of all lesions calculated from the portal phase images was 12.6 HU, and was 4.02 HU higher than the values based on true unenhanced images (p = 0.020). Washout values calculated from virtual unenhanced attenuation based on the VNCp were also significantly different (p = 0.0304) while those calculated from VNCd and from iodine concentration correlated with the corresponding values based on the true unenhanced values (p > 0.999).

Conclusions

Our data indicate that attenuation values of adrenal adenomas based on virtual unenhanced images are significantly higher than those obtained with true unenhanced images. An incidental adrenal lesion with a virtual unenhanced attenuation lower than 10 HU can thus be safely characterized as an adenoma.     

Thrombus imaging in acute ischaemic stroke using thin-slice unenhanced CT: comparison of conventional sequential CT and helical CT

Objectives

Thin-slice helical unenhanced CT can be used for thrombus imaging but increases radiation exposure. Conventional sequential images obtained by multidetector CT can be reconstructed into thin-slice images. The purpose of this study was to evaluate if conventional sequential unenhanced CT images can replace helical unenhanced CT for thrombus imaging.

Methods

Fifty consecutive patients with acute ischaemic stroke underwent both 5-mm conventional sequential unenhanced CT and helical unenhanced CT. Each of the sequential and helical unenhanced CT images was subsequently reconstructed into four 1.25-mm images. Thrombus volumes and HU were measured semi-automatically using both types of unenhanced CT. Thrombus HU ratio (rHU) was calculated using the HU of the contralateral segment. The intraclass correlation coefficient (ICC) and Bland–Altman plots were used to assess measurement agreement.

Results

The mean rHUs were 1.47?±?0.17 for sequential unenhanced CT and 1.47?±?0.18 helical unenhanced CT (P?=?0.542). The mean thrombus volumes were 124.25?±?125.65?mm³ and 117.84?±?124.32?mm³ on sequential and helical unenhanced CT images, respectively (P?=?0.063). Measurement agreement between thrombus volumes from the two unenhanced CT images was high (ICC?=?0.981).

Conclusions

Thin-slice unenhanced CT images reconstructed from 5-mm sequential images can replace helical unenhanced CT for thrombus imaging in acute ischaemic stroke.

Key Points

? Unenhanced CT is used to evaluate intra-arterial thrombus. ? Thrombus HU and volume measurements using sequential or helical CT are comparable. ? Conventional sequential images can replace helical CT for thrombus imaging. ? Radiation dose for thrombus imaging can be reduced using sequential CT.     

Hepatocellular carcinoma in cirrhotic patients: prospective comparison of US, CT and MR imaging

Objectives

To prospectively compare the diagnostic performance of ultrasound (US), multidetector computed tomography (MDCT) and contrast-enhanced magnetic resonance imaging (MRI) in cirrhotic patients who were candidates for liver transplantation.

Methods

One hundred and forty consecutive patients with 163 hepatocellular carcinoma (HCC) nodules underwent US, MRI and MDCT. Diagnosis of HCC was based on pathological findings or substantial growth at 12-month follow-up. Four different image datasets were evaluated: US, MDCT, MRI unenhanced and dynamic phases, MRI unenhanced dynamic and hepatobiliary phase. Diagnostic accuracy, sensitivity, specificity, PPV and NPV, with corresponding 95 % confidence intervals, were determined. Statistical analysis was performed for all lesions and for three lesion subgroups (<1 cm, 1-2 cm, >2 cm).

Results

Significantly higher diagnostic accuracy, sensitivity and NPV was achieved on dynamic + hepatobiliary phase MRI compared with US, MDCT and dynamic phase MRI alone. The specificity and PPV of US was significantly lower than that of MDCT, dynamic phase MRI and dynamic + hepatobiliary phase MRI. Similar results were obtained for all sub-group analyses, with particular benefit for the diagnosis of smaller lesions between 1 and 2 cm.

Conclusions

Dynamic + hepatobiliary phase MRI improved detection and characterisation of HCC in cirrhotic patients. The greatest benefit is for diagnosing lesions between 1 and 2 cm.

