Type:
Educational Exhibit
Keywords:
Tissue characterisation, Atelectasis, Artifacts, Technical aspects, Perception image, Imaging sequences, PET-MR, MR, Thorax, Lung, Anatomy
Authors:
A. Pittaro1, F. Crimì2, D. Cecchin3, C. Giraudo1, P. Zucchetta1, F. Bui1, P. Ciet4, E. Quaia1; 1Padova/IT, 2Vicenza/IT, 3Ponte San Nicolò (PD)/IT, 4Rotterdam/NL
DOI:
10.26044/ecr2019/C-3169
Background
The use of chest-MRI has rapidly grown in the last decades,
mainly due to technological improvements of sequences,
hardware and acquisition strategies.
This resulted in a increased image quality allowing chest-MRI to be routinely used in clinical practice,
both for pediatric and adult patients.
In the pediatric population,
MRI has the main advantage to reduce radiation exposure,
being children more sensitive than adults to ionizing radiations1.
A well-known advantage of chest-MRI and MRI in general is the high tissue characterization due to multiparametric imaging (T1,
T2 and proton density) influenced by the investigated tissues properties2.
Another advantage is that intravenous contrast agents administration is not always necessary for chest investingations3 giving more possibilities of follow-up to patients where the iodinated-contrast material administration is contra-indicated.
Moreover,
vessels and lung perfusion can be investigated without using gadolinium-based contrast sequences,
either using gradient echo-based sequence (i.e.
SSFP) or using Fourier Decomposition.
Anyway,
the chest remains a challenging field for MRI,
mainly due to low signal-to-noise ratio (SNR) of the lung parenchyma related to the multiple air-tissue interfaces which create inhomogeneous local magnetic field gradients and consequently a rapid signal decay4.
Using ultra-short echo-time (UTE)4 sequences,
high SNR is achieved.
Respiratory and cardiac motions also affect images quality with ghosting and blurring.
Voluntary movements are often reduced with patient instruction or children sedation and navigated echo sequences.
If the pulsation is regular it is possible to minimize or correct the motion artifacts through cardiac-gating or respiratory gating5.
Respiratory artifacts can be minimized using breath-hold sequences,
fast imaging,
saturation pulses and spirometer-controlled protocol6.
In fact it has been demonstrated that the main advantages of using the spirometer guidance in chest-MRI are the standardization of lung volumes,
which facilitate the evaluation and the comparison between images during the follow-up,
and the reduction of motion artifacts,
since patients are trained to execute breath-hold maneuvers6.