Diffusion-weighted MRI of lymphoma: prognostic utility and implications for PET/MRI?

Purpose

With the recent introduction of PET/MRI, we investigated whether diffusion-weighted imaging (DWI) can complement PET for predicting local treatment response in Hodgkin lymphoma.

Methods

This retrospective study included 39 patients selected from a hospital database with a histological diagnosis of Hodgkin lymphoma undergoing whole-body MRI (supplemented by DWI) and PET/CT before and after two cycles of vincristine, etoposide, prednisolone and doxorubicin (OEPA). The pretreatment volume, MRI apparent diffusion coefficient (ADC) and PET maximum standardized uptake value (SUV_max) of the largest nodal mass were determined quantitatively for evaluation of the local response following two cycles of OEPA. Quantitative pretreatment imaging biomarkers (disease volume, ADC, SUV_max) were compared between sites with an adequate and those with an inadequate response using Fisher’s exact test and Mann Whitney statistics. Multivariate models predictive of an inadequate response based on demographic/clinical features, pretreatment disease volume and SUV_max without (model 1) and with (model 2) the addition of ADC were derived and crossvalidated. The ROC area under curve (AUC) was calculated for both models using the full dataset (training) and the crossvalidation (test) data.

Results

Sites with an adequate response had a significantly lower median pretreatment ADC (1.0?×?10^?3mm²s^?1) than those with an inadequate response (1.26?×?10^?3mm²s^?1; p?<?0.01). There were no significant differences in patient demographic/clinical parameters, pretreatment SUV_max or pretreatment nodal volume between sites with inadequate and adequate response. The ROC-AUCs for prediction of an inadequate response for the training and test data for model 1 were 0.90 and 0.53, and for model 2 were 0.84 and 0.71, respectively.

Conclusion

DWI complements PET for prediction of site-specific interim response to chemotherapy.     

A simple scoring system for breast MRI interpretation: does it compensate for reader experience?

Purpose

To investigate the impact of a scoring system (Tree) on inter-reader agreement and diagnostic performance in breast MRI reading.

Materials and methods

This IRB-approved, single-centre study included 100 patients with 121 consecutive histopathologically verified lesions (52 malignant, 68 benign). Four breast radiologists with different levels of MRI experience and blinded to histopathology retrospectively evaluated all examinations. Readers independently applied two methods to classify breast lesions: BI-RADS and Tree. BI-RADS provides a reporting lexicon that is empirically translated into likelihoods of malignancy; Tree is a scoring system that results in a diagnostic category. Readings were compared by ROC analysis and kappa statistics.

Results

Inter-reader agreement was substantial to almost perfect (kappa: 0.643–0.896) for Tree and moderate (kappa: 0.455–0.657) for BI-RADS. Diagnostic performance using Tree (AUC: 0.889–0.943) was similar to BI-RADS (AUC: 0.872–0.953). Less experienced radiologists achieved AUC: improvements up to 4.7 % using Tree (P-values: 0.042–0.698); an expert’s performance did not change (P?=?0.526). The least experienced reader improved in specificity using Tree (16 %, P?=?0.001). No further sensitivity and specificity differences were found (P?>?0.1).

Conclusion

The Tree scoring system improves inter-reader agreement and achieves a diagnostic performance similar to that of BI-RADS. Less experienced radiologists, in particular, benefit from Tree.

Key Points

? The Tree scoring system shows high diagnostic accuracy in mass and non-mass lesions.? The Tree scoring system reduces inter-reader variability related to reader experience.? The Tree scoring system improves diagnostic accuracy in non-expert readers.

     

Can virtual reality simulation prepare patients for an MRI experience?

