Pelvic MRI: Is Endovaginal or Rectal Filling Needed?

Magnetic Resonance Image Radiomic Reproducibility: The Impact of Preprocessing on Extracted Features from Gross and High-Risk Clinical Tumor Volumes in Cervical Cancer Patients before Brachytherapy

Background

Radiomic feature reproducibility assessment is critical in radiomics-based image biomarker discovery. This study aims to evaluate the impact of preprocessing parameters on the reproducibility of magnetic resonance image (MRI) radiomic features extracted from gross tumor volume (GTV) and high-risk clinical tumor volume (HR-CTV) in cervical cancer (CC) patients.

Methods

This study included 99 patients with pathologically confirmed cervical cancer who underwent an MRI prior to receiving brachytherapy. The GTV and HR-CTV were delineated on T2-weighted MRI and inputted into 3D Slicer for radiomic analysis. Before feature extraction, all images were preprocessed to a combination of several parameters of Laplacian of Gaussian (1 and 2), resampling (0.5 and 1), and bin width (5, 10, 25, and 50). The reproducibility of radiomic features was analyzed using the intra-class correlation coefficient (ICC).

Results

Almost all shapes and first-order features had ICC values > 0.95. Most second-order texture features were not reproducible (ICC < 0.95) in GTV and HR-CTV. Furthermore, 20% of all neighboring gray-tone difference matrix texture features had ICC > 0.90 in both GTV and HR-CTV.

Conclusion

The results presented here showed that MRI radiomic features are vulnerable to changes in preprocessing, and this issue must be understood and applied before any clinical decision-making. Features with ICC > 0.90 were considered the most reproducible features. Shape and first-order radiomic features were the most reproducible features in both GTV and HR-CTV. Our results also showed that GTV and HR-CTV radiomic features had similar changes against preprocessing sets.

Surgical Management of OHVIRA and Outcomes

STUDY OBJECTIVE

Obstructed hemivagina and ipsilateral renal anomaly (OHVIRA) includes uterine didelphys, unilateral obstructed hemivagina, and ipsilateral renal anomaly. Surgical management of this condition relies on accurate diagnosis to excise the obstructed longitudinal vaginal septum (OLVS). Vital considerations involve identifying the side affected, ipsilateral renal anomaly (IRA), thickness of the septum (TS), septal axis (SA), and distance of the septum to perineum (DSP). The study aimed to evaluate the preoperative characteristics, imaging findings, and surgical outcomes of OHVIRA.

METHODS

Institutional review board approval was obtained for this retrospective chart review. ICD-10 codes identified OHVIRA cases between 2012 and 2019 at a single children's hospital. Patient demographic characteristics, magnetic resonance imaging findings, surgical management, outcomes, and complications were reviewed. Descriptive statistics were utilized.

RESULTS

Twenty-six patients met inclusion criteria. Most were diagnosed at puberty (92%). Abdominal pain (50%) was the most common presenting complaint. The mean age of diagnosis was 13.2 years overall and 11.2 years for those with regular cycles vs 13.4 years for those with irregular cycles. Preoperative imaging showed predominant right-sided OLVS (50%), IRA (77%), and oblique SA (65%). All patients underwent vaginoscopy, septum resection, and vaginoplasty, except 1 who was managed with an abdominal drain as a neonate. Four required postoperative vaginal stent or Foley, with DSP greater than 5 cm in all cases. One intraabdominal abscess complication occurred. No instances of hematocolpos re-accumulation or reoperation were observed during the 3-year follow-up period.

CONCLUSION

This study demonstrates that detailed preoperative planning and a systematic surgical approach lead to favorable outcomes in OHVIRA irrespective of the OLVS laterality, TS, SA, or DSP.

Viscous Aqueous Gel Illustrating Natural Anatomy: The VAGINA method in gynaecological MRI simulation

Accurately defining gross tumour volume (GTV) and organs at risk (OAR) is key to successful radiation therapy (RT) treatment outcomes for patients with gynaecological cancers. With improved access to magnetic resonance imaging (MRI) for RT simulation and planning, the optimisation and tailoring of proven diagnostic MRI techniques towards RT specific planning goals is fast evolving. Modifying MRI techniques for radiation oncology (RO) with the priority of anatomy visualisation and spatial location over diagnosis and disease characterisation relies heavily on successful collaboration between radiology and radiation oncology staff. This 'How I Do It' paper describes a qualitative analysis of the adaptation of a diagnostic MRI vaginal opacification technique into an RT specific MRI simulation procedure using aqueous ultrasound gel for improving natural anatomical visualisation of the vaginal canal. This technique is explained and could be introduced in other RO departments for dedicated RT planning scans in MR-Sim sessions with minimal difficulty. We found 10-15 cc of aqueous gel delivered vaginally produced optimal MRI planning images for most patients. With this small amount of gel and careful application technique, the full extent of the vaginal vault and cervix can be well visualised on T2 Weighted (T2W) imaging, while tending not to unfold the natural fornices of the collapsed vagina, representing a significant improvement in image quality from the outdated tampon procedure.

