PresentationPDF Available

Incidental findings on the CT component of PET/CT

Authors:

Abstract and Figures

This presentation illustrates some common findings on the CT component of PET/CT. Some of these important findings may be non-FDG avid, and thus only visible at CT. Some common and less common lesions are listed.
No caption available
… 
No caption available
… 
No caption available
… 
No caption available
… 
No caption available
… 
Content may be subject to copyright.
9/25/2017
1
András Székely M.D.
Radiologist
Department of Radiology
Kenézy Gyula Hospital
Debrecen, 2017.10.26.
Incidental findings
on the CT
component of
PET/CT
Pinterest
9/25/2017
2
For ease of comparison, all CT studies presented are performed with 120 kVp, pitch
1.375, 40 mm collimation, 900 mm scan range, average tube current-time product.
The CT acquisition technique should be tailored for their intended purposes.
9/25/2017
3
An incidental finding, also known as an
incidentaloma, may be defined as “an incidentally
discovered mass or lesion, detected by CT, MRI, or
other imaging modality performed for an unrelated
reason” (Medical Dictionary).
White paper of the American College of Radiology regarding
interpretation of PET/CT studies states that the CT
component of PET/CT „cannot be ignored.It is
recommended that the interpreting radiologist or nuclear
physician report additional findings present on CT images,
even if the examination is performed purely
for anatomic localization only.
Abnormalities should be classified as being of major,
moderate, or minor clinical importance.
Although this classication is somewhat arbitrary.
9/25/2017
4
Can CT from PET/CT meet the level of
quality of a diagnostic CT?
Performing an examination that allows
attenuation correction for the PET scan yet
provides adequate diagnostic quality requires
some compromises.”
In most cases CT scans obtained at end-tidal
volume may be diagnostic.
Arms should be above the patient’s head, or if
at the side place them on pillow further away
from the body to minimize artifact.
Use water or novel low attenuation oral
contrast agents.
Iv. contrast may cause imaging artifacts on PET.
The anatomic extents of PET and CT scans must
match.
http://www.med.harvard.edu/jpnm/chetan/petct/petct.html
9/25/2017
5
Okay, but things can and will show up
„Low-dose techniques will increase
image noise but should not change
the mean HU values
9/25/2017
6
sometimes things, other times
9/25/2017
7
Clinically significant findings from the unenhanced CT
portion of PET/CT are relatively infrequent (3%).
Study by Bruzzi et al: 321 patients with NSCLC
underwent staging/restaging.
In 263 (82%) of the patients, unenhanced CT showed
1,231 abnormalities that were not 18F-FDG avid
with PET/CT.
9/25/2017
8
9/25/2017
9
9/25/2017
10
9/25/2017
11
Coronaries
The most important finding of this study is that visual detection of CAC
on PET/CT scans has a strong prediction of Myocardial Perfusion
SPECT results. Absence of CAC has a high likelihood of normal MPS
results (88%).
9/25/2017
12
Aorta
nCT may be useful to
recognize:
Dens intimal flap
Deviation of wall
calcification
Intramural haematoma
(no flap)
9/25/2017
13
The term aneurysm is used when the axial diameter of the thoracic
aorta is > 5 cm and when it measures 4-5 cm the term dilatation is
used.
Focal dilatations of the abdominal aorta that are 50% greater than the
proximal normal segment or >3 cm in maximum diameter
More frequent on the abdominal aorta.
focal
saccular
9/25/2017
14
PTX, misplaced CVC
DOI: 10.4103/0366-6999.173525
9/25/2017
15
Small pulmonary nodules
Different nodules show different malignant potential:
Li et al: GGN: 59%; Part-solid: 48%; Solid: 11%
ELCAP: GGN: 18%; Part-solid: 63%; Solid: 7%.
9/25/2017
16
2994 patients from NELSON study
4026 nodule
794 PFN (19.7%)
Avarage 43mm3
5,5 years follow-up: 0% malignant
9/25/2017
17
Pericardial and pleural effusion
https://www.slideshare.net/rishidev38/pleural-effusionpptx-cme-
march
Both are non-measurable
by RECIST 1.1
9/25/2017
18
Normal aging lung
Histopathologic studies have shown increased
collagen accumulation and progressive fibrosis
associated with normal aging.”
Predominantly bilateral basal subpleural reticular
pattern
Occasional scattered cystic air spaces
Mild bronchial dilatation
Senile emphysema
9/25/2017
19
9/25/2017
20
9/25/2017
21