Key Points

? US, CT and MRI can all identify HCC in cirrhotic patients ? US has good sensitivity but suffers from false-positive findings ? Dynamic CT and MR have similar diagnostic performance for diagnosing HCC ? Dynamic + hepatobiliary phase MRI significantly improves detection and characterisation of HCC ? The greatest benefit is for the diagnosis of lesions between 1 and 2 cm     

Discrimination and anatomical mapping of PET-positive lesions: comparison of CT attenuation-corrected PET images with coregistered MR and CT images in the abdomen

Purpose

PET/MR has the potential to become a powerful tool in clinical oncological imaging. The purpose of this prospective study was to evaluate the performance of a single T1-weighted (T1w) fat-suppressed unenhanced MR pulse sequence of the abdomen in comparison with unenhanced low-dose CT images to characterize PET-positive lesions.

Methods

A total of 100 oncological patients underwent sequential whole-body ¹⁸F-FDG PET with CT-based attenuation correction (AC), 40?mAs low-dose CT and two-point Dixon-based T1w 3D MRI of the abdomen in a trimodality PET/CT-MR system. PET-positive lesions were assessed by CT and MRI with regard to their anatomical location, conspicuity and additional relevant information for characterization.

Results

From among 66 patients with at least one PET-positive lesion, 147 lesions were evaluated. No significant difference between MRI and CT was found regarding anatomical lesion localization. The MR pulse sequence used performed significantly better than CT regarding conspicuity of liver lesions (p?<?0.001, Wilcoxon signed ranks test), whereas no difference was noted for extrahepatic lesions. For overall lesion characterization, MRI was considered superior to CT in 40?% of lesions, equal to CT in 49?%, and inferior to CT in 11?%.

Conclusion

Fast Dixon-based T1w MRI outperformed low-dose CT in terms of conspicuity and characterization of PET-positive liver lesions and performed similarly in extrahepatic tumour manifestations. Hence, under the assumption that the technical issue of MR AC for whole-body PET examinations is solved, in abdominal PET/MR imaging the replacement of low-dose CT by a single Dixon-based MR pulse sequence for anatomical lesion correlation appears to be valid and robust.     

Radiation dose from multidetector row CT imaging for acute stroke

Introduction

The objective of this study was to determine the radiation dose delivered during comprehensive computed tomography (CT) imaging for acute stroke.

Methods

All CT examinations performed over 18 months using our acute stroke protocol were included. Protocol includes an unenhanced CT head, CT angiography from the arch to vertex, CT perfusion/permeability, and an enhanced CT head. All imaging was acquired with a 64-MDCT. Examinations where any element of the protocol was repeated or omitted due to mistimed injection or patient motion were excluded. Dose-length products (DLP) for all components of each examination were obtained from dose reports generated at the time of acquisition, separating neck, and head calculations. Effective doses for each examination were calculated using the DLP and normalized values of effective dose per DLP appropriate for the body regions imaged.

Results

Ninety-five examinations were included. Mean DLP was 6,790.0 mGy·cm. Effective doses ranged from 11.8 to 27.3 mSv, mean effective dose of 16.4 mSv. Mean effective dose for acquisition of the unenhanced head was 2.7 mSv. Largest contribution to effective dose was the CTA with a mean effective dose of 5.4 mSv. Mean effective dose for the CT perfusion was 4.9 mSv.

Conclusion

A comprehensive CT acute stroke protocol delivered a mean effective dose of 16.4 mSv, which is approximately six times the dose of an unenhanced CT head. These high-dose results must be balanced with the benefits of the detailed anatomic and physiologic data obtained. Centers should implement aggressive dose reduction strategies and freely use MR as a substitute.     

Adrenal neoplasms

Adenoma, myelolipoma, phaeochromocytoma, metastases, adrenocortical carcinoma, neuroblastoma, and lymphoma account for the majority of adrenal neoplasms that are encountered in clinical practice. A variety of imaging methods are available for evaluating adrenal lesions including ultrasound, computed tomography (CT), magnetic resonance imaging (MRI), and nuclear medicine techniques such as meta-iodobenzylguanidine (MIBG) scintigraphy and positron-emission tomography (PET). Lipid-sensitive imaging techniques such as unenhanced CT and chemical shift MRI enable detection and characterization of lipid-rich adenomas based on an unenhanced CT attenuation of ≤10?HU and signal loss on opposed-phase compared to in-phase T1-weighted images, respectively. In indeterminate cases, an adrenal CT washout study may differentiate adenomas (both lipid-rich and lipid-poor) from other adrenal neoplasms based on an absolute percentage washout of >60% and/or a relative percentage washout of >40%. This is based on the principle that adenomas show rapid contrast washout while most other adrenal neoplasms including malignant tumours show slow contrast washout instead. (18)F-2-fluoro-2-deoxy-d-glucose-PET ((18)FDG-PET) imaging may differentiate benign from malignant adrenal neoplasms by demonstrating high tracer uptake in malignant neoplasms based on the increased glucose utilization and metabolic activity found in most of these malignancies. In this review, the multi-modality imaging appearances of adrenal neoplasms are discussed and illustrated. Key imaging findings that facilitate lesion characterization and differentiation are emphasized. Awareness of these imaging findings is essential for improving diagnostic confidence and for reducing misinterpretation errors.     

