DOI:10.2214/AJR.07.3564
AJR 2008; 191:W135-W150
© American Roentgen Ray Society
Applications of SPECT/CT in Nuclear Radiology
Michael C. Roarke1,
Ba D. Nguyen2 and
Barbara A. Pockaj2
1 Department of Radiology, Mayo Clinic Scottsdale, 13400 E Shea Blvd.,
Scottsdale, AZ 85259.
2 Department of Surgery, Mayo Clinic Scottsdale, Scottsdale, AZ.
Received December 18, 2007;
accepted after revision March 28, 2008.
Address correspondence to M. C. Roarke
(roarke.michael{at}mayo.edu).
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Abstract
OBJECTIVE. The purpose of this pictorial essay is to illustrate
several clinical situations in which SPECT/CT can be effectively applied in
nuclear radiology practice.
CONCLUSION. SPECT/CT has recently emerged as a valuable adjunct to
standard techniques in clinical nuclear radiology. This technique provides
significantly improved scintigraphic localization and characterization of
disease, increasingly important in this era of minimally invasive surgery and
targeted radiotherapy.
Keywords: intensity-modulated radiation therapy (IMRT) minimally invasive surgery nuclear radiology scintigraphy SPECT SPECT/CT
Introduction
In-line hybrid SPECT/CT is a recent addition to the nuclear radiology
armamentarium which generates coregistered SPECT and CT images acquired with a
single device during a single imaging session. SPECT/CT is similar
conceptually to PET/CT. The SPECT and CT images are acquired during a single,
approximately 35-minute-long imaging session.
The CT information is used for attenuation correction and anatomic
localization. Although the CT image quality from earlier generation SPECT/CT
hybrid scanners is not adequate for stand-alone diagnostic CT interpretation,
newer generation devices provide higher quality anatomic MDCT imaging.
In a manner analogous to PET/CT, SPECT/CT provides complementary, not
redundant, information because sites of abnormal radiopharmaceutical uptake on
the SPECT images can be anatomically localized on CT, anatomic abnormalities
on the CT images can draw attention to subtle abnormalities of tracer uptake
on SPECT, a lesion discovered on a preceding diagnostic imaging study can be
shown to precisely match the area of abnormal radiopharmaceutical uptake on
SPECT, and combined SPECT/CT can improve test specificity by reducing the
uncertainties associated with low-resolution SPECT alone.
In this article, we illustrate several useful clinical applications of
SPECT/CT, including localization of parathyroid adenomata, prostate cancer
localization and staging, sentinel lymph node mapping, neuroendocrine tumor
staging and localization, and as an adjunct to routine bone scintigraphy.
There are several additional SPECT/CT applications that could not be
included in this pictorial essay because of space limitations. These include
gallium and 111In-labeled leukocyte imaging of inflammation and
infection, radioiodine imaging of thyroid cancer, and, potentially, any other
application for which stand-alone SPECT would be indicated.
Image Acquisition
Although SPECT/CT technology is evolving and imaging parameters will vary
by manufacturer, the images presented in this article were acquired with the
following technical parameters. SPECT acquisitions were performed using
energy-appropriate parallel-hole collimators, large field-of-view gamma
detectors (range, 40 cm), 360° arc, 3° view angle, zoom of 1.0, and 35
seconds per stop. Images were acquired with a 128 x 128 matrix and then
reconstructed using a 2D ordered-subset expectation maximization iterative
technique (10 subsets and two iterations). CT images were acquired using
single-detector step-and-shoot technique, 10-mm slice interval, current of 2.5
mA, voltage of 140 kV, 256 x 256 matrix, and a Hann filter. Total
imaging time for most studies was approximately 35 minutes, with the SPECT
acquisition requiring approximately 25 minutes and the CT acquisition,
approximately 10 minutes.
