KEYWORDS: Magnetic resonance imaging, Absorption, Signal detection, Tumors, Photodynamic therapy, Tissue optics, Luminescence, In vitro testing, Diffusion, Data acquisition
Losses in treatment light transmission during interstitial PDT were found to correlate with T1 hyperintensity in post-therapeutic non-contrast-enhanced T1-weighted MRI. This finding might be related to iPDT-induced early formation of methemoglobin.
Autosomal-dominant acute porphyria, a group of rare metabolic diseases, can lead to life-threatening neurovisceral attacks. Currently, no efficient screening test is available. Elevated urinary porphobilinogen (PBG) in addition to elevated porphyrins is highly specific for an attack of acute porphyria. This study proposes and evaluates a custom-made device, algorithm, and methods for a two-step quantification of urinary porphyrins and PBG. The first step is oxidation of the nonfluorescent porphyrinogens and subsequent fluorescence-spectroscopic determination of total urinary porphyrins (TUP) using second derivative spectral fitting. Photo-oxidation is compared with chemical oxidation methods. The second step is the quantification of porphobilinogen in case of elevated TUP. Heat-induced conversion products of PBG, namely uroporphyrin and porphobilin, are determined by fluorescence and absorption spectroscopy. The results of TUP quantification using the developed second derivative fitting algorithm show that both inaccuracy and imprecision were below 15% for concentrations of 0.2 μmol/L and higher. Heating of PBG generates porphobilin, which was detected using its absorption at 480 nm, and uroporphyrin, which was detected using its fluorescence at 615 nm. The change of fluorescence and absorption allows for a quantitative discriminability of PBG concentrations below 20 mg/L. For this indirect quantification of PBG, the resulting inaccuracy and imprecision are below 15% for both methods. The detection and quantification of TUP and porphobilinogen in urine with this proposed spectrophotometric approach is possible, requires only minimal sample processing and yields a result within 15 min, thus could be helpful in closing the screening gap for acute porphyria.
Autosomal-dominant acute porphyria, a group of rare diseases, can lead to life-threatening neurovisceral attacks. No efficient screening test is available today. Elevated urinary porphobilinogen in addition to elevated porphyrins is highly specific for an attack of acute porphyria. This study proposes and evaluates a custom-made device, algorithm, and methods for a two-step quantification of urinary porphyrins and porphobilinogen. The first step is oxidation of the nonfluorescent porphyrinogens and subsequent fluorescence-spectroscopic determination of total urinary porphyrins (TUP) using second derivative spectral fitting. Photo-oxidation is compared with chemical oxidation methods. The second step is the quantification of porphobilinogen in case of elevated TUP. Heat-induced conversion products of porphobilinogen, namely uroporphyrin and porphobilin, are quantified by fluorescence and absorption spectroscopy. Results show that the preferred method combination is TUP quantification (lower limit of quantification: 0.2 μmol / L) after photo-oxidation with subsequent absorption-spectroscopic determination of porphobilin after heating for indirect quantification of porphobilinogen (quantification range: 0 to 20 mg / L). Urinary porphobilinogen and porphyrins of one acute porphyria patient were quantified with <10 % deviation from an external reference determination. The spectrophotometric approach requires only minimal sample processing and yields a result within 15 min, thus closing the screening gap for acute porphyria.
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print or electronic format on
SPIE.org.
INSTITUTIONAL Select your institution to access the SPIE Digital Library.
PERSONAL Sign in with your SPIE account to access your personal subscriptions or to use specific features such as save to my library, sign up for alerts, save searches, etc.