MR imaging of solitary pulmonary lesion: emphasis on tuberculomas and comparison with tumors

Differential diagnosis of uncommon prostate diseases: combining mpMRI and clinical information

The differential diagnosis of abnormalities in the prostate is broad, covering common (acinar adenocarcinoma, benign prostatic hyperplasia, chronic prostatitis, hemorrhage, cysts, calcifications, atrophy and fibrosis) and less common conditions (tumors other than acinar adenocarcinoma, granulomatous prostatitis containing tuberculosis, abscesses and other conditions, and idiopathic disorders such as amyloidosis and exophytic benign prostatic hyperplasia). Recent advances in magnetic resonance imaging (MRI) of the prostate gland and imaging guidelines, such as the Prostate Imaging Reporting and Data System version 2.1 (PI-RADS v2.1), have dramatically improved the ability to distinguish common abnormalities, especially the ability to detect clinically significant prostate cancer (csPCa). Overlap can exist in the clinical history and imaging features associated with various common/uncommon prostate abnormalities, and biopsy is often required but is invasive. Prostate abnormalities can be divided into two categories: category 1, diseases for which PI-RADS scores are suitable for use, and category 2, diseases for which PI-RADS scores are unsuitable for use. Radiologists must have an intimate knowledge of other diseases, especially uncommon conditions. Past relevant history, symptoms, age, serum prostate-specific antigen (PSA) levels, MRI manifestations, and the applicability of the PI-RADS assessment should be considered when diagnosing prostate abnormalities.

3T magnetic resonance for evaluation of adult pulmonary tuberculosis

OBJECTIVES

To evaluate image quality and detection rate of four 3T magnetic resonance imaging (MRI) sequences and MRI performances in pulmonary tuberculosis (TB) when compared to computed tomography (CT).

METHODS

Forty patients with pulmonary tuberculosis separately underwent CT and 3T-MRI with T1-weighted free-breathing star-volumetric interpolated breath-hold examination (Star-VIBE) and standard VIBE, T2-weighted two-dimensional fast BLADE turbo spin-echo (2D-fBLADE TSE) and three-dimensional isotropic turbo spin-echo (3D-SPACE). Four MRI sequences were compared in terms of detection rate and image quality, which consisted of signal to noise ratio (SNR), contrast to noise ratio (CNR) and 5-point scoring scale. The total sensitivity was also compared between CT and MRI. Inter-observer agreement on 5-point scoring scale was calculated by Cohen's kappa (k). SNR, CNR and 5-point scoring scale were compared using two-tailed pared t-test. Using CT as a reference, the MRI detection rate of pulmonary abnormality was evaluated by Pearson's Chi-square test. Furthermore, the sizes of the nodules (≥5 mm) were compared using intraclass correlation coefficient.

RESULTS

In this study, Free-breathing Star-VIBE had significantly better SNR and identical CNR compared with standard VIBE. 2D-fBLADE TSE had statistically higher SNR but uniform or inferior CNR compared with 3D-SPACE. Inter-observers showed excellent agreement on 5-point scoring scale. The average score of Star-VIBE and VIBE had no difference. The average score of 2D-fBLADE TSE was higher than 3D-SPACE. There were no statistical differences in the detection rates of non-calcified parenchymal lesions between Star-VIBE and standard VIBE, 2D-fBALDE TSE and 3D-SPACE. MRI is comparable to CT in detecting consolidation, cavity, non-calcified nodules of ≥5 mm and tree-in-bud signs compared to CT. MRI detected non-calcified nodules of ＜5 mm, 5-10 mm, ≥10 mm and calcified nodules with sensitivity of 69.6%, 90.6%, 100% and 89.5% respectively. In addition, the sizes of the nodules (≥5 mm) had statistical consistency. MRI is more sensitive in detecting caseous necrosis, liquefaction, active cavity, abnormalities of lymph nodes and pleura.

CONCLUSIONS

T1-weighted free-breathing Star-VIBE and T2-weighted 2D-fBLADE TSE, both with satisfactory image quality, are suitable for patients with pulmonary TB who need long-term follow-ups in clinical routine, especially for children, young women and pregnant women.