Hyperparathyroidism
The literature regarding SPECT versus SPECT/CT in evaluation of
hyperparathyroidism has been somewhat conflicting, with studies reporting
increased value of SPECT/CT
[1–3],
whereas others claim little incremental benefit
[4]. However, the consensus
seems to be that SPECT/CT has the most utility in patients with ectopic
parathyroid adenoma, those with distorted neck anatomy due to prior surgery,
and those with prior failed parathyroid surgery. Whereas planar techniques can
depict the relative position of the abnormality, cross-sectional multiplanar
imaging will precisely specify the depth of the focus and its position with
respect to the surrounding and adjacent structures (Fig.
1A,
1B,
1C). For example, the surgical
approach to an adenoma adjacent to a thyroid gland lobe will require a
less-involved procedure than one that is located deeper in the prevertebral or
retroesophageal space (Figs.
2A,
2B,
3A,
3B,
4). The addition of the CT
component in hybrid SPECT/CT therefore would be expected to improve
mediastinal focus localization even further because both the scintigraphic and
corresponding CT abnormality can be pinpointed simultaneously. This
information should serve to clarify presurgical planning and can potentially
decrease intraoperative search time.

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Fig. 1A —64-year-old man with primary hyperparathyroidism referred for
parathyroid imaging before anticipated minimally invasive gamma
probe–guided parathyroidectomy. Left anterior oblique planar
99mTc sestamibi (740 MBq [20 mCi] IV) image shows focus of tracer
retention inferior in relation to normal left thyroid lobe
(arrow).
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Fig. 1B —64-year-old man with primary hyperparathyroidism referred for
parathyroid imaging before anticipated minimally invasive gamma
probe–guided parathyroidectomy. Multiplanar SPECT/CT (B)
pinpoints this uptake to 11-mm left paratracheal nodule (arrow) that
was overlooked on earlier chest CT (arrow, C). This uptake is
just inferior in relation to left thyroid lobe in left
tracheal–esophageal groove, 2–3 cm above axial level of sternal
notch. At surgery, 1,400 mg left inferior parathyroid adenoma was resected
from this location.
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Fig. 1C —64-year-old man with primary hyperparathyroidism referred for
parathyroid imaging before anticipated minimally invasive gamma
probe–guided parathyroidectomy. Multiplanar SPECT/CT (B)
pinpoints this uptake to 11-mm left paratracheal nodule (arrow) that
was overlooked on earlier chest CT (arrow, C). This uptake is
just inferior in relation to left thyroid lobe in left
tracheal–esophageal groove, 2–3 cm above axial level of sternal
notch. At surgery, 1,400 mg left inferior parathyroid adenoma was resected
from this location.
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Fig. 2A —87-year-old woman who presented with hypercalcemia and
inappropriate parathyroid hormone (PTH) levels. Parathyroid scintigraphy with
SPECT/CT was requested. Planar scintigraphy after IV injection of 740 MBq (20
mCi) 99mTc sestamibi revealed midline focus of radiopharmaceutical
uptake in lower neck. SPECT/CT images localize this radiopharmaceutical uptake
to retroesophageal region (arrows).
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Fig. 2B —87-year-old woman who presented with hypercalcemia and
inappropriate parathyroid hormone (PTH) levels. Parathyroid scintigraphy with
SPECT/CT was requested. Planar scintigraphy after IV injection of 740 MBq (20
mCi) 99mTc sestamibi revealed midline focus of radiopharmaceutical
uptake in lower neck. Unfused low-dose localizer–attenuation correction
CT image shows soft-tissue nodule (arrow), confirmed as ectopic
parathyroid adenoma at surgery.
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Fig. 3A —63-year-old woman with hypercalcemia and inappropriate
parathyroid hormone (PTH) levels who underwent parathyroid scintigraphy with
SPECT/CT after IV injection of 740 MBq (20 mCi) 99mTc sestamibi.
SPECT/CT (A) shows focus of tracer uptake in anterior mediastinum
(arrow, A) that matched a soft-tissue nodule (arrow,
B) on the CT (B) consistent with ectopic parathyroid adenoma.
