The role of multidetector CT arthrography in the investigation of suspected intra-articular hip pathology

The aim of this study was to evaluate the role of multidetector CT (MDCT) arthrography in the diagnosis of intra-articular hip pathology. A retrospective review of 96 patients who had undergone CT hip arthrography was performed. Data regarding the presence of a labral tear, paralabral cyst, chondral loss, acetabular version, femoral morphology and fibrocystic change were collected. We detected 28 labral tears (24 anterior, 2 anterolateral, 1 lateral and 1 posterolateral). An abnormal labral-chondral transitional zone was seen in 9 patients and 4 patients had surface labral fraying. We identified three paralabral cysts. Acetabular cartilage loss was detected in 45 and femoral cartilage loss in 9 patients. An abnormal anterior femoral head and neck junction was present in 18 hips and fibrocystic change in 8. Acetabular retroversion was present in 11 hips. 63 sets of patient notes were reviewed, of which 49 were in-patients with abnormal MDCT arthrogram findings. Surgical correlation was available in 27 patients. There was a discrepancy between the findings of a labral tear in one patient (false negative, 90% sensitivity and 100% specificity) and the presence of acetabular cartilage loss (88% sensitivity and 100% specificity) and femoral cartilage loss (94% sensitivity and 100% specificity) in three patients. MDCT arthrography affords accurate detection of intra-articular hip pathology.The investigation of suspected intra-articular hip pathology is challenging. Arthroscopy represents the gold standard but is invasive, necessitates a general anaesthetic and is best reserved for patients in whom concomitant therapeutic intervention is to be undertaken. Much of the radiology literature has focused on the use of MR arthrography of the hip to detect labral and cartilage pathology [1–5]. A number of groups have also studied the role of non-contrast MRI in the detection of labral tears associated with femoroacetabular impingement and acetabular dysplasia [6–9]. Both non-contrast MRI and MR arthrography have limitations in terms of spatial resolution, which can make the detection of subtle labral and cartilage pathology challenging [4]. Modern spiral multidetector CT (MDCT) technology allows submillimetre spatial resolution and has revitalised interest in the role of CT arthrography in the wrist, shoulder, knee, elbow and ankle [10–17]. There are few published data on the utility of this technique in the investigation of intra-articular hip pathology. Several studies have investigated the ability of MDCT arthrography to assess cartilage loss in the hip and have demonstrated that its accuracy is equal to, or can outperform, MR arthrography [18–20]. There are limited reports regarding the ability of MDCT arthrography to assess labral pathology [9]. The aim of this study was to evaluate the role of MDCT arthrography in the diagnosis of intra-articular hip pathology in a consecutive group of patients.     

3.0 T conventional hip MR and hip MR arthrography for the acetabular labral tears confirmed by arthroscopy

Objective

To evaluate the value of hip MR for diagnosing acetabular labrum tears, and to further compare the diagnostic performances of conventional MR with MR arthrography in acetabular labrum tears.

Methods

90 patients undergoing both hip MR examination and subsequent hip arthroscopy were retrospectively evaluated. Of these patients, 34 accepted both conventional MR and MR arthrography; while the other 56 only underwent conventional MR examination. All hip MR images were independently reviewed by two radiologists, and further compared with the results of hip arthroscopy.

Results

59 of 90 patients were confirmed with acetabular labral tears by hip arthroscopy and 31 without tears. The sensitivity, specificity, positive predictive value (PPV) and negative predictive value (NPV) of conventional MR for evaluating the acetabular labral tears were 61.0%, 77.4%, 83.7% and 51.1% (radiologist A), and 66.1%, 74.2%, 82.9% and 53.4% (radiologist B), respectively, with good consistency between the two observers (K = 0.645). The sensitivity, specificity, PPV and NPV of MR arthrography for assessing the acetabular labral tears were 90.5%, 84.6%, 90.5% and 84.6% (radiologist A), and 95.2%, 84.6%, 90.9% and 91.7% (radiologist B), respectively, with excellent good consistency between the two observers (K = 0.810). The sensitivity and NPV of MR arthrography for diagnosing the acetabular labral tears were significantly higher than those of conventional MR (both P < 0.05).

Conclusion

Hip MR arthrography is a reliable evaluation modality for diagnosing the acetabular labral tears, and its diagnostic performance is superior to that of conventional MR at 3.0 T.     

How often do surgeons intervene on shoulder labral lesions detected at MR examination? A retrospective review of MR examinations correlated with arthroscopy

Objective:

We report the prevalence of surgical intervention on shoulder labral lesions detected at MR examinations and how surgeons describe labral tears seen at MR examinations in their arthroscopy reports.

Methods:

A retrospective review of 100 consecutive patients aged 50 years or younger who had shoulder labral tears on MR and went on to have surgery performed. It was determined whether surgical intervention was performed on the MR lesions.

Results:

Of these 100 patients, 72 had superior labral anterior to posterior (SLAP) tears, 38 had posterior labral tears and 28 had anterior labral tears on MR examination. All 100 patients went on to arthroscopy. All lesions described on MRI were described on arthroscopy. Of the 72 SLAP tears, 64 were described as fraying on arthroscopy with 51 debrided. The remaining eight SLAP tears were tacked surgically. Of the 38 posterior labral tears, 36 were described as fraying on arthroscopy with 29 debrided and 2 had surgical tacking performed. Of the 28 anterior labral tears described on MR examination, 26 had surgical tacking performed and 2 were debrided. There were four SLAP tears, two anterior labral tears and three posterior labral tears seen on arthroscopy but not seen on MR examination.

Conclusion:

In this series, a high percentage of SLAP tears and posterior labral tears described on MR examination did not have surgical tacking. Most anterior labral tears had surgical tacking. Based on the above, our surgeons request we describe superior and posterior labral lesions as fraying and/or tearing, unless we can see a displaced tear. Most anterior labral lesions are treated with surgical tacking.

Advances in knowledge:

MRI allows for sensitive detection of labral tears. The tears often are not clinically significant.Labral tears are common injuries that often require surgical intervention. In our practice, we commonly see labral tears on MR examination and report them to surgeons. With modern high-resolution MRI, as well as increased awareness of labral tears by radiologists, labral tears are commonly reported findings on MR examinations. Sensitivities and specificities for detection of labral tears as compared with those from arthroscopy at 3.0 T have been reported as follows: superior labral anterior to posterior (SLAP) tears (90% sensitive and 100% specific), anterior labral tears (89% sensitive and 100% specific) and posterior labral tears (86% sensitivity and 100% specific).¹ Sensitivities of 100% for anterior labral tears, 86% for superior labral tears and 74% for posterior labral tears as compared with those from arthroscopy have been reported using high-resolution 1.5 T conventional MR examinations.²In our practice, we have been told by our surgeons that we describe some SLAP tears and posterior labral tears on MR that they find on arthroscopy to be degenerative fraying. For this reason, we sought to find (1) how often does a surgeon intervene on labral tears and (2) how do surgeons describe labral tears seen at MR examinations in their arthroscopy reports.     

3.0T常规MRI与MR髋关节造影诊断髋臼唇撕裂的对比研究

目的 在3.0 T场强中,比较常规髋关节MRI及MR髋关节造影对髋臼唇撕裂的诊断价值.方法 回顾分析44例髋关节病变患者的患侧髋关节常规MRI及MR髋关节造影资料,将每例患者的臼唇划分为前、上、后3处区域(共计132处),确定有无撕裂,并进行分型.其中5例患者经髋关节镜检查.对于常规MRI及MR髋关节造影获得的臼唇撕裂及分型数据差异比较采用Wilcoxon秩和检验,一致性比较采用Kappa检验.结果 常规MRI与MR髋关节造影诊断完全相同者计116处臼唇,只有16处存在诊断差异.其中,前者诊断无撕裂而后者诊断撕裂者9处,前者诊断撕裂但后者诊断无撕裂者6处,其余1处两者均诊断为撕裂但分型不同.常规MRI与MR髋关节造影的评价差异没有统计学意义(Z=0.347,P＞0.05),且具有极好的一致性(K=0.781,P＜0.01).在接受关节镜的5例患者中,常规MRI、MR髋关节造影及关节镜结果均完全吻合.结论 对髋臼唇撕裂,3.0 T常规髋关节MRI可获得与MR髋关节造影基本相同的诊断效果.     

