MRI Imaging Methods
The MRI image is formed by reconstructing signals generated from the resonance of hydrogen nuclei in a magnetic field. Therefore, the concept used in MRI images is “signal,” rather than the “density” concept used in CT images. In MRI images, lesions are described using the term “abnormal signal focus.” Because the imaging principles of MRI are completely different from those of CT, there are many differences between MRI images and CT images:
1. MRA: Magnetic Resonance Angiography, a technique that visualizes blood vessels using MRI, generally does not require the injection of contrast agents for safe and non-invasive vascular enhancement. It allows for observation from multiple angles, but currently, MRA’s display of small blood vessels and small lesions is still not satisfactory and cannot completely replace DSA.
2. EPI: Echo Planar Imaging, currently the fastest imaging technology, can acquire a complete image within 30ms. EPI technology can be combined with all conventional imaging sequences.
3. MRS: Magnetic Resonance Spectroscopy, a method that uses the chemical shift phenomenon in MR to determine molecular composition and spatial distribution. It is a non-invasive technique for studying the metabolism, biological changes, and quantitative analysis of living organ tissues.
4. MR Water Imaging: This technique uses long TR and very long TE to obtain heavily T2-weighted images, allowing static or slowly flowing liquids in the body to present high signals, while solid organs and rapidly flowing liquids such as arterial blood present low signals. Through MIP reconstruction, images similar to direct imaging of water organs can be obtained.
1. Multi-axial Images: MRI images not only include transverse images but also often include sagittal and coronal images.
2. Multi-parameter Images: MRI images have T1-weighted images (T1WI), T2-weighted images (T2WI), proton density-weighted images (PDWI), diffusion-weighted images (DWI), fluid-attenuated inversion recovery images (FLAIR), fat-suppressed images (STIR), magnetic resonance spectroscopy images (MRS), magnetic resonance angiography images (MRA), magnetic resonance urography (MRU), and magnetic resonance cholangiopancreatography (MRCP), etc. The signal performance of the same tissue varies on different weighted images.
3. Multi-sequence Imaging: An MRI examination requires selecting the appropriate scanning sequence, commonly used sequences include SE sequence (Spin Echo Sequence), GRE sequence (Gradient Echo Sequence), IR sequence (Inversion Recovery Sequence), FLAIR (Fluid Attenuated Inversion Recovery), STIR (Fat Suppression Sequence), etc. The signal performance of the same tissue varies on different scanning sequences.
Due to the aforementioned “three multiples” characteristics of MRI images, the same patient can have various different MRI images, which requires more careful observation compared to CT. However, like CT examinations, MRI examinations mainly consist of plain scans and enhanced scans, and the images are also black-and-white grayscale images, with similar reading methods.
Step 1: Understand the patient’s condition and clinical data to clarify the purpose and focus of each patient’s MRI reading.
Step 2: Understand the information on the MRI images.
This includes the type of MRI equipment, magnetic field strength, scanning technical conditions, and the pulse sequences used, whether it is T1WI, T2WI, or PDWI, whether it is a transverse image, sagittal image, or coronal image, whether it is a plain scan or enhanced scan, scanning layer thickness, and the patient’s name, gender, age, etc. This information is very helpful for diagnosis.
Step 3: Observe each plain scan image in an orderly and careful manner.
1. Generally, read the transverse images first (from top to bottom or bottom to top), then the sagittal images (from right to left or left to right), and finally the coronal images (from front to back or back to front); one can also read the sagittal images first, then the transverse images and coronal images.
2. For each position, read T1WI first, then T2WI, and then other weighted images (PDWI, FLAIR images, STIR images, DWI, MRA, MRCP, MRU, etc.); one can also read T2WI first, then T1WI, and then other weighted images.
3. Carefully observe each image, noting whether each organ or structure is normal, and strive to provide a reasonable explanation for each image, then construct a three-dimensional image of a specific organ or structure through reasoning.
Step 4: Analyze each organ and structure from multiple aspects, including morphology and signal.
In terms of morphology, mainly observe changes in the size, shape, and contour of the organs; in terms of signal, mainly observe whether the organ’s signal has consistency (universality) or localized increases or decreases. For localized signal changes, pay attention to the location of the lesion, the signal characteristics on different weighted images, the size, number, shape, contour, margin, and changes in adjacent structures. For MRS images, also observe changes in the chemical composition within the lesion; additionally, observe whether there is any change in the position of the organ.
Any lesion signal lower than the signal of the organ or structure it is in is called a low-signal focus; if the lesion signal is higher than that of the organ or structure, it is called a high-signal focus; if the lesion signal is equal to or close to that of the organ or structure, it is called an isosignal lesion; if the lesion has a combination of high, low, and iso-signal changes, it is referred to as a mixed signal focus.
Step 5: Carefully observe each enhanced scan image.
MRI enhanced scans are generally only performed with T1WI, so the enhanced images should be compared with the plain T1WI for observation, paying attention to analyzing whether the lesion has enhancement, the degree of enhancement, and the form of enhancement. For dynamic enhancement, pay attention to observing the enhancement characteristics of lesions at different phases (such as arterial phase, portal phase, etc.) to facilitate qualitative diagnosis.
