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CT Imaging

Specific CT protocols

• Renal colic: no contrast, assess for stones, sensitivity 96-100%, specificity 92-100%
• CT w/ contrast: diagnose/evaluate cysts/masses
• CT urography: 3-phase imaging for hematuria, assess non-contrast, arterial phase, and excretory phase
• CT fluoroscopy: useful for real-time imaging, such as biopsy, drain placement, mass ablation
• Adrenal protocol: assesses post-contrast washout to differentiate adenoma from other masses

Genitourinary indications

• Adrenal: masses, cyst
• Kidney: Bosniak class for cysts, masses, upper tract disease, stones, trauma, infection
• Bladder: infection, cancer, trauma
• Prostate: abscess/infection, cancer staging
• Scrotum: infection (Fournier)
• Testis: assess retroperitoneal disease

XR Imaging (Still images + Fluoroscopy)

Kidney/Ureter/Bladder (KUB) plain film

• Indications: assess residual contrast from prior imaging, assess stone disease, assess stent/drain position, assess ileus
• Stones: may not be visible due to overlying gas or radiolucency, can be confused with pelvic vascular calcifications (phleboliths)

Retrograde pyelogram

• Indications: ureteral obstruction (trauma, stone, neoplasm, hematuria), filling defects, allow for percutaneous access
• Option 1: cannulate ureteral orifice and inject to visualize entire upper tract
• Option 2: place catheter in renal pelvis, then inject while withdrawing to assess upper tract
• Tips: sterilize urine prior, avoid overinjection (can cause pyelovenous/lymphatic backflow), use open-ended or whistle-tip (prevents backflow) catheters, clear air before injecting
• May be difficult if hematuria or difficult angle of ureteral orifice with bladder neck

Loopogram/Pouchogram

• Indications: contrasted imaging of urinary diversions to assess for obstruction, infection, hematuria, pain, cancer recurrence after urinary diversion
• Technique: insert catheter into conduit/pouch past fascia, gently inject constrast until upper tracts opacify, may need oblique images to fully image loop/pouch, assess postdrainage imaging, reflux expected as long as patient has refluxing anastomosis

Retrograde urethrogram

• Indications: evaluate length/location/severity of urethral stricture, extravasation/hematuria after trauma, assess for foreign bodies, diverticula/fistula
• Technique: position patient obliquely, place penis on stretch, gently inject contrast via meatus

Cystography

• Technique: fill bladder via gravity with 300+mL or until patient uncomfortable
• Views: take pre-fill, max fill, and post-fill images, take in two-views
• No difference between XR and CT cystography for assessing bladder trauma
• Static: assess diverticula, fistula, trauma, post-surgical extravasation
• Voiding: assess reflux, bladder outlet obstruction, urethral integrity

IV Urography

• Bowel prep: consider to provide better visualization
• Technique: give contrast bolus 50-100mL, take pre-contrast, nephrogenic phase, and then q5min images until GU tract completely visualized
• Kidney appearance: 3-4x height of L2, usually between T11 and L3, runs parallel to psoas shadow, smooth contour
• On-table IVU: give 2mL/kg bolus (max 150mL), image after 2-10min, confirms kidney location, function, and extravasation
• Indications: supine/upright to confirm renal ptosis, confirm contralateral kidney in emergent trauma, assess stone materal layering

Angiography

• Can be diagnostic and therapeutic (perform embolization)
• Renal indications: renal artery stenosis, renal trauma, vascular imaging and embolization
• Adrenal indications: adrenal vein sampling

Nuclear Medicine

Radiotracer	Indication	Notes
99Tc-DTPA	Renal obstruction Renal function Renovascular hypertension Ureteral reflux	Dependent on GFR Excreted through filtration
99Tc-DMSA	Cortical defects Ectopic kidneys	Not good for imaging collecting system Bound in renal tubules
99Tc-MAG3	Renal plasma flow Renal obstruction Renovascular hypertension Renal transplant function	Cannot evaluate GFR (bound to plasma proteins) Cleared by tubular secretion
11C-choline	mPCa recurrence after treatment	Not useful for primary disease
18F-fluciclovine (Axumin)
99Tc	Bone scan for metastatic disease (PCa, RCC, BCa, UTUC)	Confirmatory imaging to differentiate cancer from benign lesions
Na18F
68Ga-PSMA (gozetotide)	mPCa in primary and recurrent cancer
Piflufolastat F-18
Flotufolastat F-18
68Ga DOTATATE	Neuroendocrine tumors	Useful for metastatic PCC or extraadrenal tumors, but not benign PCC
111In Pentetreotide
18F-DOPA (Fluorodopa)	Pheochromocytoma	Less sensitive for metastatic disease
18F-Dopamine (Fluorodopamine)
18F-FDG	Identify cancers using aerobic glycolysis	Locates areas of increased metabolic activity Assess for recurrence
123I MIBG	Identify pheochromocytoma	Preferred over 131I MIBG

Renal scintigraphy

• Indications: assess renal split function, renal obstruction, cortical defects/scarring, renal vascular hypertension, renal transplant function, vesicoureteral reflux
• Optimization of the results: ensure pre-imaging hydration, stop any medications that may affect renal blood flow, focus on location of renal anatomy
• Flow phase: 2s images x2min then 1s images x1min, assess abnormal vascular lesions
• Renal phase: 1min images x30min, assess split renal function and cortical defects
• Excretory phase: 1min images x30min, assess renal obstruction
• T1/2: time it takes from administration of diuretic (at maximum activity) for the collecting system to reach 50% activity
• Catheter placement: consider to maximize antegrade flow and prevent iatrogenic obstruction

Renal scintigraphy findings

• Decreased renal perfusion: flow curve with normal aortic spike, but no visualized renal uptake
• Obstruction (based on T1/2): present if > 20min, absent if < 10min, equivocal if 10-20min
• Transplant kidney: acute rejection shows poor perfusion/uptake, otherwise normal curve with ATN, cyclosporine toxicity, interstitial nephritis

Non-prostatic oncologic imaging (FDG-PET)

• Bladder cancer: indicated for possible metastasis if other imaging findings equivocal and unable to obtain biopsy
• Kidney cancer: indicated for possible metastasis
• Penile cancer: helpful to confirm presence of inguinal LN metastases if palpable LN to determine need for neoadjuvant chemotherapy
• Testis cancer: helpful to assess residual mass after chemotherapy in seminoma-only patients, sensitivity 78% and specificity 86%, no benefit in NSGCT

PSMA PET/CT

• Indications: initial workup of unfavorable intermediate or high risk localized prostate cancer, metastatic prostate cancer, evaluation for biochemical recurrence after local therapy
• Detection rates: 31-42% for PSA < 0.5, 45-57% for PSA 0.5-1, 57-84% for PSA 1-2, 77-86% for PSA 2-5, 90-97% for PSA > 5 ng/mL

Radiation Exposure

Radiation Dosage

• Radiation exposure: charge per unit mass (C/kg), also measured in roentgens (r)
• Absorbed dose: energy absorbed from exposure, measured in Gray (Gy), 100Gy = 1 rad
• Equivalent dose: absorbed dose with a conversion factor, measures amount of energy absorbed by different tissues, measured in Sieverts (Sv), 1 Sv = 100 rem
• Recommended annual dose limit: 50 mSv

Limiting exposure

• Fluoroscopy tips: use single images, pulsed images, collimate images, increase kVp (rather than mA) if underpenetrated, keep image intensifier above table (and XR tube below table), radiation scattered from patient is source of highest radiation exposure to staff
• General tips: minimize time, maximize distance to source, shield other areas of the body