The prevalence of vertebral
compression fractures (VCF) in
women aged 50 and over has been
estimated at 26% when defined as a
reduction in vertebral height >15%.
The pain of acute fracture usually
lasts 4 to 6 weeks with intense pain
at the site of fracture.
Their height, weight, breathing,
posture, self-esteem will all be
altered.
Women with low bone mass have a
seven-fold increase in risk of
fracture, compared with a 25-fold
increase in risk in women with low
bone mass and a single fracture
(Ross et al, 1991). Patients with
vertebral compression fracture are
also at risk of concomitant peripheral
fracture.
9/25/2017
22
9/25/2017
23
Because attenuation should not be
altered by a low-dose technique, if the
mean attenuation of an adrenal mass is
<10 HU on a low-dose CT examination,
one may conclude that the adrenal mass
is likely to be a benign adenoma.
If a lesion is >10 HU and 1 to 4 cm in an
asymptomatic patient without cancer, 1-
year follow-up CT or MRI may be
considered, if no prior studies for
comparison are available. Prior
examinations that show stability for 1
year can eliminate the need for further
workup, so every effort should be made
to obtain prior CT or MRI examinations
in these situations
For adrenal masses >4 cm, dedicated
adrenal MRI or CT should be considered
to further characterize.
In 5/39 lesions where attenuation
> 10 HU by regular CT, were < 10
HU when measured by low dose
CT. These 5 lesions would have
therefore have been incorrectly
characterized as benign rather than
indeterminate
nCT shows that the lesion (arrows) is of
low attenuation (6 HU), which is
consistent with a lipid-rich adenoma.
9/25/2017
24
9/25/2017
25
Other than angiomyolipomas, renal masses detected incidentally on
unenhanced CT scans often cannot be accurately characterized.
9/25/2017
26
It may be appropriate to interpret incidental renal
masses as simple cysts unless suspicious features are present. It
should be well marginated, water density (0-20 HU), display no
septa/nodularity/wall thickening/calcification (maybe a little Ca2+).
This holds true for small lesions (x<3cm), especially for lesions
smaller than 1 cm.
9/25/2017
27
If a renal mass is small (3 cm),
homogeneous, and 70 HU, recent data
suggest that the mass can be
confidently diagnosed as a benign
hyperattenuating cyst (Bosniak category
II) .
9/25/2017
28
The recommendations shown in the pancreatic flowchart also apply
to low-dose unenhanced CT examinations. The importance of
comparison with prior CT or MRI examinations cannot be
overemphasized to potentially avoid further workup. Specifically, for
lesions 2 cm, stability over 1 year is highly suggestive of a benign
lesion and may eliminate the need for follow-up imaging.
9/25/2017
29
Establishing a cyst as mucinous is important because of their higher risk
for the presence or future development of malignancy:
Mucinous cystic neoplasms typically have peripheral calcification,
whereas serous tumors have central calcification.
Location within the pancreas: mucinous cystic tumors can be suspected
when a cyst is present in the tail of the pancreas in a perimenopausal
woman.
Main pancreatic duct involvement
The presence or absence of septae (mucinous cystic neoplasms generally
are multilocular, with large cysts).
https://www.slideshare.net/IhabSamy/cystic-tumors-of-the-
pancreas
9/25/2017
30
The recommendations in the
flowchart apply to low-dose
unenhanced procedures as well as
standardradiation dose
enhanced examinations
9/25/2017
31
9/25/2017
32
Cirrhosis
The I. segment and the left
lobe enlarges.
Right lobe atrophies.
9/25/2017
33
Ascites, pneumoperitoneum
Non-measurable by RECIST 1.1
Hokama A, Nakamura M, Kinjo F, Fujita J. The falciform ligament
sign of pneumoperitoneum. J Emerg Trauma Shock 2011;4:440
9/25/2017
34
Diverticulitis
9/25/2017
35
9/25/2017
36
Conclusion
Clinically significant findings from the unenhanced CT
portion of PET/CT are relatively infrequent (3%).
Some common lesions were shown and recommendations
were given to assist PET/CT reading physicians in making
informed decisions about reporting such lesions.
Beware of the clown!
If unsure, ask your friendly radiologist!
9/25/2017
37
Thank you for your attention!
andras.szekely@gmail.com
drszekelyandras.hu
radiologia.hu
ResearchGate has not been able to resolve any citations for this publication.