Renal imaging at 7 Tesla: preliminary results

Objective

To investigate the feasibility of 7T MR imaging of the kidneys utilising a custom-built 8-channel transmit/receive radiofrequency body coil.

Methods

In vivo unenhanced MR was performed in 8 healthy volunteers on a 7T whole-body MR system. After B₀ shimming the following sequences were obtained: 1) 2D and 3D spoiled gradient-echo sequences (FLASH, VIBE), 2) T1-weighted 2D in and opposed phase 3) True-FISP imaging and 4) a T2-weighted turbo spin echo (TSE) sequence. Visual evaluation of the overall image quality was performed by two radiologists.

Results

Renal MRI at 7T was feasible in all eight subjects. Best image quality was found using T1-weighted gradient echo MRI, providing high anatomical details and excellent conspicuity of the non-enhanced vasculature. With successful shimming, B₁ signal voids could be effectively reduced and/or shifted out of the region of interest in most sequence types. However, T2-weighted TSE imaging remained challenging and strongly impaired because of signal heterogeneities in three volunteers.

Conclusion

The results demonstrate the feasibility and diagnostic potential of dedicated 7T renal imaging. Further optimisation of imaging sequences and dedicated RF coil concepts are expected to improve the acquisition quality and ultimately provide high clinical diagnostic value.     

Imaging findings of primary adrenal tumors in pediatric patients

Apart from neuroblastomas, adrenal tumors are rarely seen in children. The most common adrenal tumors are adrenocortical carcinoma and pheochromocytoma. Adrenocortical carcinoma is usually a large heterogeneous, well-marginated mass with solid/cystic areas and calcifications, with poor prognosis. Most of the pheochromocytomas are benign tumors and usually show intense contrast enhancement, the pattern of which may be diffuse, mottled, or peripheral on computed tomography and magnetic resonance imaging. The purpose of this article is to evaluate primary nonneurogenic adrenal tumors.

In children, neoplastic and non-neoplastic lesions might be seen in the adrenal region. Pediatric adrenal lesions may be found incidentally, can be suspected in children that suffer endocrine, metabolic, neurological problems or with an abdominal mass. In fetal life, adrenal glands are much larger than in adults because of the existence of a prominent fetal cortex. Their prominent fetal size is also seen in early neonatal life. Ultrasonography (US) is the initial imaging technique to examine the adrenal glands in newborns. In older children, due to the physiologic atrophy of the fetal adrenal cortex, adrenal limbs are thinner than the adjacent crura of the diaphragm. Consequently, they are much more difficult to specify with US, but can be easily identified on computed tomography (CT) or magnetic resonance imaging (MRI). US is the primary modality for imaging the pediatric abdomen. CT or MRI are used as a problem-solving tool for lesion characterization, to determine the relationship to adjacent tissues, and to differentiate benign from malignant masses after initial US evaluation (1). In older children MRI should be preferred rather than CT examination. In adults, abdominal CT examinations assess tumor washout of contrast material based upon multi-phase CT, which is necessary to characterize adrenocortical masses (especially adenomas). However, pediatric CT examinations should be done in single portal venous phase to comply with “Image Gently” and “as low as reasonably achievable” (ALARA) principles.Primary adrenal tumors are classified according to their origin and function. They might originate from the medulla or cortex, and they are hyperfunctioning or nonfunctioning. Primary medullary tumors encompass a spectrum of sympathetic neuroectodermal tumors, which are neuroblastoma, ganglioneuroblastoma, ganglioneuroma, and pheochromocytoma, all of which stem from the neural crest and may take place anywhere along the sympathetic chain aside from the adrenal gland itself. Neoplasms arising from the adrenal cortex are adrenocortical carcinoma and adenoma.In the literature, few studies have reported imaging findings of pediatric adrenal tumors, including all types of involvement (i.e., benign, malignant, and metastatic) (1–3). The aim of this article is to describe the imaging findings of primary nonneurogenic adrenal tumors.     

