MRI of the female pelvis at 3T compared to 1.5T: Evaluation on high-resolution T2-weighted and HASTE images

Quantitative 3D Analysis of Levator Ani Muscle Subdivisions in Nulliparous Women: MRI Feasibility Study

BACKGROUND

The levator ani muscle (LAM) is crucial for pelvic floor stability, yet its quantitative MRI assessment is only a recent focus. Our study aims to standardize the quantitative analysis of the LAM morphology within the 3D Pelvic Inclination Correction System (3D-PICS).

METHODS

We analyzed 35 static MR datasets from nulliparous women examining the pubovisceral (PVM), iliococcygeal (ICM), coccygeal (COC), and puborectal muscle (PRM). The PVM consists of three origin-insertion pairs, namely the puboanal (PAM), puboperineal (PPM) and pubovaginal muscle (PVaM). The analysis included a quantitative examination of the morphology of LAM, focusing on the median location (x/y/z) (x: anterior-posterior, y: superior-inferior, z: left-right) of the origin and insertion points (a), angles (b) and lengths (c) of LAM. Inter-rater reliability was calculated.

RESULTS

Interindividual variations in 3D coordinates among muscle subdivisions were shown. In all, 93% of all origin and insertion points were found within an SD of <8 mm. Angles to the xz-plane range between -15.4° (right PRM) and 40.7° (left PAM). The PRM is the largest pelvic muscle in static MRI. The ICC indicated moderate-to-good agreement between raters.

CONCLUSIONS

The accurate morphometry of the LAM and its subdivisions, along with reliable inter-rater agreement, was demonstrated, enhancing the understanding of normal pelvic anatomy in young nulliparous women.

MRI of Adenomyosis: Where Are We Today?

Purpose of Review: The purpose of this review is to (i) summarize the current literature regarding the role of magnetic resonance imaging (MRI) in diagnosing adenomyosis, (ii) examine how to integrate MRI phenotypes with clinical symptomatology and histological findings, (iii) review recent advances including proposed MRI classifications, (iv) discuss challenges and pitfalls of diagnosing adenomyosis, and (v) outline the future role of MRI in promoting a better understanding of the pathogenesis, diagnosis, and treatment options for patients with uterine adenomyosis. Recent Findings: Recent advances and the widespread use of MRI have provided new insights into adenomyosis and the range of imaging phenotypes encountered in this disorder. Summary: Direct and indirect MRI features allow for accurate non-invasive diagnosis of adenomyosis. Adenomyosis is a complex and poorly understood disorder with variable MRI phenotypes that may be correlated with different pathogeneses, clinical presentations, and patient outcomes. MRI is useful for the assessment of the extent of findings, to evaluate for concomitant gynecological conditions, and potentially can help with the selection and implementation of therapeutic options. Nevertheless, important gaps in knowledge remain. This is in part due to the lack of standardized criteria for reporting resulting in heterogeneous and conflicting data in the literature. Thus, there is an urgent need for a unified MRI reporting system incorporating standardized terminology for diagnosing adenomyosis and defining the various phenotypes.

Useful MRI Findings for Minimally Invasive Surgery for Early Cervical Cancer

Simple Summary

Radical hysterectomy and lymph node dissection are extensive procedures with severe post-operative morbidities and should be avoided on patients with low risk of recurrence. Still, due to lack of good prognostic tools, radical surgery is performed on most patients with early stage cervical cancer, leading to overtreatment and unnecessary morbidities. The recent International Federation of Gynecology and Obstetrics (FIGO) staging system accepts the use of magnetic resonance imaging (MRI) in addition to physical examination. Currently, 3 Tesla (3T) MRI is available widely and, due to its high soft tissue contrast, can provide more useful information on precise estimation of tumor size and metastasis than can physical examination in patients with cervical cancer. Therefore, this imaging modality can help gynecologic oncologists to determine whether minimally invasive surgery is necessary and can be used for early detection of small recurrent cancers.

Abstract

According to the recent International Federation of Gynecology and Obstetrics (FIGO) staging system, Stage III cervical cancer indicates pelvic or paraaortic lymph node metastasis. Accordingly, the new FIGO stage accepts imaging modalities, such as MRI, as part of the FIGO 2018 updated staging. Magnetic resonance imaging (MRI) is the best imaging modality to estimate the size or volume of uterine cancer because of its excellent soft tissue contrast. As a result, MRI is being used increasingly to determine treatment options and follow-up for cervical cancer patients. Increasing availability of cancer screening and vaccination have improved early detection of cervical cancer. However, the incidence of early cervical cancers has increased compared to that of advanced cervical cancer. A few studies have investigated if MRI findings are useful in management of early cervical cancer. MRI can precisely predict tumor burden, allowing conization, trachelectomy, and simple hysterectomy to be considered as minimally invasive treatment options for early cervical cancer. This imaging modality also can be used to determine whether there is recurrent cancer following minimally invasive treatments. The purpose of this review is to highlight useful MRI features for managing women with early cervical cancer.

MR Imaging in the 21st Century: Technical Innovation over the First Two Decades

Clinical MRI systems have continually improved over the years since their introduction in the 1980s. In MRI technical development, the developments in each MRI system component, including data acquisition, image reconstruction, and hardware systems, have impacted the others. Progress in each component has induced new technology development opportunities in other components. New technologies outside of the MRI field, for example, computer science, data processing, and semiconductors, have been immediately incorporated into MRI development, which resulted in innovative applications. With high performance computing and MR technology innovations, MRI can now provide large volumes of functional and anatomical image datasets, which are important tools in various research fields. MRI systems are now combined with other modalities, such as positron emission tomography (PET) or therapeutic devices. These hybrid systems provide additional capabilities.

