SPECT/CT in Endocrine Diseases and Dosimetry Heather A. Jacene, MD Division of Nuclear Medicine Russell H. Morgan Dept. of Radiology and Radiological Science Johns Hopkins University Baltimore, MD
Disclosures Neither I, nor my immediate family members, have any financial relationships with a commercial organization that may have interest in the content of this presentation.
SPECT Better lesion detection than planar images
Transaxial
Objectives To discuss, Diagnostic accuracy and limitations of SPECT/CT Hyperparathyroidism Thyroid cancer Use of SPECT/CT for dosimetry
Theme - SPECT Lack of anatomic detail Decreases confidence Interpretation errors
Theme SPECT/CT Precise lesion localization Less equivocal findings Road map comparison to high resolution imaging Improves image interpretation Changes patient management
Hyperparathyroidism
Hyperparathyroidism Etiology 80-85% solitary adenoma 10-15% hyperplasia 2-3% multiple adenomas, carcinoma Surgery Cure rate >90% Minimally invasive surgery
Parathyroid Scintigraphy Primary hyperparathyroidism, sensitivity Planar 74-87% SPECT 91-96% Rubello et al. Clin Nucl Med 2002 Sharma Slides et al. are Surgery not to be reproduced 2006 Krausz et al, without World permission J Surg of author. 2006
Parathyroid Scintigraphy SPECT/CT precise localization Facilitates surgical planning (42%) Mediastinum Neck distorted anatomy Rubello et al. Clin Nucl Med 2002 Sharma et al. Surgery 2006 Krausz et al, World J Surg 2006
Planar, SPECT, vs. SPECT/CT Lavely et al. J Nucl Med 2007;48:1084 Early Planar SPECT SPECT/CT Late Planar SPECT SPECT/CT 19 combinations Location
Planar, SPECT, vs. SPECT/CT Lavely et al. J Nucl Med 2007;48:1084 Accuracy Dual phase planar Dual phase SPECT Early SPECT/CT Early SPECT/CT + any late 78% 80% 81% 86%
66 year old female Primary Hyperparathyroidism Routine labs Calcium 11 mg/dl PTH 154 pg/ml Borderline osteoporosis Ultrasound - 2-cm left thyroid nodule FNA showed adenomatoid nodule
52 year old female Primary Hyperparathyroidism Calcium 12.2 mg/dl; PTH 145 pg/ml US possible parathyroid adenoma No scintigraphy due to claustrophobia Central neck dissection NO adenoma Sestamibi adenoma in chest?
CT SPECT Fused MIP
Hyperparathyroidism Summary SPECT/CT precise localization Facilitates surgical planning Limitations Resolution of CT scanner Visualizing anatomic abnormality
Thyroid Cancer
Author N SPECT/CT vs. Comments Year Even-Sapir 2001 27 CT Planar/SPECT 6 thyroid cancer 5 mci 131 I Ruf 25 SPECT 100 mci 131 I 2004 Inconclusive planar findings Tharp 71 Planar Diagnostic 131 I dose in 17 2004 Remnant ablation/therapy in 54 Increased focus on planar
SPECT/CT vs. Planar, SPECT Better lesion localization 44-50% Changes interpretation 38-57% Alters therapy 17-41% Even-Sapir et al. J Nucl Med 2001;42:998 Ruf et al. Nucl Med Commun 2004;25:1177 Tharp et al. Eur J Nucl Med 2004; 31:1435
More Accurate Diagnoses Physiologic Substernal goiter Endometrial Pathologic Renal metastases Intratracheal metastasis vonfalck et al. Clin Nucl Med 2007;32:751 Aide et al. Thyroid 2007;17:1305 Rachinsky et al. Thyroid 2007;17:901 Dumcke et al. Clin Nucl Med 2007;32:156
39 year old female Papillary Thyroid Cancer (PTC)
11 year old female Thyroid Cancer Cervical adenopathy Total thyroidectomy and neck dissections 5.7 cm multifocal follicular variant PTC Extrathyroidal extension Unclear resection margins Nodal metastases Withdrawn for 131 I
Anterior Posterior Rt Lateral Lt Lateral
CT SPECT Fused
T2 T1 post-contrast
Thyroid Cancer Summary Better lesion localization Changes interpretation Alters therapy
Dosimetry SPECT/CT Thyroid cancer Radioimmunotherapy
Incorporation of SPECT/CT CT based compensation methods Attenuation Scatter Collimator-detector response Septal penetration 3D images better organ/tumor definitions Sgouros et al. J Nucl Med 2004;45:1366 Lawaraja et al. J Nucl Med 2005;46:840 He et al. Phys Med Biol 2005;50:4169 Song et al. J without Nucl permission Med 2006;47:1985 of author.
