DIAGNOSTIC RADIOLOGY RESIDENCY TRAINING PROGRAM PROGRAM ...
DIAGNOSTIC RADIOLOGY RESIDENCY TRAINING PROGRAM
OHIO UNIVERSITY COLLEGE OF OSTEOPATHIC MEDICINE
Michael W. Keleher, D.O., Program Director
Nicholas T. Peponis, D.O., Chairman
Requirements of Applicants:
All applicants should be graduates of a college of osteopathic medicine approved by the
American Osteopathic Association. The applicant shall have satisfactorily completed a
minimum one-year AOA approved internship. The applicant should meet the moral, ethical, and
professional requirements of the hospital. The applicant shall be licensed to practice medicine in
the State of Ohio.
The Residency Training Program in Radiology and Nuclear Medicine is to be conducted under
the direction of the Chairman of the Department and under the direct supervision of the Program
The program will be supported at the teaching level by other associate radiologists of the
Richard W. Adams, DO J. James Jerele, DO
Raja A. Jurdi, MD Les Hood, DO
Thomas M. Anderson, DO Arthur L. Antry, DO
Nicholas T. Peponis, DO Ryo Benson, MD
Roger S. Ruben, DO Derry Cole, DO
Roy E. Farneman, DO
A residency is offered for a period of one year, subject to renewal upon recommendation
of the program director by approval of members of the Department of Radiology &
Nuclear Medicine. The training period shall include a minimum of four (4) years. A
resident shall not expect automatic renewal of contract for the training program. The
resident’s performance shall be reviewed on an annual basis by the trainers in the
department of Radiology/Nuclear Medicine as well as other individuals involved in the
medical education at Doctors Hospital. The resident shall meet the standards required by
the Department, Doctors Hospital/OUCOM, and the AOA and AOCR.
The residency training program is 48 months in duration and shall include the following areas of
1. General radiology including chest, musculoskeletal, GI, GU, emergency, radiology – 17
months (includes mammography 3 months)
2. Nuclear Radiology – 6 months equivalent
3. Diagnostic Ultrasound – 4 months equivalent
4. Angiography and Interventional radiology – 4 months
5. Computed tomography – 4 months equivalent
6. Pediatric radiology – 3 months
7. Neuroradiology – 2 months
8. Magnetic Resonance Imaging – 4 months equivalent
9. 9. Elective – 4 months AFIP
The general educational content of the program is intended to include:
1. The integration of osteopathic concepts as appropriate to the specialty.
2. A minimum of 24 hours of formal instruction in radiation biology including, the cellular and
subcellular effects of radiation, tissue kinetics and responses, radiological facts modifying
effects, total body effects and histopathological responses.
3. Up to 80 hours of education in the principles of x-ray and Nuclear Physics or a minimum of
40 hours of intensive training given by a qualified physicist.
4. Training in nuclear radiology that provides appropriate instruction in Physics,
instrumentation, radiopharmacology, radiation protection, the clinical evaluation of patients,
participation in performance and interpretation of nuclear studies and the performance of routine
radionuclide organ imaging sufficient to meet NRC licensure requirements.
5. Training in magnetic resonance imaging that includes exposure to both imaging techniques
and principles as well as interpretation.
6. Weekly instruction by the Department of Radiology in the relationship of clinical radiology
and Physics as well as integration of training with other departments, such as surgery, pathology,
medicine, and pediatrics.
7. Opportunities for the resident to follow patients to surgery for the purpose of correlating
radiologic findings and to follow cases to pathology to develop an understanding of the gross
pathology of surgical specimens. The resident shall review gross and microscopic findings of
tissue in cases of special interest to the Department of Radiology, attend autopsies, especially
those of interest to the Department of Radiology and participate in clinical-pathologic and tumor
PLAN --- The majority of the routine training in diagnostic radiology is given on a progressive
basis, dependent upon the increasing competence of the individual resident. However, there are
monthly periods of time during which, in addition to his routine work, each resident is assigned
to a service and is responsible for all of certain examinations and specialized procedures
performed under the supervision of a staff radiologist. Reading from the basic reading list
should relate to the studies performed on that service. Thus, each resident has an equal
opportunity to assume responsibility and receive personal instruction in all of the special phases
of diagnostic radiology, nuclear medicine, computed tomography, ultrasound and magnetic
Instruction in Physics is provided by lectures and demonstrations in Nuclear Medicine, by a
consulting physicist and by staff radiologists. The department provides resident courses in
Physics and radiology as required.
