Journal of Clinical and Diagnostic Research, ISSN - 0973 - 709X

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On Sep 2018




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Prof. Somashekhar Nimbalkar
Head, Department of Pediatrics, Pramukhswami Medical College, Karamsad
Chairman, Research Group, Charutar Arogya Mandal, Karamsad
National Joint Coordinator - Advanced IAP NNF NRP Program
Ex-Member, Governing Body, National Neonatology Forum, New Delhi
Ex-President - National Neonatology Forum Gujarat State Chapter
Department of Pediatrics, Pramukhswami Medical College, Karamsad, Anand, Gujarat.
On Sep 2018




Dr. Kalyani R

"Journal of Clinical and Diagnostic Research is at present a well-known Indian originated scientific journal which started with a humble beginning. I have been associated with this journal since many years. I appreciate the Editor, Dr. Hemant Jain, for his constant effort in bringing up this journal to the present status right from the scratch. The journal is multidisciplinary. It encourages in publishing the scientific articles from postgraduates and also the beginners who start their career. At the same time the journal also caters for the high quality articles from specialty and super-specialty researchers. Hence it provides a platform for the scientist and researchers to publish. The other aspect of it is, the readers get the information regarding the most recent developments in science which can be used for teaching, research, treating patients and to some extent take preventive measures against certain diseases. The journal is contributing immensely to the society at national and international level."



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Sri Devaraj Urs Academy of Higher Education and Research , Kolar, Karnataka
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Dr. Saumya Navit

"As a peer-reviewed journal, the Journal of Clinical and Diagnostic Research provides an opportunity to researchers, scientists and budding professionals to explore the developments in the field of medicine and dentistry and their varied specialities, thus extending our view on biological diversities of living species in relation to medicine.
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Professor and Head
Department of Pediatric Dentistry
Saraswati Dental College
Lucknow
On Sep 2018




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Dr. Arunava Biswas
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Assistant Professor
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Best regards,
C.S. Ramesh Babu,
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Muzaffarnagar Medical College,
Muzaffarnagar.
On Aug 2018




Dr. Arundhathi. S
"Journal of Clinical and Diagnostic Research (JCDR) is a reputed peer reviewed journal and is constantly involved in publishing high quality research articles related to medicine. Its been a great pleasure to be associated with this esteemed journal as a reviewer and as an author for a couple of years. The editorial board consists of many dedicated and reputed experts as its members and they are doing an appreciable work in guiding budding researchers. JCDR is doing a commendable job in scientific research by promoting excellent quality research & review articles and case reports & series. The reviewers provide appropriate suggestions that improve the quality of articles. I strongly recommend my fraternity to encourage JCDR by contributing their valuable research work in this widely accepted, user friendly journal. I hope my collaboration with JCDR will continue for a long time".



Dr. Arundhathi. S
MBBS, MD (Pathology),
Sanjay Gandhi institute of trauma and orthopedics,
Bengaluru.
On Aug 2018




Dr. Mamta Gupta,
"It gives me great pleasure to be associated with JCDR, since last 2-3 years. Since then I have authored, co-authored and reviewed about 25 articles in JCDR. I thank JCDR for giving me an opportunity to improve my own skills as an author and a reviewer.
It 's a multispecialty journal, publishing high quality articles. It gives a platform to the authors to publish their research work which can be available for everyone across the globe to read. The best thing about JCDR is that the full articles of all medical specialties are available as pdf/html for reading free of cost or without institutional subscription, which is not there for other journals. For those who have problem in writing manuscript or do statistical work, JCDR comes for their rescue.
The journal has a monthly publication and the articles are published quite fast. In time compared to other journals. The on-line first publication is also a great advantage and facility to review one's own articles before going to print. The response to any query and permission if required, is quite fast; this is quite commendable. I have a very good experience about seeking quick permission for quoting a photograph (Fig.) from a JCDR article for my chapter authored in an E book. I never thought it would be so easy. No hassles.
Reviewing articles is no less a pain staking process and requires in depth perception, knowledge about the topic for review. It requires time and concentration, yet I enjoy doing it. The JCDR website especially for the reviewers is quite user friendly. My suggestions for improving the journal is, more strict review process, so that only high quality articles are published. I find a a good number of articles in Obst. Gynae, hence, a new journal for this specialty titled JCDR-OG can be started. May be a bimonthly or quarterly publication to begin with. Only selected articles should find a place in it.
An yearly reward for the best article authored can also incentivize the authors. Though the process of finding the best article will be not be very easy. I do not know how reviewing process can be improved. If an article is being reviewed by two reviewers, then opinion of one can be communicated to the other or the final opinion of the editor can be communicated to the reviewer if requested for. This will help one’s reviewing skills.
My best wishes to Dr. Hemant Jain and all the editorial staff of JCDR for their untiring efforts to bring out this journal. I strongly recommend medical fraternity to publish their valuable research work in this esteemed journal, JCDR".