Evaluation of shoulder pathology: three-dimensional enhanced T1 high-resolution isotropic volume excitation MR vs two-dimensional fast spin echo T2 fat saturation MR

Objective:

To evaluate the diagnostic accuracy of three-dimensional (3D) enhanced T₁ high-resolution isotropic volume excitation (eTHRIVE) shoulder MR for the detection of rotator cuff tears, labral lesions and calcific tendonitis of the rotator cuff in comparison with two-dimensional (2D) fast spin echo T₂ fat saturation (FS) MR.

Methods:

This retrospective study included 73 patients who underwent shoulder MRI using the eTHRIVE technique. Shoulder MR images were interpreted separately by two radiologists. They evaluated anatomic identification and image quality of the shoulder joint on routine MRI sequences (axial and oblique coronal T₂ FS images) and compared them with the reformatted eTHRIVE images. The images were scored on a four-point scale (0, poor; 1, questionable; 2, adequate; 3, excellent) according to the degree of homogeneous and sufficient fat saturation to penetrate bone and soft tissue, visualization of the glenoid labrum and distinction of the supraspinatus tendon (SST). The diagnostic accuracy of eTHRIVE images compared with routine MRI sequences was evaluated in the setting of rotator cuff tears, glenoid labral injuries and calcific tendonitis of the SST.

Results:

Fat saturation scores for eTHRIVE were significantly higher than those of the T₂ FS for both radiologists. The sensitivity and accuracy of the T₂ FS in diagnosing rotor cuff tears were >90%, whereas sensitivity and accuracy of the eTHRIVE method were significantly lower. The sensitivity, specificity and accuracy of both images in diagnosing labral injuries and calcific tendonitis were similar and showed no significant differences. The specificity of both images for the diagnosis of labral injuries and calcific tendonitis was higher than the sensitivities.

Conclusion:

The accuracy of 3D eTHRIVE imaging was comparable to that of 2D FSE T₂ FS for the diagnosis of glenoid labral injury and calcific tendonitis of SST. The 3D eTHRIVE technique was superior to 2D FSE T₂ FS in terms of fat saturation. Overall, 3D eTHRIVE was inferior to T₂ FS in the evaluation of rotator cuff tears because of poor contrast between joint fluid and tendons.

Advances in knowledge:

The accuracy of 3D eTHRIVE imaging is comparable to that of 2D FSE T₂ FS for the diagnosis of glenoid labral injury and calcific tendonitis of SST.Decreasing MR examination time is important for improving patient comfort and reducing motion artefact.¹ Three-dimensional (3D) MRI with isotropic resolution can create multiplanar reformatted (MPR) images and enable the creation of similar sequences with different image planes, resulting in decreased scan time.^2–4 3D isotropic MR can minimize partial volume artefact using thin slice thickness (SL), which can analyse lesions without interslice gaps.⁵ Recently, a new 3D imaging sequence called 3D enhanced T₁ high-resolution isotropic volume excitation MR (eTHRIVE) was developed.⁶ The eTHRIVE is a 3D T₁ weighted gradient sequence with dual half-scan and improved fat suppression that enables fast dynamic scanning with submillimetre in-plane resolution.⁷ Lee et al⁶ reported that eTHRIVE has the advantage of high-contrast resolution that reveals better diagnostic results through multiplanar reconstruction. These techniques were used to evaluate ligaments of the wrist within a shorter imaging time. However, to the best of our knowledge, no preliminary study has used eTHRIVE to evaluate shoulder joint pathology. The purpose of this study was to evaluate the diagnostic accuracy of eTHRIVE shoulder MR regarding the detection of rotator cuff tears, labral lesions and calcific tendonitis of the rotator cuff in comparison with two-dimensional (2D) fast spin echo T₂ fat saturation (FS) MR.     

Evaluation of the acetabular labrum at 3.0-T MR imaging compared with 1.5-T MR arthrography: preliminary experience

Institutional review board approval and informed consent were obtained for this HIPAA-compliant study. The purpose of this study was to prospectively compare imaging of the acetabular labrum with 3.0-T magnetic resonance (MR) imaging and 1.5-T MR arthrography. Eight patients (four male, four female; mean age, 38 years) with hip pain suspicious for labral disease were examined at both MR arthrography and MR imaging. Presence of labral lesions, paralabral cysts, articular cartilage lesions, subchondral cysts, osteophytes, and synovial herniation pits was recorded. There was arthroscopic correlation of findings in five patients. MR imaging depicted four surgically confirmed labral tears that were identified at MR arthrography, as well as one that was not visualized at MR arthrography. MR imaging helped identify all other pathologic conditions that were diagnosed at MR arthrography and helped identify one additional surgically confirmed focal articular cartilage lesion. These results provide encouraging support for evaluation with 3.0-T MR imaging over 1.5-T MR arthrography.     

Contrast-enhanced MRI of the subdeltoid,subacromial bursa in painful and painless rotator cuff tears

Objective

Although shoulder pain is often associated with rotator cuff tears, many tears are asymptomatic and are not the cause of the patient''s pain. This may explain the persistence of symptoms in some patients despite technically successful rotator cuff repair. It has been proposed that rotator cuff tears cause pain through subdeltoid/subacromial bursal inflammation. The aim of this study was to determine whether bursal inflammation seen on MRI is associated with pain in patients with rotator cuff tears of the shoulder.

Methods

The shoulders of 255 patients were screened with ultrasound. 33 full-thickness rotator cuff tears (18 with shoulder pain and 15 without pain) were identified and subsequently studied using contrast-enhanced MRI of the shoulder. Enhancement of the subacromial bursa was scored independently by two musculoskeletal radiologists. Logistic regression was used to determine whether bursal enhancement was independently associated with pain.

Results

There was a significant association between pain and age, with greater likelihood of pain in younger patients. Bursal enhancement was common in both painful and painless tears. No statistically significant link between pain and bursal enhancement was seen, even after accounting for age.

Conclusion

Although enhancement of the subdeltoid/subacromial bursa was common, no evidence was found to support the hypothesis that bursal enhancement is associated with pain in rotator cuff tears. It is therefore unlikely to determine reliably which patients would benefit from rotator cuff repair.

Advances in knowledge

Bursal enhancement and thickening does not reliably correlate with symptoms or presence of rotator cuff tear.Rotator cuff tears are a common cause of pain in the shoulder. Surgical repair is an effective treatment, but a significant proportion of patients (5–12.5%) fail to achieve a satisfactory outcome [1-4]. Long-term outcome of surgery correlates poorly with the integrity of the cuff repair [5-7] and persistence of pain is a major factor [1]. In some cases, this may be because the shoulder pain is not due to rotator cuff damage at all [8]. Other painful shoulder pathologies are common, particularly in the elderly, including glenohumeral and acromioclavicular arthritis [9], and bone marrow oedema [10]. Asymptomatic rotator cuff tears are common, with increasing incidence with age and a reported prevalence of up to 80% in subjects aged over 80 years [11]. A significant proportion of these are full-thickness tears with one study reporting full-thickness tears in 28% of people over the age of 60 [12]. Rotator cuff tears may remain asymptomatic despite their large size [13] and, although the size of tears often increases, symptoms may develop or resolve with conservative treatment [14-16]. As yet there is no clear consensus regarding the indications for rotator cuff surgery [17,18]. A technique to determine whether a known rotator cuff tear is responsible for an individual patient''s pain would therefore be of great clinical value in developing patient management plans. While MRI has been shown to be accurate for detecting rotator cuff tears [19,20], there is no convincing evidence to date that it can be used to determine whether a full-thickness tear is symptomatic [12,21].The mechanism by which rotator cuff tears cause pain is poorly understood. Tears are associated with histological inflammation of the subdeltoid/subacromial bursa and this has recently been proposed as a cause of pain [22]. Synovial inflammation in the bursa in symptomatic rotator cuff tears could potentially be detected by the associated enhancement in the inflamed bursa seen on MRI after the administration of intravenous contrast agent, in the same way that synovial volume in joints in inflammatory arthritis has been shown to correlate with histological measures of inflammation [23]. The aim of this study was to use contrast-enhanced MRI to assess subacromial bursitis in patients with painful and painless rotator cuff tears in order to test the hypothesis that synovial enhancement at the subacromial bursa is greater in patients with shoulder pain.     