The Radiology Department library as well as the hospital library contains important and current
textbooks, journals, and references on basic sciences, clinical disciplines related to radiology in
addition to the majority of texts and journals related directly and exclusively to Radiology and
Nuclear Medicine. Journals are bound regularly and kept in the hospital library for
Reference. Every resident in Radiology is expected to keep up with the required reading list on
their own time, emphasizing recommended selections in basic texts that are fundamental and of
Because of the tremendous increase in the scope of the entire field of Radiology, it is important
that the resident discipline themselves from the very beginning to gain maximum benefit from
each portion of the training program. Every resident will be given equal opportunity. Some may
progress more rapidly due to individual abilities, but those who are slower to learn are given the
extra needed teaching help by the staff in Radiology.
There will be informal and formal teaching responsibilities by the resident to fellow residents in
other departments, interns, clinical clerks, and medical students of Ohio University College of
Osteopathic Medicine. Teaching others is an important part of the resident’s training program
and learning course. It is assumed that the resident will have the obligation of acquiring basic
information regarding the various aspects of radiology from texts, journals, etc. The prime
method of teaching will be on a one-to-one “over the shoulder” basis at the viewbox, fluoroscopy
table, and at daily required morning educational hours.
Practical work under direct supervision, together with didactic work, will include the following
A. Radiographic anatomy and physiology
B. X-ray and radiation physics
C. Operative radiographic procedures
D. Darkroom procedures and film processing
E. Fluoroscopic procedures and precautions
Image intensifiers & television, videotape, & cine radiography
F. Radiographic interpretations
1. Bone, joint, & associated pathologies
2. Chest – cardiovascular, pulmonary
3. Biliary tract – oral, operative, percutaneous, T-tube cholangiography
4. Gastrointestinal tract including hypotonic & air contrast studies
5. Urinary tract – IVU, retrograde, and voiding cystourethrography
6. Sinus and mastoid disease – skull
7. Special examination and procedures, including:
c. Myelography (cervical, thoracic, lumbar)
d. Mammographic needle localizations, stereotactic breast biopsy
e. Endoscopic retrograde cholangio-pancreatography
f. Linear tomography
g. Angiography & venography – visceral, peripheral, cerebral
k. Interventional urinary tract & biliary tract procedures
l. Percutaneous biopsy & drainage procedures
m. Angioplasty – peripheral, aortic, renal
8. Tumor pathology and diagnosis
9. Radiobiology and radiopathology
10. Ultrasonography including Doppler imaging
11. Computerized tomography
12. Magnetic Resonance Imaging, Neuro, spine, body, extremity, vascular, abdominal, and
1. Morning educational meetings are mandatory and of great value. The Program is under the
supervision of the Program director and the most senior resident. These are held daily
throughout the year and include lectures on Physics by a physicist, lectures, slides with
audio, films, and videotapes on diagnostic and therapeutic aspects of Radiology, Nuclear
Medicine, and Ultrasound as well as diagnostic film conferences. The Educational
Committee designee will construct monthly lecture and conference schedules with input from
the residents and Radiologists.
2. As a radiologic consultant to clinical clerks, interns, and resident staff, with consultation
from staff radiologists and under their supervision.
3. Participate in the scheduled lecture program for residents and provide radiological teaching
for interns, clinical clerks, and medical students.
4. Maintain an up-to-date log documenting statistical report of work activities, conferences
attended, reading assignments, in house or outside training, i.e., physics, and radiobiology.
The log should reflect correlation of radiographic, nuclear medicine, ultrasound,
computerized tomography, and magnetic resonance imaging findings on interesting cases
with surgical and autopsy findings. The log will be submitted to the Program Director
monthly for approval and be available semi-annually for the DME.
5. Care of emergency room and outpatient clinic patients insofar as radiology is involved in
their diagnosis and care, under supervision.
6. Participate in activities of Tumor Board.
7. Attendance of a course in Radiology and radiation Physics, Radiology, Physics of Nuclear
Medicine and Clinical Nuclear Medicine – this might include the AOCR Physics review
courses and/or courses available from other entities at the discretion of the Program Director.