Molecular Imaging of Pulmonary Inflammation and Infection

Infectious and inflammatory pulmonary diseases are a leading cause of morbidity and mortality worldwide. Although infrequently used in this setting, molecular imaging may significantly contribute to their diagnosis using techniques like single photon emission tomography (SPET), positron emission tomography (PET) with computed tomography (CT) or magnetic resonance imaging (MRI) with the support of specific or unspecific radiopharmaceutical agents. ¹⁸F-Fluorodeoxyglucose (¹⁸F-FDG), mostly applied in oncological imaging, can also detect cells actively involved in infectious and inflammatory conditions, even if with a low specificity. SPET with nonspecific (e.g., ⁶⁷Gallium-citrate (⁶⁷Ga citrate)) and specific tracers (e.g., white blood cells radiolabeled with ¹¹¹Indium-oxine (¹¹¹In) or ^99mTechnetium (^99mTc)) showed interesting results for many inflammatory lung diseases. However, ⁶⁷Ga citrate is unfavorable by a radioprotection point of view while radiolabeled white blood cells scan implies complex laboratory settings and labeling procedures. Radiolabeled antibiotics (e.g., ciprofloxacin) have been recently tested, although they seem to be quite unspecific and cause antibiotic resistance. New radiolabeled agents like antimicrobic peptides, binding to bacterial cell membranes, seem very promising. Thus, the aim of this narrative review is to provide a comprehensive overview about techniques, including PET/MRI, and tracers that can guide the clinicians in the appropriate diagnostic pathway of infectious and inflammatory pulmonary diseases.

Management of incidental pulmonary nodules: current strategies and future perspectives

Introduction: Detection and characterization of pulmonary nodules is an important issue, because the process is the first step in the management of lung cancers.Areas covered: Literature review was performed on May 15 2019 by using the PubMed, US National Library of Medicine National Institutes of Health, and the National Center for Biotechnology information. CT features helping identify the druggable mutations and predict the prognosis of malignant nodules were presented. Technical advancements in MRI and PET/CT were introduced for providing functional information about malignant nodules. Advances in various tissue biopsy techniques enabling molecular analysis and histologic diagnosis of indeterminate nodules were also presented. New techniques such as radiomics, deep learning (DL) technology, and artificial intelligence showing promise in differentiating between malignant and benign nodules were summarized. Recently, updated management guidelines for solid and subsolid nodules incidentally detected on CT were described. Risk stratification and prediction models for indeterminate nodules under active investigation were briefly summarized.Expert opinion: Advancement in CT knowledge has led to a better correlation between CT features and genomic alterations or tumor histology. Recent advances like PET/CT, MRI, radiomics, and DL-based approach have shown promising results in the characterization and prognostication of pulmonary nodules.

Differentiation of breast tuberculosis and breast cancer using diffusion-weighted, T2-weighted and dynamic contrast-enhanced magnetic resonance imaging

Background

The use of multi-parametric magnetic resonance imaging (MRI) in the evaluation of breast tuberculosis (BTB).

Objectives

To evaluate the value of diffusion-weighted imaging (DWI), T2-weighted (T2W) and dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI) in differentiating breast cancer (BCA) from BTB.

Method

We retrospectively studied images of 17 patients with BCA who had undergone pre-operative MRI and 6 patients with pathologically proven BTB who underwent DCE-MRI during January 2014 to January 2015.

Results

All patients were female, with the age range of BTB patients being 23–43 years and the BCA patients being 31–74 years. Breast cancer patients had a statistically significant lower mean apparent diffusion coefficient (ADC) value (1072.10 ± 365.14), compared to the BTB group (1690.77 ± 624.05, p = 0.006). The mean T2-weighted signal intensity (T2SI) was lower for the BCA group (521.56 ± 233.73) than the BTB group (787.74 ± 196.04, p = 0.020). An ADC mean cut-off value of 1558.79 yielded 66% sensitivity and 94% specificity, whilst the T2SI cut-off value of 790.20 yielded 83% sensitivity and 83% specificity for differentiating between BTB and BCA. The homogeneous internal enhancement for focal mass was seen in BCA patients only.

Conclusion

Multi-parametric MRI incorporating the DWI, T2W and DCE-MRI may be a useful tool to differentiate BCA from BTB.

Conventional MRI to detect the differences between mass-like tuberculosis and lung cancer

Background

The aim of this study was to investigate differences in the imaging features of mass-like tuberculosis and lung cancer on conventional MR sequences to improve the diagnostic ability for pulmonary masses.