If the lesion signal remains the same after enhancement as it was during the plain scan, indicating no signal change, it is termed non-enhanced; if the lesion signal increases, it is termed enhanced. The degree of enhancement can be slight or significant. The forms of enhancement can be generally categorized into uniform enhancement, patchy enhancement, ring enhancement, and irregular enhancement. Uniform enhancement refers to the lesion signal being consistently elevated; patchy enhancement refers to the lesion showing spot-like or patch-like signal elevation; ring enhancement refers to the appearance of linear or band-like high signal shadows around the lesion; irregular enhancement indicates that the enhancement shape of the lesion is varied, resulting in mixed signal foci.
Step 6: Combine clinical data for comprehensive analysis to arrive at the correct diagnosis.
Combine the patient’s clinical data (including the patient’s age, gender, symptoms, signs, laboratory tests, current medical history, past medical history, residence, occupational history, etc.) and other auxiliary examination results (such as CT scans, X-ray examinations, ultrasound examinations, etc.) for comprehensive analysis, ultimately arriving at the correct conclusion.
Common Disease Abbreviations
A
Addison’s Disease: Primary Chronic Adrenal Insufficiency
Af: Atrial Fibrillation
AGN: Acute Glomerulonephritis
AIDS: Acquired Immunodeficiency Syndrome (AIDS)
ALL: Acute Lymphoblastic Leukemia
AVB: Atrioventricular Block
ASD: Atrial Septal Defect
AS: Aortic Stenosis
ASO: Arterial Occlusive Disease
AI: Aortic Insufficiency
AS: Aortic Stenosis
ASO: Arterial Occlusive Disease
AT: Atrial Tachycardia
AL: Aortic Insufficiency
Alzheimer’s Disease (AD): Alzheimer’s Disease (Dementia)
AML: Acute Myeloid Leukemia
Arnold-Chiari Malformation: Chiari Malformation
ARDS: Acute Respiratory Distress Syndrome
ARF: Acute Renal Failure
AS: Ankylosing Spondylitis
ASD: Atrial Septal Defect
AMI: Acute Myocardial Infarction
AP: Angina Pectoris
APB: Atrial Premature Beat
ALT: Adult T-cell Leukemia
AA: Aplastic Anemia
AIHA: Autoimmune Hemolytic Anemia
AIH: Autoimmune Hepatitis
AP: Acute Pancreatitis
AGN: Acute Glomerulonephritis
AIN: Acute Interstitial Nephritis
AML: Arteriovenous Malformation
B
Binswanger’s Disease (BD): Subcortical Arteriosclerotic Encephalopathy (SAE)
BBB: Bundle Branch Block
Budd-Chiari Syndrome: Budd-Chiari Syndrome
C
CCF: Carotid-Cavernous Fistula
CHD: Coronary Heart Disease
CF: Heart Failure
CLL: Chronic Lymphocytic Leukemia
CGN: Chronic Granulocytic Leukemia
CHF: Congestive Heart Failure
CAP: Community-Acquired Pneumonia
CGN: Chronic Glomerulonephritis
CHD: Coronary Artery Atherosclerotic Heart Disease (Coronary Heart Disease)
CHF: Congestive Heart Failure
CF: Heart Failure
CGN: Chronic Nephritis
CRF: Chronic Renal Failure
CIN: Chronic Interstitial Nephritis
CKD: Chronic Kidney Disease
CLL: Chronic Lymphocytic Leukemia
CML: Chronic Myeloid Leukemia
Colles’ Fracture: Colles’ Fracture
COPD: Chronic Obstructive Pulmonary Disease
CRF: Chronic Renal Failure
Crohn’s Disease: Crohn’s Disease or Granulomatous Enteritis
D
DCM: Dilated Cardiomyopathy
DDH: Congenital Hip Dislocation
DIC: Disseminated Intravascular Coagulation
DLE: Discoid Lupus Erythematosus
DM: Diabetes Mellitus
DU: Duodenal Ulcer
DR: Diabetic Retinopathy
DKA: Diabetic Ketoacidosis
DN: Diabetic Nephropathy
E/F/G
Good-Pasture Syndrome: Pulmonary Hemorrhage-Renal Syndrome
Graves’ Disease (GD): Toxic Diffuse Goiter (Basedow’s Disease)
GERD: Gastroesophageal Reflux Disease
GU: Gastric Ulcer
Graves’ Disease: Hyperthyroidism
Fahr’s Disease: Idiopathic Familial Basal Ganglia Calcification
F4: F4
F3: F3
FD: Functional Dyspepsia
