3T magnetic resonance for evaluation of adult pulmonary tuberculosis

Journal Pre-proof 3T magnetic resonance for evaluation of adult pulmonary tuberculosis Qinqin Yan, Shuyi Yang, Jie Shen, Shuihua Lu, Fei Shan, Yuxin Shi

PII:

S1201-9712(20)30064-3

DOI:

https://doi.org/10.1016/j.ijid.2020.02.006

Reference:

IJID 3952

To appear in:

International Journal of Infectious Diseases

Received Date:

19 September 2019

Revised Date:

17 January 2020

Accepted Date:

9 February 2020

Please cite this article as: Yan Q, Yang S, Shen J, Lu S, Shan F, Shi Y, 3T magnetic resonance for evaluation of adult pulmonary tuberculosis, International Journal of Infectious Diseases (2020), doi: https://doi.org/10.1016/j.ijid.2020.02.006

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3T magnetic resonance for evaluation of adult pulmonary tuberculosis

Qinqin Yana,b,1, Shuyi Yangb, Jie Shenb, Shuihua Luc, Fei Shanb*, Yuxin Shib*

Shanghai Institute of Medical Imaging, Shanghai, Fudan university, Shanghai, China.

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Department of Radiology, Shanghai public health clinical center, Shanghai, China.

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Department of Tuberculosis, Shanghai public health clinical center, Shanghai, China.

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* Correspondence to:

Shan Fei, Department of Radiology, Shanghai Public Health Clinical Center, Fudan

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University, Shanghai 201508, China (E-mail: [email protected])

Shi Yuxin, Shanghai Public Health Clinical Center, Fudan University, Shanghai 201508,

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China (E-mail: [email protected])

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MRI is comparable to CT in detection of tree-in-bud signs, nodules(≥5mm) and consolidations.

MRI has more advantages in presenting caseous necrosis, liquefaction, active cavities and

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Highlights

abnormalities of lymph nodes and pleura. 

Compared to CT, MRI has lower sensitivity for detecting calcified nodules and noncalcified nodules(＜5mm).

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Free-breathing T1-weighted Star-VIBE and T2-weighted 2D-fBLADE TSE are suitable

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for chest imaging, especially for patients with poor breath-holding.

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MRI with non-radiation is an alternative tool for follow-up examinations, especially for children, young women and pregnant women.

Abstract: Objectives: To evaluate image quality and detection rate of four 3T magnetic resonance

imaging(MRI) sequences and MRI performances of 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(2DfBLADE 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

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signal to noise ratio(SNR), contrast to noise ratio(CNR) and 5-points scoring scale. The total sensitivity was also compared between CT and MRI.Inter-observers agreement on 5-points

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scoring scale was calculated by cohen’s kappa(k). SNR, CNR and 5-points scoring scale were

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compared using two-tailed pared t-test. Using CT as reference, the MRI detection rate of pulmonary abnormality was evaluated by Pearson’s Chi-square test. Furthermore, the sizes of

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the nodules (≥5 mm) were compared using intraclass correlation coefficient.

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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

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agreement on 5-points 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

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Star-VIBE and standard VIBE, 2D-fBALDE TSE and 3D-SPACE. MRI is comparable to CT in detecting consolidation, cavity, non-calcified nodules of ≥5mm and tree-in-bud signs compared to CT. MRI detected non-calcified nodules of ＜5mm, 5-10mm, ≥10mm 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, abnormalit ies 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.

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Keywords: pulmonary tuberculosis, 3T MRI, image quality, detection

Introduction：

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To date, TB is still the focus of the global public health. According to the latest WHO

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data reported, about 10 millions people had TB in 2018 with children accounting for 10%. As

delayed diagnosis and treatment[1].