Parathyroid adenoma was subsequently resected from the mediastinum, with
resolution of hypercalcemia.
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Fig. 3B —63-year-old woman with hypercalcemia and inappropriate
parathyroid hormone (PTH) levels who underwent parathyroid scintigraphy with
SPECT/CT after IV injection of 740 MBq (20 mCi) 99mTc sestamibi.
SPECT/CT (A) shows focus of tracer uptake in anterior mediastinum
(arrow, A) that matched a soft-tissue nodule (arrow,
B) on the CT (B) consistent with ectopic parathyroid adenoma.
Parathyroid adenoma was subsequently resected from the mediastinum, with
resolution of hypercalcemia.
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Fig. 4 —52-year-old man who presented with hyperparathyroidism and
was referred for 99mTc sestamibi (740 MBq [20 mCi] IV) parathyroid
scintigraphy with SPECT/CT before anticipated minimally invasive radioguided
parathyroidectomy with intraoperative parathyroid hormone (PTH) monitoring.
SPECT/CT multiplanar and SPECT maximum-intensity-projection (MIP) (far right)
images reveal focus of uptake in unusual location adjacent to proximal left
common carotid artery (arrows). During curative surgery, 22-mg
ectopic left parathyroid gland was found within left carotid sheath. Surgeon
remarked that SPECT/CT information significantly enhanced preoperative
planning of surgical approach.
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Prostate Cancer
The scintigraphic evaluation of prostate cancer presents significant
challenges. Conventional imaging with CT and bone scintigraphy are used
principally to detect extraprostatic disease, whether within local pelvic
nodes or at distant anatomic sites. After a negative conventional imaging
workup, the principal non-PET scintigraphic technique in use today is
111In capromab pendetide immunoscintigraphy. 111In
capromab pendetide has been reported to be more sensitive (60–90%) for
detection of metastatic lymph nodes than CT or MRI (5–50%)
[5]. The fusion of SPECT and CT
images has been reported to increase the diagnostic accuracy of
111In capromab pendetide scintigraphy by decreasing the number of
patients with false-positive results by 46%
[6].
Intensity-modulated radiation therapy (IMRT) is a method of treating
localized prostate cancer by providing graded dose boosting to involved areas
of the prostate. By importing the SPECT/CT images to the treatment planning
computer, the radiation oncologist can tailor the clinical treatment dose
profile to maximize radiation dose to the tumor and minimize the dose to
surrounding normal tissues (Figs.
5A,
5B,
6A,
6B,
6C,
7A,
7B,
7C,
8A,
8B). Indeed, SPECT/CT has been
reported to effectively contribute to modifications of clinical target volume
(CTV) in ways that spare more surrounding normal tissue
[7,
8].

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Fig. 5A —60-year-old man 2 years after radical prostatectomy for
Gleason 6 prostate cancer. Pathology showed tumor focally at inked surface of
left bladder base. Lymph nodes were negative for metastases. Postoperative
prostate-specific antigen (PSA) was 0.1 until 1 year later, when it rose to
0.38. His most recent PSA was 0.55. To help minimize radiation dose to bladder
and rectum, 111In capromab pendetide (222 MBq [6 mCi] IV)
scintigraphy was requested for intensity-modulated radiation therapy planning.
Planar whole-torso scintigraphy findings were negative.
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Fig. 5B —60-year-old man 2 years after radical prostatectomy for
Gleason 6 prostate cancer. Pathology showed tumor focally at inked surface of
left bladder base. Lymph nodes were negative for metastases. Postoperative
prostate-specific antigen (PSA) was 0.1 until 1 year later, when it rose to
0.38. His most recent PSA was 0.55. To help minimize radiation dose to bladder
and rectum, 111In capromab pendetide (222 MBq [6 mCi] IV)
scintigraphy was requested for intensity-modulated radiation therapy planning.
Multiplanar SPECT/CT clearly shows site of recurrence (thick arrow)
from rectum (thin arrow).
