Non-PET Tumor Imaging p3_Thallium

Jiraporn Sriprapaporn, M.D.

Nuclear Medicine

Siriraj Hospital

Mahidol University September 2015

Non-PET Oncologic Imaging_Jiraporn

Radiopharmaceuticals for Non-PET Oncologic Applications

Nonspecific

• Ga-67 citrate:

– Lymphoma

• Tl-201 chloride:

– Bone sarcomas

– Brain tumors

– Thyroid cancer

• Tc-99m sestamibi:

– Breast cancer

– Parathyroid adenomas

– Thyroid cancer

• Tc-99m tetrofosmin: Similar to sestamibi

Tumor-Type Specific

• I-131: Diff thyroid cancer (PTC, FTC)

• I-131 MIBG: Neural crest tumors (adrenal medullary imaging)

• Radiolabeled peptides: Somatostatin receptors (SSTR)

– In-111 pentetreotide (OctreoScan): Neuroendocrine tumors [NETs]

– Tc-99m HYNIC-TOC: NETs

– Tc-99m depreotide*: Lung cancer

• Radiolabeled monoclonal antibodies:

– Tc-99m arcitumomab (CEA-Scan)*: Colorectal cancer

– In-111 capromab pendetide (ProstaScint): Prostate cancer

– In-111 ibritumomab tiuxetan (Zevalin): Lymphoma

– I-131 tositumomab (Bexxar): Lymphoma

REF : modified from The Requisites


Physical Characteristics of Common Radionuclides Used for Tumor Imaging Agents

Radiotracer Physical T1/2 (hr)

Decay

Photopeaks

Injected dose mCi (MBq)

Organ receiving

highest dose rad/ mCi

(mGy/MBq)

Effective dose

rem/mCi (mSv/MBq)

keV Abundance

(%)

Ga-67* 78 EC

93 185 300 394

41 23 18 4

10 (370) Colon

0.74 (0.2) 0.44 (0.12)

Tl-201* 73 EC 69-83 94 3 (111) Kidneys

1.7 (0.46) 0.85 (0.23)

In-111* 67 EC 171 245

90 94

6 (222) Spleen

2.1 (0.57) 0.20 (0.054)

Tc-99m sestamibi

6 IT 140 88 20 (740) Gallbladder 0.14 (0.039)

0.033 (0.009)

modified from The Requisites, 4th Ed. SNM Guidelines

* Cyclotron-produced


• Tl-201 is cyclotron produced.

• Nonspecific tumor imaging

• Mechanism:

– Tl-201 behaves as a potassium analog

– Transmembrane electropotential gradient

– Na-K ATPase system

– Uptake also depends on cell type, viability, & regional

blood flow

• Excretion: Kidneys* (critical organ)

• Dose: 3-5 mCi IV.

• Scan time at 10-20 min. pi.+/- delayed 3 hrs


• Choroid plexus of the lateral ventricles,

• Salivary glands,

• Thyroid,

• Myocardium,

• Liver, spleen, splanchnic areas,

• Kidneys, bladder, and testes.

• Skeletal muscles,

• No bone marrow activity (if not marrow hyperplasia)

• The elimination of thallium is slow, with a Tbio of 10 days.

• Excretion: via kidneys Bladder is the critical organ. Anterior Posterior


False-positive Tl-201

• Benign bone tumors

• Stress fractures

• Inflammation

• Healing surgical wound

• Tuberculosis

TB: Abnormal Tl-201 retention at he mediastinum. (solid arrow), para-aortic region and left inguinal area (dashed arrow). Amukotuwa S, et al. International Seminars in Surgical Oncology. 2005;2:10 doi:10.1186/1477-7800-2-10


False-negative Tl-201

• Type of tumors-low or nonavid

• Small lesions

• Location of the lesion

– Close high-activity physiologic uptake area

– Deep lesions highly attenuated area (planar

images)