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one of the top ten lethal causes, about 1,600 thousands deaths were caused by TB because of

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For patients with TB, multiple computed tomography (CT) or X-ray follow-up examinations are needed at 2- or 4-month intervals during the treatment period, which ranges from six months to several years [2]. A variety of factors, such as human immunodeficiency

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virus (HIV) and multidrug-resistance (MDR), have possibly caused the unfavorable treatment and recurrence of TB, which makes the treatment time longer [3-5]. Chest X-ray is the main inspection method, but this is only initially correct in approximately 49% of pulmonary TB

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cases [6]. CT is more sensitive in detecting lesions, including lymphadenopathy, early bronchial disseminated lesions and pleural abnormalities. However, cumulative radiation exposure is closely correlated to increased risk of cancer, such as breast cancer and leukemia, especially for young women, children, pregnant women, etc[7-9]. A cumulative CT effective dose in excess of 100 mSv evidently increases cancer risk, and cohort studies have demonstrated that the expected cancer risk is greater than 6% due to the recurrent CT

examinations (>5 examinations) [9-12]. Magnetic resonance imaging (MRI) has no radiation, and provides a high soft-tissue contrast of the lesion, which is expected to be an alternative tool for pulmonary imaging. However, this is changeable for MRI in providing high-quality images for the diagnosis due to low proton density, motion artifacts and susceptibility, especially for patients with poor breath-hold [13]. Additionally, conventional MRI and functional measurements are also useful for the differential diagnosis of tumor-like tuberculomas [14-18]. Compared to malignancy, tuberculomas present with a statistically

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higher apparent diffusion coefficient (ADC) on diffusion-weighted imaging (DWI) [15,16]. In addition, these manifest with lower Ktrans and Kep on dynamic contrast-enhanced MRI

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(DCE-MRI) [17,18].

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This study is to evaluate image quality detection rate of four 3T MRI lung sequences and MRI performances of pulmonary tuberculosis-associated in comparisons with CT.T1-

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weighted free-breathing Star-VIBE and and standard breath-hold VIBE, T2-weighted 2D-

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fBLADE TSE and 3D-SPACE were compared to in terms of images quality and detection rate. The results manifested T1-weighted free-breathing Star-VIBE and T2-weighted 2DfBLADE TSE, with higher SNR and less motion artifacts, were suitable for chest imaging.

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MRI has more advantages in presenting tuberculosis-associated lesions including caseous necrosis, liquefaction, active cavities, abnormalit iesof lymph nodes and pleura.

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Subjects and methods:

Subjects and clinical information This prospective study was performed from December 2018 to May 2019 and was

approved by the institutional review board (IRB)(2019-S019) . This study was also carried out in accordance with The Code of Ethics of the World Medical Association (Declaration of Helsinki). All participants were provided informed consent to participate in this study. Forty-

five patients who were diagnosed as TB based on effective anti-tuberculosis treatment, acidfast bacillus (AFB) testing or the detection of M. tuberculosis in sputum were examined on 3T-MRI and CT. Five of them were exclude, because three patients showed mediastinal tuberculous lymphadenopathy with no lung parenchyma lesions and two patients had noncompliance during MRI examination. A patient selection flow chart was listed in Chart 1. The enrolled forty patients including 26 males with mean age of 42.8±14.0years (range 18-70 years) and 14 females with mean age of 53.3±14.8 (range 20-78 years). Among forty patients

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were 5 patients with HIV, 7 patients with diabetes and 2 patients in immuno-compromised conditions. 34 patients had some typical symptoms of pulmonary TB such as lower fever,

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cough and chest pain and so on. The other 6 patients had no obvious clinical manifestations.

42 patients

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Underwent CT examination

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Underwent MRI examination

40 patients

Images analysis Chart 1.

Notes: Exclusion criteriaa: a. no pulmonary parenchyma lesions; b. uncooperative patients. Exclusion criteriab:a.with pacemakers, neurostimulators, artificial metal heart valves, etc; b. uncooperative patients.

Lung MRI protocol All lung MRI images were obtained using 3T whole-body MRI scanner(MAGNETOM

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Skyra, Siemens Healthcare, Erlangen, Germany) with a 18-element body wrap coil. Firstly, a coronal T1-weigthed Dixon images were used to assess lesion distribution and extent.

