The shielding that reduces hand dose is the shielding people actually use. Getting the L-block window at the right height, matching syringe shields to the barrels the hospital buys, and why a vial shield with a window stays on and a solid one does not.
Bench shielding is the only radiation protection in a department that depends entirely on human behaviour. A shielded wall protects whether or not anybody thinks about it. An L-block protects only if somebody works behind it, and a syringe shield only if it fits well enough that the technologist does not put it down. The questions here are practical rather than physical. Thickness is the easy part.
An L-block puts a shielded body between the operator and the dose while a lead glass window keeps the work in view, and it fails in two ways, both geometric. If the window sits below the operator's eye line for the bench height they actually use, they lean over the top and put their head and chest in front of the shielding. And if there is not enough clear worktop behind it for a vial shield, syringe, swab tray and sharps bin, the dose gets drawn beside the block. The answer is a deeper bench, not a thicker block.
Nuclear Shields make tabletop L-blocks in 5, 12.5, 20, 30 and 50 mm of lead, the 20 mm version measuring 422 x 505 x 580 mm overall. Diagnostic technetium work is well served at 20 to 30 mm, and the 50 mm class exists for 511 keV and therapy activities. Over-specifying has a cost: a block heavy enough to be awkward gets pushed to the back of the bench.
A syringe shield is specified by the internal diameter and length of the barrel it accepts, and the ranges are narrow. Nuclear Shields list 1 ml shields at 8.8 x 72, 8.8 x 76 and 11.5 x 76 mm, 2 ml at 11.5 x 53 and 11.5 x 60 mm, 3 ml at 11.5 x 65 and 11.5 x 69 mm, 5 ml at 15.4 x 61, 65 and 68 mm, 10 ml at 18.2 x 75 and 18.2 x 85 mm, and 20 ml at 22.4 x 89 and 22.4 x 96 mm. Two nominally identical 5 ml syringes from different manufacturers are not necessarily the same barrel, so measure what the hospital actually purchases before ordering: a shield that grips too tightly or lets the barrel rattle ends up in a drawer. Then choose the type by what must stay visible and what you are shielding against.
Vials come out of shields for two reasons: somebody needs to read the label, and somebody needs to see how much is left. A shield that prevents either gets defeated several times a day. Tungsten vial shields come in 3, 4 and 6 mm walls with magnetic or sliding closures and an internal space of 27 x 61 mm, colour coded so a hot lab can keep one radionuclide separate from another at a glance. Lead glass versions pair a tungsten body with a window so the contents and the level stay visible, with an internal space of 33 x 58 mm. Check your kit and generator vials against those figures: one that will not sit properly gets handled bare.
Extremity dose is not accumulated during shielded operations. It accumulates in the gaps: a loaded syringe on the bench, a vial standing out while paperwork is written, a swab carried to a bin at the far end of the room. Four inexpensive items close them.
None of these change the physics. They change the number of seconds a day a hand spends near unshielded activity, which is what the ring dosimeter measures. If extremity readings are creeping up, the fix is almost always in this list rather than in a thicker L-block, and finding it is the job of the investigation described in personal dosimetry in a Bangladeshi nuclear medicine department.