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Fig. 6A —72-year-old man with history of Gleason 7 aneuploid prostatic
adenocarcinoma with prostate-specific antigen (PSA) recurrence 7 months after
radical prostatectomy. For this patient, 111In capromab pendetide
(222 MBq [6 mCi] IV) scintigraphy was requested before salvage external-beam
radiation therapy. Planar whole-torso image shows negative findings.
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Fig. 6B —72-year-old man with history of Gleason 7 aneuploid prostatic
adenocarcinoma with prostate-specific antigen (PSA) recurrence 7 months after
radical prostatectomy. For this patient, 111In capromab pendetide
(222 MBq [6 mCi] IV) scintigraphy was requested before salvage external-beam
radiation therapy. SPECT/CT images at 96 hours after injection (B) show
recurrent disease in left seminal vesicle fossa (arrows), visible
only as wispy increased density on CT (C).
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Fig. 6C —72-year-old man with history of Gleason 7 aneuploid prostatic
adenocarcinoma with prostate-specific antigen (PSA) recurrence 7 months after
radical prostatectomy. For this patient, 111In capromab pendetide
(222 MBq [6 mCi] IV) scintigraphy was requested before salvage external-beam
radiation therapy. SPECT/CT images at 96 hours after injection (B) show
recurrent disease in left seminal vesicle fossa (arrows), visible
only as wispy increased density on CT (C).
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Fig. 7A —78-year-old man who underwent radical retropubic
prostatectomy in 1999 for adenocarcinoma of prostate. He developed
prostate-specific antigen (PSA) recurrence in 2001, originally treated with
single Lupron injection (leuprolide acetate, TAP Pharmaceuticals), and PSA
normalized. In 2003, PSA again began rising, and he was placed on Zoladex
(goserelin acetate, AstraZeneca). In 2005, he again developed rising PSA and
was placed on Casodex (bicalutamide, AstraZeneca). Restaging CT and bone scans
were always negative. At this point, 111In capromab pendetide (222
MBq [6 mCi] IV) scintigraphy was requested for localization of occult
recurrent disease. Planar whole-torso images (not shown) showed negative
findings. SPECT/CT images obtained at 96 hours after injection detect
recurrence in CT-negative, normal-sized retroperitoneal interaortocaval lymph
node (arrows). This case shows synergism of combined SPECT/CT.
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Fig. 7B —78-year-old man who underwent radical retropubic
prostatectomy in 1999 for adenocarcinoma of prostate. He developed
prostate-specific antigen (PSA) recurrence in 2001, originally treated with
single Lupron injection (leuprolide acetate, TAP Pharmaceuticals), and PSA
normalized. In 2003, PSA again began rising, and he was placed on Zoladex
(goserelin acetate, AstraZeneca). In 2005, he again developed rising PSA and
was placed on Casodex (bicalutamide, AstraZeneca). Restaging CT and bone scans
were always negative. At this point, 111In capromab pendetide (222
MBq [6 mCi] IV) scintigraphy was requested for localization of occult
recurrent disease. Planar whole-torso images (not shown) showed negative
findings. SPECT/CT images obtained at 96 hours after injection detect
recurrence in CT-negative, normal-sized retroperitoneal interaortocaval lymph
node (arrows). This case shows synergism of combined SPECT/CT.
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Fig. 7C —78-year-old man who underwent radical retropubic
prostatectomy in 1999 for adenocarcinoma of prostate. He developed
prostate-specific antigen (PSA) recurrence in 2001, originally treated with
single Lupron injection (leuprolide acetate, TAP Pharmaceuticals), and PSA
normalized. In 2003, PSA again began rising, and he was placed on Zoladex
(goserelin acetate, AstraZeneca). In 2005, he again developed rising PSA and
was placed on Casodex (bicalutamide, AstraZeneca). Restaging CT and bone scans
were always negative. At this point, 111In capromab pendetide (222
MBq [6 mCi] IV) scintigraphy was requested for localization of occult
recurrent disease. Planar whole-torso images (not shown) showed negative
findings. SPECT/CT images obtained at 96 hours after injection detect
recurrence in CT-negative, normal-sized retroperitoneal interaortocaval lymph
node (arrows). This case shows synergism of combined SPECT/CT.