8. Attend applicable Ohio State University Radiology Lectures daily Monday through Friday
12:00 noon at the discretion of the Program Director.
9. Attend scheduled Clinical Pathological Conferences held for intern and resident staff.
10. Attend grand round programs put on by the various specialty groups when applicable and at
the discretion of the Program Director.
11. Attend Central Ohio Radiological Society Meetings.
Post Graduate Work
Residents may be afforded an opportunity to take post-graduate courses. All post-graduate work
must have prior approval from the department chairman and/or chairman of the Program
First year – 1 week post graduate work
Second year – 1 week post graduate work
Third year – 1 week post graduate work
Fourth year – 1 week post graduate work
Arrangements have been made for each resident to attend the following major areas of study
away from Doctors Hospital. On certain occasions, a position might not be available for a
resident and other areas of study may possibly be substituted. Unless given further notice from
the Program Director Chairman, each resident should plan to attend these areas of study during
1. Armed Forces Institute of Pathology – 6 weeks
2. Children’s Hospital – 3 months
3. Breast Imaging Basics Course
4. MRI Basics Course
5. Elective study (must have prior approval of site by Educational Committee)
Any additional work would have to be considered on an individual basis with the final decision
to be made by the Program Director Chairman.
Note: This time does not count against your “post-graduate” time.
All other courses such as the Radiologic Society of North America, American Roentgen Ray
Society, etc. counts toward your post-graduate time and your attendance at these courses will be
at your discretion and your allowed “post-graduate” time.
Each resident is permitted 20 days paid vacation per year. This vacation time may be used at the
resident’s discretion including attendance at post-graduate courses. All vacation time must be
scheduled with the Program Director and the Chief Resident in Radiology and the Medical
1. Daily morning educational hours are held from 7:00 a.m. – 8:00 a.m.
Monday through Friday with provided rotating schedule and attending
Staff. Case discussions, journal review, film conferences, and formal
Lectures will occur during this time period.
2. Tumor Board – Tuesdays weekly 7:00 a.m. to 8:00 a.m.
3. Formal physics lecture 2 hours per week by staff physicist.
4. OSU noon lecture series, daily 12:00 to 1:00 p.m.
5. Central Ohio Radiological Society Meetings 6 x yearly
Unscheduled time off during the workday (i.e. doctor’s appointment) should have prior approval
by the Program Director members or department chairman. The resident must always arrange
coverage of his service for the period of absence.
The following hours should be considered minimum daily hours, and the resident should stay
later or arrive earlier if activity is present on his service.
7:00 a.m. to 5:00 p.m. daily
7:30 a.m. to 7:00 p.m. Saturday/Sunday
Night Resident: 5:00 p.m. to 7:00 a.m. / 7:00 p.m. to 7:00 a.m. Saturday/Sunday
The resident on call should be present for all emergency procedures and studies even if a
radiologist is present.
Night call will be assigned in 1-week blocks and rotated among all residents. First year residents
will not be placed on night call until 6 months after their start date. Night call schedule is to be
determined by the chief resident.
Each resident is expected to interpret and dictate reports on at least 10 cases per weekday. It will
be the responsibility of the resident to acquire these cases to read from the radiologist on the
service. The amount of dictation should increase with the resident’s seniority in the program and
will vary depending on the service and individual radiologist.
Department meetings are held quarterly. Interns, externs, and other residents are invited to
In addition, you are strongly urged to attend the regular educational meetings of the Central Ohio
Radiologic Society as well as other locally available radiologic meetings.
Duties of the Chief Resident
The chief resident will be responsible for assigning case presentations, lectures to externs,
interns, and on-call schedule. He or she will also coordinate vacation schedule through the
Educational Committee with requests in writing at least 3 months in advance. It is also his
responsibility to inform each new resident that a log must be kept by each resident documenting
training in radiophysics, radiobiology, and therapy. These should include a statistical report of
work activities, conferences attended, reading assignments, and etc. He or she will be
responsible for coordination of outside student rotation schedule.
The resident must follow the AOCR guidelines for resident scientific exhibits. All exhibits are
accepted with the understanding that they are original and timely contributions to the
advancement of medical diagnosis and treatment with radiologic methods. The AOCR requires
that each resident submit one display at the annual AOCR Meeting no later than their 3rd
Scientific exhibit requirements are outlined in APPENDIX I.