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an axial T1-weighted free-breathing Star-VIBE and standard VIBE, both with Spectral

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Attenuated Inversion Recovery (SPAIR) and T2-weighted 2D-fBLADE TSE with Inversion Recovery (IR, TI=240 ms) and 3D-SPACE with SPAIR, were respectively performed for

Chest CT protocol

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each patient. The detailed parameters are presented in Table 1.

All patients underwent examination on CT 320-detector system(Aquilion Vision, Canon

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Medical Systems, Japan) in the case of breath-holding after inspiration. The following imaging parameters were applied: detector width, 80 *0.5 mm; pitch, 0.813; tube voltage, 120kV; automatic tube current with SD 10 (Sure Exp 3D set, maximum: 440mA, minimum:

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60mA). All CT images with 1 mm contiguous section thickness were reconstructed by means of adaptive iterative dose-reduction with three-dimensional processing (AIDR 3D, standard) and a high frequency reconstruction algorithm (FC56) for the lung window setting, and with a standard reconstruction algorithm (FC17) for the mediastinum window setting. The lung window width and level were adjusted appropriately by the reference standards of 1,600 and −600 Hounsfield unit (Hu). The imaging volume was from the pulmonary apex to the

costophrenic angle. The average total radiation dose is approximately 5.75 mSv for each patient.

1.Comparisons of image quality assessment 1.1 The signal-to-noise ratio (SNR) and contrast-to-noise ratio (CNR) Considering the effects noise of background, and the motion artifacts within the vessel and bronchus, the SNR and CNR were separately compared using two different methods (Method

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1 and Method 2) [19,20]. The same pixel of regions of interests(ROIs) were drawn in the

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anterior and posterior areas of each lungs to obtain the average signal intensity of the lung parenchyma(SI lung). These ROIs were at a distance of at least 20mm from the pleura and

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avoided visible pulmonary vessels and artifacts. Signal intensity in the airways(SI airways) were measured by drawing the same pixel of ROIs in the lumen of the trachea, left or right

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main bronchus. Signal intensity in the vessels(SI vessels) were measured by drawing ROIs in

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aortic arch or thoracic aorta. Signal intensity in the muscles(SI muscles) were measured by drawing ROIs in the muscle. Signal intensity in the background(SI background) was the average of ROIs which were drawn in the anterior and posterior, left and right four areas in

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the background. SD were the average of SDs of background. Method 1 SNR1 = SI lung/SD and CNR1= (SI muscle-SI lung)/SD.

Method 2 SNR2 = (SI lung /SI airway) · 100% and CNR2 = (SI lung – SI airway) /SI vessel ·

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100%

1.2. 5-points scoring scale The 5-point scoring scale was used to evaluate of effects of motion artifacts on the lesions and main pulmonary structure [21]. The T1-weighted Star-VIBE and standard VIBE, T2weighted 2D-fBALDE TSE and 3D-SPACE of images of the same patient were respectively

rated. Two radiologists with 3- and 1-year experience in thoracic imaging were blind to subjects and MRI acquisition sequences. The 5-point scoring scale was presented, as follows: 5 points the boundary of tissue structure is clear, no artifacts, can be used for diagnosis; 4 points - the boundary of tissue structure is slightly blurred, there are some artifacts, which can be used for diagnosis; 3 points - the boundary of tissue structure is blurred, there are obvious artifacts but not in the range of ROI, which almost can be used for diagnosis; 2 points - image is blurred, a small amount of artifacts in the ROI, which almost can be diagnosed; 1 point -

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image is blurred, ROI has obvious artifacts, which can not be used for diagnosis. 2.Comparisons of detecting pulmonary abnormality between CT and MRI

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All CT and MRI images were sent to Picture Archiving and Communication

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Systems(PACS) for image analysis. MRI findings of pulmonary TB included consolidation, non-calcified nodule or mass, calcified nodule, tree-in-bud sign, cavity, caseous necrosis,

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liquefaction, abnormality of pleura and lymph nodes. Using CT images as references to