In this review, MRI advances in the last two decades will be considered. We will discuss the progress of MRI systems, the enabling technology, established applications, current trends, and the future outlook.

Feasibility of a deep learning-based method for automated localization of pelvic floor landmarks using stress MR images

INTRODUCTION AND HYPOTHESIS

Magnetic resonance imaging (MRI) plays an important role in assessing pelvic organ prolapse (POP), and automated pelvic floor landmark localization potentially accelerates MRI-based measurements of POP. Herein, we aimed to develop and evaluate a deep learning-based technique for automated localization of POP-related landmarks.

METHODS

Ninety-six mid-sagittal stress MR images (at rest and at maximal Valsalva) were used for deep-learning model training and generalization testing. We randomly split our dataset into a training set of 73 images and a testing set of 23 images. One soft-tissue landmark (the cervical os [P1]) and three bony landmarks (the mid-pubic line [MPL] endpoints [P2&P3] and the sacrococcygeal inferior-pubic point [SCIPP] line endpoints [P3&P4]) were annotated by experts. We used an encoder-decoder structure to develop the deep learning model for automated localization of the four landmarks. Localization performance was assessed using the root square error (RSE), whereas the reference lines were assessed based on the length and orientation differences.

RESULTS

We localized landmarks (P1 to P4) with mean RSEs of 1.9 mm, 1.3 mm, 0.9 mm, and 3.6 mm. The mean length errors of the MPL and SCIPP line were 0.1 and -2.1 mm, and the mean orientation errors of the MPL and SCIPP line were -0.7° and -0.3°. Our method predicted each image in 0.015 s.

CONCLUSIONS

We demonstrated the feasibility of a deep learning-based approach for accurate and fast fully automated localization of bony and soft-tissue landmarks. This sped up the MR interpretation process for fast POP screening and treatment planning.

Adnexal masses characterized on 3 tesla magnetic resonance imaging - added value of diffusion techniques

Background

To assess different types of adnexal masses as identified by 3T MRI and to discuss the added value of diffusion techniques compared with conventional sequences.

Patients and methods

174 women age between 13 and 87 underwent an MRI examination of the pelvis for a period of three years. Patients were examined in two radiology departments – 135 of them on 3 Tesla MRI Siemens Verio and 39 on 3 Tesla MRI Philips Ingenia. At least one adnexal mass was diagnosed in 98 patients and they are subject to this study. Some of them were reviewed retrospectively. Data from patients’ history, physical examination and laboratory tests were reviewed as well.

Results

124 ovarian masses in 98 females’ group of average age 47.2 years were detected. Following the MRI criteria, 59.2% of the cases were considered benign, 30.6% malignant and 10.2% borderline. Out of all masses 58.1% were classified as cystic, 12.9% as solid and 29% as mixed. Оf histologically proven tumors 74.4% were benign and 25.6% were malignant. All of the malignant tumors had restricted diffusion. 64 out of all patients underwent contrast enhancement. (34 there were a subject of contraindications). 39 (61%) of the masses showed contrast enhancement.

Conclusions

Classifying adnexal masses is essential for the preoperative management of the patients. 3T MRI protocols, in particular diffusion techniques, increase significantly the accuracy of the diagnostic assessment.

Endometrial cancer: an overview of novelties in treatment and related imaging keypoints for local staging

Endometrial cancer is the most common gynaecologic malignancy in developed countries and its incidence is increasing. First-level treatment, if no contraindicated, is based on surgery. Pre-operative imaging is needed for evaluation of local extent and detection of distant metastases in order to guide treatment planning. Radiological evaluation, based on transvaginal ultrasound, MR and CT, can make the difference in disease management, paying special attention to assessment of entity of myometrial invasion, cervical stromal extension, and assessment of lymph nodal involvement and distant metastases.

Appropriate magnetic resonance imaging techniques for gross tumor volume delineation in external beam radiation therapy of locally advanced cervical cancer

Background

Accurate delineation of the gross tumor volumes (GTV) is a prerequisite for precise radiotherapy planning and delivery. Different MRI sequences have different advantages and limitations in their ability to discriminate primary cervical tumor from normal tissue. The purpose of this work is to determine appropriate MRI techniques for GTV delineation for external-beam radiation therapy of locally advanced cervical cancer (LACC).

Materials and Methods

GTVs were delineated on the MRI, CT, and PET images acquired for 23 LACC patients in treatment positions to obtain GTVs on CT (GTV-CT), on various MRI sequences including T1 (GTV-T1), T2 (GTV-T2), T1 with fat suppression and contrast (GTV-T1F+), DWI-ADC (GTV-ADC) and on PET were generated using the threshold of 40% of maximum SUV (GTV-SUV40%) as well as SUV of 2.5 (GTV-SUV2.5). MRI, CT and PET were registered for comparison. The GTVs defined by MRI were compared using the overlap ratio (OR) and relative volume ratio (RVR). The union of GTV-T2 and GTV-ADC was generated to represent the MRI-based GTV (GTV-MRI).