MR defecography in patients with dyssynergic defecation: spectrum of imaging findings and diagnostic value

Objectives

We describe the spectrum of findings and the diagnostic value of MR defecography in patients referred with suspicion of dyssynergic defecation.

Methods

48 patients (34 females, 14 males; mean age 48 years) with constipation and clinically suspected dyssynergic defecation underwent MR defecography. Patients were divided into patients with dyssynergic defecation (n = 18) and constipated patients without dyssynergic defecation (control group, n = 30). MRIs were analysed for evacuation ability, time to initiate evacuation, time of evacuation, changes in the anorectal angle (ARA-change), presence of paradoxical sphincter contraction and presence of additional pelvic floor abnormalities. Sensitivity, specificity, positive and negative predictive values and accuracy for the diagnosis of dyssynergic defecation were calculated.

Results

The most frequent finding was impaired evacuation, which was seen in 100% of patients with dyssynergic defecation and in 83% of the control group, yielding a sensitivity for MR defecography for the diagnosis of dyssynergic defecation of 100% (95% confidence interval (CI) 97–100%), but a specificity of only 23% (95% CI 7–40%). A lower sensitivity (50%; 95% CI 24–76%) and a high specificity (97%; 95% CI 89–100%) were seen with abnormal ARA-change. The sensitivity of paradoxical sphincter contraction was relatively high (83%; 95% CI 63–100%). A combined analysis of abnormal ARA-change and paradoxical sphincter contraction allowed for the detection of 94% (95% CI 81–100%) of the patients with dyssynergic defecation.

Conclusion

MR defecography detects functional and structural abnormal findings in patients with clinically suspected dyssynergic defecation. Impaired evacuation is seen in patients with functional constipation owing to other pelvic floor abnormalities than dyssynergic defecation.Dyssynergic defecation, which produces functional outlet obstruction during defecation, is one of the causes of chronic constipation. Dyssynergic defecation is a functional disorder characterised by either paradoxical contraction, an inability to relax the anal sphincter and/or puborectalis muscle, or impaired abdominal and rectal pushing forces. In the literature, many other terms such as anismus [1], dyskinetic puborectalis muscle [2], non-relaxing puborectalis syndrome [3], spastic pelvic floor syndrome [4, 5] and pelvic floor dyssynergia [6] have been used. An expert group (Rome III) [7] recently proposed the term “dyssynergic defecation” to appropriately describe the failure of co-ordination or dyssynergia of the abdominal and pelvic floor muscles involved in defecation. Different physiological tests can be used to investigate this functional disorder, including the balloon expulsion test, electromyography (EMG) of the puborectalis muscle and anorectal manometry. Defecography can be performed to rule out structural rectal abnormalities and provide an estimate of the degree of rectal emptying. As false-positive and false-negative results are common with these different tests, none can be used by itself as a gold standard for identifying patients with dyssynergic defecation.Most authorities recommend using a combination of diagnostic tests and clinical history. The Rome III expert group defined the criteria for the diagnosis of dyssynergic defecation based on clinical history, anorectal manometry, balloon expulsion test, EMG and conventional defecography (evacuation proctography) [7]. Functional imaging with conventional defecography is considered to be a useful adjunct in establishing the diagnosis of dyssynergic defecation. Delayed initiation of evacuation and impaired evacuation in particular, as seen on conventional defecography, are highly predicitive for the presence of dyssynergic defecation [8, 9]. Different structural imaging findings in conventional defecography have been described in patients with dyssynergic defecation; however, the usefulness of these findings is discussed controversially [8, 10, 11].The experience with MR defecography, which has shown to be a valuable alternative to evacuation proctography [12–15], is limited in dyssynergic defecation patients. There is only one study which has focused on the MR defecography findings in a study setting in patients with dyssynergic defecation [16]. Hence, the purpose of this study was to describe the spectrum of findings in MR defecography in patients referred with the suspicion of dyssynergic defecation and to assess the value of MR defecography in establishing this diagnosis. For the latter, the patients with dyssynergic defecation were compared with a group of constipated patients without dyssynergic defecation.     

Comparison of diffusion-weighted MRI acquisition techniques for normal pancreas at 3.0 Tesla

PURPOSE

We aimed to optimize diffusion-weighted imaging (DWI) acquisitions for normal pancreas at 3.0 Tesla.

MATERIALS AND METHODS

Thirty healthy volunteers were examined using four DWI acquisition techniques with b values of 0 and 600 s/mm² at 3.0 Tesla, including breath-hold DWI, respiratory-triggered DWI, respiratory-triggered DWI with inversion recovery (IR), and free-breathing DWI with IR. Artifacts, signal-to-noise ratio (SNR) and apparent diffusion coefficient (ADC) of normal pancreas were statistically evaluated among different DWI acquisitions.

RESULTS

Statistical differences were noticed in artifacts, SNR, and ADC values of normal pancreas among different DWI acquisitions by ANOVA (P < 0.001). Normal pancreas imaging had the lowest artifact in respiratory-triggered DWI with IR, the highest SNR in respiratory-triggered DWI, and the highest ADC value in free-breathing DWI with IR. The head, body, and tail of normal pancreas had statistically different ADC values on each DWI acquisition by ANOVA (P < 0.05).

CONCLUSION

The highest image quality for normal pancreas was obtained using respiratory-triggered DWI with IR. Normal pancreas displayed inhomogeneous ADC values along the head, body, and tail structures.Diffusion-weighted magnetic resonance imaging (DW-MRI) has increasingly expanded to abdominal organs thanks to newer technical developments. Diffusion-weighted imaging (DWI) can provide great details of functional and anatomic information that can be used in the differential diagnosis of abdominal pathological conditions. Investigators have recently reported that DWI can be utilized to detect pancreatic cancer (1, 2) and analysis of apparent diffusion coefficient (ADC) can help differentiate pancreatic masses (3–6). The single-shot spin-echo echo-planar imaging combined with parallel imaging technique is commonly employed for pancreatic DWI studies. Breath-hold DWI is the most common technique used for signal acquisition, especially on 1.5 Tesla (T) magnetic resonance (MR) system, because of its time efficiency. However, there are several disadvantages of breath-hold DWI, including poor signal-to-noise ratio (SNR), limited scan volume and significant artifacts (7, 8). Respiratory-triggered and free-breathing techniques are also used for signal acquisition in pancreatic DWI studies. Compared to breath-hold, the advantages of respiratory-triggered and free-breathing techniques are higher SNR due to multiple signal acquisitions, larger scanning range and less artifacts; their main disadvantage being the longer scanning time (9). Additionally, techniques of fat suppression, such as chemical shift selective (CHESS) and short tau inversion recovery, are essential for DWI in the pancreas for improving the contrast ratio and contrast-to-noise ratio of lesions with respect to normal pancreatic tissues (1, 6, 10).Previously, most investigations were performed using 1.5 T MR scanners. Pancreas imaging using DWI with 3.0 T MR system needs to be further clarified and understood due to its increasing application, which may be a challenging task because of specific absorption rate and various artifacts from high sensitivity to magnetic field inhomogeneity and physiological movement (11). The aim of this study was to investigate different DWI techniques to visualize normal pancreas using a 3.0 T MR scanner and determine the best image acquisition technique in terms of artifacts, SNR, and ADC.     