Dr. Mamta Gupta
Consultant
(Ex HOD Obs &Gynae, Hindu Rao Hospital and associated NDMC Medical College, Delhi)
Aug 2018




Dr. Rajendra Kumar Ghritlaharey

"I wish to thank Dr. Hemant Jain, Editor-in-Chief Journal of Clinical and Diagnostic Research (JCDR), for asking me to write up few words.
Writing is the representation of language in a textual medium i e; into the words and sentences on paper. Quality medical manuscript writing in particular, demands not only a high-quality research, but also requires accurate and concise communication of findings and conclusions, with adherence to particular journal guidelines. In medical field whether working in teaching, private, or in corporate institution, everyone wants to excel in his / her own field and get recognised by making manuscripts publication.


Authors are the souls of any journal, and deserve much respect. To publish a journal manuscripts are needed from authors. Authors have a great responsibility for producing facts of their work in terms of number and results truthfully and an individual honesty is expected from authors in this regards. Both ways its true "No authors-No manuscripts-No journals" and "No journals–No manuscripts–No authors". Reviewing a manuscript is also a very responsible and important task of any peer-reviewed journal and to be taken seriously. It needs knowledge on the subject, sincerity, honesty and determination. Although the process of reviewing a manuscript is a time consuming task butit is expected to give one's best remarks within the time frame of the journal.
Salient features of the JCDR: It is a biomedical, multidisciplinary (including all medical and dental specialities), e-journal, with wide scope and extensive author support. At the same time, a free text of manuscript is available in HTML and PDF format. There is fast growing authorship and readership with JCDR as this can be judged by the number of articles published in it i e; in Feb 2007 of its first issue, it contained 5 articles only, and now in its recent volume published in April 2011, it contained 67 manuscripts. This e-journal is fulfilling the commitments and objectives sincerely, (as stated by Editor-in-chief in his preface to first edition) i e; to encourage physicians through the internet, especially from the developing countries who witness a spectrum of disease and acquire a wealth of knowledge to publish their experiences to benefit the medical community in patients care. I also feel that many of us have work of substance, newer ideas, adequate clinical materials but poor in medical writing and hesitation to submit the work and need help. JCDR provides authors help in this regards.
Timely publication of journal: Publication of manuscripts and bringing out the issue in time is one of the positive aspects of JCDR and is possible with strong support team in terms of peer reviewers, proof reading, language check, computer operators, etc. This is one of the great reasons for authors to submit their work with JCDR. Another best part of JCDR is "Online first Publications" facilities available for the authors. This facility not only provides the prompt publications of the manuscripts but at the same time also early availability of the manuscripts for the readers.
Indexation and online availability: Indexation transforms the journal in some sense from its local ownership to the worldwide professional community and to the public.JCDR is indexed with Embase & EMbiology, Google Scholar, Index Copernicus, Chemical Abstracts Service, Journal seek Database, Indian Science Abstracts, to name few of them. Manuscriptspublished in JCDR are available on major search engines ie; google, yahoo, msn.
In the era of fast growing newer technologies, and in computer and internet friendly environment the manuscripts preparation, submission, review, revision, etc and all can be done and checked with a click from all corer of the world, at any time. Of course there is always a scope for improvement in every field and none is perfect. To progress, one needs to identify the areas of one's weakness and to strengthen them.
It is well said that "happy beginning is half done" and it fits perfectly with JCDR. It has grown considerably and I feel it has already grown up from its infancy to adolescence, achieving the status of standard online e-journal form Indian continent since its inception in Feb 2007. This had been made possible due to the efforts and the hard work put in it. The way the JCDR is improving with every new volume, with good quality original manuscripts, makes it a quality journal for readers. I must thank and congratulate Dr Hemant Jain, Editor-in-Chief JCDR and his team for their sincere efforts, dedication, and determination for making JCDR a fast growing journal.
Every one of us: authors, reviewers, editors, and publisher are responsible for enhancing the stature of the journal. I wish for a great success for JCDR."