IntroductionA Magnetic Resonance Imaging (MRI) examination is often described by patients as frightening and uncomfortable. To prepare patients for an MRI examination, this study explored the use of virtual reality (VR) simulation compared to a mock MRI scan (full-scale MRI machine replica, without internal magnets).MethodsTwenty participants underwent a VR and a mock MRI scan. Ratings of anxiety and how comfortable and relaxed the participants felt were recorded at five touchpoints during and after each simulation. Post-simulation questionnaires were used to gather responses on the experience and preferences.ResultsNo significant differences were found in participants’ ratings of how anxious they felt during or between the two simulations (χ2 (9) = 27.269, p = .126), or how relaxed they felt (χ2 (9) = 14.664, p = .101). There were also no significant differences in the reported levels of comfort between the two types of simulation (χ2 (9) = 20.864, p = .013, post hoc tests for all VR versus mock scan rankings p > .05). There were no significant differences in how real the participants thought each simulation felt, or how anxious, relaxed, and comfortable they felt following each type of simulation (p > .05). Although 65% of participants thought the mock simulation felt more real than the VR, 86% found VR simulation to be a helpful way to prepare for a real MRI exam.ConclusionVR could be a feasible and accessible alternative to mock scanning. It has the potential to improve patient experiences of potentially stressful MRI examinations.Implications for practiceVR offers clinicians a new cost-effective tool to prepare patients for an MRI examination. VR technology could be used at home, as a training tool, to familiarise clinicians and clinical trainees with the MRI procedure and better understand patients’ experiences.     

MRI for staging lymphoma: Whole‐body or less?

Purpose:

To assess whether whole‐body MRI detects more clinically relevant lesions (i.e., leading to a change in Ann Arbor stage) than an MRI protocol that only includes the head/neck and trunk (i.e., from cranial vertex to groin, excluding the arms) in patients with lymphoma.

Materials and Methods:

One hundred consecutive patients with newly diagnosed lymphoma prospectively underwent T1‐weighted and T2‐weighted short inversion time inversion recovery whole‐body MRI. The number of lymphomatous sites at MRI with a field of view (FOV) limited to the head/neck and trunk, and the additional number of lymphomatous sites at whole‐body MRI and their influence on Ann Arbor stage were determined.

Results:

At MRI with a FOV limited to the head/neck and trunk, 507 sites were classified as lymphomatous. At whole‐body MRI, 7 additional sites outside the head/neck and trunk in 7 patients (7.0%; 95% confidence interval: 3.4–13.8%) were classified as lymphomatous, but Ann Arbor stage never changed.

Conclusion:

Whole‐body MRI did not detect any clinically relevant lesions outside the FOV of an MRI protocol that only includes the head/neck and trunk. Therefore, it may be sufficient to only include the head/neck and trunk when using MRI for staging lymphoma. J. Magn. Reson. Imaging 2011;33:1144–1150. © 2011 Wiley‐Liss, Inc.     

Neuroimaging: do we really need new contrast agents for MRI?

The use of exogenous contrast media in magnetic resonance imaging of the brain has brought dramatic improvement in the sensitivity of detection and delineation of pathological structures, such as primary and metastatic brain tumors, inflammation and ischemia. Disruption of the blood brain barrier leads to accumulation of the intravenously injected contrast material in the extravascular space, leading to signal enhancement. Magnetic resonance angiography benefits from T(1)-shortening effects of contrast agent, improving small vessel depiction and providing vascular visualization even in situations of slow flow. High speed dynamic MRI after bolus injection of contrast media allows tracer kinetic modeling of cerebral perfusion. Progressive enhancement over serial post-contrast imaging allows modeling of vascular permeability and thus quantitative estimation of the severity of blood brain barrier disruption. With such an array of capabilities and ever improving technical abilities, it seems that the role of contrast agents in MR neuroimaging is established and the development of new agents may be superfluous. However, new agents are being developed with prolonged intravascular residence times, and with in-vivo binding of ever-increasing specificity. Intravascular, or blood pool, agents are likely to benefit magnetic resonance angiography of the carotid and cerebral vessels; future agents may allow the visualization of therapeutic drug delivery, the monitoring of, for example, gene expression, and the imaging evaluation of treatment efficacy. So while there is a substantial body of work that can be performed with currently available contrast agents, especially in conjunction with optimized image acquisition strategies, post processing, and mathematical analysis, there are still unrealized opportunities for novel contrast agent introduction, particularly those exploiting biological specificity. This article reviews the current use of contrast media in magnetic resonance neuroimaging, discusses some of the developing strategies for new applications of imaging with these agents and finally offers some views and indications for contrast agents currently under development, as well as some speculation on unsolved problems in neuroimaging, and opportunities for novel contrast agents.     

