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412
J. F. Feller et al.
time, likely reecting the growth of the remaining prostate tissue. A PSA doubling time of <12
months is suspicious for recurrence. When
encountered without a suspicious lesion on
mpMRI, we recommend either a systematic
biopsy or a PSMA scan, depending on the PSA
velocity and patient preference. If there is a suspicious lesion on mpMRI, we recommend the
patient have a targeted plus systematic biopsy.
Most patients with local recurrence are candidates for repeat LFT [15, 17, 22], as well as radical prostatectomy if necessary [15, 23–25].
However, ablations that extend slightly outside of
the capsule have the potential to create focal
adhesions to the periprostatic tissues. The interventional radiologist who performed the LFT
should describe the location and extent of any
such extracapsular treatments to a urologist evaluating the patient for radical prostatectomy.
Outcomes
As a relatively new technique, there is a paucity
of outcome data for transrectal LFT compared to
the traditional treatment strategies. Since most
prostate cancer is slow-growing, rates of cancerspecic survival after monitoring, radical prostatectomy, and radiation are reported out to 15
years [26]. By comparison, the rst transrectal
LFT performed in a human was in 2010, over 13
years ago at the time of this writing. For this reason, the existing phase II trials of transrectal LFT
focus instead on rates of local recurrence, failurefree survival (i.e., the percentage of patients who
can avoid salvage whole gland therapy), and side
effects [19]. This section will describe the most
signicant studies of transrectal LFT performed
to date. The foundational studies of transperineal
MRI-guided prostate LFT will be described separately in the “In-Bore Transperineal Magnetic
Resonance Imaging-Guided Laser Ablation”
chapter.
Walser etal. at the University of Texas Medical
Branch at Galveston described their experience
with transrectal MRI-guided LFT in 120 patients
with low- and intermediate-risk disease [15]. The
median follow-up time was 34 months, ranging
from 17 to 55 months. They reported the local
recurrence of clinically signicant cancer in 41%
of their patients but were able to treat 100% of
those patients with repeat LFT. Salvage prostatectomy was performed in 2% of their patients.
They reported no statistically signicant change
in IPSS or SHIM scores. Rates of metastases
were not reported.
Chao et al. at New York University reported
5-year outcomes of 30 men who underwent transrectal MRI-guided LFT for low- and
intermediate- grade prostate cancer [17]. They
reported local recurrences in 40% of their
patients. Still, they were able to treat 90% of
them with a focal therapy (either repeat LFT,
cryoablation, or HIFU), and 87% of all of their
patients were able to avoid salvage whole gland
therapy. At the end of the follow-up period, 7% of
their patients had metastatic disease, but there
was 100% prostate cancer-specic survival. In an
earlier paper on the same cohort of patients, they
reported no statistically signicant change in
IPSS or SHIM scores [18].
The longest follow-up to date was reported by
Feller etal. from Desert Medical Imaging in 2020
as 10-year interim results from an ongoing phase
II clinical trial [22]. The group performed transrectal MRI-guided LFT on 158 men with lowand intermediate-grade prostate cancer. They
performed a biopsy of the treatment site in 122
men at 6 months and found clinically signicant
cancer in 26%. However, they were able to repeat
LFT in most cases, and 94% of their patients
could avoid salvage whole-gland therapy by 10
years. They reported 100% prostate-cancerspecic survival, and only 1% of their patients
developed metastasis. Furthermore, they reported
no statistically signicant change in IPSS or
SHIM scores. At the time of this writing, the clinical trial (NCT02243033) is ongoing, and the
group will continue to publish and present interim
results until achieving 20 years of follow-up.
Thus far, there have been no randomized controlled trials comparing LFT to either radical
prostatectomy or radiation therapy. However, a
group at the West China Hospital attempted to
compare these therapies by performing two analyses of age-matched patients in the SEER data-
33 Transrectal Laser Focal Therapy ofProstate Cancer
413
base. Zheng etal. compared 12,433 patients who
underwent radical prostatectomy to 442 patients
who had LFT, with approximately 5 years of follow- up [27]. They reported no signicant difference in cancer-specic mortality but higher
all-cause mortality in the LFT group. Zhou etal.
compared 93,469 patients who underwent radiation therapy to 428 patients who had LFT [28].
They did not report the length of follow-up time.
