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A practical MRI-based reconstruction method for a new endocavitary and interstitial gynaecological template.

Richart J, Otal A, Rodriguez S, Nicolás AI, DePiaggio M, Santos M, Vijande J, Ballester F, Perez-Calatayud J - J Contemp Brachytherapy (2015)

Bottom Line: The differences observed in the positioning were significantly smaller than 1 mm in all cases.The presented algorithm also allows the use of only T2W sequence either for contouring or reconstruction purposes.The proposed method is robust and independent of the visibility of the artifact at the tip of the needle.

View Article: PubMed Central - PubMed

Affiliation: Radiotherapy Department, Benidorm Hospital, Benidorm, Alicante.

ABSTRACT

Purpose: There are perineal templates for interstitial implants such as MUPIT and Syed applicators. Their limitations are the intracavitary component deficit and the necessity to use computed tomography (CT) for treatment planning since both applicators are non-magnetic resonance imaging (MRI) compatibles. To overcome these problems, a new template named Template Benidorm (TB) has been recently developed. Titanium needles are usually reconstructed based on their own artifacts, mainly in T1-weighted sequence, using the void on the tip as the needle tip position. Nevertheless, patient tissues surrounding the needles present heterogeneities that complicate the accurate identification of these artifact patterns. The purpose of this work is to improve the titanium needle reconstruction uncertainty for the TB case using a simple method based on the free needle lengths and typical MRI pellets markers.

Material and methods: The proposed procedure consists on the inclusion of three small A-vitamin pellets (hyperintense on MRI images) compressed by both applicator plates defining the central plane of the plate's arrangement. The needles used are typically 20 cm in length. For each needle, two points are selected defining the straight line. From such line and the plane equations, the intersection can be obtained, and using the free length (knowing the offset distance), the coordinates of the needle tip can be obtained. The method is applied in both T1W and T2W acquisition sequences. To evaluate the inter-observer variation of the method, three implants of T1W and another three of T2W have been reconstructed by two different medical physicists with experience on these reconstructions.

Results and conclusions: The differences observed in the positioning were significantly smaller than 1 mm in all cases. The presented algorithm also allows the use of only T2W sequence either for contouring or reconstruction purposes. The proposed method is robust and independent of the visibility of the artifact at the tip of the needle.

No MeSH data available.


A) 3D T1W MRI images showing two different paraxial slices (left) and the choice of two points to determine the direction of one needle. Upper right and lower right show the position of points P1 and P2 in parasagittal and para-coronal views, respectively. B) T2 MRI images showing two different paraxial slices (left) and the choice of two points to determine the direction of one needle. Upper right and lower right show the position of points P1 and P2 in para-sagittal and para-coronal views, respectively
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Figure 0003: A) 3D T1W MRI images showing two different paraxial slices (left) and the choice of two points to determine the direction of one needle. Upper right and lower right show the position of points P1 and P2 in parasagittal and para-coronal views, respectively. B) T2 MRI images showing two different paraxial slices (left) and the choice of two points to determine the direction of one needle. Upper right and lower right show the position of points P1 and P2 in para-sagittal and para-coronal views, respectively

Mentions: The coordinates of these three points B1, B2, and B3, define the reference plane shown in Figure 1B. Additionally, two points describe the direction for each needle, which is a straight line. These points can be anywhere on the needle, so they are chosen by selecting two separate slices that present good image contrast. Figure 3A shows an example of a case reconstructed based on 3D T1W sequence. On the left-hand side, two para-axial images show the positions of points P1 and P2. The location of these two paraxial images are represented with a green line on the upper right (sagittal) and on the lower right (coronal) frames of Figure 3A. In the same way, an example of a case reconstructed based on T2W sequence is shown in Figure 3B.


A practical MRI-based reconstruction method for a new endocavitary and interstitial gynaecological template.

Richart J, Otal A, Rodriguez S, Nicolás AI, DePiaggio M, Santos M, Vijande J, Ballester F, Perez-Calatayud J - J Contemp Brachytherapy (2015)

A) 3D T1W MRI images showing two different paraxial slices (left) and the choice of two points to determine the direction of one needle. Upper right and lower right show the position of points P1 and P2 in parasagittal and para-coronal views, respectively. B) T2 MRI images showing two different paraxial slices (left) and the choice of two points to determine the direction of one needle. Upper right and lower right show the position of points P1 and P2 in para-sagittal and para-coronal views, respectively
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4663216&req=5

Figure 0003: A) 3D T1W MRI images showing two different paraxial slices (left) and the choice of two points to determine the direction of one needle. Upper right and lower right show the position of points P1 and P2 in parasagittal and para-coronal views, respectively. B) T2 MRI images showing two different paraxial slices (left) and the choice of two points to determine the direction of one needle. Upper right and lower right show the position of points P1 and P2 in para-sagittal and para-coronal views, respectively
Mentions: The coordinates of these three points B1, B2, and B3, define the reference plane shown in Figure 1B. Additionally, two points describe the direction for each needle, which is a straight line. These points can be anywhere on the needle, so they are chosen by selecting two separate slices that present good image contrast. Figure 3A shows an example of a case reconstructed based on 3D T1W sequence. On the left-hand side, two para-axial images show the positions of points P1 and P2. The location of these two paraxial images are represented with a green line on the upper right (sagittal) and on the lower right (coronal) frames of Figure 3A. In the same way, an example of a case reconstructed based on T2W sequence is shown in Figure 3B.

Bottom Line: The differences observed in the positioning were significantly smaller than 1 mm in all cases.The presented algorithm also allows the use of only T2W sequence either for contouring or reconstruction purposes.The proposed method is robust and independent of the visibility of the artifact at the tip of the needle.

View Article: PubMed Central - PubMed

Affiliation: Radiotherapy Department, Benidorm Hospital, Benidorm, Alicante.

ABSTRACT

Purpose: There are perineal templates for interstitial implants such as MUPIT and Syed applicators. Their limitations are the intracavitary component deficit and the necessity to use computed tomography (CT) for treatment planning since both applicators are non-magnetic resonance imaging (MRI) compatibles. To overcome these problems, a new template named Template Benidorm (TB) has been recently developed. Titanium needles are usually reconstructed based on their own artifacts, mainly in T1-weighted sequence, using the void on the tip as the needle tip position. Nevertheless, patient tissues surrounding the needles present heterogeneities that complicate the accurate identification of these artifact patterns. The purpose of this work is to improve the titanium needle reconstruction uncertainty for the TB case using a simple method based on the free needle lengths and typical MRI pellets markers.

Material and methods: The proposed procedure consists on the inclusion of three small A-vitamin pellets (hyperintense on MRI images) compressed by both applicator plates defining the central plane of the plate's arrangement. The needles used are typically 20 cm in length. For each needle, two points are selected defining the straight line. From such line and the plane equations, the intersection can be obtained, and using the free length (knowing the offset distance), the coordinates of the needle tip can be obtained. The method is applied in both T1W and T2W acquisition sequences. To evaluate the inter-observer variation of the method, three implants of T1W and another three of T2W have been reconstructed by two different medical physicists with experience on these reconstructions.

Results and conclusions: The differences observed in the positioning were significantly smaller than 1 mm in all cases. The presented algorithm also allows the use of only T2W sequence either for contouring or reconstruction purposes. The proposed method is robust and independent of the visibility of the artifact at the tip of the needle.

No MeSH data available.