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evaluate the size and distribution of consolidation, non-calcified nodule or mass, calcified nodule, tree-in-bud sign, cavity. Consolidations were defined as patchy hyper-intensity which cover the intensity of vessels. As for non-calcified nodules or mass, a round-like non-calcified

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lesion with a diameter not less than 3cm was defined non-calcified nodules or mass were classified as lesions with diameter＜5mm, 5-10mm and ≥1cm. Calcified nodules were nodules accompanied with calcification. Cavity was described as gas-filled space within

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pulmonary consolidation, a mass, or a nodule. Tree-in-bud signs are 2-4 mm nodules or the linear hyper-intensity along the peripheral bronchus. Caseous necrosis was defined as moderate or slightly low signal on T2-weighted image [22-23]and liquefaction was obviously high signal on T2-weighted image. Normally, the pleura manifests as a smooth line of softtissue attenuation internal to the rib or paravertebral region, which is less than 1 mm at the mediastinal window of the high-resolution CT, and is invisible on the MRI. Merely thickness

and effusion were present on the MRI [24]. Liquid with a depth of more than 2 mm was considered as effusion in the present study. Lymphadenopathy refers that the short axis of the lymph node, which is more than 1 cm on the CT mediastinal window. In addition to the increase in volume, lymph nodes abnormality also consists of variable signals on the T2weighted MRI. The size of nodules or masses were measured in the largest diameter. The MRI findings of lesions range were divided into full display, partial display, and no display. If there

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are full display or partial display, we viewed it as positive(100%). Statistical Analysis: The statistical analysis was performed using IBM SPSS Statistics version 23.0 (IBM

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Corp., Armonk, NY, USA). A two-tailed paired t-test was used to compare SNR and CNR

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between T1-weighted Star VIBE and standard VIBE, T2-weighted fBLADE TSE and 3D SPACE. Cohen’s kappa coeffificient (k) was calculated to assess the degree of agreement

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about 5-points scoring scale of MRI images. A k value of <0.00 was considered to indicate

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poor agreement. A k value of 0.00–0.20, 0.21–0.40, 0.41–0.60, and 0.61–0.80 was considered to indicate slight, fair, moderate, and substantial agreement, respectively. A value within 0.81–1.00 was considered to indicate excellent agreement[25]. The MRI sensitivities of

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detecting pulmonary lesions were calculated as the ratio of detection and were compared using a Pearson chi-square test. A value of p<0.05 was considered statistically significant. Intra-class correlation coefficient was used to compare the size of the nodules between CT

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and MRI. Results:

1 Comparisons of image quality assessment The results of the image quality assessment of SNR and CNR are presented in the Table 2. Using Method 1, the SNR of Star-VIBE was significantly higher than that of the standard VIBE (P<0.01), while the CNR of both has no difference (P>0.05). Both the SNR and CNR

of 2D-fBLADE TSE were statistically higher, when compared to those of 3D-SPACE (P<0.01). Using Method 2, the SNR of Star-VIBE is significantly higher (P<0.01), and the CNR was statistically indifferent, when compared to standard VIBE (P>0.05). The SNR of 2D-fBLADE TSE was obviously higher, when compared to 3D-SPACE (P<0.01), while the CNR of 2D-fBLADE TSE was lower, when compared to 3D-SPACE (P<0.01). The two different methods for measuring the SNR and CNR practically reached an agreement. The kvalue of two physicians came to a excellent agreement on the image quality with 5-poitns

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scoring scale, with a k-value of 1.00, 0.85, 0.85 and 0.83 for Star-VIBE, standard VIBE, 2DfBLADE TSE and 3D-SPACE, respectively. . Free-breathing Star-VIBE with average grade

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of 4.88±0.33 was slightly higher than standard VIBE with average grade of 4.75±0.54. But

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the difference had no statistical significance(P＞0.05). Compared with T2-weighted 2DfBLADE TSE with a average grade of 4.54±0.55, 3D-SPACE had relatively more respiratory

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artifacts in lung fields outside lesions with a average grade of 3.54±1.11(P ＜ 0.01). Figure

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1A-1D shows how to rate using the 5-point scoring scale.