They also found no signicant difference in
cancer- specic mortality but higher all-cause
mortality in the LFT group. The most likely
explanation for these ndings in both studies is
that the LFT group generally had a worse performance status and more medical comorbidities,
neither of which was reported in either study.
Neither study also specied how many of the
ablations took a transrectal versus transperineal
approach, what the specialties of the operators
were, what laser systems were employed, or what
imaging guidance was used.
Complications
Transrectal LFT is well-tolerated in general.
Walser et al. ablated 120 patients and reported
mild hematuria was the most common adverse
event (7.4%). Other grade I adverse events were
erectile dysfunction (5.0%), urinary retention
(4.1%), pain (2.5%), dysuria (1.7%), irritative
urinary symptoms (1.7%), bladder hematoma
(0.8%), and spermatocele (0.8%). Grade II
adverse events were urinary tract infection
(3.3%), epididymitis (1.7%), erectile dysfunction
(2.5%), fever (0.8%), hematuria (0.8%), rectal
bleeding (0.8%), urinary retention (0.8%), and
rectourethral stula (1.7%). Both rectourethral
stulas resolved after 4–6 weeks of continuous
urinary catheterization. Only one grade III complication, a urinary tract infection requiring IV
antibiotics (0.8%), was reported [15].
In our own high-volume practice, we have
also encountered hematochezia (grade III rectal
bleeding) once (Fig. 33.7). While this is a rare
complication, all practitioners performing transrectal LFT must be prepared to intervene rapidly
if this occurs. We rst remove the needle guide
from the rectum and subsequently insert a
24-French Foley catheter into the rectum with a
75 mL balloon. The balloon is inated with
saline, and gentle traction is applied to tamponade the bleeding. The catheter is irrigated and
aspirated to clear out as much blood as possible.
After about 10 min, 5 mL of saline are aspirated
from the balloon, and the catheter is irrigated and
a
Fig. 33.7 62-year-old man with GG2 prostate cancer
centered in the right apex. Pre-ablation sagittal
T2-weighted MRI image (a) demonstrates the needle
tense viscous lidocaine gel within the rectum (blue
arrows). Intraprocedural sagittal T2-weighted image (b)
shows the laser cannula within the prostate, and now the
rectum is distended with blood (red arrows). The patient’s
vital signs remained stable, however given the rapid accu-
b
c
mulation of blood in the rectum, the decision was made to
terminate the procedure early. The needle guided was
removed from the rectum and a 24 French Foley catheter
with 75 mL balloon was inserted (yellow arrows), inated,
and pulled back to tamponade the bleeding. The catheter
was ushed to evacuate the blood products, and eventually removed after a slow, stepwise withdrawal of uid
from the balloon. The patient was brought back for completion of the BPH portion of the procedure 2 months later
414
J. F. Feller et al.
aspirated again to evaluate for new bleeding. If
new blood is identied, the 5 mL are reinjected
into the balloon, and another trial of partial balloon deation is reattempted in 10min. This process is repeated until it is clear the bleeding has
stopped even with minimal uid in the balloon, at
which point the Foley catheter is removed from
the rectum.
We have also rarely seen patients with mild
stress incontinence after an ablation. The majority of these patients report only a couple of drops
of urine when coughing, laughing, or tensing
their core. We recommend Kegel exercises three
times per day as long as needed to see improvement. In our practice, we have not had patients
fail conservative measures and require surgical
treatment.
Temporary lateral cutaneous femoral nerve
palsy has been observed in two patients with a
slender build, prompting the necessity of proper
positioning, padding, and comfort devices tailored to individual body habitus.
Long-term adverse effects for each patient
depend in large part on the location and size of
the ablation. For example, an ablation close to
either of the cavernosal nerve bundles increases
the risk of erectile dysfunction. Ablating close to
the external urethral sphincter increases the risk
of causing urinary incontinence. An ablation
close to the ejaculatory ducts increases the risk of
anejaculation. Ablations in the transitional zone
and/or median lobe can lead to retrograde ejaculation. The specic risks associated with the
treatment of each patient’s targeted lesion(s)
should be discussed with the patient during their
consultation.
Controversies
Some practices perform MRI-guided LFT via a
transperineal approach, while others perform it
via a transrectal approach. There have been no
head-to-head studies comparing the two
approaches, so all arguments in favor of one versus the other are purely conjectural and empirical. As with prostate biopsies, the most commonly
cited argument for taking a transperineal
approach is to decrease the risk of infection that a
transrectal approach would logically have. This
makes sense intuitively, especially with the additional risk of having devascularized necrotic tissue in the ablation zone. However, several studies
have shown no signicant risk of prostatic or
periprostatic abscess formation [15, 18, 22].