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Fig. 8A —61-year-old man with newly diagnosed localized prostate
adenocarcinoma. Obtained at 120 hours after injection, 111In
capromab pendetide (222 MBq [6 mCi] IV) SPECT/CT image localizes focal
right-sided prostate carcinoma (arrow).
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Fig. 8B —61-year-old man with newly diagnosed localized prostate
adenocarcinoma. Separately acquired intensity-modulated radiation therapy
(IMRT) treatment planning CT image based on incorporation of SPECT/CT data
shows tumor location (thick arrow) with respect to 82-, 75.6-, 70-,
and 60-Gy isodose lines (thin arrows). By contouring dose profile,
site of highest tumor concentration can receive boosted dose, while dose is
reduced to surrounding normal tissues.
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Sentinel Lymphoscintigraphy
Sentinel lymphoscintigraphy has become a standard procedure used to
identify the location of at-risk nodal basins in patients with head and neck,
skin, and breast cancers. Although lymphoscintigraphy can be performed
successfully using planar gamma camera imaging, precise localization of nodes
can nonetheless be difficult in anatomically complex regions such as the head
and neck or when in-transit body wall nodes are found during mapping of
lymphatic drainage from torso lesions. SPECT/CT offers enhanced preoperative
sentinel lymph node (SLN) localization (Figs.
9A,
9B,
10A,
10B,
11A,
11B,
11C,
11D,
12A,
12B,
13A,
13B,
13C) in such cases
[9,
10].

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Fig. 9A —68-year-old man with locally recurrent left forehead melanoma
who underwent preoperative lymphoscintigraphy after circumferential
perilesional intradermal injections of 99mTc filtered sulfur
colloid (5.55 MBq [0.150 mCi]). Left lateral planar lymphoscintigram, with
head outline for preoperative landmark identification, shows forehead
injection site (small arrow) and intraparotid (large arrow)
and jugulodigastric (arrowhead) sentinel lymph nodes.
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Fig. 9B —68-year-old man with locally recurrent left forehead melanoma
who underwent preoperative lymphoscintigraphy after circumferential
perilesional intradermal injections of 99mTc filtered sulfur
colloid (5.55 MBq [0.150 mCi]). Multiplanar SPECT/CT of the intraparotid node
(arrows) shows that SPECT/CT is particularly useful when localizing
nodes in difficult anatomic locations, such as within parotid, and helps to
decrease risk to structures such as facial nerve.
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Fig. 10A —75-year-old man who noticed raised pimple on right midback.
Shave biopsy revealed malignant melanoma involving dermis with no epidermal
involvement. For this patient, 99mTc filtered sulfur colloid (5.55
MBq [0.150 mCi]) lymphoscintigraphy was requested. Planar scintigraphic images
show intense activity at right-back injection site, with closely adjacent
in-transit node (thin arrows) and lymphatic channels coursing to
right axillary sentinel nodes (thick arrows).
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Fig. 10B —75-year-old man who noticed raised pimple on right midback.
Shave biopsy revealed malignant melanoma involving dermis with no epidermal
involvement. For this patient, 99mTc filtered sulfur colloid (5.55
MBq [0.150 mCi]) lymphoscintigraphy was requested. SPECT/CT images reveal
precise location of in-transit node (arrows). SPECT/CT images provide
radiologist with precise location and depth for placing ink marks on skin. At
surgery, all sentinel nodes were negative.
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Fig. 11A —75-year-old man with history of wide local excision and
negative sentinel lymph node biopsy for desmoplastic melanoma on back 3 years
earlier who presented with local recurrence. Planar dynamic posterior
postinjection 99mTc filtered sulfur colloid (5.55 MBq [0.150 mCi]
intradermally) lymphoscintigraphy image shows rapid drainage from injection
site (arrowhead) toward left axilla (thin arrows) and to
right axilla (large arrow).