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2 Comparisons of the detected pulmonary abnormalities The comparisons of the detection rate for inter-sequences are presented in the Table 3. The detection rate of inter-sequences between T1-weighted Star-VIBE and standard VIBE was comparable (P>0.05). The T2-weigted 2D-fBALDE TSE has a higher detection rate of tree-

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in-bud sign and nodule (<10 mm), when compared to 3D-SPACE, but the differences was no statistically significant (P>0.05). A direct comparison of imaging performances between CT and 3T-MRI was summarized in the Table 4. Compared to CT, MRI could manifest 69.6% of well-definite nodules with a size of approximately 3-5 mm. The MRI sensitivity of detecting nodules with size less than 5mm was statistically lower than CT(P＜0.01). For non-calcified nodules of size 5-10mm, ≥10mm, the sensitivity was 90.6% and 100% respectively. and there

was no significant difference, when compared CT performances (P>0.05). And the overall sensitivity of nodules ≥5mm was up to 96.0%. About 25.7% of non-calcified nodules(≥5mm) showed ring-like higher signal peripherally and slightly low signal in the center. The consistency of the nodule size (≥5 mm) was excellent between CT and T1-weighted StarVIBE, with an ICC value of 0.9902 (95% CI: 0.9832-0.9942). In comparison of CT, the total sensitivity of calcified nodules was up to about 88.5% on MRI images(P ＜ 0.05). Calcified nodules showed on T1-weighted images were fully displayed with low intensity accounting

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for 96.1% and slightly high intensity accounting for 3.9%. And about 10.5% of calcified

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nodules was full display with low intensity, 7.0% was partial display with peripherally high intensity and 82.5% was no display on T2-weighted images. Figure2. showed the MRI

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performances of mass accompanied with calcification. However, the 3T-MRI detection rate of pulmonary abnormality were almost paralleled to CT in describing non-calcified

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nodules(≥5mm), tree-in-bud sign, consolidation and cavity(P＞0.05). .Compared to CT,

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94.7% of tree-in-bud signs were visible on 3-T-MRI, which was comprised of partial display accounting for 47.2% and full display accounting for 52.8%(Figure3.). All of cavities and

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consolidations were fully display on 3T-MRI images. Cheese-like cavities appeared as stratification or concentric circle signs on the T2-weighted images. Peripherally dilated draining bronchus, liquid level, or necrosis were presented within 50.0% of the cavities (n=6, Figure 4). However, these features were not obvious on the CT images. Additionally,caseous

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necrosis and qualification were important signs of worsening lesions. In the present study, 31.6% of nodules and consolidations (n=30) progress to partial or complete caseous necrosis, which presents as moderate or slightly low intensity on T2-weighted images (Figure 5A). Approximately 5.3% of the liquefaction was detected within the nodules and cavities (n=5, Figure 5B). In contrast, it is difficult for CT to distinguish caseous necrosis due to the visible minimal differences in density on the mediastinum and lung window. Approximately 22

enlarged lymph nodes were detected on the CT mediastinum window and T2-weighted images, respectively. In addition, MRI found small lymph nodes( ＜ 1cm)(n=22) abnormal signal, which included 18.2%(n=4) of obviously high intensity, 36.4%(n=8) of slightly high intensity and 45.4%(n=10) of moderate or slightly low intensity. By comparison, CT diagnosed lymph nodes as negative if it was less than 1cm. On the mediastinal window of plain CT, approximately 17.5% (n=7) of patients presented with a small amount of fluid, while four of these patients had a smooth line-like pleural thickness. In contrast, seven

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additional patients are found with a small amount of local fluid intensity on the T2-weighted

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images, in cases of consolidations of the adjacent pleura.