Another argument for taking a transperineal
approach is more accessible to midline lesions
anterior to the urethra; however, in our practice,
we treat lesions in this location by simply performing overlapping ablations from both the
right and left sides of the urethra (Fig.33.8).
The main advantage of taking a transrectal
approach is to increase the precision and control
of needle placement. While a laser cannula may
have to travel 10cm from the perineal skin to a
target within the prostate, it would typically only
have to travel about half that distance from the
rectum to the target. The shorter the distance in
the soft tissue the needle must traverse, the less
the needle is deected from its intended trajectory. The uncertainty of needle placement with
the transperineal approach has been described by
Cepek etal. and cited as a likely explanation for
incomplete treatments [29]. The DynaTRIM
device used in transrectal ablations allows for
ne adjustments of the laser cannula trajectory in
eight different directions, whereas a laser cannula
delivered through a perineal grid can only be
advanced along a predetermined path. Robots
designed to insert the laser cannula are currently
being investigated to improve the precision of
transperineal ablations [30, 31].
Transperineal biopsies are also more painful
than transrectal biopsies and have, therefore, traditionally been performed under general anesthesia. However, periprostatic nerve block has been
shown to be an effective method of pain control
for transperineal biopsies, allowing them to be
done more recently with the patient awake. Early
transperineal ablations described by Lindner
et al. were performed under general anesthesia
[23]; however, most studies of transperineal ablations since have been done with conscious sedation [32, 33].
The relatively limited access to MRI scanners
for procedures and the technical expertise
33 Transrectal Laser Focal Therapy ofProstate Cancer
415
a
e
Fig. 33.8 63-year-old man with GG2 prostate cancer.
Axial T2-weighted (a) and ADC (b) MRI images show a
1.0cm PI-RADS 4 lesion in the midline anterior midgland
transitional zone (red arrows). Intraprocedural axial
oblique T2-weighted MRI images demonstrate the laser
cannula to the right (c) and left (d) of the foley catheter
b
f
required to perform MRI-guided procedures has
led to interest among urologists in using MRI-US
fusion to perform LFT [34]. Natarajan etal. at the
University of California-Los Angeles (UCLA)
Health Clark Urology Center reported short-term
results on a small group of patients treated with
MRI-US fusion-guided LFT [35]. Ten men with
intermediate-risk prostate cancer were ablated.
Temperature was monitored with an average of
two transperineal probes inserted into the prostate, as well as a transrectal monitor. There were
no signicant decreases in urinary or sexual function. MRI-US fusion biopsy performed at 6
months found residual intermediate-risk cancer
in four patients (40%).
The most obvious limitation of this approach
is the temperature monitoring. While the temperature probes are able to give information
about 3–4 locations, MRI thermometry reports
the temperature in every voxel of the image in
two planes. Greater awareness of the temperature in the ablation zone and surrounding tissues allows for larger ablations, increasing the
odds of oncologic control. In this study, the
average PSA dropped by 17%, and the rate of
residual clinically signicant cancer was 40%;
c
(yellow arrows). Postcontrast axial T1-weighted MRI
image (e) demonstrates the ablation zone (blue arrows)
anterior to the urethra (yellow arrow) encompassing the
entire lesion. The patient’s PSA dropped 78% from preablation to post-ablation, and 5-year surveillance MRI (f)
demonstrates no evidence of recurrent disease
d
by comparison, Feller etal. reported an average
PSA drop of 37% and a rate of residual clinically signicant cancer of 26% with in-bore
MRI-guided LFT [22]. There have been no
phase II clinical trials of MRI-US fusion LFT,
so it remains to be seen how efcacy will compare to in-bore MRI-guided LFT with a longer
follow-up period.
Conclusion
Transrectal MRI-guided laser focal therapy
allows for precise treatment of prostate cancer
using real-time MR thermometry. Phase I and II
clinical trials have repeatedly demonstrated
safety, with a much lower side-effect prole than
radical prostatectomy or radiation therapy.
Although studies have shown a relatively high
local recurrence rate, they have also shown that
most recurrences can be treated with repeat focal
ablation. In addition to longer follow-ups demonstrating the noninferiority of cancer-specic survival, we need randomized control trials to
compare transrectal LFT directly to whole gland
therapies.
