Imaging Flashcards
imaging methods in obs and gynae?
US mainly CT MRI X ray screening fluroscopy (e.g hysterosalpingograms) functional imaging (PET CT)
indications for imaging?
pelvic pain
assessment of pelvic masses
investigation of abnormal menstrual bleeding
post menopausal bleeding
investigation of infertility
interventional radiology (e.g fallopian tube recanalisation, uterine artery embolisation etc)
how are US scan images stored?
electronically via PACS
- scans done outside of radiology clinic may not appear on PACS
2 main US techniques?
transabdominal
- scan using a standard general abdominal US transducer
- first line
transvaginal
- scan using a dedicated endocavity high-frequency transducer
- 2nd line
often both used in same appointment
how is transabdominal US performed?
pelvic organs are scanned through anterior abdominal wall
should perform a brief assessment of upper abdomen (ensure theres no hydronephrosis, ascites or any other pathology causing the pelvic symptoms)
patient must have a full bladder
why must the patient have a full bladder for transabdominal US?
distended bladder acts as an acoustic window
distended bladder displaces gas filled loops out of the pelvis (bowel gas scatters the US beam and degrades image quality)
advantages of TA US?
safe
readily available
no ionising radiation and therefore ideal for children and women of reproductive age
disadvantages of TA US?
difficult to obtain good image in obese patients or people with gaseous distention of bowel
operator dependant
difficult to produce exact same image every time the patient attends clinic which means US is often not used for assessing the response to cancer treatment etc
important landmarks in scanning for ovaries?
external iliac arteries
follow them down and should lead to ovary
how is TV (transvaginal) US different to TA?
higher frequency
shorter wavelength
better spatial resolution
requirements before TV US and why?
patient must have an empty bladder
- can make scan uncomfortable
- higher frequency is more likely to be scattered in body so transducer has to be close as possible to the target organ
advantage of TV US?
excellent depiction of pelvic organs
disadvantages of TV US?
more invasive
not suitable for individuals who have not been sexually active
can sometimes just demonstrate the tip of the iceberg and may not depict the full extent of large pelvic masses
how can TV US be used in ovarian disorders?
can assess size of ovary (e.g PCOS)
can visualise follicles
when is CT scan used?
2nd line after US in patients presenting with acute pain
assess post surgical complications (bowel obstruction, abscesses etc)
stage gynae malignancy (esp ovarian and endometrial)
assess response to treatment in patients after chemotherapy
advantages of CT?
quick
can do chest, abdomen and pelvis in one scan
can now get images in all 3 planes
disadvantages of CT?
high radiation dose
- especially to the ovaries
only used sparingly in children and patients of reproductive age
does not provide optimal depiction of different pelvic organs (MR better for tissue resolution)
dark, hypodense area within a cyst?
fat
- fat within a cyst = dermoid cyst
which type of MRI is more fluid sensitive?
T2
- fluid is bright
what is bright on T1 MRI?
fat, protein, blood
advantages of MRI?
excellent depiction of pelvic organs
no radiation so suitable in children and reproductive age patients
can give good idea about composition of soft tissue masses (do they contain fluid, fat, blood etc)
disadvantages of MRI?
time consuming
poor depiction of lung parencyma (therefore do CT is lung metastases suspected)
not tolerated in claustrophobia
contra-indicated in people with pacemakers, any artificial metallic implant, nerve stimulators, cochlear implants etc
uses of MRI in gynae?
cancer staging (esp cervical cancer)
further evaluation and characterisation of adnexal and uterine masses where pelvis US or other imaging didnt give diagnosis
evaluation of patients with sub-fertility
MR of pituitary gland is performed in patients with suspected prolactinoma
what is?
presence of endometrial tissue outwith the endometrium
diagnosis of endometriosis?
can be diagnosed via MRI
- endometriosis deposits contain altered blood and haemoglobin degredation products which cause characteristic MR signal changes
- altered blood returns high signal on T1 (white) and lower signal on T2 (grey)
- may need to do fat suppression as fat can also look white on T1
what is a dermoid cyst?
AKA ovarian teratoma
contain tissues derived from ectoderm, mesoderm and endoderm, so can therefore contain an admixture of many tissue types (hair, teeth etc) bu most are mainly fat
- the fat has predictable MR and CT charactersitics
what is HSG?
hysterosalpingography
X ray screening procedure (real time imaging) for assessment of tubal patency in infertile patients
can also assess outline of uterine cavity
procedure usually completed within 3-5 misn
how is HSG done?
cervix cannulated and radiopaque contrast instilled to fill uterine cavity
how is cancer staged?
TNM via CT
how does ovarian cancer disseminate?
via peritoneal spread
features of ovarian cancer?
ascites
omental and peritoneal nodules are common
sub-diaphragmatic deposits
deposits on surface of liver
malignant pleural effusion (can result from spread via pleuro-peritoneal communication)
ovarian cancer metastases sites?
lymph nodes
lung
liver
not common and tend to be seen in people where the cancer has been modulated by chemo or in cancers with the BRCA1 mutation
diagnosis of ovarian cancer?
initial diagnosis often by US
staging = CT
important factors when staging cervical cacner?
spread into parametrium
extension into vagina
infiltration of adjacent organs (rectum, uterus, bladder etc)
- metastases to regional lymph nodes (internal iliac and obturator)
which is better for cervical cancer imaging CT or MRI?
MRI (esp T2) is far better at depicting local disease but CT is often used to determine whether or not there are distant metastases
what is the best imaging for endometrial cancer?
transvaginal US best for detecting abnormally thickened endometrium
MR used to assess the degree of myometrial invasion but CT used to look for distant nodal metastases and pulmonary mets