Pheochromocytoma as a frequent false-positive in adrenal washout CT: A systematic review and meta-analysis

Objective

To evaluate the proportion of pheochromocytomas meeting the criteria for adenoma on adrenal washout CT and the diagnostic performance of adrenal washout CT for differentiating adenoma from pheochromocytoma.

Methods

MEDLINE and EMBASE were searched to 28 March 2017. We included studies that used adrenal washout CT for characterisation of pheochromocytomas. Two independent reviewers assessed the methodological quality using Quality Assessment of Diagnostic Accuracy Studies-2. Proportions were pooled using an inverse variance method for calculating weights (random-effects). Sensitivity and specificity were pooled using hierarchical logistic regression modelling and plotted in a hierarchical summary receiver-operating-characteristics (HSROC) plot.

Results

Ten studies (114 pheochromocytomas) were included. The pooled proportion of pheochromocytomas meeting the criteria for adenomas was 35 % (95 % CI 20–51). For eight studies providing information on diagnostic performance, the pooled sensitivity and specificity for differentiating adenoma from pheochromocytoma were 0.97 (95 % CI 0.93–0.99) and 0.67 (95 % CI 0.44–0.84), respectively. The area under the HSROC curve was 0.97 (95 % CI 0.95–0.98).

Conclusions

There was a non-negligible proportion of pheochromocytomas meeting the criteria for adenoma on adrenal washout CT. Although overall diagnostic performance was excellent for differentiating adenoma from pheochromocytoma, specificity was relatively low.

Key Points

? Non-negligible proportion of pheochromocytomas can be mistaken for adenoma. ? Adrenal washout CT showed good sensitivity (97%) but relatively low specificity (67%). ? Findings other than washout percentage should be used when diagnosing pheochromocytomas

     

Urinary stone detection and characterisation with dual-energy CT urography after furosemide intravenous injection: preliminary results

Objectives

To investigate the added advantage of IV furosemide injection and the subsequent urine dilution in the detection of urinary calculi in the excretory phase of dual-source dual-energy (DE) computed tomography (CT) urography, and to investigate the feasibility of characterising the calculi through diluted urine.

Methods

Twenty-three urinary calculi were detected in 116 patients who underwent DECT urography for macroscopic haematuria with a split bolus two- or three-acquisition protocol, including a true unenhanced series and at least a mixed nephrographic excretory phase. Virtual unenhanced images were reconstructed from contrast-enhanced DE data. Calculi were recorded on all series and characterised based on their X-ray absorption characteristics at 100 kVp and 140 kVp in both true unenhanced and nephrographic excretory phase series.

Results

All calculi with a diameter more than 2 mm were detected in the virtual unenhanced phase and in the nephrographic excretory phase. Thirteen of these calculi could be characterised in the true unenhanced phase and in the mixed nephrographic excretory phase. The results were strictly identical for both phases, six of them being recognised as non-uric acid calculi and seven as uric acid calculi.

Conclusions

Mixed nephrographic excretory phase DECT after furosemide administration allows both detection and characterisation of clinically significant calculi, through the diluted urine.

Key points

? Urinary tract stones can be detected on excretory phase through diluted urine. ? Urinary tract stone characterisation with dual-energy CT (DECT) is possible through diluted urine. ? A dual energy split-bolus CT urography simultaneously enables urinary stone detection and characterisation.     

Cerebral venous thrombosis: role of CT, MRI and MRA in the emergency setting

Purpose

It is often difficult to diagnose cerebral venous thrombosis (CVT), an uncommon condition that more frequently affects young subjects, is responsible for 1%–2% of strokes in adults and has a subtle clinic onset. The aim of this study was to evaluate the role of computed tomography (CT), magnetic resonance imaging (MRI) and MR venography in the emergency setting and to discuss the risk factors, clinical presentation, outcome and follow-up of this disease.

Materials and methods

We retrospectively studied 40 patients with CVT admitted to the emergency department between 1996 and 2006 and examined with unenhanced CT, MRI and MR venography. Fourteen patients also underwent digital subtraction angiography (DSA).