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Discussion:

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CT is an important examination to evaluate chest lesions. However, accumulative radiation from frequent CT scans is worrying and cannot be ignored. MRI without radiation

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is especially suitable for children, young women, pregnant patients and patients who need long-term follow-up examination. Motion artifacts, relatively low SNR and spatial resolution

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are the critical causes resulting in poor image quality in the clinical routine. Conventional breath-hold technique is unsuitable for patients with pulmonary function incompetence such as the elderly and patients with wide-range lesions and so on. conventional T2-weighted sequences such as TSE have an obvious blurring effect and inferior T2-contrast caused by

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T2-decaying [26,27].In this study, free-breathing T1-weighted Star-VIBE and T2-weighted 2D-fBLADE TSE, with higher SNR and less motion artifacts, were suitable for imaging of pulmonary TB through the comparison of image quality and detection rate. The 3D StarVIBE sequence can provide higher SNR with thinner thickness. And this free-breathing sequences are also feasible for children, patients with poor breath-holding. Due to rotated kspace sampling in a non-Cartesian manner, Star-VIBE and 2D-fBLADE TSE had higher

SNR and minimal motion artifacts, which further verified that non-Cartesian acquisition and reconstruction was effective for the motion correction and improvement of SNR[28-29]. But the temporal resolution of free-breathing Star-VIBE reduced. Compared with the standard VIBE, which requires about 30-50s, the free-breathing Star-VIBE need approximately two minutesfor the whole adult lungs scanning. Therefore, a breath-hold standard VIBE can save time for patients with good compliance. Additionally, as previously reported[26], 2DfBLADE TSE showed clearer interface of lesions-lung with minimal T2-decalying compared

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to 3D-SPACE. Although 3D-SPACE had advantages of reduction of partial volume artifacts due to thin continue acquisitions and no data missed because of layer-free images[30-31], it

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was failed to evaluate the lung field outside lesions because of respiratory artifacts. A greater

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flip angle and thickness of 3D-SPACE would further be explored to reduce motion artifacts. Pulmonary TB is a long course of disease, and consist of a complex mixture of new and

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old lesions. Historically, CT diagnoses active or inactive TB via imaging features, such as

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consolidation, tree-in-bud signs, thick-walled cavity, etc. However, it remains difficult to distinguish caseous necrosis on plain CT. Compared with CT in detecting of pulmonary abnormality, 3T-MRI was parallel to CT in identification of most features including

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consolidation, non-calcified nodules(≥5mm), tree-in-bud sign and cavity. In addition, it is superior in terms of the manifestation of caseous necrosis, liquefaction and small amounts of pleural effusion on T2-weighted images. MRI is sensitive for demonstrating the liquid level,

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necrosis and dilated draining bronchus within the active cavity, which is a reminder for atypical pulmonary tuberculosis with no sputum or negative sputum acid-fast staining. In contrast to CT, calcified nodules are detected by MRI with statistically lower sensitivity. As signs of improved or cured lesions, calcification can easily be distinguished via low or no signal on T2-weighted images. In the present study, part of consolidations or nodules with incomplete calcification had a high signal on the T2-weighted images, which might indicate

the remaining inflammation or early-stage of improvement of active lesions. Centrilobular nodules have been recognized as an important sign of bronchial dissemination. In the present study, approximately 30.4% of nodules with a size of 3-5 mm were invisible on the MRI. Therefore, an initial CT examination is very important for the overall evaluation of lesions. Based on pathology and corresponding signal characteristics on T2-weighted images, the procession of lesions was classified as (1) inflammatory stage: slightly high intensity; (2) caseous necrosis: iso-intensity or slightly low intensity in the center with peripheral higher-

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intensity; (3) qualification: obviously high intensity; (4) calcification and fibrosis: low intensity[32-34]. In addition, lymphadenopathy presents variable signal characteristics on the

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T2-weighted images. For small lymph nodes diagnosed as negative by CT, the same signal

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abnormalities were observed on the T2-weighted images. The MRI might suggest a higher sensitivity for lymph node involvement, as previously reported [33,35].

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. In the experience of the investigators, conventional MRI is an alternative tool for the

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follow-up of patients, which is a good strategy for concerns on ionizing radiation due to frequent recurrent CT or X-ray examinations. The present study also provides free-breathing MRI protocols with qualified image quality, which is suitable for children and patients with

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poor breath-holding.

