Download Considerations regarding the role of 99m Tc-tetrofosmin

Lidia Ionescu, Cipriana Stefanescu, Carmen Vulpoi,
Doina Butcovan, D. Ferariu, C. Radulescu, C. Diaconu
University of Medicine and Pharmacy, Iasi
CT –mainstay of thymic investigation
 Thoracic CT scan has a reliable sensitivity and
specificity in detecting thymic lesions
 Elective method of diagnosis
 One major difficulty is to differentiate for certain
between thymic lymphoid hyperplasia and thymoma.
 But in equivocal cases, other investigations can add
suplimentary informations.
MV, male, 46 years old, 6w. history of MG- Oss. III,
CT suspicious for thymoma,
Op. 2004, histology- thymic lymphoid hyperplasia + mediastinal
ectopies, post.op.- complete remission
GE, 19 years old man, Hashimoto thyroiditis, hemolytic
anemia, (Hb-4g/dl), CT- thymoma, op.dec 2005,
histology- thymic lymphoid hypertrophy
PF, female, 21 years old, MG- OSS III,
CT- thymic hyperplasia, op. 1997
Histology- lymphocitic thymoma
Imaging investigations
 But in equivocal cases, thymic scintigraphy can add
suplimentary informations to CT aspects.
 Equivocal cases:
 Association of thyro-thymic lesions
 Tumor recurrence
 Type of thymic lesions
 Ectopic thymomas
Scintigraphy with 99mTc-tetrofosmin
 Frequently used in the assessment of myocardial
perfusion, conducted to incidental extracardiac uptake
and detection of a mediastinal mass as it showed in few
reported cases in the literature (Kotsalou I, Hawkins M)
 This investigation is not yet included in the algorithm of
diagnosis for mediastinal mass
 But it must be considered a valuable alternative when
conventional investigations fail to confirm a clinical
suspicion, resulting in adequate decision making.
Thymic scintigraphy
 Pathological uptake of 99mTc tetrofosmin appears in
benign and malignant tumors through an incomplete
understood mechanism.
 But the increased number of mitochodrias and the
degree of perfusion of the lesion seem to play an
important role.
Thymic scintigraphy
 Thymic scintigraphy can asses after the degree of up-
take of the radiotracer on the early and late images
 Normal thymus,
 Hyperplasia and
 Thymoma
 Tumor recurrence
 Ectopic thymomas
The 99m-Tc Tetrofosmin scintigraphy
 Performed with standard doses, according to the
worldwide accepted protocol.
 An informed consent for the investigation is obtained
from all the patients.
 An AXIS Gamma camera (Philips), Siemens doublehead detection and SPECT was used and acquired data
were analyzed with an IBM specialized software.
99m Tc Tetrofosmin
 Lipophile molecule that crosses the cellular
membranes according to electrochemical gradient and
fluidity of the membrane.
 It accumulates mainly in the mitochondria, which
explains the fixation in cells with intense metabolism.
Equivocal cases
 The association hyperthyroidy-myasthenia gravis is
present mainly in autoimmune thyropathies such as
Hashimoto’s thyroiditis or Grave’s disease
 Usually myasthenia gravis is secondary to
hyperthyroidy due to thymus hyperplasia and an
adequate antithyroid drug treatment or surgery result
in remission of thymic hyperplasia.
Associated lesions
 Murakami, Yasuhiro Hosoi demonstrated the presence
of thymic hyperplasia in Grave’s disease patients,
calculating on CT scan images the size and density of
the thymus on untreated and treated Grave’s disease
patients.
 The conclusion was that thymic hyperplasia regresses
in treated patients either with antithyroid drugs or
total thyroidectomy
Thyro-thymic lesions
 Yamanaka K, Nakayama H. reported a case of Grave's
disease associated with a mediastinl mass in whom CT
scan RMI were suggestive for a thymoma.
 The patient underwent total thyroidectomy and
thymectomy at the same stage. Pathology report
showed a thymic hyperplasia.
AM, 46-year-old woman, 2007 multinodular goitre and
myasthenia gravis
Thyroid profile (TSH-0.1 µUI/ml, fT4-1.2ng/dl),
Thyroid total volume of 65.9 ml. (Prof. dr. C. Vulpoi)
Compressive goiter
Retrosternal goiter
Total thyroidectomy for MNG-2007,
Myasthenia gravis aggravated
Normal Chest
Normal thymus
Thymic scintigraphy
Hypercaptation of 99mTc-tf. consistent with a thymoma
Hyperthyroidism+ectopic thymoma
 The thyroid lesion more obvious, was first treated and
myasthenia gravis considered wrongly to be secondary
and remitting after total thyroidectomy.
 On thymic scintigrapy was evident the hypercaptation
in lower anterior mediastinum with a high suspicion of
a thymoma.
 Pathology report of the specimen was mixt thymoma
with capsular microscopic invasion-Masaoka II stage.
Repeat CT scan
Antero- inferior mediastinal mass
Thymectomy, 6 months following TT, june 2008
Paramedian low retrosternal
mass
Well-encapsulated mass
Hyperthyroidism+ectopic thymoma
 The thyroid lesion more obvious, was first treated and
myasthenia gravis considered wrongly to be secondary
and remitting after total thyroidectomy.
 On thymic scintigrapy was evident the hypercaptation
in lower anterior mediastinum with a high suspicion of
a thymoma.
 Pathology report of the specimen was mixt thymoma
with capsular microscopic invasion-Masaoka II stage.
Myasthenia gravis, invasive thymoma
Inflammatory pericarditis
 C T, 64-year-old woman
 8 year-history of MG, CT- evident tumour
 op. 2002-thymectomy+pleurectomy
 Pathology report- Invasive thymoma-Masaoka III
 Post-operative radiotherapy 44 Gy,
 Chemotherapy 1 year- CPh+PDN
 2003- post-radiotherapy transient myxedema
CT, 60 years old, thymoma+MG, Oss.IV, op. 2002,
Lymphocitic thymoma (type I malignant thymoma)-Masaoka II
( well encapsulated but microscopic capsular invasion),
adhesions to left M. pleura which was resected
Radiotherapy 44 Gy, chemotherapy, 1 year CP+PDN
Pericarditis at 1 year postRxT
Remission of MG 5 years, 2008- AChE
POSTOPERATIVE THYMIC SCINTIGRAPHY
LACK OF RADIOTRACER FIXATION IN THE
ANTERIOR MEDIASTINUM
CT aspects-2009
The absence of the tumour recurrence,
pericarditis
2009
Inflammatory pericarditis