Echogenic strands and spacers therein

1. A strand for use in brachytherapy, comprising:

encapsulating material;

a seed disposed within the encapsulating material;

a spacer formed by at least two strings twisted together, the spacer disposed within the encapsulating material and arranged adjacent to the seed;

wherein a length of the spacer is defined by a length of the at least two strings twisted together;

wherein the at least two strings of the spacer do not cover the seed; and

at least one chamber formed along the length of the spacer, the at least one chamber adapted to improve ultrasound visibility relative to the spacer;

wherein each of the at least one chamber is formed between the encapsulating material and a groove at an abutment of two of the at least two strings.

2. The strand of claim 1 , wherein the chamber has a generally helical shape.

3. The strand of claim 1 , wherein at least two chambers are formed between the spacer and the encapsulating material.

4. The strand of claim 1 , wherein the chamber is adapted to house one of a gas and a liquid having an ultrasonic reflectivity greater than an ultrasonic reflectivity of the patient tissue.

5. The strand of claim 1 , wherein the seed is a first seed; and further comprising:

a second seed disposed within the encapsulating material such that the spacer is arranged between the first seed and the second seed; and

the length of the spacer extends generally between the first seed and the second seed.

6. The strand of claim 1 , wherein the encapsulating material includes an elongated hollow tube.

7. A strand for use in brachytherapy, comprising:

encapsulating material;

a first seed disposed within the encapsulating material;

a second seed disposed within the encapsulating material;

a spacer formed by at least two strings twisted together, the spacer disposed within the encapsulating material and arranged between the first seed and the second seed;

wherein a length of the spacer that separates the first seed from the second seed is defined by a length of the at least two strings twisted together; and

at least one chamber having a generally helical shape formed along at least a portion of the length of the spacer, the at least one chamber adapted to improve ultrasound visibility relative to the spacer;

wherein each of the at least one chamber is formed between the encapsulating material and a groove at an abutment of two of the at least two strings.

8. The strand of claim 7 , wherein at least two helical chambers are formed between the spacer and the encapsulating material.

9. The strand of claim 7 , wherein:

the spacer includes three strings twisted together such that the spacer has a generally helical shape; and

three chambers are formed between the spacer and the encapsulating material.

10. The strand of claim 7 , wherein the chamber is adapted to house one of a gas and a liquid having an ultrasonic reflectivity greater than an ultrasonic reflectivity of the patient tissue.

11. The strand of claim 7 , wherein the at least two strings are formed of a polymeric material.

12. A strand for use in brachytherapy comprising:

a pair of treatment seeds;

a spacer adapted to separate the pair of treatment seeds from one another, the spacer including

three polymeric strings twisted together so that the spacer has an outer circumferential surface, wherein the three twisted together polymeric strings have an axial length adapted to substantially define a space between the pair of treatment seeds; and

three helical grooves, each helical groove being formed in the outer circumferential surface where two of the three polymeric strings abut and each helical groove extending along the length of the spacer; and

encapsulating material covering said seeds and said spacer such that said three helical grooves and said encapsulating material form three chambers that improve ultrasound visibility of the spacer.