Thanking you
With sincere regards
Dr. Rajendra Kumar Ghritlaharey, M.S., M. Ch., FAIS
Associate Professor,
Department of Paediatric Surgery, Gandhi Medical College & Associated
Kamla Nehru & Hamidia Hospitals Bhopal, Madhya Pradesh 462 001 (India)
E-mail: drrajendrak1@rediffmail.com
On May 11,2011




Dr. Shankar P.R.

"On looking back through my Gmail archives after being requested by the journal to write a short editorial about my experiences of publishing with the Journal of Clinical and Diagnostic Research (JCDR), I came across an e-mail from Dr. Hemant Jain, Editor, in March 2007, which introduced the new electronic journal. The main features of the journal which were outlined in the e-mail were extensive author support, cash rewards, the peer review process, and other salient features of the journal.
Over a span of over four years, we (I and my colleagues) have published around 25 articles in the journal. In this editorial, I plan to briefly discuss my experiences of publishing with JCDR and the strengths of the journal and to finally address the areas for improvement.
My experiences of publishing with JCDR: Overall, my experiences of publishing withJCDR have been positive. The best point about the journal is that it responds to queries from the author. This may seem to be simple and not too much to ask for, but unfortunately, many journals in the subcontinent and from many developing countries do not respond or they respond with a long delay to the queries from the authors 1. The reasons could be many, including lack of optimal secretarial and other support. Another problem with many journals is the slowness of the review process. Editorial processing and peer review can take anywhere between a year to two years with some journals. Also, some journals do not keep the contributors informed about the progress of the review process. Due to the long review process, the articles can lose their relevance and topicality. A major benefit with JCDR is the timeliness and promptness of its response. In Dr Jain's e-mail which was sent to me in 2007, before the introduction of the Pre-publishing system, he had stated that he had received my submission and that he would get back to me within seven days and he did!
Most of the manuscripts are published within 3 to 4 months of their submission if they are found to be suitable after the review process. JCDR is published bimonthly and the accepted articles were usually published in the next issue. Recently, due to the increased volume of the submissions, the review process has become slower and it ?? Section can take from 4 to 6 months for the articles to be reviewed. The journal has an extensive author support system and it has recently introduced a paid expedited review process. The journal also mentions the average time for processing the manuscript under different submission systems - regular submission and expedited review.
Strengths of the journal: The journal has an online first facility in which the accepted manuscripts may be published on the website before being included in a regular issue of the journal. This cuts down the time between their acceptance and the publication. The journal is indexed in many databases, though not in PubMed. The editorial board should now take steps to index the journal in PubMed. The journal has a system of notifying readers through e-mail when a new issue is released. Also, the articles are available in both the HTML and the PDF formats. I especially like the new and colorful page format of the journal. Also, the access statistics of the articles are available. The prepublication and the manuscript tracking system are also helpful for the authors.
Areas for improvement: In certain cases, I felt that the peer review process of the manuscripts was not up to international standards and that it should be strengthened. Also, the number of manuscripts in an issue is high and it may be difficult for readers to go through all of them. The journal can consider tightening of the peer review process and increasing the quality standards for the acceptance of the manuscripts. I faced occasional problems with the online manuscript submission (Pre-publishing) system, which have to be addressed.
Overall, the publishing process with JCDR has been smooth, quick and relatively hassle free and I can recommend other authors to consider the journal as an outlet for their work."



Dr. P. Ravi Shankar
KIST Medical College, P.O. Box 14142, Kathmandu, Nepal.
E-mail: ravi.dr.shankar@gmail.com
On April 2011
Anuradha

Dear team JCDR, I would like to thank you for the very professional and polite service provided by everyone at JCDR. While i have been in the field of writing and editing for sometime, this has been my first attempt in publishing a scientific paper.Thank you for hand-holding me through the process.