Results

The differences between GTV-T2 and other MRI GTVs are significant (P < 0.05). The average ORs for GTV-T1, GTV-T1F+, and GTV-ADC related to GTV-T2 were 86.3%, 81.6%, and 61.6% with the corresponding average RVRs 113.8%, 112.3% and 77.2%, respectively. There is no significant difference between GTV-T1 and GTV-T1F+. GTV-ADC was generally smaller than GTV-T2, however, encompassed suspicious regions that are uncovered in GTV-T2 (up to 16% of GTV-T2) because of different imaging mechanisms. There was significant difference between GTV-MRI, GTV-SUV2.5, GTV-SUV40%, and GTV-CT. On average, GTV-MRI is 18.4% smaller than GTV-CT.

Conclusions

MRI provides improved visualization of disease over CT or PET for cervical cancer. The GTV from the union of GTV-T2 and GTV-ADC provides a reasonable GTV including tumor region defined anatomically and functionally with MRI and substantially reduces the conventional GTV defined on CT.

Image Distortions on a Plastic Interstitial Computed Tomography/Magnetic Resonance Brachytherapy Applicator at 3 Tesla Magnetic Resonance Imaging and Their Dosimetric Impact

PURPOSE

To quantify magnetic resonance imaging (MRI) distortions on a plastic intracavitary/interstitial applicator with plastic needles at a field strength of 3 T and to determine the dosimetric impact, using patient data.

METHODS AND MATERIALS

For 11 cervical cancer patients, our clinical MRI protocol was extended with 3 scans. From the first scan, a multi-echo acquisition, a map of the magnetic field (B₀) was calculated and used to quantify the field inhomogeneity. The expected displacements of the applicator were quantified for the clinical sequence using the measured field inhomogeneity and the clinical sequence's bandwidth. The second and third scan were our routine clinical sequence (duration: <5 minutes each), acquired consecutively using opposing readout directions. The displacement of the applicator between these scans is approximately twice the displacement due to B₀ inhomogeneity. The impact of the displacement on the dose was determined by reconstructing the applicator on both scans. The applicator was then shifted and rotated the same distance as the observed displacement to create a worst-case scenario (ie, twice the actual displacement due to B₀ inhomogeneity). Next, the dose to 98%/90% (D₉₈/D₉₀) of the clinical target volume at high risk, as well as the dose to the most irradiated 2 cm³ for bladder and rectum, were calculated for the original plan as well as the shifted plan.

RESULTS

For a volume of interest containing the intrauterine device and the ovoids the 95th percentile of the absolute displacement ranged between 0.2 and 0.75 mm, over all patients. For all patients, the difference in D₉₈/D₉₀ in the opposing readout scans with the original plan was at most 4.7%/4.3%. For the dose to the most irradiated 2 cm³ of bladder/rectum, the difference was at most 6.0%/6.3%.

CONCLUSIONS

The dosimetric impact of distortions on this plastic applicator with plastic needles is limited. Applicator reconstruction for brachytherapy planning purposes is feasible at 3 T MRI.

Value of diffusion-weighted MRI in diagnosis of uterine cervical cancer: a prospective study evaluating the benefits of DWI compared to conventional MR sequences in a 3T environment

BACKGROUND

Imaging of cervical carcinoma remains challenging as local infiltration of surrounding tissues cannot always be discriminated safely. New imaging techniques, like diffusion-weighted imaging (DWI) have emerged, which could lead to a more sensitive tumor detection.

PURPOSE

To evaluate the benefits of DWI for determination of size, local infiltration, and tumor grading, in patients with primary and recurrent cervical cancer.

MATERIAL AND METHODS

In this prospective, study we enrolled 50 patients with primary (n = 35) and recurrent (n = 15) tumors. All patients underwent 3T magnetic resonance imaging (MRI) including conventional (e.g. T1/T2 ± fs ± contrast) sequences and DWI (b-values of 0, 50, 400, 800 s/mm(2)). All images were analyzed by three readers with different experience levels (1, 3, 6 years), who compared image quality, tumor delineation, dimensions, local infiltration, lymph node involvement, and quantified ADC values compared to the histopathological grading.

RESULTS

Additional use of DWI resulted in significantly better (P < 0.001) tumor delineation for the least experienced reader, but not for experienced readers. Tumor dimensions were assessed almost equally (P > 0.05) in conventional sequences and DWI. Use of DWI led to an increase in sensitivity of infiltrated adjacent tissue (from 86% to 90%) and detection of lymph node metastases (from 47% to 67%). Quantitative assessment of carcinomas showed lower ADC values (P < 0.001) with significant inverse correlations between different grading levels.

CONCLUSION

Our study demonstrates the overall benefits using DWI in 3T MRI resulting in a higher reader confidence, sensitivity of tissue infiltration, and tumor-grading for cervical cancer.

