multiparametric mr imaging of the prostate

Sagittal plane can be used on patients with hip prosthesis in order to minimize image distortions and susceptibility artifacts. order to minimize image distortions and susceptibility ar[r]

HAI DUONG GENERAL HOSPITAL

Overview and Role of Radiology Technician

HAI DUONG GENERAL HOSPITAL Reporter: Nguyen

Reporter: Nguyen Manh Manh Cuong Cuong

INTRODUTION

Prostate cancer is the most common form of cancer

and it ranks second in mortality rate among the male y g

population worldwide Early diagnosis is the most effective

method in dealing with and curing it.

Diagnostic methods include:

+ Digital rectal exam (DRE).

+ Prostate-specific antigen (PSA).

+ Transrectal ultrasound (TRUS) and Biospy.

+ MRI.

h h l i l k l i h l i i

The MRI Technologist plays a key role in the resultant examination

quality, as preparation, positioning and communication with the patient,

protocol set up and selection of the acquisition parameters are crucial for

obtaining high quality, high resolution images of the prostate gland.

Sequence Rationale/investigated

parameter

Technique Role in

prostate cancer assessment with mpMRI

Limitations

CONTENT

1 Request technicque for mpMRI prostate.

To provide

resolution and

high-contrast representation of

the zonal anatomy of the

prostate, as well as of

• 2D turbo spin-echo with high spatial resolution: field of view 12–20 cm to cover the prostate and the seminal vesicles; slice thickness ≤ 3 mm with no gap;

pixel size ≤ 0.7 mm

(phase) x ≤ 0.4 mm (frequency)

• Sagittal, oblique transverse,

• Detection and localisation:

dominant sequence for assessing TZ findings

• Locoregional staging:

• Nonspecific tumour appearance, overlapping with that of non-malignant

conditions (e.g.,

inflammation or

Sequence Rationale/investig

ated parameter

Technique Role in prostate

cancer assessment with mpMRI

Limitations

To exploit restricted

diffusion of water

molecules as a

marker of increased

cellularity and

• Fat-saturated, free-breathing single-shot spin-echo echo-planar imaging

• At least two b values to generate the ADC map (e.g.,

minimum 50–100 s/mm2, maximum 800–1000 s/mm2);

extrapolated ultra-high b-values (≥ 1400 s/mm2) can also be used

Detection and localisation:

• dominant sequence for assessing PZ findings

• secondary role in assessing category

3 findings found by

• Sensitive to artefacts from air in the rectum and/or motion

• Distortions

• Relatively unstandardised technique, leading to limited reproducibility

of the quantitative

DWI neoplastic

reorganisation of

normal glandular

tissue

to generate the ADC map

• Ultra-high b values can be

acquired to increase tumour conspicuity (not for the ADC map generation in less performing systems)

• Field of view 16–22 cm, slice thickness ≤ 4 mm without gap, pixel size ≤ 2.5 mm (phase and frequency) TR ≤ 3000 ms TE

T2WI in the TZ analysis of ADC (no

definite cut-off values)

• Significant overlap of ADC values between benign conditions and tumours with different aggressiveness

CONTENT

Sequence Rationale/investigated

parameter

Technique Role in prostate

cancer assessment with mpMRI

Limitations

To detect earlier and • Sequential acquisition of a

T1 i ht d 2D 3D

• To upgrade

bi fi di

• Variable

h t tt

DCE

more intense contrast

enhancement of cancer

compared to normal

prostatic tissue, as the

expression of tumoural

neoangiogenesis

T1-weighted 2D or 3D gradient-echo sequence with high temporal resolution (≤ 10 s, ideally ≤ 7 s, with TR

< 5 ms and TE < 100 ms)

Acquisition before, during and after contrast injection (at least

2 min) to detect early enhancement

• Field of view encompassing

ambiguous findings

in the PZ

enhancement pattern

of cancer, overlapping with non-malignant

conditions (e.g.,

inflammation or benign prostatic hyperplasia)

• Longer acquisition time (> 2 min) to

DCE

(denser, poorly formed

vessels with increased

capillary permeability)

Field of view encompassing the whole gland and seminal vesicles

• Slice thickness ≤ 3 mm without gap, and pixel size

≤ 2 mm (phase and frequency)

• If possible fat-saturated or subtracted images

• Oblique transverse plane

• Contrast injection rate 2–

time (  2 min) to assess the permeability

In prostate cancer, citrate levels fall (due to consumption of citrate

to supply energy to proliferating cells), while choline levels increase

(corresponding to increased cell membrane synthesis).

CONTENT

2 Techique

Patient preparation and positioning

- The patient should not eat or drink any solid food for at least 4-6 hours

in an attempt to reduce motion artifacts from bowel peristalsis

in an attempt to reduce motion artifacts from bowel peristalsis.

- A full bladder should be avoided

- Have an intravenous cannula placed

- If possible, the patient should evacuate the rectum just prior to the

examination in order to eliminate the presence of air The presence of air produces

susceptibility artifacts and distortions, which mainly affect the DWI acquisition p y , y q

- An antiperistaltic agent can be used to further reduce the motion artifacts

from bowel peristalsis.

-CONTENT

The patient needs to be as comfortable as possible to reduce any motion artifact

+ Prone - feet first position is an alternative

+ When a surface coil is used, the prostate gland should be on the center of the coil , p g

+ Center the laser beam localizer over the prostate

Imaging protocol and slice positioning

CONTENT

Imaging protocol and slice positioning

Field strength: 1.5T – 3T:

+ 3T: increased SNR, higher image quality through improved spatial and temporal resolution, and/or reduced acquisition times

3 Technical Considerations

temporal resolution, and/or reduced acquisition times

+ 1.5T: An additional item to consider is patient safety and artifact generation Some medical implants may be incompatible at 3T for safety reasons In

some cases, safety is not an issue but the implant may generate sufficient artifact to

obscure or degrade the image In these cases, MR Imaging should be performed at 1.5T

Coil selection: ERC and Body Coil Although many papers suggest the use of ERC at 1.5T

scanners, high quality imaging can be obtained at both 1.5T and 3T without the use of an

ERC

+ ERC: H igh resolution imaging.