416
J. F. Feller et al.
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Part X
Post-treatment Assessment of Focal
Therapy Outcomes
Role ofProstate MRI forPostfocal
Treatment Assessment
andSurveillance
OmerTarikEsengur, DavidG.Gelikman,
andBarisTurkbey
34
Introduction
In prostate cancer (PCa) management, the advent
and renement of multiparametric MRI (mpMRI)
have revolutionized the assessment of PCa, offering insights into the prostate’s anatomical and
pathological landscape. The use of mpMRI in
clinical practice has particularly enhanced the
evaluation of the prostate gland following organpreserving focal therapy (FT) techniques, underscoring the need for precise imaging methods to
accurately assess treatment efcacy and detect
early signs of recurrence. As a versatile imaging
tool, mpMRI, with its detailed soft tissue resolution and functional assessment capabilities, has
emerged as a cornerstone in this paradigm, providing a comprehensive evaluation of prostate
tissue and aiding in the identication of residual
or recurrent disease.
The role of mpMRI in posttreatment assessment is multifaceted, involving the identication
of treatment-induced changes, delineation of normal posttherapeutic anatomy, and differentiation
between benign posttreatment effects and pathologic alterations indicative of residual disease or
recurrence. The unique ability of mpMRI to provide high-resolution images through the combi-
O. T. Esengur · D. G. Gelikman · B. Turkbey (*)
Molecular Imaging Branch, National Cancer Institute,
National Institutes of Health, Bethesda, MD, USA
e-mail: omer.esengur@nih.gov;
david.gelikman@nih.gov; turkbeyi@mail.nih.gov
nation of T1-weighted (T1W) and T2-weighted
(T2W) sequences, coupled with functional data
from diffusion-weighted imaging (DWI) and
dynamic contrast-enhanced (DCE) imaging,
offers a comprehensive view of the prostate
gland’s structural and vascular alterations following traditional and targeted therapies [1]. This is
pivotal in guiding clinical decisions, planning
salvage treatments, and ensuring a tailored
approach to patient management.
This chapter aims to provide a critical review
of the latest ndings in medical literature regarding the role of mpMRI in the posttreatment assessment and surveillance of PCa, particularly
following FT.We will further explore the mpMRI
ndings of the postintervention prostate gland,
delineating the imaging hallmarks associated with
different FT modalities. The success and failure
rates of mpMRI in diagnosing recurrent disease
post-FT will also be discussed, thereby offering a
comprehensive overview of its diagnostic prowess and limitations. By integrating the recent studies in this eld, this chapter will provide a nuanced
understanding of the latest place of mpMRI in
enhancing posttreatment surveillance.
Anatomy oftheProstate Gland
An essential component of the male reproductive
system, the prostate gland, is an exocrine gland
known for its role in semen production. Situated
© The Author(s), under exclusive license to Springer Nature Switzerland AG 2024
T. J. Polascik et al. (eds.), Imaging and Focal Therapy of Early Prostate Cancer,
https://doi.org/10.1007/978-3-031-66754-1_34
419
420
O. T. Esengur et al.
deep in the pelvis near the base of the bladder and
surrounding the urethra, it acts as an accessory
gland mostly composed of glandular, brous, and
smooth muscle tissue. This walnut-sized gland is
accessible during a digital rectal examination,
highlighting its anatomical prominence.
In terms of gross anatomy, the gland lies posterior to the pubic symphysis, inferior to the bladder, anterior to the rectum, superior to the perineal
membrane. The base wraps around the neck of
the urinary bladder. The apex surrounds the proximal part of the urethra, hence the nomenclature
prostatic urethra. The gland consists of ve anatomic lobes named after their position relative to
the urethra. While the anterior lobe does not contain any glandular epithelium, the posterior lobe
contains and is the most common part of the
gland that has tendency to malignancy [2]. In
addition to the median lobe located between the
ejaculatory ducts and the urethra, there are two
lateral lobes such as the left and right lobe which
are notably the most common site of benign prostatic hyperplasia (BPH) [3].
From the point of microscopic anatomy, the
prostate is distinguished by its zonal architecture.
The peripheral zone (PZ), the predominant site
for PCa, constitutes the largest portion of the
glandular prostate. The central zone (CZ),
embracing the ejaculatory ducts, and the transition zone (TZ), often the origin of BPH, complete
the zonal arrangement of the prostate [4]. A
brous capsule envelops the prostate, demarcating it from neighboring structures. Notably, this
capsule houses smooth muscle bers, instrumental in the expulsion of prostatic uid during ejaculation [4]. There is also the surgical
pseudocapsule, the structure that creates the border between the TZ and the PZ.