[An Examination for Uterine Dynamic Study with Phase-sensitive Inversion-recovery]

The depth of myometrial invasion in patients with endometrial carcinoma is recognized as an important factor that closely correlates with prognosis. Preoperative assessment of myometrial invasion is essential for planning surgery. To enhance the contrast between myometrium and endometrium including myometrial invasion with endometrial carcinoma, we optimized the sequence parameter with phase-sensitive inversion-recovery (PSIR) in gadolinium dynamic study of uterine corpus. On a 1.5-T magnetic resonance imaging (MRI), images were acquired by three-dimensional (3D) T1 -turbo field echo (TFE) with PSIR sequence and gadolinium-diethylenetriamine pentaacetic acid( Gd-DTPA) diluted phantom (0-5 mmol/L) and myometrium model (manganese chloride tetrahydrate+agar). We calculated the null point and the contrast-to-noise ratio (CNR) at multiple TFE inversion delay times, 200 ms-maximum in each combination; flip angles (FAs), 5-35 degrees; TFE factor, 20-40; and shot interval (SI), 500-1000 ms. We assumed that dynamic scanning time was 30 seconds when the sensitivity encoding factor was 2, namely, in this study, the scanning time was 1 minute with no sensitivity encoding. In addition, we compared CNR between optimized PSIR sequence ande-Thrive. We recognized a successful CNR of the 3D PSIR parameter was TFE inversion delay times, 335 ms; FA, 25 degrees; TFE factor, 20; and SI, 500 ms. In each gadolinium-DTPA diluted phantom, the average CNR of the optimized PSIR sequence was approximately 1.7 times (maximum: 3 times) higher than e-Thrive. Optimizing sequence parameter of PSIR is applicable in gadolinium dynamic study of uterine corpus.

Quantification of image distortions on the Utrecht interstitial CT/MR brachytherapy applicator at 3T MRI

PURPOSE

To quantify distortions on MR images of the Utrecht interstitial CT/MR applicator at a field strength of 3T using an MRI-only method.

MATERIALS AND METHODS

An MR-compatible phantom suspending the applicator in water was built and imaged on a Philips Ingenia 3T MRI scanner. A map of the magnetic field (B0) was calculated from multiecho images and used to quantify the field inhomogeneity. The expected displacements of the applicator could be quantified using the measured field inhomogeneity and sequence bandwidth. Additionally, two scans were acquired using opposing readout gradients. These scans were rigidly matched and their displacement was compared with the expected displacements from the B0 map. These same methods were applied in 4 patients. By rigid matching of the scans acquired with opposing readout direction the applicator displacement due to image distortion from B0 inhomogeneity as well as patient movement and organ deformation was determined.

RESULTS

According to the B0 map, the displacement on the intrauterine device of the plastic brachytherapy applicator was <0.4 mm for both the phantom and patients. Displacements obtained by the opposing readout method were ≤0.8 mm for each patient with a mean ± SD over the patients of 0.3 ± 0.1 mm.

CONCLUSION

The results of our study indicate that the B0 method agrees with the opposing readout method. Displacements caused by magnetic field inhomogeneity on 3T MRI were small compared with displacements due to patient movement and organ deformation.

Magnetic resonance imaging relaxation times of female reproductive organs

BACKGROUND

Relaxation time of female reproductive organs affects the tissue contrast of magnetic resonance image (MRI), and is used for quantitative analysis.

PURPOSE

To evaluate the relaxation times of normal female reproductive organs in the luteal phase of the menstrual cycle.

MATERIAL AND METHODS

On a 1.5-T MRI, relaxation times were measured in pelvic tissues (endometrium, junctional zone, myometrium, follicle, and stroma) of 32 female healthy volunteers (33.5 ± 6.8 years). The Look-Locker sequence was used to measure T1 relaxation times. Furthermore, a multiple spin-echo method with 32 different echo times was used to measure T2 relaxation times. The images were obtained in the luteal phase of each volunteer's menstrual cycle.

RESULTS

The measured relaxation times (means ± standard deviations) were as follows: endometrium (T1, 1703 ± 147 ms; T2, 214 ± 35 ms), junctional zone (T1, 1168 ± 63 ms; T2, 72 ± 12 ms), myometrium (T1, 1314 ± 103 ms; T2, 138 ± 20 ms), follicle (T1, 2267 ± 49 ms; T2, 603 ± 68 ms), and stroma (T1, 1481 ± 129 ms; T2, 126 ± 29 ms).

CONCLUSION

Reliable MRI measurements of T1 and T2 relaxation times of normal female reproductive organs in the luteal phase of the menstrual cycle are useful as references to recognize the normal value.

Magnetic resonance manifestations of villoglandular papillary adenocarcinoma of the uterine cervix with a fern-leaf-like appearance

Villoglandular papillary adenocarcinoma (VGPA) is a rare subtype of cervical adenocarcinoma that generally affects young women and has a favorable prognosis. Its preoperative diagnosis is important to avoid excessive surgery. We report the magnetic resonance (MR) findings of a case in which the cervical tumor showed a fern-leaf-like appearance on high resolution T2-weighted images obtained at 3 tesla. MR imaging clearly showed this pathological feature that may suggest this disease.

Hidradenitis suppurativa: MRI features in anogenital disease

BACKGROUND

Hidradenitis suppurativa is a rare chronic inflammatory disorder of apocrine gland-bearing skin, which commonly affects the anogenital region. There has been very little literature to date on the MRI appearances of anogenital hidradenitis suppurativa.

OBJECTIVE

The aim of this study was to assess the MRI features of anogenital hidradenitis suppurativa in the largest cohort of patients to be published to date.

DESIGN

After an institutional review board waiver, patients with hidradenitis suppurativa who were undergoing MRI for anogenital disease between 2005 and 2012 were identified from our institutional database. The MRI appearances were recorded by 2 radiologists in consensus, blinded to clinical details. Location of disease, number of tracts, presence of anal fistula, and supralevator involvement were recorded. Patient demographics were also noted.

SETTINGS

This study was conducted at the Department of Radiology, Guy's and St Thomas' National Health Service Foundation Trust.

