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Chapter 18
Interventional Treatment ofThyroid
Nodules
AuhWhanPark, TimHuber, andJungHwanBaek
Current Practice onThyroid Nodules
High-resolution ultrasound (US) detects thyroid nodules in 19–68% of healthy,
asymptomatic individuals [1, 2]. The clinical importance of thyroid nodules is to
exclude thyroid cancer occurring in 5–15% among the detected thyroid nodules [3, 4].
In the 2015 American Thyroid Association (ATA) Management Guidelines for
Adult Patients with Thyroid Nodules and Differentiated Thyroid Cancer [5], an
algorithm for evaluation and management of patients with thyroid nodules bases on
US pattern and ne-needle aspiration (FNA) cytology was suggested. Three main
steps exit for workups in the algorithm.
A. W. Park (*)
Department of Radiology, University of Virginia Health System, Charlottesville, VA, USA
T. Huber
Dotter Department of Interventional Radiology, Oregon Health and Science University,
Portland, OR, USA
e-mail: huberti@ohsu.edu
J. H. Baek
Department of Radiology and Research Institute of Radiology, University of Ulsan College of
Medicine, Asan Medical Center, Seoul, South Korea
Switzerland AG 2022
H. Yu et al. (eds.), Diagnosis and Management of Endocrine Disorders in
Interventional Radiology, https://doi.org/10.1007/978-3-030-87189-5_18
259© The Author(s), under exclusive license to Springer Nature
260
• Suspected thyroid nodule
TSH level
TSH
• Pattern
• Size
US
• Cytologic bethesda system
FNA
A. W. Park et al.
A summary of essential recommendations from the ATA guidelines is as follows.
Workups
Serum Thyroid Stimulation Hormone (TSH)
Serum TSH should be measured during the initial evaluation of a patient with a
thyroid nodule (Table18.1). If the serum TSH is subnormal, a radionuclide (prefer-
123
ably
I) thyroid scan should be performed. If the serum TSH is normal or elevated,
a radionuclide scan should not be performed as the initial imaging evaluation.
Thyroid Sonography
Thyroid sonography with a survey of the cervical lymph nodes should be performed
in all patients with known or suspected thyroid nodules. FNA is the procedure of
choice in the evaluation of thyroid nodules when clinically indicated. Thyroid nodule diagnostic FNA is recommended (Table 18.2). Thyroid nodules should be
assessed for malignancy risk by ATA sonographic risk pattern, not simply by size.
Not every thyroid nodule >1cm needs ne-needle aspiration (FNA), and most nodule <1cm does not need FNA.
Table 18.1 Evaluation on thyroid stimulation hormone (TSH) with a thyroid nodule
Suspected thyroid nodule
TSH: normal or elevated TSH: subnormal
Thyroid/neck sonography Radionuclide (preferably
123
I) thyroid scan
18 Interventional Treatment ofThyroid Nodules
Table 18.2 Sonographic patterns, estimated risk of malignancy, and ne-needle aspiration
guidance for thyroid nodules
Thyroid/neck sonography
High
suspicion
FNA≥1cm FNA≥1.5cm FNA≥2cm FNA not required
Table 18.3 American College of Radiology (ACR) Thyroid Imaging, Reporting and Data System
(TI-RADS)
Composition
(choose 1)
Cystic or
almost
completely
cystic
Spongiform 0 Hyperechoic 1 Taller than
Cystic and
solid
Solid or almost
completely
solid
Add points from all categories to determine TI-RADS level
0 points 2 points 3 points 4 points 5 points
TR1 TR 2 TR 3 TR 4 TR 5
Benign Not suspicious Mildly
No FNA No FNA FNA if
Intermediate
suspicion
Echogenicity
(choose 1)
0 Anechoic 0 Wider
1 Isoechoic 1 Lobulated 2 Macrocalcications 1
2 Hypoechoic 2 Irregular 2 Peripheral (rim)
Very
hypoechoic
Low suspicion Very low
Margin
(choose 1)
than tall
wide
3 Extra-
↓
suspicious
≥2.5cm
FNA if
≥1.5cm
suspicion
Shape
(choose 1)
0 Smooth 0 None 0
3 Ill-dened 0 Large comet tail
thyroid
extension
Moderately
suspicious
FNA if
≥1.5cm FNA
if ≥1.0cm
Benign
No nodule/size cutoff
(1cm)
Echogenic foci
(choose 1)
artifacts
calcications
3 Punctate echogenic
foci
Highly suspicious
FNA if ≥1.0cm FNA if
≥0.5cm
261
0
2
3
According to a study by Yoon etal. [6], the ATA guidelines were unable to classify 3.4% of 1293 nodules, of which 18.2% were malignant. In 2017, the American
College of Radiology (ACR) published a white paper on Thyroid Imaging, Reporting
and Data System (TI-RADS), as shown in Table18.3 [7].