MRI

072 心内及心旁占位性病变的磁共振成象[德]/Grotz J et al∥DMW.-1986;111:-1594 作者用MRI检查心旁肿瘤、主动脉瘤、心内肿瘤与血栓共21例,见到①心外占位性病变:支气管癌2例,要求MRI查明周围毗邻关系,1例证实未侵犯心脏,对升主动脉则有挤压,但无肿瘤浸润;另1例发现上腔静脉梗阻;肾癌转移1例,直接位     

Is Contrast Medium Really Needed for Follow-up MRI of Untreated Intracranial Meningiomas?

BACKGROUND AND PURPOSE:Recent concerns relating to tissue deposition of gadolinium are favoring the use of noncontrast MR imaging whenever possible. The purpose of this study was to assess the necessity of gadolinium contrast for follow-up MR imaging of untreated intracranial meningiomas.MATERIALS AND METHODS:One-hundred twenty-two patients (35 men, 87 women) with meningiomas who underwent brain MR imaging between May 2007 and May 2019 in our institution were included in this retrospective cohort study. We analyzed 132 meningiomas: 73 non-skull base (55%) versus 59 skull base (45%), 93 symptomatic (70%) versus 39 asymptomatic (30%). Fifty-nine meningiomas underwent an operation: 54 World Health Organization grade I (92%) and 5 World Health Organization grade II (8%). All meningiomas were segmented on T1 3D-gadolinium and 2D-T2WI. Agreement between T1 3D-gadolinium and 2D-T2WI segmentations was assessed by the intraclass correlation coefficient.RESULTS:The mean time between MR images was 1485 days (range, 760–3810 days). There was excellent agreement between T1 3D-gadolinium and T2WI segmentations (P < .001): mean tumor volume (T1 3D-gadolinium: 9012.15 [SD, 19,223.03] mm³; T2WI: 8528.45 [SD, 18,368.18 ] mm³; intraclass correlation coefficient = 0.996), surface area (intraclass correlation coefficient = 0.989), surface/volume ratio (intraclass correlation coefficient = 0.924), maximum 3D diameter (intraclass correlation coefficient = 0.986), maximum 2D diameter in the axial (intraclass correlation coefficient = 0.990), coronal (intraclass correlation coefficient = 0.982), and sagittal planes (intraclass correlation coefficient = 0.985), major axis length (intraclass correlation coefficient = 0.989), minor axis length (intraclass correlation coefficient = 0.992), and least axis length (intraclass correlation coefficient = 0.988). Tumor growth also showed good agreement (P < .001), estimated as a mean of 461.87 [SD, 2704.1] mm³/year on T1 3D-gadolinium and 556.64 [SD, 2624.02 ] mm³/year on T2WI.CONCLUSIONS:Our results show excellent agreement between the size and growth of meningiomas derived from T1 3D-gadolinium and 2D-T2WI, suggesting that the use of noncontrast MR imaging may be appropriate for the follow-up of untreated meningiomas, which would be cost-effective and avert risks associated with contrast media.