PATIENTS

Patients included were those undergoing MRI for anogenital disease in hidradenitis suppurativa between 2005 and 2012.

MAIN OUTCOME MEASURES

The distribution of sinus tracts in anogenital hidradenitis suppurativa on MRI was measured.

RESULTS

Thirty-one MRIs were performed in 18 patients (15 men; mean age, 46 years). On the baseline MRI, multiple tracts were seen in the natal cleft (16/18; 83%), the perianal (12/18; 61%), the perineal (13/18; 56%), and the gluteal (8/18; 44%) regions. A communication with the anal canal was present in only 4 patients. Three patients had supralevator extension. Seven patients had follow-up MRIs with variable response to interval treatment: 3 of 7 showed responding disease, 3 of 7 showed stable disease, and 1 of 7 showed progressive disease.

LIMITATIONS

This study was limited by its relatively small cohort of patients.

CONCLUSIONS

In hidradenitis suppurativa, anogenital disease is usually subcutaneous but extensive, with only a minority of patients demonstrating deeper involvement. MRI may help define the extent of anogenital disease and assess response to treatment.

Optimal single 3T MR imaging sequence for HDR brachytherapy of cervical cancer

Purpose

The superior image quality of 3 tesla (3T) magnetic resonance (MR) imaging in cervical cancer offers the potential to use a single image set for brachytherapy. This study aimed to determine a suitable single sequence for contouring tumour and organs at risk, applicator reconstruction, and treatment planning.

Material and methods

A 3T (Skyra, Siemens Healthcare AG, Germany) MR imaging system with an 18 channel body matrix coil generated HDR cervical cancer brachytherapy planning images on 20 cases using plastic-based treatment applicators. Seven different T2-weighted Turbo Spin Echo (TSE) sequences including both 3D and contiguous 2D scans based on sagittal, axial (transverse), and oblique planes were analysed. Each image set was assessed for total scanning time and usefulness in tumour localization via inter- and intra-observer analysis of high-risk clinical target volume (HR CTV) contouring. Applicator reconstruction in the treatment planning system was also considered.

Results

The intra-observer difference in HR CTV volumes between 2D and 3D axial-based image sets was low with an average difference of 3.1% for each observer. 2D and 3D sagittal image sets had the highest intra- and inter observer differences (over 15%). A 2D axial ‘double oblique’ sequence was found to produce the best intra- (average difference of 0.6%) and inter-observer (mean SD of 9.2%) consistency and greatest conformity (average 0.80).

Conclusions

There was little difference between 2D and 3D-based scanning sequences; however the increased scanning time of 3D sequences have potential to introduce greater patient motion artifacts. A contiguous 2D sequence based on an axial T2-weighted turbo-spin-echo (TSE) sequence orientated in all planes of the treatment applicator provided consistent tumour delineation whilst allowing applicator reconstruction and treatment planning.

3 T MRI uterine peristalsis: comparison of symptomatic fibroid patients versus controls

AIM

To compare uterine peristalsis between symptomatic fibroid patients and normal subjects and to determine the possible effect of fibroid characteristics on uterine peristalsis at high-field magnetic resonance imaging (MRI).

MATERIALS AND METHODS

The present study included 20 symptomatic fibroid patients (age range 39-53 years) and 20 normal subjects (age range 19-46 years). MRI images were obtained during the peri-ovulatory phase using 3 T MRI using a sagittal T2 turbo spin-echo sequence and a half-Fourier acquisition single-shot turbo spin-echo sequence for display on cine mode. Two radiologists independently evaluated the images for the presence of uterine peristalsis by confidence level. In cases where peristalsis was present, the images were also evaluated for peristalsis frequency and direction. For fibroid patients, uterine and index fibroid volume, fibroid burden and index fibroid location were also recorded.

RESULTS

Uterine peristalsis was significantly decreased in symptomatic fibroid patients compared with normal controls (p < 0.01). Peristalsis frequency in fibroid patients was also lower than in normal subjects. Direction of peristalsis was cervix-to-fundus for the majority of fibroid patients and controls. There was no significant relationship between fibroid characteristics, such as uterine volume, index fibroid volume, index fibroid location, and fibroid number in fibroid patients with, and fibroid patients without peristalsis.

CONCLUSION

In women with symptomatic fibroids, the presence of uterine peristalsis is significantly decreased compared to normal controls on 3 T cine MRI. The presence of fibroids appears to disturb the normal conduction of uterine peristalsis and may interfere with fluid (e.g., menses, sperm) transport.

High resolution (3 Tesla) MRI-guided conformal brachytherapy for cervical cancer: consequences of different high-risk CTV sizes

Purpose

To evaluate conventional brachytherapy (BT) plans using dose-volume parameters and high resolution (3 Tesla) MRI datasets, and to quantify dosimetric benefits and limitations when MRI-guided, conformal BT (MRIG-CBT) plans are generated.

Material and methods

Fifty-five clinical high-dose-rate BT plans from 14 cervical cancer patients were retrospectively studied. All conventional plans were created using MRI with titanium tandem-and-ovoid applicator (T&O) for delivery. For each conventional plan, a MRIG-CBT plan was retrospectively generated using hybrid inverse optimization. Three categories of high risk (HR)-CTV were considered based on volume: non-bulky (< 2_{0 cc}), low-bulky (> 20 cc and < 40 cc) and bulky (≥ 40 cc). Dose-volume metrics of D₉₀ of HR-CTV and D_2cc and D_0.1cc of rectum, bladder, and sigmoid colon were analyzed.