Bethesda System
Thyroid nodule FNA cytologic should be reported using diagnostic groups outlined
in the Bethesda system or Reporting Thyroid Cytopathology (Table18.4) [8].
262
Table 18.4 Bethesda system revised in 2017 based on post-2010 date
Categories
Nondiagnostic 5–10 (5–10) Repeat FNA with US
Benign 0–3 (0–3) Clinical and US follow-up
Atypia of undetermined signicance (AUS)/
follicular lesion of undetermined signicance
(FLUS)
Follicular neoplasm/suspicious for follicular
neoplasm (FN/SFN)
Suspicious for malignancy 50–75 (45–60) Lobectomy or near-total
Malignant 97–99 (94–96) Near-total thyroidectomy
*Adjusted risks if noninvasive follicular thyroid neoplasm with papillary-like nuclear features
(NIFTP) was not classied as a malignancy. FNA ne-needle aspiration, US ultrasound
% Risk of
malignancy (*) Usual management
10–30 (6–18) Repeat FNA, molecular
testing, or lobectomy
25–40 (10–40) Molecular testing,
lobectomy
thyroidectomy
A. W. Park et al.
Treatment
Benign Lesion
If the nodule is benign on cytology, further immediate diagnostic studies or treatment is not required.
Malignant Lesion
If a cytologic result is diagnostic for primary thyroid malignancy, surgery is generally recommended.
Thyroid Radiofrequency Ablation
In 1990, percutaneous ethanol ablation (EA) was introduced for treating AFTNs.
Although EA is very effective for cystic thyroid nodules and can achieve a volume
reduction of more than 85%, it is less effective for solid nodules. It also has several
limitations, such as unpredictable diffusion within the tumor, pain, and capsular
brosis by leaking, making future surgery challenging.
More recently, advances in thermal ablation have allowed effective treatment of
solid, benign thyroid nodules. Various energy sources are currently used in thermal
ablation, including laser, radiofrequency (RF), microwave, and high-intensity
focused ultrasound (HIFU). To date, radiofrequency ablation (RFA) has been the
18 Interventional Treatment ofThyroid Nodules
263
most exhaustively researched and proven therapy in terms of safety and clinical
efcacy. Hereafter, RFA will be mainly described in regard to thermal ablation.
The strategy for choosing between EA and thermal ablation depends on the composition of thyroid nodules [9]:
• Cystic nodule: EA
• Predominantly cystic nodule: EA rst or combined with thermal ablation
• Predominantly solid or solid nodule: thermal ablation
Indications
Thyroid RFA guidelines are designed to provide scientic information regarding the
use of this procedure in clinical practice. Several guidelines have been published
[10–17]. A systematic review of clinical practice guidelines for RFA of benign thyroid nodules was published recently [18]. There are subtle differences between
these guidelines with indications in common. According to the revised KSThR 2017
guideline [14], the indications and contraindications for treating benign thyroid
nodules are as follows.
Indications
• Patients with benign thyroid nodules producing symptoms or patients with cos-
metic concerns
• Toxic or pretoxic AFTNs
Thyroid nodules should be conrmed as benign on at least two US-guided FNA
or core needle biopsy (CNB) before RFA.A single benign diagnosis on FNA or
CNB is sufcient when the nodule has the US features highly specic for benignity
and AFTN.In addition, caution should be taken in the use of RFA in pregnant
women, patients with serious heart problems, and those with pre-existing contralateral vocal cord palsy.
Contraindications
• Follicular neoplasm or malignancy on FNA or CNB
• A nodule with US criteria suggesting malignancy, despite FNA or CNB results
• Cystic and predominantly cystic thyroid nodules, in which EA has been sug-
gested as a rst-line treatment
264
A. W. Park et al.
Anatomy
For a safe and effective procedure, knowledge of neck anatomy, particularly that of
the nerves, vessels, and other critical structures, is essential. It is of utmost importance to understand US-based thyroidal and perithyroidal anatomy.
The Thyroid Gland
The thyroid gland is a buttery-shaped midline structure lying anterior and lateral
to the trachea in the visceral space of the infrahyoid neck. In adults, each lobe is
about 40–60mm in length, 10–20mm in width, and 13–18mm in thickness. The
right and left lobes are connected by the isthmus in 2–3mm in thickness. The limits
of normal thyroid volume are 10–15mL for adult females and 12–18mL for males
[19]. The trachea, esophagus, thyroid gland, and infrahyoid muscles are enclosed by
the pretracheal fascia (Fig.18.1). The pretracheal layer of fascia is situated in the
anterior neck, spanning between the hyoid bone superiorly and the thorax inferiorly,
where it fuses with the pericardium (Fig.18.2).