Time-resolved MR angiography for detecting and grading ovarian venous reflux: comparison with conventional venography

Objective

The purpose of this study was to compare the diagnostic accuracy of time-resolved MR angiography (TR-MRA) with that of conventional venography for the detection and grading of ovarian venous reflux, which aid in the diagnosis of pelvic venous congestion.

Methods

We performed a retrospective analysis of 19 consecutive patients who underwent TR-MRA and conventional venography. The images were analysed by two radiologists in a randomised “blinded” manner. With the use of conventional venography as a gold standard, the images were reviewed to determine if differences in the detection and grading of ovarian venous reflux were seen between TR-MRA and conventional venography; the sensitivity, specificity and accuracy of TR-MRA compared with that of conventional venography were evaluated. The McNemar test was performed to determine the significance of any differences. Interobserver agreement was analysed using generalised κ statistics.

Results

There was no significant difference between TR-MRA and conventional venography for grading ovarian venous reflux (p>0.05). The sensitivity, specificity and diagnostic accuracy of TR-MRA were found to be 66.7%, 100% and 78.9%, and 75%, 100% and 84.2%, respectively, for the two observers. The weighted κ-values indicated excellent agreement between the two observers for grading ovarian venous reflux on TR-MRA (κ=0.894).

Conclusion

TR-MRA is an accurate method for accessing pelvic venous congestion.Chronic pelvic pain is a common health problem among females, and this is characterised by non-cyclic pelvic pain lasting more than 6 months [1]. It has been reported that as many as 39.1% of females have had chronic pelvic pain at some time during their lives [2]. Pelvic congestion syndrome is defined as chronic pelvic pain caused by incompetent ovarian veins, with associated venous reflux and venous engorgement [3,4].Conventional angiography is currently considered the gold standard for the detection of pelvic congestion syndrome [5]. However, this procedure is time-consuming and invasive, and it necessitates the use of ionising radiation. Several non-invasive techniques are used for the work-up of pelvic venous congestion, including sonography, CT and MRI [6-10]. Time-resolved MR angiography (TR-MRA) has been proven to be a quick and non-invasive technique that allows evaluation of the physiological blood flow [11-14].There has been a study regarding the usefulness of TR-MRA for assessing ovarian venous reflux, but to the best of our knowledge [11] the correlation with conventional venography has not been used to access the result of TR-MRA for detecting ovarian venous reflux. The purpose of this study was to compare the diagnostic accuracy of TR-MRA with that of conventional venography for the detection and grading of ovarian venous reflux, which will help make the diagnosis of pelvic venous congestion.     

Cardiac MR assessment of microvascular obstruction

Microvascular obstruction (MVO) is usually seen in a proportion of patients with acute myocardial infarction following reperfusion therapy of an occluded coronary artery. It is characterized by damage and dysfunction of the myocardial microvasculature with a no-reflow phenomenon within the infarct zone. While MVO may be demonstrated via a number of different imaging modalities, cardiac MR (CMR) enables accurate identification of MVO and also permits assessment of infarct extent and overall left ventricular function during the same imaging examination. We present a pictorial review of the characteristic appearances of MVO on CMR and highlight the importance of this imaging diagnosis for patient outcome following acute myocardial infarction.Microvascular obstruction (MVO) usually arises following reperfusion therapy in patients after a prolonged period of severe myocardial ischaemia.^1,2 It is most commonly, but not exclusively, seen in patients with a delayed presentation to definitive reperfusion treatment following acute coronary occlusion.^3,4 MVO was first described in the 1970s and is characterized by damage and dysfunction of the myocardial microvasculature resulting in a “no-reflow” phenomenon, where, essentially, blood flow cannot penetrate beyond the myocardial capillary bed.³ While several different imaging modalities may be utilized in the diagnosis of MVO, cardiac MR (CMR) has a number of distinct advantages as it enables precise delineation of both infarct site and MVO along with accurate quantification of both global and segmental left ventricular function during a single imaging examination. Accurate diagnosis of MVO is of great importance, as its presence has been shown to be an independent predictor of poor prognostic outcome following myocardial infarction, including adverse left ventricular remodelling, subsequent major adverse cardiovascular events and death.^1,4–6     

Combination of high-resolution susceptibility-weighted imaging and the apparent diffusion coefficient: added value to brain tumour imaging and clinical feasibility of non-contrast MRI at 3 T

The purpose of this study was to determine the benefit of high-resolution susceptibility-weighted imaging and the apparent diffusion coefficient for brain tumour imaging, and to assess the clinical feasibility of using a non-contrast MR protocol at 3 T. 73 patients with intra-axial tumours were enrolled into the study. Two experienced neuroradiologists reviewed three MRI sessions: (i) a non-contrast protocol including high-resolution susceptibility-weighted images and apparent diffusion coefficient; (ii) a contrast protocol including MR perfusion images; and (iii) combined contrast and non-contrast protocols. The two observers categorised tumours as glial or non-glial tumours, and then subcategorised the gliomas into low-grade or high-grade tumours. For semi-quantitative analysis, a scoring system based on the degree of intra-tumoral susceptibility signals and the visual apparent diffusion coefficient was used. The two observers diagnosed accurate tumour pathology in 52 (71%) of 73 tumours in the first review, 55 (75%) of 73 tumours in the second review and 61 (84%) of 73 tumours in the third review. The addition of the non-contrast protocol to the contrast protocol significantly differentiated glioblastoma multiforme and metastatic tumours, which was not possible with the contrast protocol alone. The sensitivity, specificity, positive predictive value and negative predictive value for glioma grading with the non-contrast protocol were 83.2%, 100%, 100% and 79.3%, respectively. The addition of both high-resolution susceptibility-weighted imaging and the apparent diffusion coefficient improved the diagnostic performance of the contrast MR protocol for brain tumour imaging and could be feasible in selected patients who cannot tolerate a contrast agent.Contrast-enhanced (CE) conventional MRI, which is commonly used in the evaluation of brain tumours, is usually included as part of the routine brain tumour imaging protocol in most institutions. Although conventional MRI with gadolinium-based contrast agents is useful for the detection and structural characterisation of brain tumours, enhancement after gadolinium reflects disruption of the blood–brain barrier rather than a true assessment of tumour vascularity [1, 2]. Recently, a number of advanced MRI techniques, such as MR perfusion, have been developed to provide biological and physiological information for the assessment of brain tumours [3, 4]. Dynamic susceptibility contrast (DSC) MR perfusion imaging has provided physiological information that allows the evaluation of neovascularity and angiogenesis in brain tumours [5, 6].High-resolution susceptibility-weighted MR imaging (HR-SWI) is a three-dimensional gradient-echo technique that is sensitive to local tissue magnetic susceptibility and is blood oxygen level dependent [7–9]. This new imaging technique has largely been used for the detection of microvenous structures, as well as for the detection of extravascular blood products [10, 11]. The development of 3 T MR scanners and parallel imaging techniques has enabled an increase in the speed, coverage and signal-to-noise ratio of MR images. Therefore, this new technique could be suitable for the examination of patients with various brain disorders in order to obtain high spatial resolution with a reasonable acquisition time.As has been demonstrated in previous reports, HR-SWI has the potential to assess non-invasively the intratumoral microvascularity associated with fast-growing tumours [12, 13]. Diffusion-weighted imaging (DWI) provides information about tumour cellularity and structural integrity by measuring differences in the apparent diffusion coefficient (ADC) [14, 15]. HR-SWI and DWI do not require contrast administration. Although gadolinium-based contrast agents are widely used in the clinical setting for the assessment of brain tumours, HR-SWI and DWI can be integrated easily into a conventional MR examination at any time, as long as no contrast agent is administered. A non-contrast MR protocol can also be applied to patients in whom are contrast agents contraindicated or who cannot tolerate a bolus injection of contrast medium.The purpose of this study was to determine the benefit of HR-SWI and the ADC for brain tumour imaging protocols, including MR perfusion imaging, and to assess the clinical feasibility of the use of non-contrast MR protocols, including HR-SWI and the ADC, at 3 T.     