Results

Tumor coverage (HR-CTV D₉₀) of the conventional plans was considerably affected by the HR-CTV size. Sixteen percent of the plans covered HR-CTV D₉₀ with the prescription dose within 5%. At least one OAR had D_2cc values over the GEC-ESTRO recommended limits in 52.7% of the conventional plans. MRIG-CBT plans showed improved target coverage for HR-CTV D₉₀ of 98 and 97% of the prescribed dose for non-bulky and low-bulky tumors, respectively. No MRIG-CBT plans surpassed the D_2cc limits of any OAR. Only small improvements (D₉₀ of 80%) were found for large targets (> 40 cc) when using T&O applicator approach.

Conclusions

MRIG-CBT plans displayed considerable improvement for tumor coverage and OAR sparing over conventional treatment. When the HR-CTV volume exceeded 40 cc, its improvements were diminished when using a conventional intracavitary applicator.

Magnetic field interactions of copper-containing intrauterine devices in 3.0-Tesla magnetic resonance imaging: in vivo study

Objective

An ex vivo study found a copper-containing intrauterine device (IUD) to be safe for women undergoing an MRI examination at a 3.0-T field. No significant artifacts caused by the metallic implant were detected. However, there are still no in vivo data about these concerns. The aim of this study was to evaluate 3.0-T magnetic field interactions of copper-containing IUDs in vivo.

Materials and Methods

Magnetic field interactions and potential adverse events were evaluated in 33 women using a questionnaire-based telephone survey. Two experienced radiologists performed artifact evaluation on MR images of the pelvis.

Results

Eighteen patients were eligible for the survey. One patient reported a dislocation of the IUD after the MR examination. All other patients had no signs of field interactions. No IUD-related artifacts were found.

Conclusion

MRI at 3.0-T is possible for women with copper-containing IUDs. However, consulting a gynecologist to check the correct position of the IUD and exclude complications after an MR examination is highly recommended. High-quality clinical imaging of the female pelvis can be performed without a loss in image quality.

Seven-Tesla MRI of the female pelvis

OBJECTIVES

The aim of this study was to investigate the feasibility of 7-T contrast-enhanced MR imaging of the female pelvis.

METHODS

Ten healthy female volunteers were examined on a 7-T whole-body MR system utilising a custom-built eight-channel transmit/receive radiofrequency body coil. The examination protocol included (1) T1-weighted fat-saturated 2D spoiled gradient echo (FLASH), (2) dynamic T1-weighted fat-saturated 3D FLASH, and (3) T2-weighted TSE sequences. For qualitative image analysis pelvic anatomy, uterine zonal anatomy and image impairment due to artefacts was assessed using a five-point scale. For quantitative analysis contrast ratios between the junctional zone and myometrium were obtained for T2-weighted MRI.

RESULTS

Two-dimensional FLASH MRI offered the best overall image quality (meancontrast-enhanced 4.9) and highest tissue contrast (meancontrast-enhanced 4.7). T2-weighted TSE imaging provided a moderate to high conspicuity of the uterine zonal anatomy with mean scores ranging from 3.5 for endometrium to 4.65 for myometrium. Overall image impairment was rated strongest for T2-weighted MRI (2.9) and least for 2D FLASH MRI (mean 4.2).

CONCLUSION

This study demonstrated the feasibility of 7-T T1-weighted MRI of the female pelvis and current constraints associated with T2-weighted MRI.

KEY POINTS

• Dynamic contrast-enhanced female pelvis MR imaging at 7 T is feasible. • Unenhanced T1-weighted MRI offers inherent hyperintense delineation of pelvic arterial vasculature. • Two-dimensional FLASH MRI provided best overall image quality and least artefact impairment.

Rectal imaging: part 2, Perianal fistula evaluation on pelvic MRI--what the radiologist needs to know

OBJECTIVE

The purpose of this article is to provide an overview of pelvic MRI for the evaluation of perianal fistulas, with a description of the technique, illustration of relevant normal anatomy, and examples of various fistula types.

CONCLUSION

MRI evaluation of perianal fistulas can be challenging, and knowledge of relevant pelvic anatomy and fistula classification remains crucial in the diagnosis. MRI is highly accurate for fistula depiction and, by providing an accurate assessment of disease status and extension, can help surgical planning to minimize recurrence and detect clinically unapparent disease.

Evaluation of artifacts and distortions of titanium applicators on 3.0-Tesla MRI: feasibility of titanium applicators in MRI-guided brachytherapy for gynecological cancer

PURPOSE

The aim of this study was to characterize the levels of artifacts and distortions of titanium applicators on 3.0-Tesla magnetic resonance imaging (MRI).

METHODS AND MATERIALS

Fletcher-Suit-Delclos-style tandem and ovoids (T&O) and tandem and ring applicator (T&R) were examined. The quality assurance (QA) phantoms for each applicator were designed and filled with copper sulphate solution (1.5 g/l). The artifacts were quantified with the registration of corresponding computed tomography (CT) images. A favorable MR sequence was searched in terms of artifacts. Using the sequence, the artifacts were determined. The geometric distortions induced by the applicators were quantified through each registration of CT and MRI without applicators. The artifacts of T&O were also evaluated on in vivo MRI datasets of 5 patients.

