Mark S. Shiroishi, MD

Medicare activity in 2024

Official CMS public-use data for Mark S. Shiroishi, data year 2024 (released May 21, 2026). It covers Original Medicare (fee-for-service) patients only, not Medicare Advantage or other insurance. It shows volume, not quality or outcomes. CMS hides any count of 10 or fewer patients.

Most frequent services

1. Ct scan head or brain without contrast (70450)88 services
2. Mri scan of brain before and after contrast (70553)80 services
3. Mri scan of brain without contrast (70551)27 services
4. Ct scan of blood vessels of head with contrast (70496)20 services
5. Ct scan of blood vessels of neck with contrast (70498)15 services

Chronic conditions among these patients

Share of this clinician’s Original Medicare patients with each condition, as published by CMS (it describes the patients, not the care given).

• High blood pressure75%
• High cholesterol74%
• Arthritis66%
• Diabetes41%
• Ischemic heart disease41%
• Depression35%

Hospitals where Mark S. Shiroishi works

Medicare's Facility Affiliation Data lists Mark S. Shiroishi at these hospitals (updated October 2, 2026). Each hospital page shows its address, phone, emergency services, Medicare rating and all its clinicians. Star rating and emergency services: Hospital General Information (CMS), data updated October 26, 2026.

• Keck Hospital of USCLos Angeles, CA · Acute Care Hospital · Medicare rating: 5 of 5 stars · Emergency services: not listed by Medicare · CCN 050696

Practice locations

Addresses where Mark S. Shiroishi is enrolled with Medicare (CMS data updated October 2, 2026). The first 5 of 9; the Medicare profile lists all.

• 125 W Hungtington DrArcadia, CA 91007
• 1441 Eastlake Ave, Suite 2424Los Angeles, CA 90089 (323) 442‑2582
• 1500 San Pablo StLos Angeles, CA 90033
• 1516 San Pablo StLos Angeles, CA 90033 (800) 872‑2273
• 1516 San Pablo St, Suite L3100Los Angeles, CA 90033 (800) 872‑2273

Group practices

Medicare enrollment lists Mark S. Shiroishi as a member of these groups (CMS data updated October 2, 2026).

• USC Care Medical Group Inc1,380 clinicians in the group
• Keck Medicine of USC Imaging Centers LLC35 clinicians in the group

Specialties

• Diagnostic Radiologyprimary

Find other Diagnostic Radiology doctors in California →

Other radiologists in Arcadia

Clinicians with the same Medicare primary specialty in Arcadia, CA — not a recommendation.

• Brian Lee, MD
• Ashish R. Vyas, MD
• Christopher Ebner, MD
• Bryce D. Beutler, MD
• Hakan Sahin, MD
• Caroline Kilian, MD
• Juliana Atallah, MD
• Lucas A. Tsikitas, MD

All radiologists in Arcadia →

Other clinicians in USC Care Medical Group Inc

Medicare enrollment lists these clinicians in the same group practice — not a recommendation.

• Anilkumar O. Mehra, MD
• Gemma D. Rosas, PT
• Ray V. Matthews, MD
• Bich Lieu T. Duong, NP
• Sarah S. Cho, PA
• Keyur Patel, MD

Clinician information

Most corrections must be made at the source: clinicians update their NPI Registry record (NPPES) and their Medicare enrollment (PECOS); this page follows the next data release.

Sources

1. Facility Affiliation Data — Centers for Medicare & Medicaid Services (CMS), data updated October 2, 2026, retrieved October 29, 2026
2. Hospital General Information — CMS, data updated October 26, 2026, retrieved November 13, 2026
3. National Downloadable File (Doctors and Clinicians) — CMS, data updated October 2, 2026, retrieved October 29, 2026
4. Medicare Physician & Other Practitioners - by Provider — CMS, data year 2024, released May 21, 2026; Medicare Physician & Other Practitioners - by Provider and Service
5. NPI Registry — U.S. Department of Health and Human Services (NPPES), the clinician’s official record
6. Medicare Care Compare — official Medicare tool to look up clinicians