Dr. Anuradha
E-mail: anuradha2nittur@gmail.com
On Jan 2020

Important Notice

Original article / research
Year : 2021 | Month : July | Volume : 15 | Issue : 7 | Page : TC01 - TC04 Full Version

Efficacy of Three Dimensional Fast Imaging Employing Steady State Acquisition Combined with Conventional MRI in Evaluation of Patients with Cerebellopontine Angle Lesions


Published: July 1, 2021 | DOI: https://doi.org/10.7860/JCDR/2021/46977.15094
Sasikumar Arya, Ealai Athmarao Parthasarathy, Rajamani Anand, Chakravarthy Anup, Kalaiarasan Ramya

1. Postgraduate Student, Department of Radiology and Imaging Sciences, Chettinad Hospital and Research Institute, Chennai, Tamil Nadu, India. 2. Associate Professor, Department of Radiology and Imaging Sciences, Chettinad Hospital and Research Institute, Chennai, Tamil Nadu, India. 3. Associate Professor, Department of Radiology and Imaging Sciences, Chettinad Hospital and Research Institute, Chennai, Tamil Nadu, India. 4. Assistant Professor, Department of Radiology and Imaging Sciences, Chettinad Hospital and Research Institute, Chennai, Tamil Nadu, India. 5. Assistant Professor, Department of Radiology and Imaging Sciences, Chettinad Hospital and Research Institute, Chennai, Tamil Nadu, India.

Correspondence Address :
Dr. Ealai Athmarao Parthasarathy,
Associate Professor, Department of Radiology, D Block, Chettinad Hospital and Research Institute, Kelambakkam, Chennai, Tamil Nadu, India.
E-mail: parthasarathyea@gmail.com

Abstract

Introduction: The Three Dimensional Fast Imaging Employing Steady state Acquisition (3D FIESTA) has higher spatial resolution between the Cerebrospinal Fluid (CSF) and cranial nerves with accurate identification of Cerebellopontine Angle (CPA) and internal auditory canal tumours and takes shorter acquisition imaging time than conventional Magnetic Resonance Imaging (MRI) scan.

Aim: To evaluate the efficacy of 3D FIESTA imaging as a screening tool for CPA lesions, hence to depict the fine anatomy of the cisternal and canalicular segments of the facial nerve and vestibulocochlear nerves in order to elucidate the aetiopathogenesis of unexplained inner ear symptoms.

Materials and Methods: The present study was a hospital based cross-sectional study which was done in Department of Radiodiagnosis, Chettinad Hospital and Research Institute, Chennai, Tamil Nadu, India. The study was conducted on 30 patients, who were referred for MRI Brain to the department and diagnosed with cerebellopontine angle lesion from August 2018 to October 2019. A 1.5 Tesla, MRI scanner was used to scan all patients with a 8 channel Neurovascular (NV) radiofrequency coil. Along with routine conventional MRI sequences, 3D FIESTA sequence was also performed. All the data was collected and analysed by Statistical Package for Social Sciences (SPSS) software version 23.0. Data for descriptive statistics i.e. frequency and percentage analysis, mean±Standard Deviation (SD), sensitivity, specificity, Positive Predictive Value (PPV) and Negative Predictive Value (NPV) were calculated.

Results: On Histopathological Examination (HPE), 63.3% were schwannoma, 16.7% meningioma, 10% epidermoid cyst and 3.3% intracanalicular lipoma. In 6.7% of patients, imaging features were in favour of CPA arachnoid cyst. The size of the intracanalicular part of tumour was underestimated in T2 weighted images (T2WI). 3D FIESTA gave a better estimated tumour area, even though slightly less but almost equivalent to that in post-contrast imaging. In this study, post-contrast imaging was considered as the gold standard. It was proven that conventional sequences like T2WI showed a sensitivity of 85.71% and specificity of 100% whereas 3D FIESTA sequence showed 100% sensitivity and specificity in assessing the CPA tumour extent and cranial nerve involvement.

Conclusion: 3D FIESTA imaging is a sensitive technique for the diagnosis of retrocochlear and CPA lesions without contrast administration. 3D FIESTA imaging can be considered as a useful screening tool for patients presenting with inner ear symptoms.