Nuclear Regulatory Commission Requirements
To qualify for medical use of Byproduct Material Groups I, II, and/or III, a physician should
1. 200 hours of basic radioisotope handling techniques including:
a. Radiation Physics and instrumentation – 100 hours
b. Radiation Protection – 30 hours
c. Pertinent mathematics – 20 hours
d. Radiation biology – 20 hours
e. Radiopharmaceutical chemistry – 30 hours
2. 1,000 hours of clinical training and experience covering all appropriate types of diagnostic
procedures to include examination of patients, calibration of dose and dosimetry, administration
of dose, follow-up of patient and discussion of case history with preceptor.
Note All of the above may be satisfied concurrently in the same training program.
3. If therapy approval is desired, the above number of hours must include specific training as
a. I 131 for hyperthyroidism and/or cardiac conditions 10 cases.
b. P-32 for polycythemia vera, leukemia, and/or bone metastases – 3 cases.
c. Colloidal P-32 for intracavitary treatment – 3 cases
d. I 131 for thyroid carcinoma - 3 cases
The Radiology Department and its staff as well as the Hospital Library have available many slide
lectures, cassettes, and videotapes dealing with Radiology & Nuclear Medicine. These will be
used to enhance the training program and further information can be obtained from the hospital
librarian. In addition, the Department of Radiology has a museum teaching file. Museum cases,
making slides, preparing conferences and participating in interdepartmental conferences, are to
be an ongoing important part of the training program.
Qualities of a “Typically Effective” Radiology Resident
1. Radiographic Technique;
The resident understands the operation of diagnostic machines, methods of performing
roentgenographic examinations, and procedures for processing films to the extent that resident
supervise technicians. The resident is able to recognize common errors in technique and to
2. Film Interpretation:
a. The resident carries on a steady, sustained effort in reading and interpreting films,
including extra hours of work, when necessary. Rate of reading (number of films per
hour; number of films per day) is variable, based on the type of films being studied,
b. comparison with old films, associated research, such as reference texts, clinical
records, contacting ward physicians; but overall rate over a long period should
compare favorably with that of colleagues of equal status.
c. The resident interprets films with a percentage of error consistent with his level of
d. The resident renders a literate report dictated with clarity and succinctness and
without ambiguity which might lead clinicians into unnecessarily extensive time-
3. Consultation with other physicians:
a. The resident is responsible for rendering prompt reports to proper individuals in cases
of “emergency” films and cases studied under his supervision.
b. The resident presents a clear-cut discussion of films.
c. The resident must be tactful and cooperative, exhibiting an interest in the clinician’s
Fluoroscopic studies include those involving examination of the chest, upper gastrointestinal
tract, large bowel, gallbladder, lungs, spinal canal, and special studies.
a. He/she performs fluoroscopic examinations requiring knowledge of contrast materials and
hazards in their use.
b. The quantity and quality of his work compares favorable with that of colleagues of equal
5. Teaching Conferences
The resident presents films, lectures, and demonstrations at teaching conferences. He/she
should be properly prepared and make credible presentations.
6. Preparation of cases for teaching files
a. The resident is responsible for maintenance of teaching, collecting, and for new
b. Each resident is responsible for contributing cases to the teaching file, and is encouraged
to contribute as many as possible.
a. The resident takes their turn at call, according to roster, and assumes responsibility for
operation of the department in the absence of the chief.
b. The resident should have a sense of responsibility and loyalty toward the department.
And should present a favorable image and give the Radiology Department “character”.
c. The resident exercises economy in care and maintenance of supplies and equipment.
d. The resident carries out assigned administrative tasks dependably and expeditiously.
In all of the resident’s duties and functions, he/she must exhibit a progressive degree of
improvement in his/her work, and in the ability to work with decreasing supervision.
Moonlighting” must no interfere in any way with the performance as a radiology resident at
With prior approval, limited moonlighting during the 3rd
years may be allowed. It is
understood that all such radiology moonlighting must be pre-approved by the resident trainer.
The resident must realize that he/she must obtain their own malpractice insurance. Hours
moonlighting are considered as a part of the 80-hour workweek as specified by the AOA.
The Journal Club is a valuable and hopefully stimulating part of any residency program. The
responsibility to have a successful Journal Club lies with the residents. The radiologists
definitely are responsible to assist and should attend, but the residents must initiate this meeting.