Anatomic-Based Reconstruction Methods Image-derived spatial activity distributions Better accuracy Better resolution Sgouros et al. J Nucl Med 2004;45:1366 Lawaraja et al. J Nucl Med 2005;46:840 He et al. Phys Med Biol 2005;50:4169 Song et al. J Nucl Med 2006;47:1985 Prideaux et al. J Nucl Med 2007;48:1008
Dosimetry SPECT/CT Thyroid cancer Radioimmunotherapy
Benua-Leeper Method Blood absorbed dose <200 cgy 48 h whole body retention <120 mci without lung metastases <80 mci with lung metastases Benua and Leeper. Frontiers in Thyroidology Slides are not 1986;1317 to be reproduced Benua et al. AJR 1962;87:171
Thyroid Cancer Lung Metastases 7% of patients with PTC >80% with distant metastases Dose limiting after the marrow 24-27 Gy (MTD) Benua and Leeper. Frontiers in Thyroidology Slides are not 1986;1317 to be reproduced Benua et al. AJR 1962;87:171
Lung Metastases Dosimetry challenging Heterogeneous tissue density Heterogeneous activity distribution Energy deposition in normal lung Prolonged retention times Benua and Leeper. Frontiers in Thyroidology Slides are not 1986;1317 to be reproduced Benua et al. AJR 1962;87:171
80 mci Rule Derived from females with lung toxicity Assumes uniform distribution Benua and Leeper. Frontiers in Thyroidology Slides are not 1986;1317 to be reproduced Benua et al. AJR 1962;87:171
Dose-Rate Method Translation of activity based method Different limits based on sex and age Still assumes uniform distribution Higher absorbed lung dose than MTD In tumor not normal lung Sgouros et al. J Nucl Med 2006;47:1977
CT transaxial CT coronal SPECT MIP transaxial SPECT MIP coronal From Song et al, J Nucl Med 2006;47:1985
Comparison of Dosimetry Methods Song et al, J Nucl Med 2006;47:1985 Doserate Benua- Leeper S value 3D Activity (mci) 116 105 17.8 46 Absorbed Dose (Gy) Lung 177 160 27 27 Tumor N/A N/A N/A 64
Dosimetry SPECT/CT Thyroid cancer Radioimmunotherapy
Normal Organ Dosimetry Most accurate with pure SPECT Least accurate with pure planar Hybrid method better than planar Planar time activity curves Single SPECT/CT anatomy/quantitation He et al. IEEE 2006;27:521
Tumor Heterogeneity
SNM 2008 Session 28 SPECT/CT in treatment planning Bone metastases (Abstract 186) Lymphoma (Abstract 187)
Patient-specific dosimetry Based on 3D imaging Radiobiologic parameters Feasible Important
SPECT/CT Limitations Size Misregistration Between SPECT and CT Bowel motion Respiratory motion Attenuation artifacts Metallic implants Dense materials (contrast) Display errors
SPECT/CT Limitations Being able to demonstrate benefits of SPECT/CT will be challenging on large scale Lack of patient follow-up Gold standard Randomized trials Still small number of studies Cost vs. number of studies
Conclusions Combined SPECT/CT imaging, Important additional information Directly impacts image interpretation Added diagnostic value over SPECT alone for endocrine disorders
Future/Investigational Uses Dosimetry studies to optimize tumor dose Thyroid Radioimmunotherapy Neuroblastoma Bone cancer/metastases