Fig. 18.1 Cross-sectional
diagram of the neck with
three layers of the deep
cervical fascia; T trachea,
E esophagus. (With
permissions from Park
[20])
T
E
Investing fascia
Pretracheal fascia
Prevertebral fascia
18 Interventional Treatment ofThyroid Nodules
265
Fig. 18.2 Sagittal view of
the pretracheal fascia; T
thyroid gland. (With
permissions from Park
[20])
Anterior
Pretracheal fascia
Posterior
Hyoid bone
Thyroid cartilage
Cricoid cartilage
T
Tracheal rings
Fibrous pericardium
The false thyroid capsule (also known as the surgical capsule or perithyroidal
sheath) has a thin layer of fascia enveloping the thyroid gland, which needs to be
dissected away from the thyroid during surgery. Most anatomists and surgeons have
described it as a thin capsule deriving from the pretracheal fascia similar to a mesentery in the abdomen. The true capsule is formed by condensation of the brous
stroma of the gland.
The space between the false capsule and the true capsule is a potential space to
inject a local anesthetic. For RFA of benign thyroid nodules, perithyroidal lidocaine
injection is recommended as a local anesthesia technique [14]. During perithyroidal
lidocaine injection, the needle tip should be positioned close to the thyroid gland.
Initially, injecting a small amount of lidocaine will create a space between the two
capsules. Additional administration of lidocaine injection will dissect the space
(Fig.18.3) and propagate the anesthetic along the posterolateral margin of the thyroid gland.
Vessels
The arteries and veins of the thyroid gland are shown in Table18.5. The common
carotid artery (CCA) and internal jugular vein (IJV) are located in the posterolat-
eral aspect of the thyroid gland. The superior thyroidal artery runs supercially on
266
a b
False capsule
T
Perithyroid space
A. W. Park et al.
Tr ue capsule
Fig. 18.3 (a) Perithyroidal hydrodissection along the pretracheal fascia; T trachea, E esophagus
(With permissions from Park [20]). (b) Lidocaine injection in the right perithyroidal space; solid
white arrow, needle tip; IJV internal jugular vein, CCA common carotid artery
Table 18.5 The vessels of the thyroid gland
Artery Vein
Superior thyroid Superior thyroid
Inferior thyroid Inferior thyroid
Thyroid ima (directly from aortic arch) Anterior jugular vein
E
Middle thyroid
the anterior border of the thyroid gland. This artery runs closely and anterolaterally
to the external branch of the superior laryngeal nerve (SLN). The inferior thyroidal
artery enters the tracheoesophageal groove in a plane posterior to the carotid space,
and branches thereof penetrate the posterior aspect of the lateral thyroid lobe
(Fig.18.4).
The anterior jugular vein begins near the hyoid bone at the conuence of several
supercial veins arising from the submaxillary region (Fig.18.5). The vein descends
along the anterior border of the sternocleidomastoid muscle and passes beneath that
muscle to drain into the external jugular vein in the lower part of the neck. This vein
is located along the approach route (in front of the isthmus) of the electrode.
Although injury to the anterior jugular vein can be easily controlled by simple manual compression, it can disturb the procedure due to persistent oozing.
Muscles
The neck is a cage-like structure encaged by muscles, classied into three groups
(Table18.6). When visualized on US, the neck muscles act as important landmarks
for the identication of the nerves (Figs.18.6 and 18.7).
18 Interventional Treatment ofThyroid Nodules
267
Superior thyroid artery
Inferior thyroid artery
Thyroid Ima artery
Fig. 18.4 The vessels of the thyroid gland; blue, vein; red, artery. (With permissions from
Park [20])
Fig. 18.5 The location of
the paired anterior jugular
veins. (With permissions
from Park [20])
Superior thyroid vein
Middle thyroid vein
Inferior thyroid vein
Anterior jugular vein
External jugular vein
Nerves
Ultrasonographic visibility of the nerve depends on the size of the nerve, the equipment used, and the location in the neck. With high-frequency electrodes
(>10–12MHz), the nerve has a honeycomb-like appearance or displays a reticular
268
Table 18.6 The muscles surrounding the thyroid gland
Anterior Lateral Posterior
Strap muscles: four pairs of muscles:
Thyrohyoid
Omohyoid
Sternohyoid
Sternothyroid
Fig. 18.6 Relationship of the neck muscles to nerves; ASM anterior scalene muscle, LCM longus
colli muscle, MSM middle scalene muscle, SCM sternocleidomastoid muscle, SHM sternothyroid
muscle, STM sternothyroid muscle, OHM omohyoid muscle, PM platysma muscle. (With permissions from Park [20])
Sternocleidomastoid muscle
Scalene muscles
Anterior
Middle
Posterior
Levator scapulae muscle
Trapezius
A. W. Park et al.
Longus colli muscle
Longus capitis muscle
Fig. 18.7 Transverse US scan of the thyroid gland; SK skin, FC fascia cervicalis, SHM sternohyoid muscle, STM sternothyroid muscle, SCM sternocleidomastoid muscle, OHM omohyoid muscle, ISM isthmus, TH trachea, RTL right thyroid lobe, LTL left thyroid lobe, IJV internal jugular
vein, CCA common carotid artery, LCM longus colli muscle. (With permissions from Park [20])