Case Study | Advanced Apps on Open Deser… · standard for detecting prostate cancer, TRUS biopsy...
Transcript of Case Study | Advanced Apps on Open Deser… · standard for detecting prostate cancer, TRUS biopsy...
© 2014 Hitachi Medical Systems America, Inc. All rights reserved.
OASIS 1.2T: MULTIPARAMETRIC MRI OF PROSTATE CANCER
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By Dr. John Feller, MD, RadiologistDesert Medical Imaging, Palm Springs, CA
© 2014 Hitachi Medical Systems America, Inc. All rights reserved.
Case Study | Advanced Apps on Open
MRI is clinically accepted as the best imaging modality
for displaying anatomical details of the prostate, and has
been a valuable diagnostic tool for aiding the detection
and localization of prostate cancer. Prostate MR is often
incorporated into the clinical workup as a staging tool after
a diagnosis is made through trans-rectal ultrasound (TRUS)
biopsy to exclude extension or metastasis of cancer outside
the prostate gland. Despite being recognized as the gold
standard for detecting prostate cancer, TRUS biopsy misses
30-35% of prostate cancers with abnormally high PSA levels
or a positive digital rectal exam - a high false negative rate
that complicates the decision path for the Urologist.
In addition, in respect to prostate cancer it does diagnose,
TRUS biopsy under-grades Gleason scores 35-45% of
the time.
Recently, MRI has offered a promising new implementation
for prostate cancer diagnosis and intervention through the
use of multiparametric techniques as an alternative to TRUS
or patients with negative TRUS-guided biopsies.
• Diffusion-weighted imaging (DWI) allowing for better
assessment of prostate cancer aggressiveness through
inverse correlation with low, intermediate, and high
Gleason scores.
• Dynamic contrast-enhanced (DCE) imaging shows
promise for better characterizing prostate cancer.
• Combined contrast methods to improve detection and
localization of prostate cancer for targeting lesions for
either biopsy or minimally invasive surgical procedures.
Multiparametric imaging of the prostate using the OASIS
1.2Topenhigh-fieldplatformallowsathoroughdiagnostic
workup to fully assess structural and functional detail. The
opendesignaddsnotonlythecommonlyunderstoodbenefit
ofpatientcomfortandaccessibility,butalsotheflexibility
for patient and interventional device positioning to enhance
the access and results of the biopsy. Leveraging current
Body coils, OASIS can achieve acceptable performance
characteristics of prostate cancer detection and localization
comparedto1.5Tand3.0Tfieldstrengths,allowingmore
imaging options for the Radiologist and the patient.
Patient History
A 73-year-old male presented with elevated serum PSA
levels (11) and symptoms including the urgency to urinate.
The patient had a history of benign prostate hyperplasia
(BPH), or enlargement of the prostate, but no obstructive
urinaryflowsymptoms.Thepatienthadalsoreceivedtwo
negative TRUS biopsies. MRI was performed to evaluate for
prostate cancer and the potential for MR guided biopsy of the
prostate gland.
John Feller, MDBoardcertifiedRadiologistwith
Desert Medical Imaging and leading
global advocate for the advancement
of Prostate MR
© 2014 Hitachi Medical Systems America, Inc. All rights reserved.
MR Imaging Technique
A number of different pulse sequences are currently used
in our clinical practice for diagnostic prostate cancer MR
exams using a RAPID Body 6ch receiver coil. Table 1
details our sequences and general parameters for T1-
weighted imaging (T1WI), T2-weighted imaging (T2WI),
diffusion weighted imaging (DWI), and dynamic contrast
enhanced imaging (DCE), each playing a role in the
assessment of the glandular zones of the prostate (central,
peripheral,transition,anteriorfibro-muscular)andadjacent
tissue structures (seminal vesicle, urinary bladder,
osseous structures).