Methods

Thirty patients with suspicious pulmonary lesions were enrolled and diagnosed with tuberculosis by pathology or comprehensive clinical diagnoses. Twenty-six cases of lung cancer were retrospectively analyzed. Transverse fat-suppressed T2-weighted (T2W) imaging and T1-weighted (T1W) imaging were obtained at 1.5 Tesla. The imaging characteristics of lesions on the T2W and T1W images were compared between the two groups. The imaging features of enlarged mediastinal lymph nodes on T2W images were studied and compared.

Results

On T2W images, there was a higher percentage of lesions containing hypointensity in the tuberculosis group (GTB) than in the lung cancer group (GLC) (P=0.004).The incidence of lesions demonstrating heterogeneous intensity was significantly greater in the GTB than in the GLC (70.0% vs. 7.7%, P=0.001). Approximately 92.3% of the lung cancer cases showed hyperintensity, a proportion substantially greater than that in the GTB (6.7%). On T1W images, more cases showed hyperintensity in the GTB than in the GLC (43.3% vs. 7.7%, P=0.003). The signal intensity ratios (SIRs) of the lesion to rhomboid muscle on T2W and T1W images were significantly different between the two groups. The mean intrasubject standard deviation (SD) of lesions in the GTB was markedly greater than that in the GLC on both T2W and T1W images. Benign mediastinal lymph nodes in the GTB showed a variety of signals on T2W images, whereas 80% of metastatic mediastinal lymph nodes displayed slight homogeneous hyperintensity, and this difference between the two groups was statistically significant.

Conclusions

Conventional MR sequences can reveal the essential differences between mass-like tuberculosis and lung cancer and may be helpful for discriminating pulmonary masses.

MRI for solitary pulmonary nodule and mass assessment: Current state of the art

Since the clinical introduction of magnetic resonance imaging (MRI), the chest has been one of its most challenging applications, and many physicists and radiologists have tried since the 1980s to use MR for assessment of different lung diseases as well as mediastinal and pleural diseases. Since then, however, technical advances in sequencing, scanners, and coils, adaptation of parallel imaging techniques, utilization of contrast media, and development of postprocessing tools have been reported by many basic and clinical researchers. As a result, state-of-the-art thoracic MRI is now substituted for traditional imaging techniques and/or plays a complementary role in the management of patients with various chest diseases, and especially in the detection of pulmonary nodules and in thoracic oncology. In addition, MRI has continued to be developed to help overcome the limitations of computed tomography (CT) and nuclear medicine examinations. It can currently provide not only morphological, but also functional, physiological, pathophysiological, and molecular information at 1.5T with a gradual shift from 1.5T to 3T MR systems. In this review, we focus on these recent advances in MRI for pulmonary nodule detection and pulmonary nodule and mass evaluation by using noncontrast-enhanced and contrast-enhanced techniques as well as new molecular imaging methods such as chemical exchange saturation transfer imaging for a comparison with other modalities such as single or multidetector row CT, 18F-fluoro-2-deoxyglucose positron emission tomography (FDG-PET), and/or PET/CT.

LEVEL OF EVIDENCE

4 Technical Efficacy: Stage 2 J. Magn. Reson. Imaging 2018;47:1437-1458.

Giant Cell Tumors of the Bone: Changes in Image Features after Denosumab Administration

Purpose:

To assess the clinical importance in the feature change in giant cell tumors of the bone (GCTB) after denosumab treatment, detected by MRI.

Methods:

In 12 patients, MRI and CT of GCTB obtained before and after the treatment retrospectively compared. The tumor size, the signal intensity (SI) ratio between the solid part of the GCTB and muscle, cystic part size, gadolinium enhancement and apparent diffusion coefficient (ADC) value were measured on MRI. The bone formation in the tumor was observed on CT and X-ray.

Results:

The mean number of denosumab injections was 19 ± 10. The follow-up period was up to 2 years. One case showed partial remission, while the other 11 cases were stable. A mean SI ratio on T₂-weighted image statistically significantly decreased from 3.9 to 1.9 after the treatment. A cystic component in the tumor was observed in five cases before the treatment, and the diameter of the cystic part decreased after the treatment in 80% of cases (4/5). All the tumors showed contrast enhancement on T₁-weighted image pre- and post-treatment (11/11). The averaged ADC values were 1.52 × 10⁻³ mm²/s before and 1.44 × 10⁻³ mm²/s after the treatment (P = 0.63). Bone formation in the tumor was observed in 58% of cases (7/12).

Conclusion:

The decrease of SI ratio on T₂-weighted image, shrinkage of cystic part and bone formation should be regarded as the effectiveness of denosumab treatment despite of no substantial change in the tumor size.