This study also had some limitations. One important limitation was a small size of samples. And all enrolled patients were also absent of follow-up. Additionally, some other

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pulmonary TB imaging features like ground-glass lesions and miliary nodules，lack of discussion. Therefore, further study need additional cases and those patients enrolled should be followed up timely. In conclusion, free-breathing T1-weighted Star-VIBE and T2-weighted 2D-fBLADE TSE, with satisfied image quality, were optimized sequencesespecially for patients with poor breath-holding. Furthermore, MRI was comparable to CT in detecting the majority of

pulmonary abnormality. MRI had more advantages to show caseous necrosis, liquefaction, active cavity, abnormality of lymph nodes and pleura, which indicated active pulmonary TB and needed further management. In general, free-radiation MRI is an alternative and ideal inspection method for pulmonary TB patients who need long-term follow-up, especially for children, young women and the pregnant.

Conflict of Interest

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No conflict of interest to declare.

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Funding Source

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The study sponsors had no involvement of study design, collection, analysis and

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interpretation of data.

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Ethical Approval

The study was approved by the ethics committee of Shanghai public health

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clinical center, Shanghai, China.

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[21]. Laqmani A , Avanesov M , Butscheidt S , et al. Comparison of image quality and visibility of normal and abnormal findings at submillisievert chest CT using filtered back projection, iterative model reconstruction (IMR) and iDose4?[J]. European Journal of Radiology, 2016, 85(11):1971-1979. [22]. Chung, M., H.S. Lee and S. Park, MR imaging of solitary pulmonary lesion: emphasis on tuberculomas and comparison with tumors. Journal of Magnetic Resonance Imaging, 2015. 11(6): p. 629-637.

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Figures:1-5

B

C

D

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Figure 1. showed two nodules with diameters 7mmand 9mm respectively in free-breathing

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Star-VIBE, standard breath-hold VIBE, 2D-fBLADE TSE and 3D-SPACE(from A to D). the white arrow in the Star-VIBE(A) was the dome, the edge of pulmonary structure is clear with

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almost no artifacts, which was rated as 5-points. Standard VIBE(B) showed minimal respiratory motion artifacts(the white arrow) and two nodules with blurred edges, which was

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rated as 4-points. 2D-fBLADE TSE(C) described clearly pulmonary vessels and the contour of two nodules with almost no artifacts, which was rated as 5-points. The white arrow indicated local pleural reaction. 3D-SPACE(D) showed a little motion artifacts in the lung

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field outside lesions, which was rated as 4-points.

A

C

B

D

Figure 2. CT images showed mass accompanied with calcification in the upper lobe of right

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lung(A and B). MRI showed heterogeneous intensity on T1-weighted fat-pressed images(C).

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Calcification was no signal with peripheral ring-like high intensity and component of solid

A

B

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was slightly high intensity on T2-weighted 2D-fBLADE TSE(D).

C Figure 3. Figure3A. CT image showed tree-in-bud sign in the middle lobe of right lung, which was

corresponding partial display in T1-weighted and full display in T2-weighted. Figure3B. CT image showed tree-in-bud sign in the middle lobe of right lung, which was corresponding full display in T1-weighted and false negative in T2-weighted. Figure3C. CT image showed treein-bud sign in the middle lobe of right lung, which was corresponding not display at all in T1-

B

C

D

G

H

F

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weighted and full display in T2-weighted.

Figure 4. CT images(A and B) showed thick-walled cavity in the upper lobe of left lung. The peripherally dilated draining bronchus were clearly described on MRI images(C and D). Additionally, local pleural effusion was seen on T2-weighted images(D). CT images(E and F) showed cavity within mass in the meddle lobe of right lung. Necrotic material was seen on MRI images(G and H). Two small lymph nodes(＜1cm) showed slightly high intensity on

T2-weighted images(H).