T1 Weighted Imaging
Unlike T2WI, T1WI is generally not helpful for contrasting
diseased from healthy tissue. The primary reason for
acquiring T1WI is for the determination of the presence and
location of hemorrhage. T1WI can contrast blood products
occurring as a consequence of biopsy sampling, where
areas of hemorrhage appear as hyperintense regions on
Figure 1 - T1 FSE axial acquisition depicts no evidence of blood products / hemorrhage
Acquisition Plane TR (msec)
TE (msec)
Thick (mm)
FOV (cm)
Matrix Other Settings
Scan Time
FSE – T1 Axial 450 10 4.0 20 256x208 4:12
FSE – T2
Axial 5700 96 4.0 20 256x704 RADAR 5:37
Coronal 5693 96 4.0 20 256x704 RADAR 5:14
Sagittal 5700 96 4.0 20 257x704 RADAR 5:37
DWIAxial 1900 62 4.0 28 96x96 B – 100 1:36Axial 1900 62 4.0 28 96x96 B – 800 2:06Axial 1900 62 4.0 28 96x96 B – 1000 2:06
3D DCE – T1 Axial 4.3 2.2 4.0 22 120x108Post gad
performing 40 acquistions
0:10 (7:57 total)
TR–Repetitiontime,TE–echotime,FOV–fieldofview
Table 1 - Details of Our Prostate Cancer Staging MR Examination as Implemented on a 1.2T Scanner (Hitachi Medical Systems America)
T1WI due to the shortening of T1 caused by blood. When
hypointensities appear on T2W images that are suggestive
of cancer, T1W images should be evaluated to rule out
hemorrhage if there is a history of prior prostate biopsy.
Using a classic fast-spin echo (FSE) with a small FOV
(< 30), the patient scan showed very little contrast between
tissues, indicating little to no hemorrhaging effects from prior
TRUS biopsies.
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© 2014 Hitachi Medical Systems America, Inc. All rights reserved.
T2 Weighted Imaging
T2WI is captured using FSE in the three orthogonal planes
(axial, sagittal, coronal) typically resulting in excellent T2
contrast for the depiction of zonal anatomy, including the
peripheral zone (PZ), central zone (CZ), and transition
zone (TZ). Imaging is done using repetition time (TR) of
5.7 seconds, effective echo times of 96 msec, small 20cm
FOV, 4mm slice thickness, and in-plane matrices of 256
X 704 deploying a radial acquisition motion compensation
technique (RADAR). Though radial acquisition techniques
add acquisition time, motion compensation is important to
implement to reduce potential artifacts from involuntary bowel
and bladder wall motion.
For our patient, T2WI showed inhomogeneous signal
intensity through the TZ associated with nodular enlargement
mostcommonlyduetoBPH(Figure2a-2b).Ill-definedT2
shortening is evident in the TZ, indicating a tumor suspicious
region far anteriorly in the midline at the base and mid
gland levels that extends to the left into the right of midline
measuring 1.3cm X 1.8cm X 2.6cm. The left PZ posteriorly
to the apex also shows T2 shortening effects. However,
in reviewing the sagittal acquisition (Figure 2d) which is
the most useful for evaluating seminal vesicle invasion,
there was no evidence of tumor progression, most likely
indicatingfibrosis.
Diffusion Weighted Imaging
One of the more important recent advances in prostate cancer
imagingistheuseofapparentdiffusioncoefficient(ADC)
values derived from diffusion weighted imaging (DWI) for
characterizing prostate tissue. With the onset of neoplasia,
the diffusion capacity of water molecules is diminished. DWI
measures the water diffusion within tissue, helping improve
the contrast between cancer and normal parenchyma. When
combinedwithT2WI,DWIdramaticallyimprovesspecificityin
prostate cancer detection.
Figure2-T2FSEwithRADARmotioncompensationwereacquiredreflectingprostate gland measurements of 5.0cm X 5.4cm x 6.1cm captured in axial (a) and sagittal (b) images, consistent with a highly enlarged prostatic gland volume of 86cc.
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Figures 2(c) and 2(d) indicate tumor suspicious region measuring 1.3cm x 1.8cm x 2.6cm in the far anterior TZ.