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Fig. 11B —75-year-old man with history of wide local excision and
negative sentinel lymph node biopsy for desmoplastic melanoma on back 3 years
earlier who presented with local recurrence. Coronal SPECT/CT images show
location of bilateral axillary nodes (arrows).
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Fig. 11C —75-year-old man with history of wide local excision and
negative sentinel lymph node biopsy for desmoplastic melanoma on back 3 years
earlier who presented with local recurrence. Coronal SPECT/CT images show
location of bilateral axillary nodes (arrows).
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Fig. 11D —75-year-old man with history of wide local excision and
negative sentinel lymph node biopsy for desmoplastic melanoma on back 3 years
earlier who presented with local recurrence. Multiplanar SPECT/CT images show
precise location and depth of periscapular in-transit sentinel node
(arrows).
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Fig. 12A —69-year-old woman with invasive ductal carcinoma of right
breast who was referred for 99mTc filtered sulfur colloid (5.55 MBq
[0.150 mCi] intradermally) lymphoscintigraphic mapping before right mastectomy
and sentinel lymph node biopsy. Anterior and lateral planar lymphoscintigrams
show injection site (arrowheads) and right axillary (thin
arrows) and internal mammary (thick arrow) sentinel lymph
nodes.
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Fig. 12B —69-year-old woman with invasive ductal carcinoma of right
breast who was referred for 99mTc filtered sulfur colloid (5.55 MBq
[0.150 mCi] intradermally) lymphoscintigraphic mapping before right mastectomy
and sentinel lymph node biopsy. SPECT/CT fusion images show internal mammary
sentinel lymph node location (arrows). Unfused CT axial comparison
view is at far right.
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Fig. 13A —77-year-old man with melanoma arising in large congenital
nevus on lower back who presented for 99mTc filtered sulfur colloid
(5.55 MBq [0.150 mCi] intradermally) sentinel lymph node mapping before wide
local excision and sentinel lymph node biopsy. Anterior and posterior planar
lymphoscintigraphy image of the torso shows drainage from radiopharmaceutical
injection site to right axillary (arrowheads), right groin (thick
arrow), and right paraspinal (thin arrows) nodal basins.
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Fig. 13B —77-year-old man with melanoma arising in large congenital
nevus on lower back who presented for 99mTc filtered sulfur colloid
(5.55 MBq [0.150 mCi] intradermally) sentinel lymph node mapping before wide
local excision and sentinel lymph node biopsy. Axial SPECT/CT pinpoints
location of right paraspinal–retroperitoneal sentinel lymph nodes on
fused SPECT/CT (B) (straight arrow, B) and unfused CT
(C) (arrow, C) images with respect to skin injection
site (curved arrow, B), providing vital preoperative anatomic
localization information.
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Fig. 13C —77-year-old man with melanoma arising in large congenital
nevus on lower back who presented for 99mTc filtered sulfur colloid
(5.55 MBq [0.150 mCi] intradermally) sentinel lymph node mapping before wide
local excision and sentinel lymph node biopsy. Axial SPECT/CT pinpoints
location of right paraspinal–retroperitoneal sentinel lymph nodes on
fused SPECT/CT (B) (straight arrow, B) and unfused CT
(C) (arrow, C) images with respect to skin injection
site (curved arrow, B), providing vital preoperative anatomic
localization information.
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In breast cancer and melanoma involving the arms, the incremental value of
SPECT/CT remains to be conclusively defined. Although the localization of
level 1 axillary nodes in breast cancer is usually straightforward with
existing techniques, precise localization of higher level axillary,
intramammary or intransit, and internal mammary nodes can be enhanced with
SPECT/CT (Fig. 12A,
12B). For melanoma of the
arms, however, SPECT/CT may be less than optimal in larger patients whose arms
cannot be completely included in the field of view without obtain ing an
additional repositioned acquisition.