Keywords

Diagnostic importance, Inner ear, Post-contrast imaging, Retrocochlear lesions, VII cranial nerves, VIII cranial nerves

The pons, cerebellum and petrous part of the temporal bone bound the CPA cistern which is filled with CSF. Lesions in this area can be identified in cross-sectional imaging. In adults, approximately 5-10% of all intracranial mass occur in the posterior fossa as CPA tumours (1). The most common of such tumours are vestibular schwannomas and meningiomas, which make up 70-80% and 10-15% of CPA tumors respectively. Most of these patients suffer from tinnitus and hearing loss. For retrocochlear lesions, Auditory Brainstem Response (ABR) is a diagnostic rule (2). Screening ABR is the most commonly used test for patients presenting with inner ear symptoms. ABR test and MRI are the two tests employed to investigate the patients. However, ABR has proven to be less sensitive as the size of the tumour decreases.

For assessment of retrocochlear lesions, MRI has high sensitivity and specificity. In a study conducted by Rigby PJ it was stated that only 7% of the patients with an acoustic schwannoma smaller than 1 cm was diagnosed by abnormal ABR (3). In the 1980s, after the introduction of MRI in the field of diagnosis of retrocochlear lesions increased the specificity and sensitivity upto 100% and which later was considered to be the most accurate diagnostic tool (4). Contrast enhanced thin section T1 weighted MRI is currently the accepted standard imaging approach. Disadvantage of conventional MRI is that it will provides soft tissue resolution, but spatial resolution which is necessary for defining cranial nerves may not be sufficient with this imaging. Recently, the T2 weighted 3D FIESTA sequence has been introduced. It doesn’t need any contrast media and has shorter imaging acquisition compared to conventional MRI.

For accurate detection of internal auditory canal and CPA small tumours, high spatial resolution with excellent image contrast between the cranial nerves and CSF is required. 3D FIESTA is used for identifying cisternal and canalicular segments of cranial nerves VII and VIII and adjacent vascular variations. It is also used for determining the relationship of Anterior Inferior Cerebellar Artery (AICA) variations between cranial nerves. 3D FIESTA is highly useful to assess these tiny details by using CSF window efficiently. It is also useful in displaying small arteries, veins with slow flow apart from distinguishing the mass and inflammation in T1W MRI after the use of paramagnetic intravenous agents.

Anatomy of CPA: The CPA is a region in the posterior fossa that consists of CSF, cranial nerves VII and VIII, AICA, and arachnoid tissue. The CPA is situated in between margins of cerebellum and pons (5). When viewed in the axial plane, the CPA cistern is a triangular space filled with CSF. The CPA cistern is contiguous with the cisterna ambiens (peri-mesencephalic) through the tentorial hiatus. The roof of CPA is formed by the tentorium and attached to petrous bone. Cerebellum is closely applied to the tentorium above and the occipital duramater below. The pia mater and arachnoid fuse and seal off the CPA cistern (6).

The FIESTA technique had been a true Fast Imaging with Steady-state Precession (FISP) sequence. Yano J and Yachandra VK (7) in 1987 said that pulse sequences where the Repeatition Time (TR), equal to or less than the Time (T2) of the sample was technically impossible. With advances in gradient and power amplifier design, by the late 1990s, true-FISP imaging was revisited. FIESTA uses very short and TEs (Echo Times), which produces images with high Signal to Noise Ratios (SNR). The FIESTA sequence is a fluid-bright sequence. While imaging the CPA and basal cisterns, CSF appears uniformly hyperintense in these sequences. This sequence clearly demonstrates the dural reflections of posterior fossa cranial nerves (4).

Hence, the present study was done to evaluate the efficacy of 3D FIESTA imaging as a screening tool for CPA lesions, which can be used to depict the fine anatomy of the cisternal and canalicular segments of the facial nerve and vestibulocochlear nerves in order to elucidate the aetiopathogenesis of unexplained inner ear symptoms.

Material and Methods

A hospital based cross-sectional study was conducted in the Department of Radiodiagnosis, Chettinad Hospital and Research Institute, Kelambakkam, Chennai on 30 patients subjected to MRI Brain scan and diagnosed with CPA lesions during the study period from August 2018 to October 2019 after obtaining the informed consent from all participants. The study was approved by the Institutions Ethical Committee (Approval letter no. 115./IHEC/06-18).

Inclusion criteria: Patients of age group 18-55 years, who were subjected to MRI brain and diagnosed with CPA lesion, or those who were referred by Ear Nose Throat (ENT) Department with headache, inner ear symptoms, facial and trigeminal nerve related symptoms were included in the study.

Exclusion criteria: Patients who were claustrophobic, or with metallic implants, cochlear implants and cardiac pacemaker and female patients with early pregnancy were excluded from the study.