Recent concerns regarding gadolinium (Gd) compounds are fueling a trend to use contrast media in MR imaging less frequently. Notwithstanding the well-established safety profile of Gd compounds, a small number of immediate adverse effects, which may be life-threatening, has been reported^1,2 at a rate of approximately 0.3%.² Furthermore, repeat administration of Gd-based contrast may lead to deposition of Gd in the dentate nucleus and the globus pallidus,^3-7 which seems to be the case with linear rather than macrocyclic Gd compounds,⁴ despite a normal renal function⁷ and an intact blood-brain barrier.⁶ Health care costs should also be considered because they are a heavy burden to modern Western societies,^8-10 and medical imaging accounts for a large proportion of these costs.¹⁰ Gd-based contrast media significantly contribute to the cost of an MR image, due to the price of the contrast medium itself and also because of the prolonged image-acquisition time. Using contrast media more sparingly could, therefore, reduce these costs considerably.The above-mentioned concerns are particularly pertinent to young patients with incidental or asymptomatic meningiomas in which frequent and long-term follow-up MR imaging is usually performed, the current standard-of-care being MR with Gd-based contrast media.¹¹ Intracranial meningiomas are, by and large, benign World Health Organization (WHO) grade I tumors derived from meningothelial cells,^12,13 representing approximately one-third of all primary central nervous system tumors¹⁴ and 15% of symptomatic intracranial masses.¹⁵ They are extra-axial lesions that usually exhibit slow growth (approximately 14%/year for WHO grade I lesions).¹⁶ However, the growth rate can be substantially higher, particularly in WHO grade II and III meningiomas, necessitating frequent MR imaging follow-up. For instance, the European Association of Neuro-Oncology advocates diligent radiologic follow-up of meningiomas. For small asymptomatic meningiomas, the recommendation of this institution is to assess the tumor dynamics with contrast MR imaging at 6 months after the initial diagnosis and then annually as long as the patient remains asymptomatic.¹¹Quantitative MR imaging parameters such as tumor volume¹⁷ are important in predicting tumor growth and behavior. Nakasu and Nakasu,¹⁸ in 2020, identified large tumor size and annual volume change of ≥2.1 cm³ as the strongest predictors of symptomatic tumor progression. Several other parameters may be important in predicting the potential for rapid tumor growth, such as male sex,¹⁸ younger age,¹⁸ absence of calcification,^18-23 peritumoral edema,^21,22,24 and hyperintensity on T2WI.^{18,19,22,25,26}Considering these points, the purpose of this retrospective cohort study was to assess the hypothesis that size and growth of untreated intracranial meningiomas derived from T1 3D-Gd and 2D-T2WI sequences show good agreement, which would, should this be the case, question the added value of Gd-based contrast media for routine follow-up MRIs of intracranial meningiomas.     

Does 11C-choline PET-CT contribute to multiparametric MRI for prostate cancer localisation?

Background and purpose

The aim of this work was to determine whether ¹¹C-choline positron emission tomography (PET)–computed tomography (CT) makes a positive contribution to multiparametric magnetic resonance imaging (MRI) for localisation of intraprostatic tumour nodules.

Patients and methods

A total of 73 patients with biopsy-proven intermediate- and high-risk prostate cancer were enrolled in a prospective imaging study consisting of T2-weighted (T2w), dynamic contrast-enhanced (DCE) and diffusion-weighted (DW) MRI and ¹¹C-choline PET-CT before radical prostatectomy. Cancerous regions were delineated on the whole-mount prostatectomy sections and on the different MRI modalities and analysed in 24 segments per patient (3 sections, 8 segments each). To analyse PET-CT images, standardized uptake values (SUV) were calculated per segment.

Results

In total, 1,752 segments were analyzed of which 708 (40.4?%) were found to be malignant. A high specificity (94.7, 93.6 and 92.2?%) but relatively low sensitivity (31.2, 24.9 and 44.1?%) for tumour localisation was obtained with T2w, DCE and DW MRI, respectively. Sensitivity values significantly increased when combining all MRI modalities (57.2?%). For PET-CT, mean SUV_max of malignant octants was significantly higher than mean SUV_max of benign octants (3.68?±?1.30 vs. 3.12?±?1.02, p?<?0.0001). In terms of accuracy, the benefit of adding PET-CT to (multiparametric) MRI was less than 1?%.

Conclusion

The additional value of ¹¹C-choline PET-CT to MRI in localising intraprostatic tumour nodules is limited, especially when multiparametric MRI is used.     

Dynamic contrast-enhanced MRI for monitoring bisphosphonate therapy in Paget’s disease of bone

Purpose

The purpose of this study was to evaluate changes in regional bone perfusion in Paget’s disease (PD) following bisphosphonate therapy. We used dynamic contrast-enhanced MRI (DCE-MRI) for assessment of bone perfusion and compared MRI findings with alkaline phosphatase (AP) as a serum marker of bone turnover.