Multiparametric Magnetic Resonance Imaging Characteristics of Prostate Tuberculosis

Objective

To describe the multiparametric magnetic resonance imaging (MRI) appearance of prostate tuberculosis.

Materials and Methods

Six patients with prostate tuberculosis were analyzed retrospectively. The mean age of the patients was 60.5 years (range, 48-67 years). The mean prostate specific antigen concentration was 6.62 ng/mL (range, 0.54-14.57 ng/mL). All patients underwent a multiparametric MRI examination.

Results

The histopathological results were obtained from biopsies in four men and from transurethral resection of the prostate in two men after the MRI examination. Nodular (33%, 2/6 patients) and diffuse lesions (67%, 4/6 patients) were seen on MRI. The nodular lesions were featured by extremely low signal intensity (similar to that of muscle) on T2-weighted imaging (T2WI). The T2WI signal intensity of the diffuse lesions was low but higher than that of muscle, which showed high signal intensity on diffusion weighted imaging and low signal intensity on an apparent diffusion coefficient map. MR spectroscopic imaging of this type showed a normal-like spectrum. Abscesses were found in one patient with the nodular type and in one with the diffuse type.

Conclusion

The appearance of prostate tuberculosis on MRI can be separated into multiple nodular and diffuse types. Multiparametric MRI may offer useful information for diagnosing prostate tuberculosis.

MRI findings of granulomatous prostatitis developing after intravesical Bacillus Calmette-Guérin therapy

AIM

To evaluate magnetic resonance imaging (MRI) findings of granulomatous prostatitis (GP) developing after intravesical Bacillus Calmette-Guérin (BCG) therapy.

MATERIALS AND METHODS

Ten patients with pathologically proven GP underwent prostatic MRI. Lesion shape and signal intensity (SI) were evaluated on T2-weighted (T2WI), T1WI, and diffusion-weighted imaging (DWI).

RESULTS

Polygonal nodular lesions with notches, diffuse lesions, and cystic lesions with mural nodules were seen in two, six, and one patients, respectively. The remaining patient had a diffuse and cystic lesion. All diffuse lesions showed higher SI than muscle on T1WI and higher SI than the normal peripheral zone (PZ) on DWI. On T2WI, six of seven diffuse lesions showed a slightly lower SI than bone marrow and the remaining one lesion was iso-intense. All nodular lesions showed a low SI similar to muscle on T2WI and were iso-intense to muscle on T1WI. On DWI, two each of the four nodular lesions showed slightly lower SI and slightly higher SI than the normal PZ, respectively. All contents within the cyst and mural nodules showed markedly high and low SI on T2WI, respectively. On DWI, all fluids within cysts showed markedly high SI. One each of the mural nodules showed slightly higher SI and slightly lower SI than the normal PZ on DWI.

CONCLUSION

Three main MRI patterns of GP were identified: diffuse, nodular, and cystic with mural nodule; among them, the diffuse type was the most common. Cystic lesions with mural nodules could accompany the lesion.

Whole-body MRI: comprehensive evaluation on a 48-channel 3T MRI system in less than 40 minutes. Preliminary results

OBJECTIVE: To evaluate a comprehensive MRI protocol that investigates for cancer, vascular disease, and degenerative/inflammatory disease from the head to the pelvis in less than 40 minutes on a new generation 48-channel 3T system. MATERIALS AND METHODS: All MR studies were performed on a 48-channel 3T MR scanner. A 20-channel head/neck coil, two 18-channel body arrays, and a 32-channel spine array were employed. A total of 4 healthy individuals were studied. The designed protocol included a combination of single-shot T2-weighted sequences, T1-weighted 3D gradient-echo pre- and post-gadolinium. All images were retrospectively evaluated by two radiologists independently for overall image quality. RESULTS: The image quality for cancer was rated as excellent in the liver, pancreas, kidneys, lungs, pelvic organs, and brain, and rated as fair in the colon and breast. For vascular diseases ratings were excellent in the aorta, major branch vessel origins, inferior vena cava, portal and hepatic veins, rated as good in pulmonary arteries, and as poor in the coronary arteries. For degenerative/inflammatory diseases ratings were excellent in the brain, liver and pancreas. The inter-observer agreement was excellent. CONCLUSION: A comprehensive and time efficient screening for important categories of disease processes may be achieved with high quality imaging in a new generation 48-channel 3T system.

