筋骨格の画像診断、基礎パート2②

ひるけ (ATC)

今回も Robert Boyles先生です。MRIや超音波､CT等、「この場合はMRI ､この場合はCT で」と言った､オーダーを出す側の観点や判断基準、それぞれの利点、欠点のお話しでした。
「MRIの画像あるなぁ。CTの画像あるなぁ。ちょっと見とこうかな｡」くらいにしか思ってなかったのです。「なぜMRIで撮ったのか、CTで撮ったのはなぜか」と言う背景については、あまり考えたことがなかったのです。

先生の似顔絵は、別アングルにしてみました。

2026.08.06 公開

画像診断基礎 ct mri

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ノートテキスト

ページ1:

Disadvantages
6
Ch.4 Computed tomography (CT)
FCTJ
good for bones
X-ray + computer
←
•
Readily available, fast, easy
• Only oxial images
• Digitized.
However, due to its
Computer tech., you
Can get
Best for:
-
- loose body in a joint.
-
subtle/complex fractures
- degenerative changes.
-spinal stenosis
- Serious trauma
different
orientation (slices)
Reformat in 3D images.
especially in
C-spine.
•
Accurate measurement of osseous alignment
•
Cheaper than MRI
• Less problematic for claustrophobic patients.
r
1. ↑ radiation dose P①⑦
.
less soft tissue contrast.
6)

ページ2:

CT image
mSv
Head
2
Neck
4
Chest
18
Put the patient
on the table.
high
radiation
exposure
They pass through
the photography.
number of
Chest X-ray
30.
55
m
=
117
etc...
- CT. ordered when bone scan showed area of
concern.
"
- It gives the surgeon an idea of Can I just
immobilize it?" "Are there any fragments that
need to be addressed?" or "Yeah, it's fractured
and we'll deal with that.

ページ3:

Ch5. MRI (magnetic resonance imaging)
TURI
Great for
soft tissue
injury
H
→
H
H
magnetic field
all align
HH
H
ON!!
radio wave).
Change
(H)
the direction.
OFF
Time lug 7 "; $
(pathology)
back to the aligned
direction.
•Soft tissue has different water content, energy
absorption, and release at different rates.
The difference in the energy levels is used to create
the images
• Nonionizing (= safe)

ページ4:

Contraindications
Disadvantages
.
米
7.
Poor imaging of bones. (CT>MRI)
↑$
Time
claustrophobic patients
Pacemakers
aneurysm.
•
Aneurysmal clips
→
•
Metals
Foreign bodies in the eye
•
Hardware
·
clip
Artery
Large area tattoos may cause distored images
• Cochlear implants
Sequencing
.
The timing of the Radio Frequency (RF) pulse
More than one sequence is used.
TI (fat); TZ (water)
different pictures of the same tissue)
better for anatomic
structure.
12-better for contrasting
hormal vs. abnormal
Tissue
TI
72
eg). Cortical bone
Ligaments
dark
dark
gray
gray
Meniscus
dark
dark
Meniscal tear
bright
gray
Abn fluid (pus) gray
bright.

ページ5:

look for
those
Search pattern (ABCDS).
"
Alignment
• Bone
Cartilage
e Dema
b
Soft tissue
MRI uses
• Early osteonecrosis (avascular necrosis)
Infection, trauma
Occult fractures
• Neoplasm (Tumor)
• Disc disease herniation
hidden silent fractures,
hot appearing on X-rays
despite the symptoms.
• Bone marrow changes (non-specific)
ACL/PCL
• Rotator catt tears / labral pathology.
.
* 93% subjects (> 60 y. o.) have degeneration
and > one L-disc bulging.
↑
"But, it doesn't mean pathology

ページ6:

Advantages
•
•
• CT over MRI
$2
- Availability 1
Time V
Thinner slices
- Cortical bone Greater resolution.
- Patients with metal implants.
MRI over CT.
-
Contrast resolution of soft tissue
Imaging Organs
* No ionizing radiation (safe)
- ↑ Imaging quality in nonaxial planes.
- No artifact from bone
-↓risk in missing disease processes
blood
white line
(fluid)
(inflamed)
Post horn LM tear
Ruptured
Achilles
Tendon.
Osteonecrosis
In normal.
← you can see white
smooth cartilage,
But this isnot.
of hip