Neuroendocrine Tumors
SPECT/CT can provide enhanced localization and staging of neuroendocrine
neoplasms with 111In octreotide and 123I MIBG,
especially for lesions within the peritoneal cavity, mesentery, and pancreas
(Figs. 14A,
14B,
15A,
15B,
16A,
16B,
16C,
17A,
17B). Differentiation from
physiologic activity in the bowel can be readily distinguished from foci just
outside the bowel. For such neuroendocrine neoplasms, studies have reported
that SPECT/CT is more accurate than SPECT or CT alone and changes or guides
management in patients with neuroendocrine tumors, particularly when other
imaging studies are equivocal
[11–17].

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Fig. 14B —42-year-old man with partially calcified pancreatic neck
mass. Obtained at 24 hours, 111In pentetreotide (222 MBq [6.0 mCi]
IV) SPECT/CT confirms that lesion on CT is somatostatin-receptor positive,
consistent with suspected neuroendocrine origin, by showing intense focal
uptake within lesion (arrows). Patient underwent exploratory
laparotomy with essential pancreatectomy, Roux-en-Y pancreaticojejunostomy,
cholecystectomy, and common bile duct exploration. Pathology confirmed islet
cell tumor.
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Fig. 15A —69-year-old woman with new cecal carcinoid found incidentally
at routine surveillance colonoscopy. CT coronal image from 111In
pentetreotide scintigraphy (222 MBq [6.0 mCi] IV) at 6 hours after injection
shows hypervascular cecal mass (arrow).
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Fig. 15B —69-year-old woman with new cecal carcinoid found incidentally
at routine surveillance colonoscopy. Multiplanar SPECT /CT and
maximum-intensity-projection (far right) images show intense 111In
pentetreotide uptake precisely at site of cecal mass (arrows),
confirming probable carcinoid. Patient underwent laparoscopy-assisted right
hemicolectomy. Pathology confirmed carcinoid tumor.
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Fig. 16A —65-year-old man who presented with abdominal bloating and gas
pains. Abdominal CT reveals 2.2-cm partially calcified irregular mass
(arrow) in right lower quadrant mesentery, with principal CT
differential diagnosis of sclerosing mesenteritis versus carcinoid. No other
abnormal intraabdominal findings are seen on CT.
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Fig. 16B —65-year-old man who presented with abdominal bloating and gas
pains. Multiplanar 111In pentetreotide scintigraphy (222 MBq [6.0
mCi] IV) SPECT/CT at 6 hours after injection (B) reveals unsuspected
focal uptake in pancreas (arrows, B), which was present in
retrospect but overlooked on arterial phase of biphasic CT (arrow,
C). Tracer uptake in the mesenteric mass was unimpressive. At
mesenteric mass resection, an invasive 2-cm ileal carcinoid was removed, with
tiny mesenteric implants in vicinity. Pancreatic deposit was not removed but
has remained stable on serial follow-up CT since patient began octreotide
acetate treatment.
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Fig. 16C —65-year-old man who presented with abdominal bloating and gas
pains. Multiplanar 111In pentetreotide scintigraphy (222 MBq [6.0
mCi] IV) SPECT/CT at 6 hours after injection (B) reveals unsuspected
focal uptake in pancreas (arrows, B), which was present in
retrospect but overlooked on arterial phase of biphasic CT (arrow,
C). Tracer uptake in the mesenteric mass was unimpressive. At
mesenteric mass resection, an invasive 2-cm ileal carcinoid was removed, with
tiny mesenteric implants in vicinity. Pancreatic deposit was not removed but
has remained stable on serial follow-up CT since patient began octreotide
acetate treatment.
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Fig. 17A —49-year-old woman with history of left adrenalectomy 4 years
earlier who presented with symptoms and laboratory findings consistent with
recurrent pheochromocytoma. Gadolinium-enhanced T1-weighted adrenal MR image
shows nodular, mildly enhancing soft-tissue mass in left adrenalectomy bed
(arrow).