Cervical cancer in the pregnant population

Cervical cancer is the second most encountered cancer in pregnant patients. The 2018 International Federation of Gynecology and Obstetrics (FIGO) staging system for cervical cancer updated the staging of primary cervical carcinoma and disease process, with formal incorporation of imaging as a vital source of information in the management process to improve accuracy. Diagnosis and treatment of the pregnant population is a complex interplay of achieving adequate diagnostic information and optimal treatment while minimizing toxicity and risks to the mother and fetus. While novel imaging techniques and anticancer therapies are rapidly developed, much information on the safety and feasibility of different therapies is not yet available in the pregnant population. Therefore, managing pregnant patients with cervical cancer is complex and requires a multidisciplinary approach.

Peritoneal vaginal fistula and contrast extravasation during MRI

Gynecological malignancies including primary cervical cancers are frequently treated with chemotherapy and radiation. Fistulas affecting the gynecological organs and surrounding cavities are a known consequence of radiotherapy due to focal necrosis of the regional mucosa. In this report, we will demonstrate a rare case of a posterior vaginal wall rupture with resulting fistulization into the peritoneal cavity in a 50-year-old female patient with squamous cell carcinoma of the cervix status postchemoradiotherapy. Magnetic resonance imaging (MRI) showed a discontinuity in the posterior vaginal wall near the fornix with extravasation of ultrasound gel used as contrast into the intraperitoneal compartment. Patient later presented with peritonitis like signs and symptoms and was treated successfully with antibiotics. Vaginal gel should be used with caution in patients with prior history of radiation due to the possibility of vaginal rupture which may lead to peritoneal vaginal fistula and contrast extravasation.

An endovaginal MRI array with a forward-looking coil for advanced gynecological cancer brachytherapy procedures: Design and initial results

PURPOSE

To develop an endovaginal MRI array that provides signal enhancement forward into the posterior parametrium and sideways into the vaginal wall, accelerating multiple-contrast detection of residual tumors that survive external beam radiation. The array's enclosure should form an obturator for cervical cancer brachytherapy, allowing integration with MRI-guided catheter placement, CT, and interstitial radiation dose delivery.

METHODS

The endovaginal array consisted of forward-looking and sideways-looking components. The forward-looking element imaged the cervix and posterior endometrium, and the sideways-looking elements imaged the vaginal wall. Electromagnetic simulation was performed to optimize the geometry of a forward-looking coil placed on a conductive-metallic substrate, extending the forward penetration above the coil's tip. Thereafter, an endovaginal array with one forward-looking coil and four sideways-looking elements was constructed and tested at 1.5 Tesla in saline and gel phantoms, and three sexually mature swine. Each coil's tuning, matching, and decoupling were optimized theoretically, implemented with electronic circuits, and validated with network-analyzer measurements. The array enclosure emulates a conventional brachytherapy obturator, allowing use of the internal imaging array together with tandem coils and interstitial catheters, as well as use of the enclosure alone during CT and radiation delivery. To evaluate the receive magnetic field ( B 1 - ) spatial profile, the endovaginal array's specific absorption-rate (SAR) distribution was simulated inside a gel ASTM phantom to determine extreme heating locations in advance of a heating test. Heating tests were then performed during high SAR imaging in a gel phantom at the predetermined locations, testing compliance with MRI safety standards. To assess array imaging performance, signal-to-noise-ratios (SNR) were calculated in a saline phantom and in vivo. Swine images were acquired with the endovaginal array combined with the scanner's body and spine arrays.

RESULTS

Simulated B 1 - profiles for the forward-looking lobe pattern, obtained while varying several geometric parameters, disclosed that a forward-looking coil placed on a metal-backed substrate could double the effective forward penetration from approximately 25 to ∼40 mm. An endovaginal array, enclosed in an obturator enclosure was then constructed, with all coils tuned, matched, and decoupled. The ASTM gel-phantom SAR test showed that peak local SAR was 1.2 W/kg in the forward-looking coil and 0.3 W/kg in the sideways-looking elements, well within ASTM/FDA/IEC guidelines. A 15-min 4 W/kg average SAR imaging experiment resulted in less than 2^o C temperature increase, also within ASTM/FDA/IEC heating limits. In a saline phantom, the forward-looking coil and sideways-looking array's SNR was four to eight times, over a 20-30 mm field-of-view (FOV), and five to eight times, over a 15-25 mm FOV, relative to the spine array's SNR, respectively. In three sexually mature swine, the forward-looking coil provided a 5 + 0.2 SNR enhancement factor within the cervix and posterior endometrium, and the sideways-looking array provided a 4 + 0.2 SNR gain factor in the vaginal wall, relative to the Siemens spine array, demonstrating that the array could significantly reduce imaging time.