Prognostic factor from MR spectroscopy in rat with astrocytic tumour during radiation therapy

Objective:

To investigate the relationship between the tumour volume and metabolic rates of astrocytic tumours using MR spectroscopy (MRS) during radiation therapy (RT).

Methods:

12 healthy male Sprague-Dawley® rats (Sprague–Dawley Animal Company, Madison, WI) were used, and a tumour model was created through injecting C6 tumour cells into the right caudate nuclei of the rats. Tumours grew for 18 days after the injection and before the imaging study and radiation treatment. MRS was performed with two-dimensional multivoxel point-resolved spectroscopy sequence using a GE Signa VH/i 3.0-T MR scanner (GE Healthcare, Milwaukee, WI) equipped with rat-special coil. RT was given on the 19th day with a dose of 4 Gy in one single fraction. The image examinations were performed before RT, and on the 4th, 10th, 14th and 20th days after treatment, respectively. GE FuncTool software package (GE Healthcare) was used for post-processing of spectrum.

Results:

Metabolic ratios of serial MRS decrease progressively with time after RT. Choline-containing components (Cho)/creatine and creatine phosphate (Cr) ratios immediately prior to RT differed significantly from those on the 10th, 14th and 20th days after RT; both Cho/N-acetyl aspartate (NAA) ratios and NAA/Cr ratios immediately prior to RT differed significantly from those on the 14th and 20th days after RT. A positive correlation between changes of tumour volume and changes of Cho/Cr, lipid and lactate/Cr and glutamate plus glutamine/Cr ratio was observed on the 4th day after RT.

Conclusion:

MRS provides potential in monitoring tumour response during RT, and the imaging biomarkers predict the response of astrocytic tumours to treatment.

Advances in knowledge:

MRS is combined with both tumour size and Ki-67 labelling index to access tumour response to radiation.More than 180,000 brain tumours (malignant and benign) are diagnosed each year in the USA. Of these, about 23,380 are primary brain tumours.¹ Among the primary brain tumours, approximately 50% are glioblastoma multiform (GBM) and 50% are gliomas. Glioma has been thought of as a disease involving multiple gene mutations.² It has always been difficult for neurologists to diagnose and treat glioma, especially GBM.³Although conventional MRI can be used to detect brain lesions, its sensitivity and specificity for distinguishing between benign and malignant lesions and differentiating between tumours and non-neoplastic lesions are limited. Similar MRI features may be present in several different tumour types. It is very difficult to differentiate high-grade and low-grade brain tumours with conventional MRI.⁴The lack of biological markers with prognostic significance impedes the development of new treatment strategies. Although some biomarkers can be identified through molecular analysis⁵ and DNA microarray,⁶ these procedures normally require diagnostic biopsies that may not be feasible owing to tumour location. With the advancement of MR spectroscopy (MRS), biologically relevant intracellular metabolites can be detected, grading of astrocytomas can be assessed and their biological behaviour and prognosis can be evaluated.⁷MRS is a unique method for performing analysis of the metabolism of organs and cells. It allows measurements of metabolites for specific atomic nuclei and their components, including choline-containing components (Cho), creatine and creatine phosphate (Cr), N-acetyl aspartate (NAA), lipid and lactate (LL) levels and glutamate plus glutamine (Glx). The most commonly studied metabolites in the brain are NAA, Cho and Cr.^8–12 NAA is a predictor for neuronal and axonal integrity since decreased levels are usually observed after brain injury. The second most commonly observed MRS finding after brain tumours is increased Cho levels via cell membrane disruption and altered phospholipid metabolism,¹³ which are biomarkers for cell membrane turnover.¹⁴ The Cho level may be used to predict the malignancy of gliomas.¹⁵ The Cho level has been found to correlate with the cellular density of tumours.¹⁶ The Cr peak is an indicator of cell energy metabolism¹⁷ and can be used to distinguish pure tumours from pure necrosis.¹⁸ It has been found that Cho and LL levels normalized to Cr are a strong predictor of survival,¹⁹ especially when diagnostic biopsies are not feasible. Glx changes arise from both neuronal and glial cells and reflect cytoplasmic concentrations.²⁰ The ratio of Glx/Cr was increased in 10 patients of brain tumour with oedema, which is associated with injury to the myelin sheath.²¹ High Glx/Cr in vivo MRS index is a good predictor of tumour grading.²² Significant correlations have been reported with hippocampal volumetric measures and Glx/Cr in patients with schizophrenia but not in healthy controls,²³ although the relationship between volume and Glx/Cr has been explored in brain tumours. Thus, MRS potentially shows promise in brain tumour management.The Ki-67 labelling index (LI) is a promising proliferation marker in histological examination. Barbarella et al²⁴ first reported that the Ki-67 LI was correlated with Cho/Cr ratio. It is an independent predictor of both tumour recurrence and overall survival in meningioma.²⁵ It can be used to predict clinical outcome in acromegalic patients.²⁶ The Ki-67 LI increased at higher histological grades.²⁷ It is a reliable tool to accurately determine the growth fraction of neoplasms in humans and animals.²⁸ Therefore, it has been used to predict clinical outcome.In this study, we tested our hypothesis that biomarkers illuminated by MRS during radiation therapy (RT), including NAA, Cho, LL and Glx/Cr, can add significant predictive power to clinical response to RT. We present the prognostic information on these biomarkers and demonstrate that these provide useful prognosis. We investigated the relationship between tumour volume and the metabolic ratios, including Cho/Cr, LL/Cr and Glx/Cr as well as the relationship between Ki-67 LI and the metabolic ratios of these.     

Screening for atherosclerotic plaques in the abdominal aorta in high-risk patients with multicontrast-weighted MRI: a prospective study at 3.0 and 1.5 tesla

Objective

This prospective study compares MRI of atherosclerotic plaque in the abdominal aorta at 3 T with that at 1.5 T in patients suffering from hereditary hyperlipidaemia, a major risk factor for atherosclerosis.

Methods

MRI of the abdominal aorta at 1.5 and 3 T was performed in 21 patients (mean age 58 years). The study protocol consisted of proton density (PD), T₁, T₂ and fat-saturated T₂ weighted black blood images of the abdominal aorta in corresponding orientation. Two independent radiologists performed image rating. First, image quality was rated on a five-point scale. Second, atherosclerotic plaques were scored according to the modified American Heart Association (AHA) classification and analysed for field strength-related differences. Weighted κ statistics were calculated to assess interobserver agreement.

Results

Interobserver agreement was substantial for nearly all categories. MRI at 3 T offered superior image quality in all contrast weightings, most significantly in T₁ and T₂ weighted techniques. Plaque burden in the study collective was unexpectedly moderate. The majority of plaques were classified as AHA III lesions; no lesions were classified above AHA V. There was no significant influence of the field strength regarding the AHA classification.

