A new treatment regime is presenter using a low concentration formulation at a low dosage of hydrophobic photosensitizers (PS) that shows improved pharmacokinetics and an effective method for photodynamic therapy ("PDT"). The new formulation has better pharmacological effect compared to standard photosensitizer formulation with standard dosage. It was found that PDT treatments using the disclosed low concentration formulations provide for more accurate, more efficient and more convenient dosing. It was found that the inventive formulation； (1) reduces the time for a therapeutically effective level of photosensitizer to accumulate in diseased tissue； and, (2) reduces the time for achieving a sufficient ratio of photosensitizer in diseased tissue vs. healthy tissue. As a result, the formulation of the invention reduces the time interval between PS application/administration and irradiation (the drug-light interval or "DLI") and can provide for a "same day" PDT treatment option. The inventive formulation can be used for PDT treatment regimes where photosensitizers are administered in at least one preselected dose, including a low concentration therapy for PDT. In particular, when meta-(Tetrahydroxyphenyl)Chlorin (m-THPC) is the photosensitizer, then a concentration of 0.8 mg/ml to 0.04 mg/ml in a mixture of pure propylene glycol and ethanol in a 3:2 volume ratio accumulates in diseased tissue and differentiates between diseased tissue and normal tissue sufficiently quickly for 'one day' or overnight administration and activation treatment procedures to be possible.소수성 감광제(PS)용의 저농도 제형, 및 광역학 요법("PDT")을 위한 개선된 방법이 기술되어 있다. 기술된 저농도 제형을 사용한 PDT 치료는 보다 정확하고, 보다 효율적이며, 더욱 편리한 투여를 제공함이 확인되었다. 또한, 본 발명의 제형은 (1) 치료학적 유효량의 감광제가 질병 조직 내에 축적되는 시간을 감소시키고, (2) 충분한 비율의 질병 조직 내 감광제 대 건강한 조직 내 감광제를 달성하는 시간을 감소시킴이 확인되었다. 결과적으로, 본 발명의 제형은 PS 적용/투여와 조사 사이의 시간 간격(약물-빛 간격 또는 "DLI")을 단축시키고, "동일자" PDT 치료법을 제공할 수 있다. 본 발명의 제형은, PDT에 대한 저농도 요법을 포함하여, 하나 이상의 소정 용량으로 감광제가 투여되는 PDT 치료 계획에 대해