Results

Headache was the most common presenting feature (60%). Unenhanced CT showed typical signs (cord or empty delta sign) in 11 cases and nonspecific signs in the other cases. The diagnosis was achieved with MRI and MR venography in 38/40 cases (95%) and with DSA in 2/40 cases. All patients were treated with heparin. Five patients died, and only one of the remaining patients developed serious disability.

Conclusions

Knowledge of the CT, MRI and MR-venography signs of CVT is crucial and enables an early diagnosis and timely treatment with heparin in the majority of cases. DSA should be reserved for doubtful cases only.     

Diagnostic accuracy of contrast-enhanced MR angiography and unenhanced proton MR imaging compared with CT pulmonary angiography in chronic thromboembolic pulmonary hypertension

Objective

To evaluate the diagnostic accuracy of contrast-enhanced MR angiography (CE-MRA) and the added benefit of unenhanced proton MR angiography compared with CT pulmonary angiography (CTPA) in patients with chronic thromboembolic disease (CTE).

Methods

A 2?year retrospective study of 53 patients with chronic thromboembolic pulmonary hypertension who underwent CTPA and MRI for suspected pulmonary hypertension and a control group of 36 patients with no CT evidence of pulmonary embolism. The MRI was evaluated for CTE and the combined diagnostic accuracy of ce-MRA and unenhanced proton MRA was determined. CE-MRA generated lung perfusion maps were also assessed.

Results

The overall sensitivity and specificity of CE-MRA in diagnosing proximal and distal CTE were 98% and 94%, respectively. The sensitivity improved from 50% to 88% for central vessel disease when CE-MRA images were analysed with unenhanced proton MRA. The CE-MRA identified more stenoses (29/18), post-stenosis dilatation (23/7) and occlusions (37/29) compared with CTPA. The CE-MRA perfusion images showed a sensitivity of 92% for diagnosing CTE.

Conclusion

CE-MRA has high sensitivity and specificity for diagnosing CTE. The sensitivity of CE-MRA for visualisation of adherent central and lobar thrombus significantly improves with the addition of unenhanced proton MRA which delineates the vessel wall.     

Differentiation of adrenal adenomas from nonadenomas using CT histogram analysis method: A prospective study

Objective

The objective of our study was to prospectively evaluate the effectiveness of computed tomography (CT) histogram analysis method in the differentiation of benign and malignant adrenal masses.

Materials and Methods

Between March 2007 and June 2008, 94 patients (46 males, 48 females, age range: 30-79 years, mean age: 57.7 years) with 113 adrenal masses (mean diameter: 3.03 cm, range: 1.07-8.02 cm) were prospectively evaluated. These included 66 adenomas, 45 metastases and 2 pheochromocytomas. Histogram analysis method was performed using a circular region of interest (ROI) and mean attenuation, total number of pixels, number of negative pixels and subsequent percentage of negative pixels were detected on both unenhanced and delayed contrast-enhanced CT images for each adrenal mass. A mean attenuation threshold of 10 Hounsfield unit (HU) for unenhanced CT and 5% and 10% negative pixel thresholds for both unenhanced and delayed contrast-enhanced CT were calculated by a consensus of at least two reviewers and the correlation between mean attenuation and percentage of negative pixels was determined. Final diagnoses were based on imaging follow-up of minimum 6 months, biopsy, surgery and adrenal washout study.

Results

51 of 66 adenomas (77.3%) showed attenuation values of ≤10 HU and 15 (22.7%) adenomas showed more than 10 HU on unenhanced CT. All of these adenomas contained negative pixels on unenhanced CT. Eight of 66 (12.1%) adenomas showed a mean attenuation value of ≤10 HU on delayed contrast-enhanced scans and 45 adenomas (68.2%) persisted on containing negative pixels. All metastases had an attenuation value of greater than 10 HU on unenhanced CT images. 21 of 45 (46.6%) metastases contained negative pixels on unenhanced images but only seven metastases (15.5%) had negative pixels on delayed contrast-enhanced images. Two pheochromocytomas had negative pixels on both unenhanced and delayed contrast-enhanced CT images. Increase in the percentage of negative pixels yielded high correlation with mean attenuation decreases, both on unenhanced and delayed contrast-enhanced CT. Our sensitivity was 90.9% for the 10% negative pixel percentage threshold compared to 77.2% sensitivity for ≤10 HU mean attenuation threshold for unenhanced CT. Both methods gave a 100% specificity for the diagnosis of adenoma. We also obtained a 37.9% sensitivity for 5% negative pixel threshold and a slightly lower sensitivity of 28.8% for 10% negative pixel threshold compared to the 12.1% sensitivity of ≤10 HU mean attenuation threshold while maintaining 100% specificity for contrast-enhanced CT.