Characteristic magnetic resonance imaging low T2 signal intensity of necrotic lung parenchyma in children with pulmonary tuberculosis

PURPOSE

To show that necrotic areas of the lung demonstrated on computed tomographic scanning in children with primary pulmonary tuberculosis (TB) may be of low signal intensity on T2.

MATERIALS AND METHODS

Review of magnetic resonance imaging scans (T1/T2/STIR/postgadolinium T1) in 6 children scanned because of low-density necrotic areas demonstrated on computed tomography scanning prior to bronchoscopic confirmation of pulmonary TB.

RESULTS

Abnormalities included airspace consolidation in 6 children (100%); central necrosis in 6 children (100%); nodules in 2 children (33.3%); and lymphadenopathy in 6 children (100%). Low T2 signal in the areas of necrosis was demonstrated in all 6 children (100%) and in an area of at least 2 × 2 cm; 1 child also showed an area of high signal (16.67%). Airspace consolidation demonstrated T2 high signal in all the children (100%). Both children with nodules demonstrated at least 1 nodule with a low signal in addition to the majority of high-signal nodules. Post gadolinium, the consolidation and all high-signal nodules demonstrated enhancement, whereas the areas of lung necrosis and low signal nodules showed no enhancement.

CONCLUSION

Lung parenchymal necrosis in primary pulmonary TB in children may be of low signal intensity on T2 and STIR magnetic resonance imaging. This may be distal to lymphobronchial obstruction and is probably due to the caseating necrosis.

MRI of the lung (2/3). Why … when … how?

BACKGROUND

Among the modalities for lung imaging, proton magnetic resonance imaging (MRI) has been the latest to be introduced into clinical practice. Its value to replace X-ray and computed tomography (CT) when radiation exposure or iodinated contrast material is contra-indicated is well acknowledged: i.e. for paediatric patients and pregnant women or for scientific use. One of the reasons why MRI of the lung is still rarely used, except in a few centres, is the lack of consistent protocols customised to clinical needs.

METHODS

This article makes non-vendor-specific protocol suggestions for general use with state-of-the-art MRI scanners, based on the available literature and a consensus discussion within a panel of experts experienced in lung MRI.

RESULTS

Various sequences have been successfully tested within scientific or clinical environments. MRI of the lung with appropriate combinations of these sequences comprises morphological and functional imaging aspects in a single examination. It serves in difficult clinical problems encountered in daily routine, such as assessment of the mediastinum and chest wall, and even might challenge molecular imaging techniques in the near future.

CONCLUSION

This article helps new users to implement appropriate protocols on their own MRI platforms. Main Messages • MRI of the lung can be readily performed on state-of-the-art 1.5-T MRI scanners. • Protocol suggestions based on the available literature facilitate its use for routine • MRI offers solutions for complicated thoracic masses with atelectasis and chest wall invasion. • MRI is an option for paediatrics and science when CT is contra-indicated.

Recent technological and application developments in computed tomography and magnetic resonance imaging for improved pulmonary nodule detection and lung cancer staging

This review compares the emerging technologies and approaches in the application of magnetic resonance (MR) and computed tomography (CT) imaging for the assessment of pulmonary nodules and staging of malignant findings. Included in this review is a brief definition of pulmonary nodules and an introduction to the challenges faced. We have highlighted the current status of both MR and CT for the early detection of lung nodules. Developments are detailed in this review for the management of pulmonary nodules using advanced imaging, including: dynamic imaging studies, dual energy CT, computer aided detection and diagnosis, and imaging assisted nodule biopsy approaches which have improved lung nodule detection and diagnosis rates. Recent advancements linking in vivo imaging to corresponding histological pathology are also highlighted. In vivo imaging plays a pivotal role in the clinical staging of pulmonary nodules through TNM assessment. While CT and positron emission tomography (PET)/CT are currently the most commonly clinically employed modalities for pulmonary nodule staging, studies are presented that highlight the augmentative potential of MR.

Diagnostic efficacy and characteristic feature of MRI in pulmonary hamartoma: comparison with CT, specimen MRI, and pathology

OBJECTIVES

To determine the diagnostic efficacy of magnetic resonance imaging (MRI) in pulmonary hamartoma and observe the significant MRI features, other than fat or characteristic calcification revealed by computed tomography (CT).