With our DWI, we sample each slice within the 28cm FOV
with a b-value of 100, 800, and 1000 s/mm2. The b-value
of 100 is used to show the combination of DWI and T2WI
information, with higher b-values of 800 and 1000 showing
DWI effects alone, each in relatively short acquisition times
of 2:06. Combining b-value trace images with the baseline
(b-value 0) allows for calculation of the ADC image, known
also as the ADC map. The ADC map is free of all T1, T2, and
receiver coil sensitivities, and quantitative measurements of
tissue water diffusion may be made from individual voxels, or
regions-of-interest (ROIs).
a b
c d
© 2014 Hitachi Medical Systems America, Inc. All rights reserved.
Figure 3 – (a) High b-value 1000 DWI trace depicts a hyperintense dominant tumor suspicious region while the corresponding ADC map (b) demonstrates restricted diffusion areas indicated by the hypointense lesion (dark) in the same region.
Dynamic Contrast Enhanced Imaging
The goal of dynamic contrast enhanced (DCE) imaging is to
capture the passage of contrast material into and out of the
prostate using T1WI with high temporal resolution (between
5–10 sec). DCE imaging acquires data on tissue perfusion
characteristics and tumor wash-in / wash-out contrast to look
for increased angiogenesis in suspected tumors.
On OASIS, we accomplish this using a dynamic T1 weighted
3D RSSG protocol using very short TR periods of 4.3msec,
flipangleof15,andslicethicknessof4.0mm,whichacquires
120 X 108 X 256 3D matrix data at 10 second intervals
with parallel imaging factors of 1.5. We generally perform
about 40 such acquisitions consecutively, with gadolinium
(Gd) contrast automatically infused following 1 precontrast
baseline acquisition. The overall acquisition time took
approximately 7:57.
In this patient, you can see evidence of restricted diffusion in
the high b-value (1000) DWI trace and ADC map (Figure 3)
shown in the same area as the T1WI and T2WI acquisitions.
TheDWItracewithb-valueof1000clearlyreflectsa
hyperintensity in the suspected region, while the resulting
ADC map show lower ADCs (hypointense or darker) than the
surrounding healthy prostate tissue.
For our patient, the resulting DCE image acquisitions allow us to generate signal versus time kinetic curves from selected ROIs that adequately characterize the signal changes accompanying the distribution of the Gd contrast agent over the entire prostate gland. The temporal resolution of typical DCE acquisitions is fast enough to capture the rapid increaseofsignal,orwash-inphase,occurringwithinthefirst60 seconds of contrast administration as noted by the 450% enhancement peak (Figure 4). The temporal resolution is also sufficienttoallowforaquantitativeassessmentoftheratethat this signal enhances from the initial slope of the signal versus time curves. The 3D RSSG imaging data set is then transmitted to a dedicated computer-aided detection (CAD) and 3D workstation where additional 3D images were reconstructed.
a b
Figure 4 –DCE acquisitions show (a) 450% peak enhancement with a rapid wash-out kinetic curve pattern (b) correlating to region of interest color overlay in axial image.
a
b
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© 2014 Hitachi Medical Systems America, Inc. All rights reserved.
Diagnostic MR Findings
UsingT2WIalone,findingseffectivelyindicatednodularenlargement in the CZ most commonly due to BPH and a tumor suspicious region. However, by leveraging a broader Multiparametric Prostate MR protocol, we were able to combine findingsfromDWIandDCEtechniquesthatsignificantlyimproveprostate cancer sensitivity and the negative predictive value
(NPV) compared to T2WI alone.
Our diagnosis concluded that while there was no evidence of extracapsular extension, seminal vesicle invasion, or periprostatic lymphadenopathy, the TZ demonstrated characteristicssuggestiveofprostatecancerincludingill-definedT2 shortening, evidence of restricted diffusion, and a rapid washout pattern of dynamic gadolinium contrast enhancement indicating increased vascular permeability. As a result, we recommended MR targeted biopsy of the prostate gland.
MR Guided Prostate Biopsy Technique
The patient returned for the follow-up biopsy 8 weeks later to be conducted on the OASIS 1.2T MR system with a Body Flex XL receiver coil. MR guided biopsy was performed utilizing Invivo Prostate DynaCAD and DynaTRIM hardware and software.