• Differentiate benign from malignant diseases

• Determine grade of malignancy

• Localize site for biopsy

• Evaluate the tumor response

• Differentiate post-therapy tissue necrosis or

fibrosis from residual tumor &/or local

recurrence


Tl-201 Clinical Applications

• Brain tumors

• Bronchogenic carcinoma

• Thyroid carcinoma

• Parathyroid adenoma

• Bone & soft tissue sarcoma

• Breast cancer

• Lymphoma :

– Low-grade Tl > Ga uptake

– High-grade Ga > Tl uptake*

• Head & neck cancers

Kaposi sarcoma is mesenchymal tumor that involves the lymphovascular system.


• Shorter waiting time for imaging

• Tl-201 is more specific than Ga-67 to

differentiate tumors from acute inflammatory

lesions ( thallium generally shows less uptake

in benign tumors, inflammatory processes,

and remodeling bone.)

• The intracellular uptake of Tl-201 is not

affected by steroid adm., chemotherapy, or

radiation therapy.

Essentials NM AuntMinnie.com


Drawbacks of Tl-201 Scan

• Limited availability & high cost since Tl-201 is

cyclotron-produced and needed to be imported.

• Low dose of Tl-201 is used due to high radiation

exposure (long physical T1/2 of 73 hrs).

• Physical properties of Tl-201 is suboptimal for

imaging.


Clinical Applications: Brain Neoplasms

• Thallium accumulates in malignant gliomas in proportion

to the aggressiveness of the lesions.

• Low-grade lesions concentrate little or no thallium,

whereas high-grade gliomas show markedly increased

activity.

• Gliosis surrounding brain abscesses, however, may also

demonstrate marked thallium accumulation.

correlation with CT or MRI and clinical findings.


Tl-201 SPECT & Low-grade Glioma

• A 37 year-old female with low-

grade glioma, s/p ERT followed by

resection and now with recent MRI

that shows enhancement near the

vertex on the right.


Brain Tumor at Hypothalamous

Tc-99m MDP Tl-201


AIDS-related Neoplasm

• Kaposi sarcoma (KS) is a low to intermediate grade

mesenchymal tumor that involves the lymphovascular

system.

• The tumor can have multi organ involvement inclusive of

pulmonary, gastrointestinal, cutaneous and

musculoskeletal systems.

• DDx Kaposi sarcoma vs lymphoma

– Kaposi sarcoma is thallium avid but does not take up gallium,

– Lymphoma concentrates both agents.

Kaposi sarcoma Tl+ve, Ga-ve

Lymphoma Tl+ve, Ga+ve


Kaposi Sarcoma of the Lung

• Thallium-positive and a gallium-

negative lesion in the lungs.

• CXR: bilateral pulmonary infiltrate

(A).

• Planar Tl-201 images: early (B),

delayed (C) and early SPECT (D)

and delayed

• SPECT (E).

• Ga-67 scan: Planar total body Ga-

67 scan (F) and Ga-67 SPECT

(G) showing NO increased uptake

in both lungs.

• Incidentally, there is a small focal

uptake in left SPC region without

corresponding thallium uptake

which is most likely due to acute

inflammatory pathology.

Abdel-Dayem HM 1996


Kaposi Sarcoma: References

1. Abdel-Dayem HM, Bag R, DiFabrizio L, Aras T, Turoglu HT, Kempf

JS, Habbab N, Pescatore F, Sadik A, Kowalsky W. Evaluation of

sequential thallium and gallium scans of the chest in AIDS patients.

J Nucl Med. 1996 Oct;37(10):1662-7. PMID: 8862304.

2. Lee VW, Fuller JD, O'Brien MJ, Parker DR, Cooley TP, Liebman

HA. Pulmonary Kaposi sarcoma in patients with AIDS: scintigraphic

diagnosis with sequential thallium and gallium scanning. Radiology.

1991 Aug;180(2):409-12. PMID: 2068302.

Health & Medicine

Non-PET Tumor Imaging p3_Thallium