METHODS

Six hamartomas were included and surgically resected, and we prospectively studied MRI in cases showing suggestive findings of hamartoma or indeterminate nodule on CT. We analyzed the tumor on CT and MRI (available enhancement study in 4) focusing on cleftlike structure in comparison with specimen MRI (n = 3) and histopathologic findings: presence, shape, and distribution of the cleftlike structure and signal intensity and enhancement of the cleftlike structure and main portion.

RESULTS

Computed tomography revealed suggestive findings of pulmonary hamartoma (fat or popcorn calcification) in only 3. All MRI revealed cleftlike structures particularly evident on T2-weighted images with same detectability as its specimen MRI: peripheral linear or curvilinear inclusions with sometimes intratumoral cleftlike space (n = 3), variable signal intensity, and frequent enhancement (3 in 4) pathologically correlated with the variable mesenchymal tissue components and amount arrayed along respiratory epithelial cells lining the cleft and richer vascularity than main portion of pulmonary hamartoma.

CONCLUSIONS

Magnetic resonance imaging study is a useful diagnostic tool, when a discrete pulmonary nodule demonstrates neither fat nor calcification on CT, for detecting the quite typical cleftlike structure in a pulmonary hamartoma and could provide diagnostic confidence.

Dynamic contrast enhancement patterns of solitary pulmonary nodules on 3D gradient-recalled echo MRI

OBJECTIVE

The purpose of this study was to determine whether contrast enhancement features on 3D volumetric gradient-recalled echoMR images allow differentiation of benign from malignant solitary pulmonary nodules.

MATERIALS AND METHODS

Forty patients with solitary pulmonary nodules (range of greatest diameter, 7-40 mm) detected on CT underwent unenhanced MRI and contrast-enhanced MRI performed in 10 consecutive dynamic 3D volumetric gradient-recalled echo sequences every 30 seconds. Contrast enhancement patterns (homogeneous, heterogeneous, rim, peripheral, and central) of the lesions were visually evaluated, and time-intensity curves of the lesions were drawn.

RESULTS

Twenty patients had benign lesions (nine, tuberculoma; one, aspergilloma; nine, round atelectasis; one, postinflammatory nodule). The other 20 patients had malignant lesions (18, primary lung cancer; two, metastasis). At visual analysis, all 20 malignant lesions displayed peripheral enhancement with progressive heterogeneous fill-in on the late images. All nine tuberculomas and the aspergilloma had rim enhancement, and all nine round atelectasis lesions and the postinflammatory nodule had early intense homogeneous enhancement. Regarding the time-intensity curves, all malignant lesions except one lung cancer lesion had early peak enhancement with rapid washout. All benign lesions displayed early increasing enhancement with an early plateau in the second minute after contrast administration (nine tuberculomas and one aspergilloma) or a late plateau in the fourth minute (nine round atelectasis lesions and one postinflammatory nodule).

CONCLUSION

Rim contrast enhancement is highly valuable in the diagnosis of tuberculoma. Time-intensity curve types can be taken into consideration for noninvasive differentiation of lung cancer, tuberculoma, and round atelectasis.

Dynamic magnetic resonance imaging of solitary pulmonary nodules: utility of kinetic patterns in differential diagnosis

OBJECTIVE

The aim of this study was to evaluate the clinical feasibility of dynamic magnetic resonance (MR) imaging with a 3-dimensional (3D) gradient recalled echo (GRE) volumetric interpolated breath-hold examination (VIBE) sequence to differentiate between benign and malignant solitary pulmonary nodules (SPNs).

METHODS

Dynamic 3D GRE VIBE was performed in 45 patients with SPNs. For each lesion, the morphologic parameters, including the edge configuration, presence of peripheral enhancement (PE), and an internal signal on T2-weighted images, and the kinetic enhancement parameters were evaluated.

RESULTS

All 29 of the malignant SPNs had internal enhancement, whereas 13 (81%) of the benign SPNs did not exhibit internal enhancement. A washout pattern was only observed in the malignant SPNs. The presence of PE was found in 56% of the benign SPNs and in 50% of the malignant SPNs. The lesion size was significantly different between malignant SPNs with PE and those without PE (P <0.01). The positive predictive value for malignancy was 91% (29 of 32 malignant SPNs). The negative predictive value was 100% (13 of 13 benign SPNs).

CONCLUSIONS

A combination of morphologic criteria and kinetic information is useful for differentiating between benign and malignant SPNs. In particular, internal enhancement with PE and positive visual washout is thought be a useful tool.