Conclusion

The CT histogram analysis is a simple and easily applicable method which provides higher sensitivity than the commonly used 10 HU threshold mean attenuation method of unenhanced CT and can replace it for the diagnosis of an adenoma. But with contrast-enhanced CT, although 100% specificity is being maintained, the sensitivities obtained are very poor for each method and is therefore likely to limit CT histogram analysis to be used as a clinically useful adjunct in the diagnosis of adenoma.     

Cerebral amyloid angiopathy-related inflammation: imaging findings and clinical outcome

Introduction

We aim to investigate the clinical onset, computed tomography (CT) and magnetic resonance (MR) imaging findings, and follow-up of patients with cerebral amyloid angiopathy (CAA)-related inflammation, an uncommon but clinically striking presentation of CAA.

Methods

We retrospectively reviewed the clinical manifestations, CT/MR imaging findings, and outcome of ten consecutive patients with CAA-related inflammation. In each patient, a brain CT study was performed at hospital admission, and brain MR imaging was carried out 2 to 4 days later. Clinical and radiologic follow-up findings were evaluated in all patients.

Results

The most common clinical onset was rapidly progressive cognitive decline, followed by focal neurological signs. Brain CT/MR showed unenhanced expansive subcortical lesions, corresponding to areas of vasogenic edema, associated with chronic lobar, cortical, or cortical–subcortical micro/macrohemorrhages. Clinical symptoms recovered in a few weeks under treatment in eight patients and spontaneously in the remaining two. MRI follow-up at 2 to 12 months after treatment showed resolution of the lesions. Three patients experienced symptomatic disease recurrence, with new lesions on CT/MR.

Conclusion

In the absence of histological data, early recognition of the clinical symptoms and typical radiologic features of CAA-related inflammation is essential to enable timely establishment of proper treatment.     

PET/MRT in der Herzbildgebung

Clinical/methodical issue

The positron emission tomography/magnetic resonance imaging (PET/MRI) technique represents a new hybrid imaging modality in nuclear cardiology.

Standard radiological methods

The standard radiological method in this field is PET/computed tomography (CT).

Methodical innovations

For morphological correlation MRI is used instead of CT. Furthermore, the creation of attenuation maps (μ-maps) has to be accomplished using MRI data.

Performance

For this new hybrid imaging modality only limited data are so far available, especially in the field of nuclear cardiology; however, the available data show a relatively good agreement between both modalities with the PET/CT as the modality of reference.

Achievements

In comparison to PET/CT a major advantage of PET/MRI is the lower radiation dose to the patient; however, the more complex workflow using this new imaging modality also has to be taken into account. Furthermore, some indications are still at an experimental stage using the PET/MRI.

Practical recommendations

In daily practice, PET/MRI should be considered especially in younger patients due to the lower exposure to radiation. Furthermore, there are some advantages for this modality in the field of nuclear cardiology, such as imaging of inflammatory myocardial processes (e.g. cardiac sarcoidosis) or myocardial viability imaging.     

Are the washout values currently accepted for lesion characterization in dedicated adrenal CT adequate for diagnosis?