The vascularization of the prostate is predominantly through inferior vesical and middle rectal
arteries which are branches of the internal iliac
artery, with venous drainage managed by the
periprostatic plexus connecting to the internal
iliac veins. Autonomic nerves, including sympathetic bers from the hypogastric plexus and
parasympathetic bers from the pelvic splanchnic nerves, innervate the prostate, orchestrating
both ejaculation and glandular secretion [5, 6].
The lymphatic drainage of the gland is done
mostly by the internal iliac, sacral, and obturator
nodes; as well as some done by the external iliac,
presacral, and paraaortic lymph nodes [4, 7].
mpMRI of the prostate combines anatomical
and functional imaging techniques, offering a
detailed view of prostate anatomy and pathology.
In the context of normal prostate anatomy,
mpMRI typically includes T1W, T2W, DWI, and
DCE imaging. Understanding the appearance of
the normal prostate on mpMRI is crucial for distinguishing benign from pathological ndings.
On T2W images, the normal PZ appears as a
uniformly hyperintense region which shows a
stark contrast to TZ and CZ that yield an intermediate T2 signal intensity. The higher T2 signal
intensity of the PZ is attributed to the higher uid
content of the zone due to its glandular structure
[4, 8]. As age progresses, and in the presence of
BPH, the TZ tends to undergo hypertrophy, exerting pressure on the PZ.This interaction is delineated by a low-signal intensity band, the
pseudocapsule, on T2W images, effectively separating these zones. Under these imaging conditions, the TZ and CZ are almost indistinguishable
in majority of the patients and CZ appears as
bilateral symmetric hypointense band extending
towards the base of the prostate. The urethra
manifests as an area of relatively high signal
intensity on T2W scans, which refers to its lumen.
Similarly, both the periprostatic venous plexus
and the adipose tissue in the retropubic space of
Retzius are characterized with high signal intensity on T2W MRI.In contrast, the puboprostatic
ligament and the pubococcygeus muscle are discernible due to their low signal intensity. The
external boundary of the prostate, referred as the
“capsule,” is also visualized as a low-signal outer
line [4, 8] (Fig.34.1).
Conversely, on T1W images, the prostate,
venous plexus, and seminal vesicles generally
exhibit relatively low signal intensity, rendering
the zonal anatomy indistinct. Notably, on the posterolateral side, the neurovascular bundles can be
identied as they join with the gland. These
appear hypointense and are accentuated by the
high signal periprostatic fat surrounding them
[8].
34 Role ofProstate MRI forPostfocal Treatment Assessment andSurveillance
421
a
Fig. 34.1 T2W MRI in a 76-year-old man with an elevated prostate-specic antigen level of 5.4 ng/mL.Patient
has an enlarged prostate secondary to transition zone
hyperplasia without any evidence of malignancy. (a)
Axial T2-weighted image shows prostate gland anatomy.
The benign prostatic hyperplasia nodule is observed as a
hypointense area on the left anterior transition zone (asterisk). The brous capsule of the prostate (white arrowheads) is seen as a hypointense border around the gland
and the pseudocapsule (black arrowheads) is seen as
another hypointense border located between the transition
zone (TZ) and the peripheral zone (PZ). The neurovascular bundle (arrow) of the gland is seen on the left postero-
b
c
lateral side as a hypointense structure surrounded by the
hyperintense periprostatic fat. (b) Axial T2-weighted
image shows normal prostate gland base and normal seminal vesicles (asterisks). The urinary bladder (UB) is
located anteriorly to the gland. (c) Sagittal T2-weighted
image shows normal prostate gland and seminal vesicle
anatomy (asterisk). The peripheral zone (PZ) is seen as a
hyperintense U-shaped area while the transition zone (TZ)
is seen as a hypointense area. The central zone (CZ) is the
hypointense area expanding towards the base of the gland.
The urinary bladder (UB) is located superior to the
prostate
Posttreatment MRI Findings
Now that we have provided basic details about
prostate anatomy and its MRI ndings, we will
discuss posttreatment MRI ndings following
some of the more common FT modalities in this
section (Table34.1). Posttreatment MRI ndings
after FT can provide valuable insights into treatment effectiveness, assessment of the burden of
tissue destruction, and identifying residual or
recurrent disease.