The Journal Club will either be scheduled monthly during the morning educational hour or
separately after hours.
All residents are encouraged to utilize the following journals, which are available either in the
department or hospital library.
The American Journal of Roentgenology
Acta Radiologica - Diagnostic
Acta Radiologica – Therapeutic
British Journal of Radiology
Canadian Journal of Radiology
Radiologic Clinics of North America
Seminars in Nuclear Medicine
Seminars in Roentgenology
Seminars in Oncology
Journal of Nuclear Medicine
Journal of Clinical Ultrasound
The Radiology Department also has a large and varied selection of textbooks in Radiology,
Radiation Therapy, Nuclear Medicine, CT, Ultrasound, and MRI. The most recent acquisitions
are posted on the bulletin board in the residents office. The resident should, on his own initiative
read material of interest and particularly regarding the rotation that he is assigned to. The
radiologist will hopefully help in directing your reading (maybe even give reading assignments),
but this cannot be guaranteed and will depend on the various rotations to which you are assigned.
The department makes every effort to keep up with ever expanding and expensive proliferation
of educational materials available on the market including textbooks and videotapes. This is by
no means an all-inclusive list and will become antiquated yearly with continued progress and
publications. This list is probably outdated even as you are reading it now.
The minimum RECOMMENDED library reference textbooks are as follows: APPENDIX II
The first year primarily involves the acquisition of basic science fundamentals and general
clinical knowledge in diagnostic radiology. Reading assignments in texts and journals stress
fundamentals. Initial exposure to computed tomography, ultrasonography, and nuclear medicine
will occur in this year.
Specifically during the first week, part of the time should be spent with department directors and
coordinators in order to obtain appreciation of the general operation of the department, as
familiarity with the daily routine is necessary. This can best be accomplished by your following
outpatients and house patients from the time they present themselves to the department to the
time they leave. Familiarize yourself with the clerical aspects of our filing system; follow the
patient through the actual x-ray procedure, the films through the darkroom into the jacket, and
subsequent filing. This should be done without interfering with the smooth and efficient
operation of the department and without going into unnecessary detail. Primarily you are to
observe, listen, and at the appropriate time ask pertinent questions. You are also to assist and
participate with intravenous and other radiologic procedures when requested. During this week
you become informed as to your relationship to the hospital and its other departments by
conversations with fellow residents.
Second week to the third month, although this time interval is flexible and dependent upon your
progress, you are to spend whatever time is required in the darkroom to learn darkroom
procedure and processing operation. During this time, it is wise to have read the theoretical
aspects of the darkroom operation. Staff radiologists and senior residents will teach you
fluoroscopic techniques, familiarize you with radiation hazards, protective devices, and contrast
media. By about the third month, all residents when not involved with department routine i.e.,
fluoroscopy, intravenous studies, therapy, isotope procedures, checking films and patients, are to
spend full time observing and listening to film interpretation. You are to assist in every way
in the disposition of cases. This includes phone calls to referring physicians, residents, interns,
etc., to obtain or communicate information. Also at this time, you are encouraged to ask
appropriate questions concerning film interpretation. During lulls and off-hours, textbook and
current literature is encouraged.
Suggested texts for the first six months:
1. Christiansen Radiological Physics
2. Normal Radiographic Anatomy by Meschan
3. Radiology by Traveras
4. Radiology by Brant & Helms
During the first year, your reading should stress radiography of the chest, GI, and genitourinary
tract as well as Orthopedic Radiology.
It is important for radiologists to be able to take their own films and instruct technologists as to
additional views, technique modification, etc. when they are presented with difficult cases.
During this year, therefore, emphasis should be placed on radiographic technology.
The first year resident will be on backup call with a senior resident from the beginning of the
residency. The schedule will be determined by the chief resident. All calls the first 3 months
will be with an assigned senior resident. Depending upon individual progress at or about the
second to the third month, the resident will start to independently take after-hours calls. He may
be backed up by a more senior resident and staff radiologist when necessary.
By the third to the sixth month, the resident should be able to perform gastrointestinal,
myelographic, arthrographic, cholangiographic and cardiac fluoroscopy. He must however
consult with a staff radiologist when difficulties are encountered.