RESULTS

T1-weighted MRI with 1-mm slice thickness was found as a favorable MR sequence. Applying the sequence, the artifacts at the tandem tip of T&O and T&R were determined as 1.5 ± 0.5 mm in a superior direction in phantom studies. In the ovoids of T&O, we found artifacts less than 1.5 ± 0.5 mm. The artifacts of a T&O tandem in vivo were found as less than 2.6 ± 1.3 mm on T1-weighted MRI, whereas less than 6.9 ± 3.4 mm on T2-weighted MRI. No more than 1.2 ± 0.6 mm (3.0 ± 1.5 mm) of distortions, due to a titanium applicator, were measured on T1-weighted MRI (T2-).

CONCLUSION

In 3.0-Tesla MRI, we found the artifact widths at the tip of tandem were less than 1.5 ± 0.5 mm for both T&O and T&R when using T1-weighted MRI in phantom studies. However, exclusive 3.0-Tesla MRI-guided brachytherapy planning with a titanium applicator should be cautiously implemented.

Dual-source parallel radiofrequency excitation body MR imaging compared with standard MR imaging at 3.0 T: initial clinical experience

PURPOSE

To prospectively compare the image quality and homogeneity of magnetic resonance (MR) images obtained by using a dual-source parallel radiofrequency (RF) excitation body MR imaging system with parallel transmission and independent RF shimming with the image quality and homogeneity of single-source MR images obtained by using standard sequences for routine clinical use in patients at 3.0 T.

MATERIALS AND METHODS

After institutional review board approval and informed patient consent were obtained, a dual-source parallel RF excitation 3.0-T MR system with independent RF shimming and parallel transmission technology was used to examine 28 patients and was compared with a standard 3.0-T MR system with single RF transmission. The RF power was distributed to the independent ports of the system body coil by using two RF transmission sources with full software control, enabling independent control of the phase and amplitude of the RF waveforms. Axial T2-weighted fast spin-echo (SE) and diffusion-weighted (DW) liver images, axial T2-weighted fast SE pelvic images, and sagittal T1- and T2-weighted fast SE spinal images were obtained by using dual- and single-source RF excitation. Two radiologists independently evaluated the images for homogeneity and image quality. Statistical significance was calculated by using the nonparametric Wilcoxon signed rank test. Interobserver agreement was determined by using Cohen kappa and Kendall tau-b tests.

RESULTS

Image quality comparisons revealed significantly better results with dual-source rather than single-source RF excitation at T2-weighted liver MR imaging (P = .001, kappa = 1.00) and better results at DW liver imaging at a statistical trend level (P = .066, tau-b > 0.7). Owing to reduced local energy deposition, fewer acquisitions and shorter repetition times could be implemented with dual-source RF excitation pelvic and spinal MR imaging, with image acquisition accelerating by 18%, 33%, and 50% compared with the acquisitions with single-source RF excitation. Image quality did not differ significantly between the two MR techniques (P > .05, tau-b > 0.5).

CONCLUSION

Dual-source parallel RF excitation body MR imaging enables reduced dielectric shading, improved homogeneity of the RF magnetic induction field, and accelerated imaging at 3.0 T.

High-field magnetic resonance imaging of the pelvis: uterus, ovary, and prostate gland

Today, magnetic resonance imaging (MRI) is a standard imaging modality for various pathologic disorders in the human pelvis. It has given proof of its usefulness in the diagnosis of several benign and malignant disorders, and it is routinely used for the local staging of different tumors even when confined to specific parts of a pelvic organ. Signal-to-noise ratio and motion artifacts of the examined organ and adjacent bowel structures are major factors for image quality. Setting at 3 T with surface coils avoids technical limitations and discomfort of additional endovaginal or endorectal coils. Definition of high field seems fuzzy because of the availability of MRI machines with 3, 7 T, or higher; therefore, the general aspects of MRI of pelvic structures with emphasis on uterus, ovary, and prostate gland and attention to promising newer techniques such as 3 T, dynamic contrast imaging, and diffusion-weighted imaging are reviewed in this article.

MR imaging of endometrial carcinoma for preoperative staging at 3.0 T: comparison with imaging at 1.5 T

PURPOSE

To prospectively compare magnetic resonance imaging (MRI) at 3.0 T and 1.5 T in the same patients for preoperative evaluation of endometrial carcinoma.

MATERIALS AND METHODS

Thirty consecutive patients with endometrial carcinoma underwent MRI at both 3.0 T and 1.5 T as well as surgery. Quantitative and qualitative analyses were performed. Two radiologists independently evaluated images. MR findings were compared with surgicopathologic findings.

RESULTS

Image homogeneity of T2-weighted images at 3.0 T was significantly inferior to that at 1.5 T (P = 0.007). The scores of image homogeneity and susceptibility artifacts were not significantly different between 3.0 T gadolinium-enhanced imaging and 1.5 T imaging (P = 0.09 and 0.36). Kappa statistics showed good interobserver agreement between the two radiologists for local-regional staging on T2-weighted images (kappa>0.6). The area under the receiver operating characteristic curve (Az) values for T2-weighted imaging in terms of myometrial invasion, cervical invasion, and lymph node metastases were 0.88 (3.0 T) versus 0.91 (1.5 T), 0.84 versus 0.83, and 0.94 versus 0.95 for reader 1, respectively. There were no significant differences between imaging at 3.0 T and at 1.5 T in Az values for either reader (P > 0.35).

