4DTHYROID®: The Facts

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4DTHYROID® is a new service that offers a unique approach for assessing and diagnosing malignant thyroid lesions. As incidence of thyroid malignancy is increasing, ultrasound is the preferred technology for visualizing the thyroid gland and detecting thyroid malignancy. It defines the shape, size, texture, and vascularity of the thyroid gland and any lesion within or adjacent to the gland.

Most ultrasound machines provide 2-dimensional (2D) images. The current 2D technology has several drawbacks which can lead to the misdiagnosing of thyroid cancer. By utilizing 3-dimensional (3D) and 4-dimensional (4D) ultrasound technology, we may improve the accuracy of diagnosing thyroid malignancy. 4D ultrasound is also known as “Real-Time 3D ultrasound.” This technology overcomes some of the limitations encountered with the conventional 2D ultrasound. Potential benefits of 4D ultrasound include:

1. The ability to review volume data after the patient has left the examination room.
2. The possibility of viewing and using different sections of planes for the evaluation of anatomic structures other than original acquisition plane.
3. The possibility of rotating the volume plane dataset so that anatomic structures can be examined from different perspectives.
4. The availability of coronal view in 4D ultrasound can make the difference in a clinical diagnosis in many instances.

4D ultrasound allows for the visualization of the anatomic structures in real-time. 4D ultrasound is a reproducible technique in diagnosing thyroid malignancy. Utilization of this technology, can allow the operator to visual any desired plane through the thyroid gland. With 4D imaging, a 3D image is continuously updated in real-time. Due to the improved processing power of computers used in advanced ultrasound equipment, we can acquire and display the 3D datasets with their multiplanar reformations and renderings in real time. It is important to understand that 3D ultrasound is a dataset that contains a large number of 2D planes (B-mode images).

Figure 1 – B Mode transducer in a housing that swivels on a motor in fan like motion. Image courteous of: Nirvikar, Dahiya, M.D. http://www.gehealthcare.com/usen/ultrasound/education/products/cme_3d4d.html

Pyramid of Volume Information

Figure 2 – Pyramid of Volume Information: This volume shape can then be dissected in any plane, to get what we have been talking of as multiplanar imaging. It is like taking a block of un-sliced cheese and cutting it any plane you want. Image courteous of: Nirvikar, Dahiya, M.D. http://www.gehealthcare.com/usen/ultrasound/education/products/cme_3d4d.html

For example, if a book on a shelf is one 2D plane, then all the books on the shelf is the entire dataset. Once the volume is acquired using a dedicated 3D probe you can “walk” through the volume in a manner similar to looking at all the books on a shelf, meaning you can walk through the various 2D planes that make up the entire volume. Whereas 3D ultrasound is a static display of the various reformatting techniques, based on the acquisition of a static volume, 4D ultrasound displays a continuously updated and newly acquired volume in any 4D ultrasound allows for the visualization of the anatomic structures in real-time. 4D ultrasound is a reproducible technique in diagnosing thyroid malignancy. Utilization of this technology, can allow the operator to visual any desired plane through the thyroid gland. With 4D imaging, a 3D image is continuously updated in real-time. Due to the improved processing power of computers used in advanced ultrasound equipment, we can acquire and display the 3D datasets with their multiplanar reformations and renderings in real time. It is important to understand that 3D ultrasound is a dataset that contains a large number of 2D planes (B-mode images).

For example, if a book on a shelf is one 2D plane, then all the books on the shelf is the entire dataset. Once the volume is acquired using a dedicated 3D probe you can “walk” through the volume in a manner similar to looking at all the books on a shelf, meaning you can walk through the various 2D planes that make up the entire volume. Whereas 3D ultrasound is a static display of the various reformatting techniques, based on the acquisition of a static volume, 4D ultrasound displays a continuously updated and newly acquired volume in any rendering modality creating the impression of a moving structure. Real-time capacity is not generally available with all three-dimensional ultrasound.

This new technology may provide more detailed information about malignant thyroid lesions. It can assess the volume of benign and malignant thyroid lesion more precisely as compared to 2D ultrasound technology. It can help differentiate malignant lesions from benign thyroid lesions due to irregular surface and unique vascularity pattern. It also can improve diagnostic accuracy of thyroid nodule biopsy and lymph node biopsy due to real-time multiplanar images of the lesion under investigation. 4D will reduce the risk of misdiagnosing malignant thyroid lesion.