During this period, the resident begins to report on his findings. Throughout his residency, all
interpretations are to be checked by a staff radiologist whose name goes on the report, who
reviews the films, and corrects any errors. The dictating resident’s initials also go on the report.
During the second year in addition to the on-going training and activity of the first year, the first
half of this year will emphasize techniques, indications, and interpretation of additional special
procedures. These include:
5. Linear tomography
7. Computed tomography
8. Magnetic Resonance Imaging
During this year, you are expected to participate in radionuclide treatment administration and
post-therapy rechecks. In addition, you are encouraged to actively partake in the discussions in
Tumor Board Meetings as well as in clinical staging of neoplasms and conversations dealing
with the efficacy of utilizing surgery, radiation therapy, chemotherapy, or any combination of
these modalities in the management of oncologic problems. It is anticipated that there will be
close collaboration in these matters with the Department of Medicine, Surgery, and Pathology.
During the first part of the third year, correlation of radiographic and nuclear medicine imaging
procedures in tumor diagnosis will be stressed. Two months will be spent in the Nuclear
Medicine laboratory for exposure to in vitro and in vivo imaging procedures. This will
supplement and reinforce the theoretic or didactic experience obtained in lectures.
In addition, there should be involvement in general and special radiographic procedures as well
as the responsibility of guiding junior residents. Training in diagnostic ultrasound and
fundamentals of computerized axial tomography and magnetic resonance imaging will be
provided. This will include basic physics, instrumentation, techniques, cross-sectional anatomy,
principles of examination, and interpretation.
Elective time, AFIP, and Children’s Hospital experiences will occur in the third year or the
beginning of the fourth year.
As well as continued building of your general knowledge and expertise in the multiple modalities
of imaging to which you have been exposed to, you will apply concentrated effort to the
acquisition of angiographic and interventional diagnostic and therapeutic skills.
Additional emphasis should be placed upon the more specialized exams within the various
disciplines such as Nuclear Cardiology, Nuclear SPECT Imaging, Computed Tomographic
reconstruction and 3D Imaging as well as carotid, Doppler, and fetal ultrasound imaging.
Completion of elective time will occur in first half of the fourth year if not previously completed.
1. Fraser and Pare: Diseases of the chest
2. ACR Syllabus Series
3. REED: Chest Radiology Plain Film Pattern and Differential Diagnosis
1. Eisenberg: Gastrointestinal Radiology: A Pattern Approach
2. ACR Syllabus
3. Laufer: Double Contrast GI Radiology
4. Singleton: Radiology of the Alimentary Tract in Infants and Children
1. Meyer: Dynamic Radiology of the Abdomen
2. Davidson 2nd
Ed: Radiologic Diagnosis of Renal Parenchymal Disease
3. ACR Syllabus Series
4. Emmett and Witten: Clinical Urology
1. Resnick: Bone and Joint Imaging
2. ACR Syllabus Series
3. Weissman: Orthopedic Radiology
4. Keats: Normal Roentgen Variants
5. Freiberger, Kaye: Arthrography
1. ACR Syllabus
2. Homer: Mammography-Interpretation
1. Som: Head and Neck Imaging
2. Latchaw: MR and CT Imaging of the Head, Neck and Spine
3. Osborn: Introduction of Cerebral Angiography
4. Cohen: MRI of Children
5. McLure: The Anatomic Basis of Neuroradiology
6. ACR Syllabus
1. ACR Syllabus
2. Caffey: Pediatric X-ray Diagnosis
3. Swischuk: Differential Diagnosis in Pediatric Radiology
4. Swischuk: Emergency Radiology of the Acutely Ill or Injured child
1. Mettler: Essentials of Nuclear Medicine
2. ACR Syllabus
3. Kadir: Diagnostic Angiography
1. Johnshonrude: A Practical Approach to Angiography
2. ACR Syllabus
3. Abrahams: Arteriography
1. Sardi and Sample: Diagnostic Ultrasound
2. ACR Syllabus
3. Callen: Ultrasonography in OB/GYN
4. Mittelstaedt: Abdominal Ultrasound
1. Lee and Sagel: CT Body with MRI Correlation
1. Stark and Bradley: Magnetic Resonance Imaging
2. MINCK: Musculoskeletal MRI
3. Beltram: MSK/MRI
4. Edelman: Clinical Magnetic Resonance Imaging