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Fig. 17B —49-year-old woman with history of left adrenalectomy 4 years
earlier who presented with symptoms and laboratory findings consistent with
recurrent pheochromocytoma. Multiplanar 131I MIBG (18.5 MBq [0.500
mCi]) IV, unfused (top row, black arrows) and fused (bottom row,
white arrows), SPECT/CT images of abdomen at 48 hours after injection
confirm presence and location of recurrent pheochromocytoma. This recurrence
was then successfully surgically resected.
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Bone Scintigraphy
Bone scintigraphy is a sensitive technique for detection of bone metastases
and assessment of treatment response in neoplastic disease, especially for
those with a tendency toward osteoblastic metastases (i.e., prostate, breast).
Although many bone foci can be adequately characterized on the basis of
location, appearance, and knowledge of preceding trauma, osteomyelitis,
surgery or arthritis, or comparison with prior studies, a substantial number
of abnormal foci remain indeterminate without the addition of radiographs, CT
scans, or MRI. SPECT/CT (Figs.
18A,
18B and
19A,
19B,
19C,
19D) can often clarify the
true nature, benign versus malignant, of such indeterminate foci
[18].

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Fig. 18A —70-year-old man with newly diagnosed Gleason 8 prostate
cancer; prostate-specific antigen (PSA) 7.1 ng/mL. At 2.5 hours after
injection, 99mTc MDP (740 MBq [20 mCi] IV) planar bone scintigram
shows indeterminate focus of uptake (arrow) in right mid lumbar
spine. Metastasis cannot be excluded.
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Fig. 18B —70-year-old man with newly diagnosed Gleason 8 prostate
cancer; prostate-specific antigen (PSA) 7.1 ng/mL. Multiplanar unfused (top
row) and fused (bottom row) SPECT/CT images show degenerative disk-related
osteophyte at L3–L4 (arrows), which explains uptake on bone
scan. No radiographs or additional imaging was required, and the patient
proceeded directly to robotic retropubic prostatectomy.
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Fig. 19A —56-year-old previously healthy man with 5-month history of
left upper back pain who was referred by physical medicine to assess for
suspected costovertebral arthritis. At 2.5 hours after injection,
99mTc MDP (740 MBq [20 mCi] IV) planar bone scintigraphy image of
posterior ribs shows very mild focal uptake involving left seventh through
tenth posterior ribs, most notably in posteromedial ninth rib
(arrow).
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Fig. 19B —56-year-old previously healthy man with 5-month history of
left upper back pain who was referred by physical medicine to assess for
suspected costovertebral arthritis. Coronal SPECT/CT images show left
paraspinal soft-tissue mass (arrow, B) adjacent to medial
margin of ninth rib tracer uptake (arrow, C).
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Fig. 19C —56-year-old previously healthy man with 5-month history of
left upper back pain who was referred by physical medicine to assess for
suspected costovertebral arthritis. Coronal SPECT/CT images show left
paraspinal soft-tissue mass (arrow, B) adjacent to medial
margin of ninth rib tracer uptake (arrow, C).
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Fig. 19D —56-year-old previously healthy man with 5-month history of
left upper back pain who was referred by physical medicine to assess for
suspected costovertebral arthritis. Axial unfused CT image shows lytic mass
invading left ninth rib and vertebra (arrows). Biopsy revealed
plasmacytoma. In this case, SPECT/CT was pivotal in identifying source of
patient's pain and provided localization information for CT-guided biopsy.
Note unsharp CT image component in this case, which is result of
single-detector, step-and-shoot capability of SPECT/CT unit used in acquiring
these images. Newer-generation scanners provide MDCT capability, with
correspondingly improved CT image resolution.
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Conclusion
SPECT/CT is a powerful new tool that exploits the synergism between the
anatomic data available from CT and the metabolic information provided by
radiopharmaceuticals to provide enhanced localization and staging of
neoplastic disease.
Acknowledgments
We thank Chris Tollefson and Steven Schild for their assistance in
gathering images used in this pictorial essay.
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