Conclusion

Abdominal aortal plaque screening is basically feasible at both field strengths, whereas the image quality is rated superior at 3 T. However, the role of the method in clinical practice remains uncertain, since substantial findings in the high-risk collective were scarce.Atherosclerosis is a systemic disease of the vessel wall that mainly occurs in medium-sized and large arteries; its thrombotic or thromboembolic complications are the main cause of mortality and morbidity in industrialised countries [1,2]. It is characterised by a thickening of the vessel wall, especially the intima, and is histologically composed of a lipid core with an overlying fibrous cap. The main plaque components are fibrous elements (e.g. connective tissue, collagen, proteoglycans), lipids (e.g. cholesterol, phospholipids), smooth muscle cells and inflammatory cells (e.g. macrophages, T lymphocytes). The composition of the atherosclerotic plaque determines its vulnerability [3-6]. The so-called “vulnerable plaque” consists of a large lipid core and a thin fibrous cap, although the characteristics of the vulnerable plaques vary depending on the arterial region (i.e. coronaries, carotids, aorta) [6-8]. Rupture of atherosclerotic plaques as a result of an endothelial lesion is the most frequent cause of the unpredictable onset of acute thromboembolic vascular events such as myocardial infarction, ischaemic stroke or sudden cardiac death [9,10]. Therefore, it is necessary to characterise plaque components and determine them at an early stage to prevent cardiovascular events. Several invasive and non-invasive imaging modalities are used to study atherosclerotic vessel lesions: conventional (B-mode) ultrasound, intravascular ultrasound (IVUS), conventional angiography, CT, angioscopy and MRI [5,10]. Most of them identify luminal diameter or stenosis, wall thickness and plaque volume, but are not able to determine plaque components [5,11]. Several recent studies showed that in vivo and ex vivo MRI as a non-invasive method can characterise the composition of atherosclerotic plaques such as fibrous tissue, lipid core, calcification, haemorrhage and thrombus [5,10,12-18]. The aim of this characterisation is the determination of the risk of plaque rupture.Most of the previous publications regarding plaque imaging in the human aorta are of studies performed at 1.5 T. Newer publications show the advantages of high field strength, such as faster imaging with parallel imaging techniques and higher signal-to-noise ratio (SNR) [19,20].The purpose of this study was to compare in vivo multimodality MR plaque imaging of the human aorta at 1.5 T and 3 T in a patient collective at high risk for atherosclerosis, in which atherosclerotic wall alterations can be expected. The evaluation focused on image quality and on the analysis of atherosclerotic plaque components according to the American Heart Association (AHA) classification [3,21].In the context of the prospective study, plaque imaging was always performed in addition to whole-body MR angiography (WBMRA) and is therefore part of a whole-body screening approach.     

Cardiac MR assessment of cardiac myxomas

Cardiac myxomas are the most common benign primary cardiac tumour to present in adulthood. While most patients present with symptoms of cardiac obstruction, embolic phenomena or constitutional impairment, up to a fifth of patients remain asymptomatic and are incidentally diagnosed on imaging. Although echocardiography is usually the initial imaging modality used to evaluate these patients, cardiac MRI (CMR) has emerged over the past decade as the primary imaging modality in the assessment of patients with cardiac tumours. The superior tissue characterization capability of CMR means that it is able to determine the nature of some tumours pre-operatively and performs well in differentiating myxomas from thrombus. We present a pictorial review highlighting the key CMR features of myxomas and show how these lesions can be differentiated from thrombus and other cardiac masses.Primary cardiac tumours are uncommon with a reported prevalence at autopsy of 0.002%.¹ The majority are benign, with myxomas accounting for almost 50% of all primary cardiac tumours.² Myxomas are more common in female patients, and while they can occur at any age, they usually present in adults between the fourth and seventh decades of life.^3,4 Most patients typically present with at least one manifestation of the classic triad of cardiac obstructive symptoms, embolic phenomena and constitutional symptoms, but 20% are identified in asymptomatic patients as an incidental imaging finding.³Echocardiography is usually the initial imaging modality used in the assessment of a suspected cardiac mass but remains rather operator dependent with a restricted field of view and can be particularly challenging in patients with large body habitus.^2,4,5 Cardiac MRI (CMR) enables accurate assessment of the location and functional impact of cardiac masses in any imaging plane without exposing patients to ionizing radiation.^2,5 In particular, CMR performs better than echocardiography at determining the nature of cardiac lesions and can differentiate myxomas from thrombus.^2,5 Given that most cardiac lesions are not easily amenable to catheter-directed biopsy, accurate imaging differentiation of cardiac myxomas from other types of cardiac masses is of vital importance in guiding further management.     

The challenge of segmental small bowel motility quantitation using MR enterography

Objective:

Analysis of “cine” MRI using segmental regions of interest (ROIs) has become increasingly popular for investigating bowel motility; however, variation in motility in healthy subjects both within and between scans remains poorly described.

Methods:

20 healthy individuals (mean age, 28 years; 14, males) underwent MR enterography to acquire dynamic motility scans in both breath hold (BH) and free breathing (FB) on 2 occasions. Motility data were quantitatively assessed by placing four ROIs per subject in different small bowel segments and applying two measures: (1) contractions per minute (CPM) and (2) Jacobian standard deviation (SD) motility score. Within-scan (between segment) variation was assessed using intraclass correlation (ICC), and repeatability was assessed using Bland–Altman limits of agreement (BA LoA).

Results:

Within-scan segmental variation: BH CPM and Jacobian SD metrics between the four segments demonstrated ICC R = 0.06, p = 0.100 and R = 0.20, p = 0.027 and in FB, the CPM and Jacobian SD metrics demonstrated ICC R = −0.26, p = 0.050 and R = 0.19, p = 0.030. Repeatability: BH CPM for matched segments ranged between 0 and 14 contractions with BA LoA of ±8.36 and Jacobian SD ranged between 0.09 and 0.51 with LoA of ±0.33. In FB data, CPM ranged between 0 and 10 contractions with BA LoA of ±7.25 and Jacobian SD ranged between 0.16 and 0.63 with LoA = ±0.28.

Conclusion:

The MRI-quantified small bowel motility in normal subjects demonstrates wide intersegmental variation and relatively poor repeatability over time.

Advances in knowledge:

This article presents baseline values for healthy individuals of within- and between-scan motility that are essential for understanding how this process changes in disease.Dynamic “cine” MRI acquired during MR enterography is increasingly utilized to assess bowel motility in a range of conditions, notably inflammatory bowel disease and enteric dysmotility syndromes.^1–4 Analysis of the data remains primarily subjective in clinical routine, but the ability to apply quantitative techniques makes this a potentially powerful methodology to explore gastrointestinal physiology in disease as well as an emerging application as a biomarker for drug efficacy.^5–7Despite the growing literature, a consensus has yet to be reached as to the best method of quantitatively analysing small bowel data and indeed a range of motility metrics are proposed.^2,3,8–12 The most commonly used metric is the change in luminal diameter at a fixed anatomical position through the time series. By tracking bowel diameter, a characteristic curve can be produced with the number of contractions expressed per minute (CPM) to give an intuitive and broadly accepted metric for small bowel motility (SBM).^{2–4,9,11,13–15} To date, several studies have reported a relationship between CPM and dysmotility in disease, either compared with a histopathological standard or “normal” reference bowel loops.^2–4,12 An array of additional metrics derived both from bowel diameter measures and more abstract processing techniques have further been implemented with varying degrees of effectiveness in disease and health.^{2,4,5,8,10,14,16}Although intuitively attractive, the robustness of assessing overall enteric motility using only an isolated loop of bowel has received relatively little attention to date irrespective of the precise metric applied. It is unclear how representative the selected bowel loops are of overall SBM and if normal motility intrinsically differs between bowel segments, for example, between the jejunum and ileum. Furthermore, the repeatability of single loop metrics, even in normal individuals, is not well described, knowledge of which is vital if segmental analysis is to be used to diagnose, guide treatment and monitor enteric pathology.The purpose of this study is to explore segmental variation in SBM in healthy volunteers measured using two commonly reported small bowel metrics [CPM and Jacobian standard deviation (SD)] looking at (1) within-scan motility variation between different segments and (2) between-scan variation (repeatability) across two time points.     

Detection of residual brain arteriovenous malformations after radiosurgery: diagnostic accuracy of contrast-enhanced four-dimensional MR angiography at 3.0 T

Objective

To evaluate the diagnostic accuracy of four-dimensional MR angiography (4D-MRA) at 3.0 T for detecting residual arteriovenous malformations (AVMs) after Gamma Knife® (Elekta Instrument AB, Stockholm, Sweden) radiosurgery (GKRS).

Methods

We assessed 36 angiographically confirmed AVMs in 36 patients who had been treated with GKRS. 4D-MRA was performed after GKRS and the time intervals were 39.4±26.0 months [mean±standard deviation (SD)]. 4D-MRA was obtained at 3.0 T after contrast injection, with a measured voxel size of 1×1×1 mm and a temporal resolution of 1.1 s (13 patients) or a voxel size of 1×1×2 mm and a temporal resolution of 0.98 s (23 patients). X-ray angiography was performed as the standard reference within 53±47 days (mean±SD) after MRA. To determine a residual AVM, the 4D-MRA results were independently reviewed by two readers blinded to the X-ray angiography results. We evaluated diagnostic sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV) and accuracy of 4D-MRA for detection of a residual AVM.