EH: Hypertensive Disease (Primary Hypertension)
FNH: Focal Nodular Hyperplasia
ERCP: Endoscopic Retrograde Cholangiopancreatography
EP: Epilepsy
H
HB-GN: Chronic Hepatitis B-Related Nephritis
HAP: Hospital-Acquired Pneumonia
HCM: Primary Hepatocellular Carcinoma
HCM: Hypertrophic Cardiomyopathy
HD: Hodgkin’s Disease
HIE: Hypoxic-Ischemic Encephalopathy in Newborns
HL: Hodgkin’s Lymphoma
HE: Hepatic Encephalopathy
HOA: Hypertrophic Osteoarthropathy
I/J
IBD: Inflammatory Bowel Disease
IPF: Idiopathic Pulmonary Fibrosis
IDD: Insulin-Dependent Diabetes
IIM: Idiopathic Inflammatory Myopathy
IGT: Impaired Glucose Tolerance
IDA: Iron Deficiency Anemia
HD: Hodgkin’s Disease
ITP: Idiopathic Thrombocytopenic Purpura
JAS: Juvenile Ankylosing Spondylitis
ITP: Allergic Purpura
JRA: Juvenile Rheumatoid Arthritis
K
Kawasaki Disease: Kawasaki Disease or MCLS (Mucocutaneous Lymph Node Syndrome)
M
Mirizzi Syndrome (MS): Mirizzi Syndrome
Mikulicz Syndrome: Mikulicz Syndrome (Chronic Painless Sialadenitis)
MDS: Myelodysplastic Syndrome
MM: Multiple Myeloma
MG: Myasthenia Gravis
MS: Multiple Sclerosis
MODS: Multiple Organ Dysfunction Syndrome
MI: Myocardial Infarction
MVP: Mitral Valve Prolapse
Moyamoya Disease: Moyamoya Disease (Cerebral Basal Vascular Malformation)
N/O
NF: Neurofibromatosis
NHI: Non-Hodgkin’s
NHD: Non-Hodgkin’s Disease
NS: Nephrotic Syndrome
OA: Osteoarthritis
P
Parkinson’s Disease (PD): Parkinson’s Disease
PAP: Pulmonary Alveolar Proteinosis
PEM: Protein-Energy Malnutrition
PKU: Phenylketonuria
PIE: Interstitial Lung Emphysema
PID: Pelvic Inflammatory Disease
PTE: Pulmonary Embolism
PCP: Pneumocystis Pneumonia
PD: Parkinson’s Disease
PDA: Patent Ductus Arteriosus
PH: Pulmonary Hypertension
P-J: Mucosal Melanosis-Polyp Syndrome (Melanotic Polyp Disease)
PsA: Psoriatic Arthritis
PS: Pulmonary Stenosis
PAT: Paroxysmal Atrial Tachycardia
PNH: Paroxysmal Nocturnal Hemoglobinuria
PST: Paroxysmal Supraventricular Tachycardia
R
RCC: Renal Cell Carcinoma
RA: Rheumatoid Arthritis
RCM: Restrictive Cardiomyopathy
RHD: Rheumatic Heart Disease
RBBB: Right Bundle Branch Block
RAEB: Refractory Anemia with Excess Blasts
RS (Reiter’s Syndrome): Reactive Arthritis (ReA)
S/T
SAH: Subarachnoid Hemorrhage
SCA: Spinocerebellar Ataxia
SCLC: Small Cell Lung Cancer
SLE: Systemic Lupus Erythematosus
SIRS: Systemic Inflammatory Response Syndrome
SpA: Spondyloarthritis
SPA: Ankylosing Spondylitis
SSc: Systemic Sclerosis
SLE: Systemic Lupus Erythematosus
SSS: Sick Sinus Syndrome
SBE: Subacute Bacterial Endocarditis
SAP: Severe Acute Pancreatitis
SSSS: Staphylococcal Scalded Skin Syndrome or Staphylococcal Burn Syndrome
Sturge-Weber Syndrome: Sturge-Weber Syndrome
T2DM: Type 2 Diabetes Mellitus
TB: Tuberculosis
TIA: Transient Ischemic Attack
TS: Tuberous Sclerosis, also known as Bourneville (Neurocutaneous Syndrome)
SD: Ventricular Septal Defect
THD: Ischemic Heart Disease
TIP: Thrombotic Thrombocytopenic Purpura
U
UA: Unstable Angina
UDH: Heart Valve Disease
UC: Ulcerative Colitis
WD: Wilson’s Disease
Wilson’s Disease: Wilson’s Disease
Common Examination and Surgical Names
CABG: Coronary Artery Bypass Grafting
ESWL: Extracorporeal Shock Wave Lithotripsy
ENBD: Endoscopic Nasal Biliary Drainage
ERCP: Endoscopic Retrograde Cholangiopancreatography
EL: Endoscopic Band Ligation for Esophageal Variceal Bleeding
EST: Endoscopic Sphincterotomy
LC: Laparoscopic Cholecystectomy
LS: Laparoscopic Splenectomy
KUB: Kidney, Ureter, and Bladder X-ray
IP: Intravenous Pyelography
IU: Intravenous Urography
PBP: Percutaneous Balloon Pulmonary Valvuloplasty
PTC: Percutaneous Transhepatic Cholangiography
PTCA: Percutaneous Transluminal Coronary Angioplasty
TCD: Transcranial Doppler Ultrasound