Full-Body Cardiovascular and Tumor MRI for Early Detection of Disease: Feasibility and Initial Experience in 298 Subjects

OBJECTIVE

High diagnostic accuracy, emerging whole-body concepts, and lack of side effects combine to render MRI a natural candidate for screening purposes. The aim of this study was to evaluate the technical feasibility of a comprehensive multiorgan-targeting MRI examination and determine the frequency of findings in subjects without a history of serious disease.

SUBJECTS AND METHODS

The study group was composed of 331 subjects. The MRI protocol (mean examination time, 63 min) encompassed the target organs: the brain, arterial system, heart, and colon. Diagnoses were deemed relevant if the physician had to inform the subject about the findings. Subjects with a history of serious illnesses were excluded from subsequent analysis (n=33). All analyses were performed for the resulting subgroup of 298 subjects (247 men, 51 women; mean age, 49.7 years).

RESULTS

All 298 examinations were diagnostic excluding eight MR colonography components in which remaining stool hampered reliable diagnosis. Follow-up or radiologic confirmation could be obtained in 75% of all cases with relevant findings (128/169); only one false-positive result was encountered. Of the study group, 21% exhibited signs of atherosclerotic disease. Two cerebral infarctions and one myocardial infarction, previously unknown, were encountered; 12% had peripheral vascular disease. Twelve colonic polyps and nine pulmonary lesions were correctly detected. Of all MRI examinations, 29% revealed relevant additional findings in nontargeted organs. Only one minor allergoid reaction was encountered.

CONCLUSION

The presented data point toward an increased use of MRI for screening in the future, but to date screening MRI should not be performed outside a research setting because the cost-benefit relation is unclear.

Solitary Pulmonary Nodules

OBJECTIVE

The aim of this prospective study was to compare the diagnostic performances of dynamic MR imaging and CT for the differentiation of benign and malignant solitary pulmonary nodules (SPNs).

METHODS

Eighty-one patients with SPNs (32 malignant, 49 benign) underwent dynamic MR imaging (n=31), dynamic CT (n=27), or both (n=23). The degree of peak enhancement of benign and malignant SPNs was compared on both dynamic MR imaging and CT. Receiver operating characteristic (ROC) analysis was performed to compare the diagnostic performances of dynamic MR imaging and CT.

RESULTS

The malignant SPNs revealed significantly greater degrees of peak enhancement on dynamic MR imaging (mean +/- SD [p%SI] 131.2 +/- 46.1 versus 54.2 +/- 45.3; range [p%SI] 82.6-260.0 versus -0.7-171.7; P <0.0001) and CT (mean +/- SD [DMI] 37.8 +/- 15.1 versus 17.9 +/- 21.8; range [DMI] 14.1-68.2 versus -5.4-107.6; P=0.0004). Although dynamic MR imaging was somewhat superior to dynamic CT, the diagnostic performances of the 2 modalities based on ROC analysis were not statistically significant.

CONCLUSIONS

Dynamic MR imaging and CT seem to be equally well suited for the differentiation between benign and malignant SPNs.

Pulmonary Dirofilariasis

OBJECTIVE

The purpose of this study was to describe the computed tomography (CT) and pathologic features of 5 nodules of pulmonary dirofilariasis in 4 patients.

METHODS

Four patients with 5 nodules of pathologically confirmed pulmonary dirofilariasis who under went CT were enrolled, and the imaging interpretations were retrospectively compared with the histopathologic characteristics.

RESULTS

Three of the 4 patients had a solitary nodule, and the remaining patient had 2 nodules. All the nodules were distributed in the right lower lobe and were attached to the pleura. They were all round or oval in shape and ranged in size from 11 to 22 mm in largest diameter (mean=17 mm). On thinner section CT, the nodules had a well-defined smooth margin with or without a shallow notch; they were connected to the arterial branch and, occasionally, to the venous branch. On contrast-enhanced CT, all the nodules contained a homogeneous low-attenuation area, which corresponded to areas of coagulative necrosis on histopathologic examination.

CONCLUSION

Although the CT findings of a pulmonary dirofilariasis nodule are nonspecific, awareness of the findings on contrast-enhanced CT and the pathologic appearance of this rare benign condition may facilitate its differentiation from a malignant nodule.

Simulated pulmonary nodules implanted in a dedicated porcine chest phantom: sensitivity of MR imaging for detection

PURPOSE

To evaluate the diagnostic accuracy of common magnetic resonance (MR) imaging sequences for detection of small pulmonary nodules by using a chest phantom and porcine lungs containing simulated lesions.