All the patients who visited the Department of Radiodiagnosis of the selected study research institute during the study period and fulfilling the inclusion criteria were included in the study.

MRI Acquisition

A 1.5 Tesla SIGNA GE HDxt MRI scanner was used to scan all patients with an 8 channel NV (NAVIGATOR) radiofrequency coil. The bore size of the machine was 60 cm. Along with routine conventional MRI sequences 3D FIESTA sequence was added. The images thus obtained were evaluated and a diagnosis was made. The results were then analysed using appropriate statistical methods.

FIESTA Capital

This sequence uses gradients to produce a constant or steady amount of transverse magnetisation. This spin coherence is maintained by using short TRs. This sequence requires shimming to decrease inhomogeneity below 1 ppm (parts per million) as it is very sensitive to field inhomogeneities. The TR of this sequence is much smaller than the T2 of the tissue under investigation. The difference in the ratio of T2/T1 in the tissue provides image contrast in FIESTA. Tissues with long TR values would have increased signal as short TRs are used in this sequence. The ratio of T2 to T1 values of the tissue along with high SNR values improves the image contrast which makes true FISP imaging unique. This technique contains submillimetre sections which help in imaging of small tumours. The perilymph and endolymph fluid present within the inner ear appear hyperintense on this sequence which helps in better visualising the cochlear and semicircular canals, which was not possible on T1 weighted sequences.

On the basis of obtained images, tumours are classified as stated in study by Mohammed Jawad MS (8) into small (1-10 mm), medium (10-25 mm), large (26-40 mm) and giant (>40 mm) tumours based on their size.

Statistical Analysis

The collected data were analysed with International Business Management (IBM). SPSS software version 23.0. To describe the data descriptive statistics frequency and percentage analysis was used for categorical variables and the mean±Standard Deviation (SD) was used for continuous variables. The Receiver Operator Characteristic (ROC) curve analysis was used to find the sensitivity, specificity, PPV and NPV to assess the efficacy of the tools. The probability value of 0.05 is considered a significant level in the above statistical tool. Post-contrast sequences were analysed using Image J Software.

Results

Out of total sample of the study i.e. 30 patients, 18 (60%) were females and 12 (40%) were males. A 17 (56.7%) of total patients who presented with symptoms belonged to the age group of 41 to 60 years, 8 (26.7%) between 21 to 40 years and 5 (16.6%) between 61 to 80 years. Total 53.3% patients had lesions on the left side and 46.7% had lesions on the right side. Patients presented with symptoms of hearing loss 20 (30.3%), vertigo 17 (25.8%), tinnitus 9 (13.6%), facial palsy 6 (9.1%), trigeminal nerve dysfunction 2 (3.0%) and headache 12 (18.2%). (Table/Fig 1) shows distribution based on size of lesions.

A 36.7% of tumours showed homogeneous enhancement. Heterogeneous enhancement was noted in 53.3% of tumours especially in large and giant tumours and three cases didn’t show any enhancement. Total 40% of tumours had cystic changes. Post-contrast T1 weighted images demonstrated an area of hypointensity within the brightly enhanced lesion. This finding was suggestive of necrosed tissue within the lesion. This was a very significant finding as cystic acoustic schwannoma may expand at the rate of 10 times faster growth as compared to non-cystic lesions. The FIESTA sequence did demonstrate these lesions but in some cases, the changes were not to its full extent. Out of 30 lesions, two lesions showed restriction on diffusion weighted imaging which later proved to be epidermoid cysts on HPE. Out of 30 lesions, 25 (83.3%) cases had intracanalicular components and 10 cases (33.3%) of tumours showed widening of Internal Acoustic Canal (IAC). Out of 25 cases of intracanalicular tumours, the canal extension in two lesions was found only on FIESTA and post-contrast study and was missed on routine conventional sequences.

Also two lesions which were purely intracanalicular without a CPA component were exclusively diagnosed in the FIESTA sequence and post-contrast study. In lesions, which had IAC extension, the intracanalicular tumour size was measured in T2 weighted image, 3D FIESTA. Multiple comparison charts were put up in order to compare the difference in mean areas of the intracanalicular tumour in three different sequences. When these areas were compared, it was found that size of the intracanalicular part of tumour was underestimated in T2 weighted images. 3D FIESTA gave a better estimated tumour area, even though slightly less but almost equivalent to that in post-contrast imaging (Table/Fig 2).