Materials and methods

We examined 20 patients (8 women, 12 men, 66?±?11 years) with symptomatic PD of the axial skeleton. Patients were selected for infusion therapy with the bisphosphonate pamidronate. The most affected bone of lumbar spine or pelvis was examined by DCE-MRI prior to therapy and after a 6-month follow-up. The contrast uptake was evaluated using a two-compartment model with the parameters amplitude A and exchange rate constant K_ep. Color-coded parametric images were generated to visualize bone vascularization.

Results

After a 6-month follow-up there was a significant decrease in alkaline phosphatase and in DCE-MRI parameters A and K_ep (p?<?0.0001). Patients without previous bisphosphonate treatment showed a significantly greater decrease in alkaline phosphatase and K_ep (p?<?0.001).

Conclusion

DCE-MRI shows a significant reduction in regional bone perfusion in PD following parenteral bisphosphonate treatment. Reduction in bone perfusion is greater in bisphosphonate-naïve patients than in those who had been previously treated.     

Can we reduce dose to ureters as avoidance organs for MRI based brachytherapy for cervical cancer? A dosimetric feasibility study

BACKGROUND AND PURPOSEUreteral stenosis (US) is an underreported complication of brachytherapy (BT) for cervical cancer (CC), with limited data on toxicity risk reduction. A previous study demonstrated ureter EQD2 D0.1cc > 77 Gy correlated with US development. We sought to assess feasibility of this constraint while maintaining similar HR-CTV coverage.MATERIALS AND METHODSPatients with locally advanced CC treated with EBRT plus HDR MRI-based brachytherapy boost without hydronephrosis at diagnosis and with ureter dose EQD2 D0.1cc > 77 Gy were included. Replan was attempted to achieve HR-CTV D90 ≥ 80–85 Gy and ureter dose reduction. Ureter distance from lateral margin of HR-CTV and tandem was recorded. t-test was performed to compare ureteral dose and HR-CTV D90.RESULTsOf 25 patients were identified. Hundred percent received 45 Gy in 25 fractions to the pelvis ± paraaortic lymph nodes and 80% receiving median additional parametrial dose of 5.4 Gy. Replan meeting ureteral dose of ≤77 Gy was feasible in 18 of 25 patients, with a reduction in median ureter D0.1cc from 82.3 to 76.8 Gy (p < 0.001). Median HR-CTV D90 was similar (84.7 vs. 85.0 Gy). Replan achieved D0.1cc ≤77 Gy in 56% of patients who experienced US. All unilateral US cases occurred in the ureter closest to HR-CTV.CONCLUSIONSOptimization to reduce ureter dose to ≤77 Gy is feasible when ureters are visible and contoured. Ureters may be considered as potential OAR during MRI-based brachytherapy treatment. Reduced ring to tandem total reference air kerma (TRAK) ratio may provide an additional metric by which to lower US risk.     

MRI术语

鉴于磁共振成像(MRI)在本学科领域中的迅速发展,为帮助国内同道在阅读MRI文献时译文尽可能准确、规范和统一,我们将收集整理的MRI词汇在此栏目以连载方式刊出。对于对译文与注释的不同意见或增补,也欢迎广大专家和同道共同讨论。     

腕关节MRI

腕关节疾病中最常见的为神经、肌肉、骨关节及软组织的损伤和病变。腕关节软组织疾病的诊断目前多根据症状、体征、X光平片检查，做出诊断往往较晚，影响治疗和功能恢复。磁共振成像（MRI）以其软组织分辨力强，可三维成像、多序列多回波成像，非侵入性、无放射损伤等特点，正逐步代替传统的腕关节病变的影像学诊断方法。     

臂部MRI

作者应用高分辨力的 MR 扫描,研究正常人臂部肌肉周围的筋膜及腱膜在 MRI 上的不同信号强度。30例健康男性,21～26岁。MR 场强1.5T,仰卧位以12.7cm 的表面线圈把臂部与躯干严格地分隔。作平行于长轴的矢状面扫描后,再自臂的下段2/5范围内行横断面摄影,层厚10mm,层间隔5mm。结果见到,肱二头肌、肱骨和肱三头肌之间的筋膜