CONCLUSION

3.0 T MRI is an equivalent imaging modality to 1.5 T imaging for presurgical evaluation of endometrial carcinoma, although not significantly superior to 1.5 T imaging.

Combined use of T2-weighted and diffusion-weighted 3-T MR imaging for differentiating uterine sarcomas from benign leiomyomas

The objective of our study was to compare diffusion-weighted imaging (DWI) alone and DWI combined with T2-weighted MRI for the differentiation of uterine sarcomas from benign leiomyomas. T2-weighted imaging and DWI were performed in 103 patients with 103 myometrial tumours, including 8 uterine sarcomas and 95 benign leiomyomas on 3-T MR imaging. The signal intensity (SI) of the tumour on T2-weighted images was quantified as the tumour-myometrium contrast ratio (TCR) by using the following formula: (SI(tumour)-SI(myometrium))/SI(myometrium). The TCR or apparent diffusion coefficient (ADC) value alone and then the ADC value combined with T2-weighted imaging were evaluated for differentiation between sarcomas and leiomyomas. The mean ADC value of sarcomas was 0.86 +/- 0.11 x 10(-3) m(2)/s, which was significantly lower than that of leiomyomas 1.18 +/- 0.24 x 10(-3) m(2)/s; however, there was a substantial overlap. The mean TCR of sarcomas was 0.66 +/- 0.71, which was significantly higher than that of the leiomyomas, -0.37 +/- 0.34; however, again, there was a considerable overlap. When ADC was less than 1.05 x 10(-3) mm(2)/s and TCR was greater than 0 this condition was considered to confirm a sarcoma; a combination of ADC and TCR achieved a significant improvement without any overlap between sarcomas and leiomyomas (sensitivity 100%, specificity 100%). Our preliminary results indicate that combined DWI and T2-weighted MR imaging is better than DWI alone in the differentiation of uterine sarcomas from benign leiomyomas.

Uterine cervical carcinoma: preoperative staging with 3.0-T MR imaging--comparison with 1.5-T MR imaging

PURPOSE

To prospectively evaluate the efficacy of 3.0-T magnetic resonance (MR) imaging in the preoperative staging of cervical carcinoma compared with that at 1.5-T imaging, with surgery and pathologic analysis as the reference standards.

MATERIALS AND METHODS

Institutional review board approval and informed consent were obtained. Thirty-one consecutive patients (age range, 27-71 years; mean age, 51.1 years) underwent 3.0- and 1.5-T MR imaging. Quantitative and qualitative analyses were performed. Two radiologists independently evaluated images in terms of local-regional staging. MR findings were compared with surgicopathologic findings.

RESULTS

Mean tumor signal-to-noise ratios, mean cervical stroma signal-to-noise ratios, and mean tumor-to-cervical stroma contrast-to-noise ratios at 3.0-T imaging were significantly higher than those at 1.5-T imaging (P = 9.1 x 10(-6), P = 1.8 x 10(-6), and P = .008, respectively). Image homogeneity at 3.0-T imaging was significantly inferior to that at 1.5-T imaging (P = .005). There were no significant differences in terms of the degree of susceptibility artifacts. Interobserver agreement between the two radiologists for local-regional staging was good or excellent (kappa = 0.65-0.89). Sensitivity, specificity, and area under the receiver operating characteristic curve for radiologist 1 in the evaluation of parametrial invasion were (a) 75% for both 3.0- and 1.5-T imaging, (b) 70% for both 3.0- and 1.5-T imaging, and (c) 0.82 for 3.0-T imaging and 0.85 for 1.5-T imaging, respectively. Corresponding values for vaginal invasion were (a) 67% for both 3.0- and 1.5-T imaging, (b) 68% for 3.0-T imaging and 72% for 1.5-T imaging, and (c) 0.62 for 3.0-T imaging and 0.67 for 1.5-T imaging, respectively. Corresponding values for lymph node metastases were (a) 57% for both 3.0- and 1.5-T imaging, (b) 83% for 3.0-T imaging and 88% for 1.5-T imaging, and (c) 0.72 for 3.0-T imaging and 0.78 for 1.5-T imaging, respectively. Neither radiologist noted significant differences between values obtained with 3.0-T imaging and those obtained with 1.5-T imaging (P > .5 for all comparison pairs).

CONCLUSION

In this study, 3.0-T MR imaging was characterized by high diagnostic accuracy in the presurgical evaluation of patients with cervical carcinoma, although 3.0-T imaging was not significantly superior to 1.5-T imaging.

Clinical advantages of 3.0 T MRI over 1.5 T

Since approval by the FDA in 2000, human MR imaging (MRI) at 3.0 T has been increasingly used in clinical practice. In spite of the potential technical challenges, a number of clinical advantages of 3.0 T MRI over 1.5 T have been identified in the recent years. This article reviews the benefits and the current knowledge of 3.0 T whole-body MRI from an evidence-based perspective and summarizes its clinical applications.

MR Imaging of Gynecologic Diseases at 3T

MR imaging using anatomic, chemical, and functional information offers huge potential for the management of the gynecologic patient. By differentiating benign from malignant disease with very high specificity, it can aid the selection of patients requiring further treatment and determine the level of urgency. Staging accuracy, which equals that obtained at laparotomy, allows appropriate clinical expertise to be organized before surgery or the deferment of surgery until later in the treatment pathway and is a cost-effective use of resources. This article compares and contrasts MR imaging of gynecologic conditions at 1.5 and 3T and defines a role for high field imaging for these clinical conditions.