Results

A residual AVM was identified in 13 patients (13/36, 36%) on X-ray angiography. According to Readers 1 and 2, 4D-MRA had a sensitivity of 79.6% and 64.3%, a specificity of 90.9% and 100%, a PPV of 84.6% and 100% and an NPV of 90% and 81.5%, respectively, and a diagnostic accuracy of 86.1% for Readers 1 and 2, for detecting residual AVMs after GKRS.

Conclusion

The diagnostic accuracy of 4D-MRA at 3.0 T seems high, but there is still the possibility of further improving the spatiotemporal resolution of this technique.Arteriovenous malformations (AVMs) of the brain are congenital vascular anomalies consisting of a complex web of feeding arteries and draining veins, linked by an abnormal capillary bed—the so-called nidus. Although they can remain silent over a long period of time, because of their possible long-term morbidity or life-long risk of bleeding (approximately 2–4% per year), brain AVMs are usually treated by surgical resection, by complete obliteration by either endovascular embolisation or Gamma Knife® (Elekta Instrument AB, Stockholm, Sweden) radiosurgery (GKRS) or by a combination of all three [1-3].GKRS is increasingly used for the treatment of small or residual AVMs after surgical resection or embolisation. After GKRS, the microvascular structures within the AVM begin to be obliterated by the endothelial cell damage and proliferation of smooth muscle cells, which usually continues for 2–3 years [4]. Because the risk of bleeding persists as long as complete obliteration is not obtained, most physicians usually follow up patients at a regular interval to evaluate the response to GKRS. X-ray angiography is a gold standard for post-therapeutic monitoring of AVMs. However, it is an invasive procedure, and its potential neurological complications, ranging in incidence from 0% to 12.2%, hinder its use as a routine follow-up study [5,6]. Consequently, several non-invasive MRI and MR angiography (MRA) techniques have been proposed as a non-invasive alternative to X-ray angiography to assess the response of AVMs and adjacent brain parenchyma.Time-of-flight (TOF) MRA is a commonly used MRA technique for the assessment of residual AVMs after GKRS. However, TOF MRA produces only static images of AVMs and lacks haemodynamic information. Another non-invasive technique, contrast-enhanced four-dimensional MRA (4D-MRA), is an emerging new technique without these limitations and demonstrates a good correlation with X-ray angiography with respect to the Spetzler–Martin classification on initial assessment of AVMs prior to treatment [7-13]. However, the diagnostic accuracy of 4D-MRA for the detection of residual AVMs after GKRS is not well known. Only Gauvrit et al [14] reported that the sensitivity and specificity for the detection of residual AVMs after GKRS were 81% and 100%, respectively. But their study was performed using a 1.5 T MRI system.Therefore, the purpose of this study was to evaluate the diagnostic performance of 4D-MRA for detecting residual AVMs after GKRS at 3.0 T, compared with X-ray angiography.     

Ultrashort echo time MRI of pulmonary water content: assessment in a sponge phantom at 1.5 and 3.0 Tesla

PURPOSE

We aimed to develop a predictive model for lung water content using ultrashort echo time (UTE) magnetic resonance imaging (MRI) and a sponge phantom.

MATERIALS AND METHODS

Image quality was preliminarily optimized, and the signal-to-noise ratio (SNR) of UTE was compared with that obtained from a three-dimensional fast gradient echo (FGRE) sequence. Four predetermined volumes of water (3.5, 3.0, 2.5, and 2.0 mL) were soaked in cellulose foam sponges 1.8 cm³ in size and were imaged with UTE-MRI at 1.5 and 3.0 Tesla (T). A multiple echo time experiment (range, 0.1–9.6 ms) was conducted, and the T2 signal decay curve was determined at each volume of water. A three-parameter equation was fitted to the measured signal, allowing for the calculation of proton density and T2*. The calculation error of proton density was determined as a function of echo time. The constants that allowed for the determination of unknown volumes of water from the measured proton density were calculated using linear regression.

RESULTS

UTE-MRI provided excellent image quality for the four phantoms and showed a higher SNR, compared to that of FGRE. Proton density decreased proportionally with the decreases in both lung water and field strength (from 3.5 to 2.0 mL; proton density range at 1.5 T, 30.5–17.3; at 3.0 T, 84.2–41.5). Minimum echo time less than 0.6 ms at 1.5 T and 1 ms at 3.0 T maintained calculation errors for proton density within the range of 0%–10%. The slopes of the lines for determining the unknown volumes of water with UTE-MRI were 0.12±0.003 at 1.5 T and 0.05±0.002 at 3.0 T (P < 0.0001).

CONCLUSION

In a sponge phantom imaged at 1.5 and 3.0 T, unknown volumes of water can be predicted with high accuracy using UTE-MRI.The volume of extravascular lung water increases in response to a variety of cardiac and respiratory injuries (1). In pulmonary edema of cardiac origin, the volume of water in the interstitial and alveolar compartments is related to the degree of cardio-pulmonary dysfunction (1). In acute lung injury occurring in septic or burn shock and in other critically ill patients, increased extravascular water overloads the pulmonary weight. The resulting multifocal collapse in the dependent regions of the lung rapidly reduces the alveolar-capillary gas exchange (2). A stress failure of the pulmonary capillaries leading to pulmonary edema also occurs after exposure to toxic or highly noxious infectious agents (3). In addition to lung injury and respiratory distress syndrome, pulmonary edema due to altered fluid dynamics or vascular permeability manifests in postsurgical lung (4) and renal disease (5). In acute events of pulmonary edema, the lung water content is a marker of the severity of the disease and must be promptly quantified to guide fluid therapy and ventilator strategies (6). In chronic disorders, the volume of interstitial water reflects the activity of the infiltrative process, and this volume decreases after the administration of antifibrotic drugs (7).High-resolution computed tomography (HRCT) is the standard imaging technique for assessing lung anatomy. In addition, HRCT can suggest increased extracellular water in areas of the lung that appear as ground-glass opacities. Unfortunately, HRCT examinations are associated with an absorbed dose of ionizing radiation, which is of particular concern in young subjects and in longitudinal studies (8). A diagnostic method that could measure regional lung water without radiation exposure would have the potential to monitor noninvasively the progression of the disease and its response to therapy.Lung water content can be determined using ¹H magnetic resonance imaging (MRI) (9–11). Because most of the lung tissue consists of water, the peak amplitude of the magnetic resonance (MR) signal obtained following the excitation pulse reflects the concentration of water protons (9). Unfortunately, conventional MR sequences have difficulties in measuring lung signal because of the rather long echo times (TEs) of these sequences, compared to the short T2* of lung water. Therefore, previous attempts at measuring lung water by MRI potentially underestimated the true water content by up to 40% (10). Half radiofrequency excitations and subsequent radial mapping from the center of the k-space have enabled TEs of approximately 0.1 ms, which are sufficiently short to detect the peak amplitude of the signal that determines the true proton density (12–18).We hypothesized that ultrashort TE (UTE) MRI could provide reliable estimates of proton density and thus normative data for the analysis of unknown water content in a sponge phantom. Therefore, the aim of this study was to develop a predictive model for lung water content using UTEMRI and a sponge phantom.     

Iron overload: accuracy of in-phase and out-of-phase MRI as a quick method to evaluate liver iron load in haematological malignancies and chronic liver disease

Objectives

The purpose of this prospective study was to evaluate the accuracy of in-phase and out-of-phase imaging to assess hepatic iron concentration in patients with haematological malignancies and chronic liver disease.