The exact extent and lateral depth of the IAC tumour is of much importance for the surgeon. Far lateral tumour impacting the fundus with extension above and below the transverse crest of the IAC, complicates tumour removal and decreases the chances of hearing preservation (Table/Fig 3).

Depth of tumour extension is essential especially with a sub-occipital approach for surgical resection. Tumours occupying more than two-thirds of the length of the IAC complicate resection because the tumour cannot be directly visualised and cochlear nerve dissection is more difficult and the risk for residual tumour also increases. With the exact size of the extra-canalicular and intracanalicular tumors, the type of approach for tumour resection can also be chosen.

In two cases, the vascular loop of Anterior Inferior Cerebellar Artery (AICA) was diagnosed. One patient had Type 1 and another had Type II vascular loop. Vascular loop was missed on routine conventional sequence and post-contrast study which was diagnosed only on 3D FIESTA sequence. In this study, use of contrast agents was not required to distinguish the AICA and its variations in the CPA. Especially due to variations, sequence selection before the surgery is highly important so as to obtain an accurate image of the anatomic course of cranial nerves in the CPA and their complex adjacency with vascular structures and to decide on decompression surgery. The 3D FIESTA images showed that 81 temporal bones had type I vascular loops (65.9%), 33 had type II (26.8%), and 9 had type III vascular loops (7.3%).

In the imaging of these tiny details, 3D FIESTA sequence stands out as a highly successful sequence using CSF window efficiently. The intracanalicular VII and VIII nerve complex involvement was well assessed in 3D FIESTA and post-contrast imaging in four cases which were not assessed in T2 weighted image (Table/Fig 4).

The V Cranial Nerve (CN) involvement was seen in four cases of giant tumours which was well-assessed with 3D FIESTA and contrast study. The T2 weighted image did not provide details on 5th nerve involvement (Table/Fig 5).

On Histopathological examination (HPE), majority of tumours (63.3%) were comfirmed to be schwannoma, 16.7% meningioma, 10% epidermoid cyst and 3.3% intracanalicular lipoma. Two cases (6.7%) were diagnosed to be arachnoid cyst based on the imaging features and these patients were put on follow-up. In 24 cases, there were no postoperative complications. Among the remaining six, two patients had CSF leak, two cases had meningitis and one patient had cranial nerve palsy and one had worsening of hearing loss.

In this study, complications were noted in patients with large or giant tumours. Therefore the risk to develop postoperative complications can increase with larger tumours. In this study, post-contrast imaging was considered as the gold standard. It was proved that conventional sequences like T2WI showed a sensitivity of 85.71% and specificity of 100% whereas 3D FIESTA sequence along with post-contrast images and confirmations, showed 100% sensitivity and specificity in assessing the CPA tumour extent and cranial nerve involvement.

Discussion

The technique of 3D FIESTA could be potentially used for assessment of exact tumour size in CPA and intracanalicular tumour extension. Small tumours arising within the IAC were diagnosed with FIESTA sequence which was missed in other conventional routine sequences. The intracanalicular VII and VIII nerve complex involvement by the tumour was better assessed with 3D FIESTA as compared to conventional sequences. Trigeminal nerve involvement in case of giant tumours was diagnosed with FIESTA.

Thin section contrast-enhanced T1-weighted imaging is currently considered as the standard imaging technique. FIESTA sequence was found to have a diagnostic capability almost equivalent to that of post-contrast study. 3D FIESTA is useful in imaging of tumours especially like acoustic schwannomas (4),(5). Whereas the imaging features of epidermoid cysts were better assessed with other conventional sequences because of its cyst-like signal intensity and the diagnosis was sought with DWI sequence. In cases of CPA arachnoid cysts and lipoma, there had been no added imaging benefits with 3D FIESTA sequence compared to other sequences (6).

It is believed that 3D FIESTA sequence with its ability of high resolution imaging helped to diagnose vascular variations like vascular loops and predict their involvement in symptom origin. The diagnosis was considered complete after the FIESTA sequence in patients who were not found to have any pathology in the conventional sequences and was confirmed with HPE. Those patients in whom FIESTA sequence demonstrates pathology or lesion in the CPA should be further investigated by post-contrast T1-weighted sequences (6). In addition, in cases where contrast cannot be administered, such as in pregnant patients or patients who are sensitive to gadolinium, the FIESTA sequence can be used in isolation to exclude acoustic schwannomas (9).