SNR better than surface phased array coils.

The cost of the ERC, as well as the supplies and added time involved in the procedure, make the use of this method less practical

Deforms the shape of the gland.

Cannot be used for whole pelvis

Uncomfortable for patients.

CONTENT

Imaging Parameters

T2W imaging:

Planes: sagittal coronal axial

Slice thickness and spacing: ≤3 mm with no

gap between the slices

FOV: 16-22 cm, centered to the prostate gland

Spatial resolution: ≤0.7 mm (phase) and ≤0.4

mm (frequency), not interpolated.

Phase-encoding direction: R-L on axial and

coronal sequences and A-P on sagittal

sequences

Parallel imaging (PI): An acceleration factor of 2 is most common.

Saturation bands: anterior sat bands should be used on the sagittal T2-w

Saturation bands: anterior sat bands should be used on the sagittal T2 w

sequence to minimize motion artifacts from breathing.

Signal averages (NEX/NSA/ΝΑQ): high resolution T2-w imaging requires

multiple signal averages Typically ≥3 signal averages should be used.

Receiver Bandwidth (rBW): high rBW should be used, an rBW of at least

27.7kHz should be selected.

Echo Spacing: as low as possible

TR: ≥4000 msec

TE: 80-120 msec

ETL/Turbo factor: ≥16

CONTENT

Imaging Parameters

Diffusion-weighted imaging (DWI)

Plane(s): Axial Sagittal plane can be used on patients with hip prosthesis in

order to minimize image distortions and susceptibility artifacts

order to minimize image distortions and susceptibility artifacts.

b-values: Diffusion-weighted acquisition should include low (50-100

s/mm2), high (800-1000 s/mm2) and very high (≥1400 s/mm2) b-values with

corresponding apparent diffusion coefficient (ADC) map.

Diffusion directions: Diffusion-sensitizing gradients in 3 orthogonal

directions should be used (trace or isotropic DWI).

Fat suppression: Fat saturation is necessary to eliminate chemical shift

tif t

artifacts .

TR: ≥4000 ms

TE: as low as possible to reduce image distortions and improve SNR

Slice thickness and spacing: ≤4 mm (ideally ≤3 mm) with no gap between

the slices.

CONTENT

Imaging Parameters

FOV: 16-32 cm (ideally 16-22 cm), centered to the prostate gland FOV may be larger

than T2-w sequence in order to gain SNR.

Spatial resolution (pixel size): p (p ) ≤2.5 mm in phase and frequency encoding directions, p q y g ,

not interpolated.

Phase-encoding direction: A-P.

Parallel imaging : the use of PI technique is necessary to further reduce susceptibility

artifacts, image distortion, and shot time.

Sat bands: anterior sat bands can be used to minimize the motion artifacts from

breathing Sat bands can also minimize wrap-around artifacts on patients with a large

body habitus.

Signal averages (NEX/NSA/NAQ): Multiple signal averages should be used at high

and very high b-values in order to gain SNR and maintain an adequate image quality.

Receiver Bandwidth (rBW): very high rBW should be used in order to minimize the

echo spacing, which results in reduced image distortions and susceptibility artifacts

Typically, an rBW of at least 62.5kHz should be selected.

Dynamic contrast-enhanced imaging (DCE):

Sequence: 2D or 3D T1 GRE pulse sequence can be used However 3D T1

Sequence: 2D or 3D T1 GRE pulse sequence can be used However, 3D T1

GRE technique is preferred.

Plane(s): Axial Sagittal plane can be used on patients with hip prosthesis in

order to minimize image distortions and susceptibility artifacts

Slice thickness and spacing: ≤3 mm with no gap

FOV: 16-22 cm, centered to the prostate gland

Spatial resolution: ≤2 mm in phase and frequency encoding directions, not

Fat suppression: Fat suppression (or subtraction) is recommended when

qualitative (visual) assessment is required Fat suppression is not necessary

when quantitative assessment is needed q

Flip Angle (FA): 15-20°

TR/TE: minimum

TA: ≥2 min (ideally 4-5 min)

Flow rate: 2-3 ml/sec

Signal averages (NEX/NSA/NAQ): 1 or Partial Fourier in order to increase

the temporal resolution of DCE acquisition.

Receiver Bandwidth (rBW): very high rBW should be used in order to

Receiver Bandwidth (rBW): very high rBW should be used in order to

minimize the echo spacing, which results in reduced image distortions and

susceptibility artifacts Typically, an rBW of at least 62.5kHz should be

selected.

Sat bands: Sat bands should not be used.

CONTENT

Data analysis: DCE images can be evaluated qualitatively,

semi-quantitatively and/or semi-quantitatively Quantitative analysis provides

information about ktrans plasma flow and extravascular/extracellular

information about ktrans, plasma flow, and extravascular/extracellular

volume, assisting in the differentiation and accurate characterization of

pathology.

Multiparametric prostate MRI combines anatomical,

functional and (occasionally) quantitative data in order to

significantly increase the accuracy of the method in prostate

cancer diagnosis.

The MRI Radiographer/Technologist occupies a very

important role since the acquisition of a high-quality

examination depends vastly on patient preparation and

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THANKS!!!!