4D ultrasound can assess vascularization of benign and malignant thyroid lesions in greater detail. The vascular tree in a malignant thyroid nodule is different than in a benign thyroid lesion. In a malignant lesion, the vascular tree demonstrates an irregular pattern and different intensity within the lesion. A benign lesion has primarily peripheral vascularity pattern whereas a malignant lesion has central and irregular vascularity pattern. 4D ultrasound also allows assessment of abnormal vessel branching and vessel caliber change tortuousity, both are characteristics of malignant tumors. 4D Ultrasound may improve our ability to predict malignant thyroid lesions prior to Fine Needle Aspiration Biopsy (FNAB) as compared to 2D ultrasound.

3D Volume rendering is an important aspect of a 4DTHYROID® examination. It may become a useful tool in assessing and staging thyroid malignancy prior to surgery. With 3D ultrasound, the border of a thyroid lesion can be seen in a more detailed fashion. 4D ultrasound can reveal the surface irregularity of thyroid lesions. Based on our experience during 4D ultrasound examinations, a benign thyroid lesion has a smooth and regular surface, while a malignant thyroid lesion has an irregular surface and shape.

With 4D ultrasound, a volume of a region of interest within the thyroid gland can be acquired and stored. This volume can be further analyzed in different ways, such as multiplanar display, virtual navigation, surface rendering and tomographic imaging. The multiplanar display allows the examiner to navigate through the volume dataset in the 3 planes simultaneously and determine the precise location of an anatomic structure or abnormality of interest. Other methods and algorithms have recently become commercially available to automatically slice 3D volume dataset and display a series of 6 or 9 parallel tomographic images on the screen, similarly to the display methods traditionally used in Computed Tomography (CT) and Magnet Resonance Imaging (MRI).

3D images of malignant thyroid nodule

Figure 3A and 3B – 3D images of malignant thyroid nodule shown without and with power Doppler. Figure 3B depicts a chaotic vascularity pattern.

This new display modality has been described for prenatal visualization of anatomic fetal structures and diagnosis of congenital anomalies. There is evidence that the volumetric measurement by 3D and 4D ultrasound is more accurate than volume estimation from 2D measurement. This difference was more pronounced for irregularly shaped objects. Our team has made the same observation with regard to benign and malignant thyroid lesions.

Malignant nodule

Figure 5 – Malignant nodule: 3D parallel images through the lesion demonstrating irregular margins of a small malignant thyroid lesion.

References

1. AACE/AME/ETA Thyroid Nodule Guidelines, Endocr Pract. 2010;16 (Suppl 1)
2. Azizi G, Malchoff C; Three-Dimensional (3D) Ultrasound Images of Thyroid Gland and FNA Biopsy of the Thyroid Nodule (3D Thyroid). Endocrine Practice. July/August 2011.
3. Baskin J, Duick D, Levine R , Thyroid Ultrasound and Ultrasound-Guided FNA.
4. Lees W (2001) Ultrasound Imaging in Three and Four Dimensions, Semin Ultrasound CT MR 22(1): 85 – 105.
5. Davies L, Welch HG 2006 Increasing Incidence of Thyroid Cancer in the United States, 1973–2002. JAMA 295:2164– 216.
6. Wu HH, Jones JN, Osman J. Fine-Needle Aspiration Cytology of the Thyroid: Ten Years Experience in a Community Teaching Hospital. Diagn Cytopathol. 2006;34:93-96. [EL
7. Gyneconcology 120(2011) 340- 246) Juan Luis Alcazar, reference list: 6,13,14) 6/12/2011.
8. Nirvikar Dahiya MD; The Basics of 3D/4D Ultrasound: www.GE.com/online CME/3DUS.
9. Riccabona M, Nelson TR, Petorious DH. 3D US Accuracy of Distance and Volume Measurement. Ultrasound obstet Gynecol 1996; 7:429-434.
10. Hyun Cheol Kim Investigative Radiology; Original article; Volume 46, Number 4,April 2011.
11. Appelbaum L, Kane RA Focal Hepatic lesions; US-Guided Biopsy- Radiology. 2009; 250: 453- 458.
12. Howard MH, Nelson RC, An Electronic Device for Needle Placement during Sonographic Guided Percutanneus Intervention. Radiology. 2001;218; 905-911.
13. Alcazar JL, Jurado M, 3D US for Assessing Women with Gynecological Cancer; Gynecologic Oncology 120(2011)340-346.
14. Goncalves L, Lee W, Espinoza J, Romero R, 3D and 4D Ultrasound in Obstetric Practice; JUltrasound Med 2005; 24:1599-1624.
15. Nelson T.R., Downey D.B., Pretorius D.H. et al. Three-dimensional ultrasound. Philadelphia: Lippincott Williams & Wilkins, 1999.
16. Rankin R.N., Fenster A., Downey D.B. et al. Three-dimensional sonographic reconstruction: techniques and diagnostic applications. // Amer. J. Roentgen., 1993. V.161. p. 695-702.