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B

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Figure 5. Figure5A. CT images(A and B) showed nodule in the upper lobe of left lung. T2weighted image showed corresponding slightly low intensity with ring-like slightly high

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intensity which indicated caseous necrosis. Figure5B. CT images(A and B) showed nodule in the upper lobe of left lung. T2-weighted image showed corresponding obviously high intensity which indicated qualification. Figure5C. T2-weighted image showed pleural

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thickness and a small amount of pleural effusion.

Table1. Detailed parameters of Star-VIBE, standard VIBE, 2D-fBLADE TSE, 3D-SPACE Sequences Star-VIBE Standard VIBE 3D-SPACE

TR/TE/ms 2.79/1.39 3.67/1.81 1600/108

Voxel size/mm Average

Breathing

1.2*1.2*2.0

1

Free-breathing

1.1*1.1*3.0

2

Breath-holding

1.2*1.2*2.0

2

Free-breathing

1.2*1.2*3.0

1

Free-breathing

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fBLADE TSE 1870/69

Scan tim Thicknes s/mm FOV/mm e/s 103 2 380 30-50 3 350 160 2 380 115 3 380

Table 2. Comparisons of SNR and CNR in the T1-weighted and T2-weighted sequences Star-VIBE SNRa

40.86±10.86

CNRa

204.63±53.29

Standard VIBE 8.09±2.72

P-value

2D-fBLADE TSE 3D-SPACE

P-value

＜0.01

17.51±3.41

13.15±4.96

＜0.01

＞0.05

92.71±34.85

121.86±37.1 8

＜0.01

194.94±57.41 SNRb

0.69±0.13

0.37±0.15

＜0.01

0.68±0.30

0.52±0.23

＜0.01

CNRb

0.06±0.03

0.05±0.03

＞0.05

0.39±0.33

0.28±0.21

＞0.05

Notes:

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SNR a and CNR a : used the formula of Method 1. SNR = SI lung / SD and CNR = (SI muscle - SI lung) / SD

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SNR b and CNR b : used the formula of Method 2. SNR = (SI lung / SI airway) ×100% and

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CNR = (SI lung - SI airway) / SI vessel ×100%

Table 3. Comparisons of detection rates of MRI inter-sequences T2-weighted sequences

P-value

Star-VIBE

Standard VIBE

2D-fBLADE TSE

3D-SPACE

Pa

Pb

Tree-in-bud sign

63.3%

70.0%

79.3%

55.2%

＞0.05

0.05

Nodules <5 mm

69.6%

69.6%

21.7%

17.4%

＞0.05

＞0.05

5-10 mm

86.7%

83.3%

74.1%

66.7%

＞0.05

＞0.05

≥10 mm

100%

100%

96.2%

96.2%

＞0.05

＞0.05

Consolidation

100%

100%

100%

100%

＞0.05

＞0.05

Cavity

100%

100%

100%

100%

＞0.05

＞0.05

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Notes:

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T1-weighted sequences

P a : The P-value is from the comparisons of T1-weighted Star-VIBE and standard VIBE.

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P b: The P-value is from the comparisons of T2-weighted 2D-fBLADE TSE and 3D-SPACE.

Table4. Comparisons of the detected pulmonary abnormalitiesbetween CT and MRI MRI a

MRI sensitivity

23

16

69.6%*

5-10 mm

32

29

90.6%

≥10 mm

42

42

100%

Calcified nodules

57

51

89.5%*

Consolidation

24

24

100%

Tree-in-bud

38

36

94.7%

Cavity

12

12

100%

Caseous necrosis

-

30

100%

Liquefaction

0

5

100%

Pleurisy

7

14

Lymph nodes ≥10 mm

22

22

＜10 mm

22

22

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Notes:

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Nodules ＜5 mm

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CT a

Abnormalities

CT a : The number of lesions were detected on the mediastinal or lung window of CT.

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MRI a: The numbers of lesions detected on T1-weighted Star-VIBE or T2-weighted 2DfBLADE TSE.

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*The Pearson’s chi-square test has statistical differences(P<0.05)