High-Intensity Focused Ultrasound (HIFU)
HIFU is a noninvasive therapeutic technique that
uses focused ultrasound waves to heat and destroy
targeted tissue within the body. In the context of
PCa, HIFU is used to ablate or destroy cancerous
tissue within the prostate gland. During the procedure, a transrectal or transurethral probe is
used to deliver focused ultrasound energy to the
prostate, resulting in a localized increase in tem-
perature that destroys the targeted tissue. HIFU is
considered a minimally invasive treatment option
for localized PCa and is associated with fewer
side effects than standard whole-gland treatments
[17, 18].
Understanding the post-HIFU MRI ndings
can reveal important information about the
response to the therapy and distinguishing recurrence from normal therapy associated changes. A
recent study by Ahn et al. [9] describes the
mpMRI qualities of the glandular area treated
with HIFU with very low likelihood of recurrence as capsular retraction or a scar on T2W
images, absence of abnormalities or lesions on
DWI, absence of enhancement on DCE images;
while describing very likely recurrent lesions as
mass-like or marked hypointensities on T2W
imaging, focal diffusion restrictions on DWI, and
mass-like or focal early enhancement on DCE
(Fig. 34.2). Ahn et al. [9] also dened a recurrence scoring after a Likert scale and the diagnostic performance of this scale assigned to
post-HIFU MRI showed a sensitivity and specicity of 0.37 and 0.97, respectively, in predicting
422
Focal early
enhancement [9]
Focal diffusion
restrictions [9]
marked
hypointensities [9]
Focal
enhancement [11]
Diffusion
restriction on
ADC maps [11]
Hypointense lesion
[11]
Focal
hyperperfusion
[12]
Restricted water
diffusion [13]
[12]
Restricted
perfusion [13]
Focal early
enhancement [15]
Hyperintense
lesion [15]
Hypointense lesion
[15]
Hypointense
lesion on ADC
[15]
O. T. Esengur et al.
enhancement [16]
– Focal early
Hypointense lesion
[16]
Lack of enhancement [9] Mass-like or
Successful treatment Recurrent disease
T2WI DWI DCE T2WI DWI DCE
Table 34.1 T2WI, DWI, and DCE MRI features of FT modalities shown according to their status (successful treatment or recurrent disease) post-FT
HIFU Capsular retraction or scar [9] Lack of abnormality or visible
Early postop: hypovascular
anomaly [11]
lesion on high b value and the
ADC map [9]
3-months post-FT: ill-dened
or bandlike decreased ADC
boundary encircling the ablation
FLA Early postop: hypointense
3-months post-FT: lack of
enhancement [11]
12-months post-FT: similar
enhancement pattern with tissue
peripheral to the ablation site [11]
Progressive enhancement within
the ablation zone [10]
signal, scarring [11]
12-months post-FT: increase in
frequency of scarring and
decrease in ill-dened or
bandlike decreased ADC
signal [11]
Restricted water diffusion [12] Decreased contrast perfusion [12] Hypointense lesion
zone [10]
3-months post-FT: patchy or
band-like hypointensity [11]
12-months post-FT: T2 scarring
[10, 11]
IRE Hypointense diffuse scarring
at 3-months, absent at 23-months
post-FT) [14]
Intralesional enhancement (absent
on early postop) [14]
Restricted diffusion [15] Perilesional enhancement (present
area [12]
post-FT: Hyperintense lesion
with a hypointense rim [14]
17-months post-FT: hypointense
lesion [14]
FC Between 3- and 6-months
Lack of enhancement [15]
Scarring and capsule retraction
of the peripheral hyperintensity of
the gland, hypointense areas with
no enhancement [16]
– 6-months post-FT: disappearance
[15]
volume of the treated lobe and a
large, homogeneous area of
necrosis [16]
6-months post-FT: atrophy of the
treated lobe, irregularly shaped
small uid cavities inside the
PDT 1-week post-FT: increased
hypointense lesion [16]
therapy, HIFU high-intensity focused ultrasound, FLA focal laser ablation, IRE irreversible electroporation, FC focal cryotherapy, PDT photodynamic therapy
T2WI T2-weighted imaging, DWI diffusion weighted imaging, DCE dynamic contrast enhancement, ADC apparent diffusion coefcient, MRI magnetic resonance imaging, FT focal