PURPOSEWe aimed to investigate the accuracy of density characteristics and washout values of lesions detected on computed tomography (CT) at the cutoff values obtained from the literature by taking the pathological results of adrenalectomy specimens as reference and to determine the cutoff values of parameters evaluated on CT for the differentiation of adenoma and nonadenoma lesions in the study group.METHODSHospital records and standard CT imaging data (noncontrast early phase [65 s] and late phase [15 min] ) of 84 patients with 87 lesions who underwent adrenalectomy between January 2012 and December 2018 were retrospectively reevaluated by two radiologists in consensus. The patients were categorized as having adenoma and nonadenoma lesions according to the pathology results. The sensitivity, specificity and diagnostic accuracy of CT parameters (density values and washout percentages) were evaluated. Differences in the CT parameters (size, noncontrast and early-late enhancement density and absolute and relative washout values) were investigated. The optimal cutoff values of CT parameters were determined by ROC analysis.RESULTSNoncontrast CT had a specificity of 87.75% and 95.9%, sensitivity of 60% and 48.6%, diagnostic accuracy of 77.7% and 89.47% for adenomas, at the cutoff values of ≤10 HU and ≤0 HU, respectively. For absolute washout value ≥ 60%, the sensitivity, specificity and accuracy were 64.7%, 52.38% and 56.75%, respectively; while these rates were 76.47%, 56.52% and 62.16%, respectively, for relative washout value ≥40%. Adenomas and nonadenomas showed significant difference in terms of size (p < 0.0001), unenhanced attenuation (p < 0.0001), relative washout (p = 0.020) and delay enhancement (p < 0.001). But there were no differences in terms of absolute washout (p = 0.230) and early enhancement (p = 0.264). The cutoff values for the differentiation of adenomas and nonadenomas were as follows: size ≤44 mm, noncontrast density <20 HU, early-phase density ≥45 HU, delayed-phase density ≤44 HU, absolute washout 74.83% and relative washout 57.76%.CONCLUSIONThe current washout criteria used in the differentiation of adenoma and nonadenoma lesions in dynamic CT imaging can give false negative and positive results. According to the existing criteria, the most reliable parameter in adenoma–nonadenoma differentiation is ≤ 0 HU noncontrast CT density value.

According to the autopsy studies, adrenal masses are among the most common tumors detected in humans (1). In autopsy series, this prevalence has been reported as 1% to 9.8% (1). With the advances in imaging techniques and their increasing use, there has also been a recent increase in radiologically reported adrenal masses (2–5), varying between 0.35% and 5% for CT examinations (6). Adenomas are the most common adrenal lesions in patients without primary malignancy (1, 7, 8). Although adrenal gland is a common site for distant metastases in patients with known malignancies, adenomas are more common than metastases in these patients. Since the majority of adrenal adenomas are benign and nonfunctional lesions, a clinical and radiological follow-up is sufficient. In nonadenoma lesions, a biopsy or direct surgical resection can be recommended according to the characteristics of the patient. Therefore, determination of whether a detected adrenal mass is an adenoma or nonadenoma is critically important in patient management and changes the form of treatment (9).Computed tomography (CT) is the radiological method of choice in the characterization of adrenal mass lesions (8, 10). Adenomas have low density values in noncontrast CT scans due to their intracytoplasmic fat content (3, 6, 10, 11). However, as much as 30% of adrenal adenomas are poor in fat, thus making it impossible to distinguish them from other masses based on noncontrast CT density (8, 10). In this case, most authors reported that the washout character determined by dynamic contrast-enhanced CT examination differentiates adrenal adenomas from other lesions (10–13). Due to their rich capillary network, adenomas are stained early with the contrast agent, causing them to exhibit a high level of washout (8). However, some nonadenoma lesions, particularly pheochromocytoma, have been reported to show a similar washout pattern (4, 14–18). In the literature, there are many studies that investigated noncontrast and contrast-enhanced CT density and the washout criterion for the differentiation of adenoma and nonadenoma lesions (4, 6, 10–18). However, the scan parameters used in these studies, the characteristics of the devices, the time of wash-in and washout, contrast agent dose, and iodine concentration are not standard and show differences (e.g., 2.5–10 mm collimation; 3–5 mm reconstruction intervals; 80–140 kVp; 150–370 mA; 0.75–3:1 pitch; nonhelical, helical, or multi-slice device; 35–120 s wash-in time; 3–45 min washout time; 100–150 mL contrast agent dose; 300–370 mg/L iodine concentration). In a study using different minutes as washout criteria in the same lesions, different specificity and sensitivity values were found according to the washout time (19). In studies evaluating the effectiveness of adrenal CT in the literature, the reference method also differs. For these reasons, the available literature data is far from being standard. Nonadenoma lesions, which are evaluated as adenoma based on the available data, may cause serious problems in patient management.In the current study, we aimed to investigate the accuracy of density characteristics and washout values of lesions detected on CT at the cutoff values obtained from the literature by taking the pathological results of adrenalectomy specimens as reference to determine the cutoff values of parameters evaluated on CT for the differentiation of adenoma and nonadenoma lesions in the study group.