CONCLUSIONS

Higher SNR gynecological imaging is supported by forward-looking and sideways-looking coils. A forward-looking endovaginal coil for cervix and parametrium imaging was built with optimized metal backing. Array placement within an obturator enhanced integration with the brachytherapy procedure and accelerated imaging for detecting postexternal-beam residual tumors.

Magnetic Resonance Imaging in the Evaluation of Female Infertility

Pelvic MRI plays an important adjunctive role in the clinical workup of female infertility. Hysterosalpingography is the first line imaging modality in evaluation of female infertility, and hysterosalpingo-contrast sonography can also be used to evaluate both the uterine cavity and fallopian tubes. Pelvic MRI can be helpful in the workup of female infertility, particularly in cases of Mullerian duct anomalies, fibroids, adenomyosis, endometriosis, and tubal disease. These conditions and their appearance on imaging will be reviewed in this article.

Recommendations for MRI technique in the evaluation of pelvic endometriosis: consensus statement from the Society of Abdominal Radiology endometriosis disease-focused panel

Endometriosis is a common entity causing chronic pain and infertility in women. The gold standard method for diagnosis is diagnostic laparoscopy, which is invasive and costly. MRI has shown promise in its ability to diagnose endometriosis and its efficacy for preoperative planning. The Society of Abdominal Radiology established a Disease-Focused Panel (DFP) to improve patient care for patients with endometriosis. In this article, the DFP performs a literature review and uses its own experience to provide technical recommendations on optimizing MRI Pelvis for the evaluation of endometriosis.

MRI of female genital tract congenital anomalies: European Society of Urogenital Radiology (ESUR) guidelines

Objective

To develop imaging guidelines for the MR work-up of female genital tract congenital anomalies (FGTCA).

Methods

These guidelines were prepared based on a questionnaire sent to all members of the European Society of Urogenital Radiology (ESUR) Female Pelvic Imaging Working Group (FPI-WG), critical review of the literature and expert consensus decision.

Results

The returned questionnaires from 17 different institutions have shown reasonable homogeneity of practice. Recommendations with focus on patient preparation and MR protocol are proposed, as these are key to optimised examinations. Details on MR sequences and planning of uterus-orientated sequences are provided.

Conclusions

The multiplanar capabilities and soft tissue resolution of MRI provide superb characterisation of the wide spectrum of findings in FGTCA. A standardised imaging protocol and method of reporting ensures that the salient features are recognised, contributing to a correct diagnosis and classification of FGTCA, associated anomalies and complications. These imaging guidelines are based on current practice among expert radiologists in the field and incorporate up to date information regarding MR protocols and essentials of recently published classification systems.

Key Points

• MRI allows comprehensive evaluation of female genital tract congenital anomalies, in a single examination.

• A dedicated MRI protocol comprises uterus-orientated sequences and vaginal and renal evaluation.

• Integration of classification systems and structured reporting helps in successful communication of the imaging findings.

Electronic supplementary material

The online version of this article (10.1007/s00330-020-06750-8) contains supplementary material, which is available to authorized users.

Assessment of the Effectiveness of the Vaginal Contrast Media in Magnetic Resonance Imaging for Detection of Pelvic Pathologies: A Meta-analysis

OBJECTIVE

Magnetic resonance imaging (MRI) is an excellent modality for pelvic imaging. The anatomy of uterine cavity and vagina is optimally evaluated when the walls, which may spontaneously be collapsed, are distended. Distension of these cavities during pelvic MRI for evaluation of gynecologic diseases has been conducted with vagina, filled with ultrasound gel or saline solution. In this meta-analysis, we aim to assess the effectiveness of vaginal contrast media in MRI for improving the detection of pelvic pathologies.

METHODS

The PubMed, MEDLINE, EMBASE, Web of Science, Google Scholar, Science Citation Index, and Cochrane Library databases were systematically searched through March 2019 for studies of the accuracy of MRI using vaginal contrast media in the diagnosis and staging of pelvic pathologies. Four eligible studies of a total of 120 patients were included in the meta-analysis. The sensitivity rates and relative risk for MRI, before and after vaginal contrast medium administration, were pooled, and their 95% confidence intervals (CIs) were determined.

RESULTS

The pooled sensitivity rate for MRI before administering intravaginal contrast medium in detecting pelvic pathologies was 63% (95% CI, 54%-72%), and that after was 89% (95% CI, 83%-93%). The interstudy heterogeneity rate (assessed using the I statistic) was relatively low: 13% (P = 0.33) and 0% (P = 0.45) before and after vaginal contrast medium use, respectively. The average relative risk was 1.54 (SD, 0.22; 95% CI, 1.18-1.89; median, 1.50; range, 1.34-1.80). This demonstrated that, on average, the sensitivity rate for MRI in detecting pelvic disorders increased by 54% after the use of a vaginal contrast medium.

CONCLUSIONS

Use of vaginal contrast media improved the diagnostic ability of MRI in identifying pelvic pathologies.