The patient was placed on the MRI table in the prone position and conscious sedation was performed at the start of the procedure. The needle sleeve biopsy guide was placed in the rectum with the DynaTRIM localization device attached to the biopsy guide. Preliminary sequences were obtained to document optimal positioning. For needle placement, T2 axial and sagittal sequences were acquired summarized
in Table 2.
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Utilizing Invivo prostate biopsy software, the lesion was
localized in the TZ far anteriorly at the mid gland level. The
DynaTRIM was calibrated and the needle track pathway was
then determined obtaining coordinates for the DynaTRIM.
Once the coordinates were obtained, the biopsy sleeve was
adjustedinthesagittal,axial,andcoronalplanes.Acoronal
obliqueconfirmationscanwasperformedtoconfirmadequate
needle track position through the lesion. Using the needle
graphicconfirmationdataset,an18-gaugecorebiopsyneedle
was advanced into the lesion and a core biopsy specimen
wasobtained.Aconfirmationscanbeforeremovalofthe
needle was performed to ensure optimal needle position.
The needle was removed and the core was placed in the
specimen container.
Figure 5 – OASIS with RAPID Body Coil and Invivo DynaTRIM patient setup. Body Flex coils for larger patients are available as used in this case.
Acquisition Plane TR (msec)
TE (msec)
Thick (mm)
FOV (cm)
Matrix Other Settings
Scan Time
FSE – T2Axial 6125 96 4.0 20 320x256 RADAR 1:42
Sagittal 5550 96 4.0 20 320x256 RADAR 2:56
Table 2 - Details of Our Prostate Cancer MR Guided Biopsy as Implemented on a 1.2T Scanner (Hitachi Medical Systems America)
© 2014 Hitachi Medical Systems America, Inc. All rights reserved.
MR Guided Biopsy Findings
Thepathologyreportconfirmedthetumorsuspiciousregion
is an adenocarcinoma of the prostate with a Gleason score
of 3+4=7. As a result of the scanning and diagnosis, the
Urologist referred the patient to a local cancer center to
undergo brachytherapy radiation therapy.
Discussion
Inthiscase,wehighlightedhowopenhigh-fieldMRI
platforms like the OASIS 1.2T can achieve good performance
characteristics for the effective detection and localization of
prostate cancer. Multiparametric Prostate MRI combined
with MRI targeted biopsy of any tumor suspicious region
substantiallyimprovesthedetectionofclinicallysignificant
prostate cancer with a high NPV and the overall accuracy
of the Gleason Scoring. The ability to conduct diagnostic
andinterventionalprostateMRwithouttheconfinement
or limitations of a closed-bore MR system will allow more
imagingoptionswithimprovedinterventionalworkflowfor
the Radiologist, and a more comfortable experience for
the patient.
Desert Medical Imaging (DMI) operates four imaging centers
in California located in Indian Wells, Indio, Palm Springs,
and Yucca Valley. All four of our facilities provide magnetic
resonance imaging (MRI), spiral computed tomography (CT)
imaging, and ultrasound. With vendor relationships that
allow DMI to partake in research and development of various
products, DMI has become a leader in prostate diagnosis and
treatment,performingthefirstFocalLaserAblationofprostate
cancer in an outpatient center in the world.
Dr. John F. FellerisaBoardCertifiedDiagnosticRadiologist
with a subspecialty in Orthopedic/Sports Medicine Imaging,
BodyMRI,andLevelIICardiacCTCertification.Dr.Feller
servedasanU.S.AirForceofficerandChiefofMRIatDavid
Grant USAF Medical Center and 15 years as an Assistant
Clinical Professor in the Department of Radiology at Stanford
University. Currently he is an Assistant Clinical Professor in
the Department of Radiology at Loma Linda University and
Founding Partner of DMI.
Figure 6 – (a) Axial T2WI (b) Sagittal T2WI sequences acquired for optimal needle positioning.
a b
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© 2014 Hitachi Medical Systems America, Inc. All rights reserved.
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Hitachireservestherighttochangespecificationsdescribed
herein without prior notice. This document provides general
technical descriptions of both optional and standard features.