MATERIALS AND METHODS

Fourteen porcine lungs containing 366 porcine myocardial tissue implants were inflated inside a phantom. Two-dimensional (2D) and three-dimensional (3D) gradient-echo (GRE), T2-weighted turbo spin-echo (SE), and T2-weighted single-shot SE train MR sequences were performed. Spiral computed tomography (CT) was performed for comparison. Blinded observers read the images and recorded the sizes and locations of visible nodules by consensus. The sensitivity of each imaging method for depicting single nodules of given sizes was calculated. Specificities, positive predictive values (PPVs), and negative predictive values (NPVs) for detection of one or more nodules of various sizes were calculated.

RESULTS

Sensitivities of 3D GRE, 2D GRE, T2-weighted turbo SE, and T2-weighted single-shot SE train MR imaging and of CT were 0.50, 0.40, 0.12, 0.00, and 0.55, respectively, for detection of 1.4-mm nodules and 0.88, 0.84, 0.69, 0.06, and 0.96, respectively, for detection of 4.2-mm nodules. The 95% CIs for CT and GRE MR imaging overlapped, but those for turbo SE and single-shot SE train MR imaging differed significantly (P <.05). For detection of nodules larger than 5 mm, all examinations except single-shot SE train MR imaging yielded a specificity, PPV, and NPV of 1.00 each. For detection of nodules smaller than 5 mm, diagnostic accuracy of 3D GRE MR imaging was high: Specificity, PPV, and NPV all were approximately 0.90. Two-dimensional GRE MR imaging results were influenced by false-positive findings: Specificity was 0.64; PPV, 0.74; and NPV, 1.00.

CONCLUSION

Common MR imaging sequences such as 3D GRE have high diagnostic accuracy in depicting small pulmonary nodules when artifacts from cardiac and respiratory motion are absent.

Artificial thorax for MR imaging studies in porcine heart-lung preparations

A double-walled magnetic resonance (MR) imaging-compatible container with a flexible diaphragm was designed to hold freshly excised porcine heart-lung preparations. The saline contents simulate MR signal of an actual chest wall. Continuous evacuation keeps the lung inflated. A variety of experiments with different imaging modalities, including angiography, under close to in vivo conditions are feasible. Access to bronchial system and lung vessels allows for various studies.

Magnetic resonance imaging of pulmonary parenchymal disease using a modified breath-hold 3D gradient-echo technique: initial observations

PURPOSE

To determine the potential of a modified breath-hold 3D gradient-echo technique for visualizing pulmonary parenchymal diseases.

MATERIALS AND METHODS

Twenty-one magnetic resonance imaging (MRI) studies of the lungs were performed in 20 patients (15 male and 5 female; age range, 7.7-86.1 years) with pulmonary diseases comprising non-small-cell, small-cell, and bronchioalveolar carcinomas, endobronchial mucoepidermoid carcinoma, metastases, pneumonia, Wegener's granulomatosis, chronic obstructive pulmonary disease, arterio-venous malformation, and bronchogenic cyst. Confirmation of diagnoses was obtained via histopathology (14 patients) and follow-up (6 patients). MRI studies were performed at 1.5 T before and after administration of gadolinium using a modified volumetric interpolated breath-hold examination (VIBE) sequence. All images were evaluated prospectively regarding lesion detection and characterization. MR findings were correlated with final diagnoses. Retrospective grading (scores, 1-4) was performed for general image quality (rated "poor" to "excellent"); presence of artifacts ("negligible" to "severe"); and imaging quality of pulmonary lesions (conspicuity and contrast on pre- and postgadolinium images).

RESULTS

Twenty-three solid pulmonary lesions, 25 infiltrates and segmental atelectases, and 1 cyst were detected and prospectively correctly diagnosed. Sizes ranged from 0.3-10 cm. The mean scores for image quality and presence of artifacts were 3.3 (SD, 0.7) and 1.8 (SD, 0.7), respectively. Conspicuity and contrast of pulmonary lesions received mean scores between 3.0 and 3.8 (SD, 0.4-0.7).

CONCLUSION

This MRI technique allows imaging of a wide spectrum of solid and nonsolid pulmonary parenchymal diseases with reproducible high image quality, effective suppression of artifacts, high resolution, and visualization of gadolinium enhancement.