Methods

MRI-based hepatic iron concentration (M-HIC, μmol g^–1) was used as a reference standard. 42 patients suspected of having iron overload and 12 control subjects underwent 1.5 T in- and out-of-phase and M-HIC liver imaging. Two methods, semi-quantitative visual grading made by two independent readers and quantitative relative signal intensity (rSI) grading from the signal intensity differences of in-phase and out-of-phase images, were used. Statistical analyses were performed using the Spearman and Kruskal–Wallis tests, receiver operator curves and κ coefficients.

Results

The correlations between M-HIC and visual gradings of Reader 1 (r=0.9534, p<0.0001) and Reader 2 (r=0.9456, p<0.0001) were higher than the correlations of the rSI method (r=0.7719, p<0.0001). There was excellent agreement between the readers (weighted κ=0.9619). Both visual grading and rSI were similar in detecting liver iron overload: rSI had 84.85% sensitivity and 100% specificity; visual grading had 85% sensitivity and 100% specificity. The differences between the grades of visual grading were significant (p<0.0001) and the method was able to distinguish different degrees of iron overload at the threshold of 151 μmol g^–1 with 100% positive predictive value and negative predictive value.

Conclusion

Detection and grading of liver iron can be performed reliably with in-phase and out-of-phase imaging. Liver fat is a potential pitfall, which limits the use of rSI.Iron overload is a clinically recognised condition with variety of aetiologies and clinical manifestations [1-4]. Liver iron concentration correlates closely with the total body iron stores [5]. The excess iron accumulates mainly in the liver and the progressive accumulation of toxic iron can lead to organ failure if untreated [2,4]. Several diseases causing iron overload, such as transfusion-dependent anaemia, haematological malignancies, thalassaemia, haemochromatosis and chronic liver disease, result in a large number of patients with a potentially treatable iron overload [1,2,4].Several quantitative MRI methods for iron overload measurement by multiple sequences have been established, such as proportional signal intensity (SI) methods and proton transverse relaxation rates (R₂, R₂*) [4,6,7]. A gradient echo liver-to-muscle SI-based algorithm [8] has been widely validated and used for quantitative liver iron measurement [8-11]. MRI-based hepatic iron concentration (M-HIC, μmol g^–1 liver dry weight) with corresponding R₂* [9] can be calculated with this method which is a directly proportional linear iron indicator, virtually independent of the fat fraction, as the echo times are taken in-phase [8,9]. This method showed a high accuracy in calibrations with the biochemical analysis of liver biopsies (3–375 μmol g^–1) of 174 patients. The mean difference of 0.8 μmol g^–1 (95% confidence interval of –6.3 to 7.9) between this method and the biochemical analysis is quite similar [8] to the intra-individual variability found in histological samples [12].The quantitative MRI methods are based on progressive SI decay, with the longer echo times due to relaxing properties of iron. Interestingly, this iron-induced effect is seen in MR images with multiple echoes [4,6-11], but also in dual-echo images, namely in-phase and out-of-phase imaging [13,14]. In-phase and out-of-phase imaging has become a routine part of liver MRI, performed initially for liver fat detection [6,13,15]. Quite recently some investigators have noticed an alternative approach of the sequence to detect liver iron overload due to the more pronounced SI decrease on in-phase images with the longer echo time [13,14]. Yet, to our knowledge, this is the first prospective study evaluating the accuracy of in-phase and out-of-phase imaging to assess hepatic iron concentration.The purpose of the study was to evaluate the capability and accuracy of dual-echo in-phase and out-of-phase imaging to assess hepatic iron concentration at 1.5 T in patients with haematological malignancies and chronic liver disease. MRI-based hepatic iron concentration (M-HIC, μmol g^–1) was used as a reference standard [8,9].     

Quantitative evaluation of ischemic myocardial scar tissue by unenhanced T1 mapping using 3.0 Tesla MR scanner

PURPOSE

We aimed to use a noninvasive method for quantifying T1 values of chronic myocardial infarction scar by cardiac magnetic resonance imaging (MRI), and determine its diagnostic performance.

MATERIALS AND METHODS

We performed cardiac MRI on 29 consecutive patients with known coronary artery disease (CAD) on 3.0 Tesla MRI scanner. An unenhanced T1 mapping technique was used to calculate T1 relaxation time of myocardial scar tissue, and its diagnostic performance was evaluated. Chronic scar tissue was identified by delayed contrast-enhancement (DE) MRI and T2-weighted images. Sensitivity, specificity, and accuracy values were calculated for T1 mapping using DE images as the gold standard.

RESULTS

Four hundred and forty-two segments were analyzed in 26 patients. While myocardial chronic scar was demonstrated in 45 segments on DE images, T1 mapping MRI showed a chronic scar area in 54 segments. T1 relaxation time was higher in chronic scar tissue, compared with remote areas (1314±98 ms vs. 1099±90 ms, P < 0.001). Therefore, increased T1 values were shown in areas of myocardium colocalized with areas of DE and normal signal on T2-weighted images. There was a significant correlation between T1 mapping and DE images in evaluation of myocardial wall injury extent (P < 0.05). We calculated sensitivity, specificity, and accuracy as 95.5%, 97%, and 96%, respectively.

CONCLUSION

The results of the present study reveal that T1 mapping MRI combined with T2-weighted images might be a feasible imaging modality for detecting chronic myocardial infarction scar tissue.In ischemic cardiac diseases, differentiating viable from nonviable myocardial tissue is important for clinical decision-making (1). The viable myocardium with decreased blood-flow such as hibernating or stunned myocardium will recover function following coronary revascularization, whereas during the chronic stage of infarction, a dense fibrotic scar replaces the infracted myocardium and this scar tissue will not recover function (2). Sometimes more aggressive treatment is needed to improve blood flow such as angioplasty, stenting, and coronary artery bypass surgery. Therefore, evaluation of viability is critical for myocardium.Positron-emission-tomography, single-photon-emission computed tomography and dobutamine echocardiography are noninvasive techniques for assessing myocardial viability. Although these techniques have proven use in clinical practice, there are several limitations that may reduce their diagnostic accuracy (3). Infracted or noninfracted myocardium is determined arbitrarily within a viewing window (i.e., the range of gray/color values to be selected for viewing) by these techniques (4). Therefore, assessment of myocardial viability will vary qualitatively and subjectively due to the pitfalls of the techniques.Recently, delayed contrast-enhancement (DE) cardiac magnetic resonance imaging (MRI) has been used for an increasing number of clinical applications in cardiac diseases. However, there are conflicting reports concerning the utility of contrast-enhanced MRI after infarct healing. Firstly, this method makes a qualitative assessment of myocardial fibrosis, similar to previously mentioned methods. In addition, with conventional DE-MRI sequences, signal intensity is expressed on an arbitrarily scale that differs from one imaging to another. Therefore, this method is not suitable for direct signal quantification (5). Furthermore, concerns about the increased risk of gadolinium-induced nephrogenic systemic fibrosis have increased gradually in populations with impaired renal function (6, 7).T1 mapping is a novel cardiac MRI technique and it allows measurements of absolute T1 relaxation times for each pixel (8). This technique involves the sampling of signal recovery during multiple measurements following a preparation pulse. The resulting relaxation time is then determined for each pixel contained in a parametric image, referred to as T1 mapping (9). In contrast to other imaging techniques, T1 mapping achieves signal quantification (in milliseconds) on a standardized scale. It reflects tissue changes without need for signal intensity thresholds, post-processing, reference region-of-interest, or contrast material. The quantitative evaluation of myocardial T1 values (T1 mapping) has been used recently to identify patients with diffuse fibrosis or myocarditis, or acute and chronic myocardial infarction (MI) (4, 10). In addition, although previous studies show that MI quantification can be achieved using a magnetic field strength of 1.5 Tesla (T) (7), to our knowledge, these values have not yet been reported on chronic infarction for 3.0 T cardiac MRI.The purpose of this study was to use high-resolution unenhanced T1 mapping to investigate the feasibility of using 3.0 T cardiac MRI to detect scar areas in myocardium resulting from chronic MI.