Longitudinal-positioning indicator and marking grid

1. A longitudinal-positioning indicator comprising:

a substrate including a first side and a second side, wherein the second side is at least partially coated with an adhesive, and wherein the substrate has a width extending in a first direction and a length extending in a second direction substantially orthogonal to the first direction; and

a set of longitudinal-positioning guidelines secured with the substrate, wherein:

the set of longitudinal-positioning guidelines has a length that extends in the second direction, and

the set of longitudinal-positioning guidelines is configured to indicate a relative position along the length of the longitudinal-positioning guidelines in the second direction based on a cross-section of the longitudinal-positioning indicator taken substantially orthogonally to the second direction.

2. The longitudinal-positioning indicator of claim 1 , wherein the set of longitudinal-positioning guidelines is disposed on the first side of the substrate.

3. The longitudinal-positioning indicator of claim 1 , wherein:

the substrate has a first radiopacity; and

the set of longitudinal-positioning guidelines has a second radiopacity that is greater than the first radiopacity.

4. The longitudinal-positioning indicator of claim 1 , wherein the set of longitudinal-positioning guidelines is formed from a plurality of guidelines of different lengths.

5. The longitudinal-positioning indicator of claim 4 , wherein:

the plurality of guidelines of different lengths are spaced apart and oriented substantially parallel to each other; and

each of the plurality of guidelines is aligned at one end and arranged based on length.

6. The longitudinal-positioning indicator of claim 5 , further comprising:

an index with a plurality of demarcations, each of the plurality of demarcations corresponding to a length of a guideline in the plurality of guidelines.

7. The longitudinal-positioning indicator of claim 1 , wherein the substrate further comprises:

an elongated body portion for the set of longitudinal-positioning guidelines; and

a margin portion extending from the elongated body portion.

8. The longitudinal-positioning indicator of claim 7 , wherein the margin portion includes a set of tabs.

9. The longitudinal-positioning indicator of claim 1 , further comprising:

a releasable backing secured to the substrate by the adhesive.

10. A marking grid for use in radiographic imaging, the marking grid comprising:

a substrate including a first side and a second side, wherein the second side is at least partially coated with an adhesive;

a set of lateral-positioning guidelines supported by the substrate; and

a set of longitudinal-positioning guidelines supported by the substrate, and

wherein the set of lateral-positioning guidelines and the set of longitudinal-positioning guidelines are configured to provide a pair of orthogonal coordinates that indicate a location within an area bounded by the marking grid, the location based on a cross-section of the marking grid taken substantially orthogonally to the set lateral-positioning guidelines.

11. The marking grid of claim 10 , wherein the substrate comprises a set of elongated apertures interspersed with the set of lateral-positioning guidelines in alternating fashion.

12. The marking grid of claim 10 , wherein the set of longitudinal-positioning guidelines includes a plurality of guidelines, and wherein the set of longitudinal-positioning guidelines is configured to indicate a longitudinal position within the area bounded by the marking grid based on a number of guidelines that appear in the cross-section of the marking grid.

13. The marking grid of claim 12 , wherein the plurality of guidelines includes guidelines of a different length, arranged in a stair-step configuration.

14. The marking grid of claim 12 , wherein the marking grid further comprises:

an index with a plurality of demarcations, each of the plurality of demarcations corresponding to a length of a guideline in the plurality of guidelines.

15. The marking grid of claim 10 , wherein the set of longitudinal-positioning guidelines includes a set of reference guidelines and an auxiliary guideline, and wherein a longitudinal-positioning coordinate is determined based on a distance between the set of reference guidelines and the auxiliary guideline.

16. The marking grid of claim 15 , wherein the set of reference guidelines includes two parallel lines, and wherein the auxiliary guideline has a cross-section that differs from cross-sections of the two parallel lines.

17. The marking grid of claim 15 , wherein the set of reference guidelines includes one line, and where the set of reference guidelines and the auxiliary guideline have rectangular cross-sections.

18. A method for identifying a location for needle insertion into a patient within an area defined by a marking grid, the marking grid including a set of lateral-positioning guidelines and a set of longitudinal-positioning guidelines configured to provide reference markers based on a cross-section of the marking grid taken substantially orthogonally to the set of lateral-positioning guidelines, the method comprising:

identifying, from a radiographic image, a target internal structure;

identifying, from reference markers associated with the set of lateral-positioning guidelines, a lateral-positioning coordinate for the target internal structure;

identifying, from reference markers associated with the set of longitudinal-positioning guidelines, a longitudinal-positioning coordinate for the target internal structure; and

determining, with reference to visual indicators on the marking grid, the location for the needle insertion using the longitudinal-positioning coordinate and the lateral-positioning coordinate.

19. The method of claim 18 , wherein the set of longitudinal-positioning guidelines includes a plurality of guidelines, and wherein the set of longitudinal-positioning guidelines is configured to indicate a longitudinal position within the area bounded by the marking grid based on a number of guidelines that appear in the cross-section of the marking grid.

20. The method of claim 18 , wherein the set of longitudinal-positioning guidelines includes a set of reference guidelines and an auxiliary guideline, and wherein a longitudinal-positioning coordinate is determined based on a distance between the set of reference guidelines and the auxiliary guideline.