title: Standardization of techniques for using planar (2D) imaging for aerosol deposition assessment of orally inhaled products.
abstract: Two-dimensional (2D or planar) imaging with (99m)Tc radiolabels enables quantification of whole-lung and regional lung depositions for orally inhaled drug products. This article recommends standardized methodology for 2D imaging studies. Simultaneous anterior and posterior imaging with a dual-headed gamma camera is preferred, but imaging with a single-headed gamma camera is also acceptable. Correction of raw data for the effects of gamma ray attenuation is considered essential for accurate quantification, for instance, using transmission scanning with a flood-field source of (99m)Tc or (57)Co. Evidence should be provided of the accuracy of the quantification method, for instance, by determining "mass balance." Lung deposition may be expressed as a percentage of ex-valve or ex-device dose, but should also be given as mass of drug when possible. Assessment of regional lung deposition requires delineation of the lung borders, using X-ray computed tomography, radioactive gas scans ((133)Xe or (81m)Kr), or transmission scans. When quantifying regional lung deposition, the lung should be divided into outer (O) and inner (I) zones. A penetration index should be calculated, as the O/I ratio for aerosol, normalized to that for a radioactive gas or transmission scan. A variety of methods can be used to assess lung deposition and distribution. Methodology and results should be documented in detail, so that data from different centers may be compared. The use of appropriate methodology will provide greater confidence in the results of 2D imaging studies, and should allay concerns that such studies are qualitative or semiquantitative in nature.
authors.affiliation: Scientific Consultant, Hunstanton, Norfolk, United Kingdom. steve.newman_1@btinternet.com
authors.forename: Stephen
authors.initials: S
authors.lastname: Newman
authors.forename: William D
authors.initials: WD
authors.lastname: Bennett
authors.forename: Martyn
authors.initials: M
authors.lastname: Biddiscombe
authors.forename: Sunalene G
authors.initials: SG
authors.lastname: Devadason
authors.forename: Myrna B
authors.initials: MB
authors.lastname: Dolovich
authors.forename: John
authors.initials: J
authors.lastname: Fleming
authors.forename: Sabine
authors.initials: S
authors.lastname: Haeussermann
authors.forename: Claudius
authors.initials: C
authors.lastname: Kietzig
authors.forename: Philip J
authors.initials: PJ
authors.lastname: Kuehl
authors.forename: Beth L
authors.initials: BL
authors.lastname: Laube
authors.forename: Knut
authors.initials: K
authors.lastname: Sommerer
authors.forename: Glyn
authors.initials: G
authors.lastname: Taylor
authors.forename: Omar S
authors.initials: OS
authors.lastname: Usmani
authors.forename: Kirby L
authors.initials: KL
authors.lastname: Zeman
mesh_terms: D000280:Administration, Inhalation; D000336:Aerosols; D016503:Drug Delivery Systems; D006801:Humans; D008168:Lung / Q000000981:diagnostic imaging*; D004364:Pharmaceutical Preparations / Q000008:administration & dosage / Q000737:chemistry / Q000378:metabolism; D011877:Radionuclide Imaging / Q000295:instrumentation / Q000379:methods* / Q000592:standards; D019275:Radiopharmaceuticals / Q000008:administration & dosage* / Q000737:chemistry / Q000493:pharmacokinetics; D013667:Technetium / Q000737:chemistry; D014018:Tissue Distribution
chemical_list: D000336:Aerosols; D004364:Pharmaceutical Preparations; D019275:Radiopharmaceuticals; D013667:Technetium