Sequence selection before the decompression surgery is highly important especially due to anatomical variation. Therefore, an accurate image of anatomic course of cranial nerves in CPA and adjacent vascular structures is necessary before decompression surgery to prevent complications during surgical intervention (9). The 3D-FIESTA sequence gains the accuracy of T1-weighted sequences acquired with gadolinium, without the need for exogenous contrast agents (3).

With the use of FIESTA sequence as a protocol for diagnosing acoustic schwannoma, the time taken for examination can be reduced by eliminating the need for contrast administration and detailed anatomy of the inner ear can be assessed (5). FIESTA only protocol without post- contrast imaging can have few disadvantages. With post contrast T1W images further characterisation of the tumour can be done, other inner ear pathologies can be diagnosed and postoperative changes can be better demonstrated (9).

With these findings, authors suggest that 3D-FIESTA imaging could be a reliable screening test for patients who complain of otologic symptoms (9). These studies suggest that contrast enhanced T1-weighted images can be avoided in patients who have contraindications for contrast agents. Therefore, the diagnosis of CPA pathology can be considered to be complete with the addition of 3D FIESTA sequence in routine sequences.

Limitation(s)

Because of slow switching rates of the gradients, in FIESTA technique, low rise times, and small slow rates, steady state free precession imaging were not clinically feasible. Problems which can be encountered in employing FIESTA sequence are increased acoustic noise, peripheral nerve stimulation and the patients with contraindications for contrast agents.

Conclusion

The 3D FIESTA sequence is a high resolution T2W sequence that provides excellent image contrast with high SNR. The 3D FIESTA sequence allows better visualisation of small vascular structures with higher anatomical details, which are clearly depicted in other sequences. A screening sequence for diagnosis should be specific, sensitive, invasive and inexpensive when compared to the contrast-enhanced T1-weighted sequence. By these criteria, the FIESTA sequence is an ideal tool for investigation of possible acoustic schwannoma and other CPA tumours with or without neural involvement.

References

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Rigby PJ. Comparison of FIESTA and gadolinium enhanced T1 weighted sequences in magnetic resonance of acoustic schwannoma-Rigby-2006-Radiographer-Wiley Online Library, cited 2019 Sep 30. Available from: https://onlinelibrary.wiley.com/doi/abs/10.1002/j.2051-3909.2006.tb00050.x. [crossref]
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Noble DJ, Scoffings D, Ajithkumar T, Williams MV, Jefferies SJ. Fast Imaging Employing Steady-state Acquisition (FIESTA) MRI to investigate cerebrospinal fluid (CSF) within dural reflections of posterior fossa cranial nerves. Br J Radiol. 2016;89(1067):20160392. [crossref] [PubMed]
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Venkatasamy A, Le Foll D, Karol A, Lhermitte B, Charpiot A, Debry C, et al. Differentiation of vestibular schwannomas from meningiomas of the internal auditory canal using perilymphatic signal evaluation on T2-weighted gradient-echo fast imaging employing steady state acquisition at 3T. Eur Radiol Exp. 2017;1(1):8. Doi: 10.1186/s41747-017-0012-7. [crossref] [PubMed]
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Mohammed Jawad MS. Cerebellopontine angle tumors; tumor size and surgical outcome. Open Access J Neurol Neurosurg, Neurosurg, 2017. Available from: https://juniperpublishers.com/oajnn/OAJNN.MS.ID.555617.php. [crossref]
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DOI and Others

10.7860/JCDR/2021/46977.15094

Date of Submission: Sep 30, 2020
Date of Peer Review: Dec 14, 2020
Date of Acceptance: Jun 06, 2021
Date of Publishing: Jul 01, 2021

AUTHOR DECLARATION:
• Financial or Other Competing Interests: None
• Was Ethics Committee Approval obtained for this study? Yes
• Was informed consent obtained from the subjects involved in the study? Yes
• For any images presented appropriate consent has been obtained from the subjects. Yes

PLAGIARISM CHECKING METHODS:
• Plagiarism X-checker: Oct 01, 2020
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• iThenticate Software: May 27, 2021 (23%)

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