Computed Tomography

Patient Interactions and Management is worth 21 of the 165 scored items. It covers everything the CT technologist does for the patient: screening and history, laboratory values, consent and time-out, positioning, monitoring and accessory devices, infection control, and the full cycle of contrast use from agent selection and venipuncture through power injection, scan timing, reaction management, extravasation, and documentation. Expect scenario questions that ask what to do first, which patient finding changes the plan, and which medication or dose is appropriate.

Scheduling and Screening

Safe CT begins before the patient arrives. Scheduling staff and technologists screen each order for the correct examination and clinical indication, contrast requirements, prior reactions, renal risk factors, pregnancy potential, and conflicts with other studies. Examination sequencing matters: iodinated contrast or barium remaining in the bowel from a recent fluoroscopic study causes streak artifact, so an abdominal CT is normally performed before a barium study, and iodinated contrast given for CT can delay a nuclear medicine thyroid scan or radioactive iodine therapy for several weeks.

Patient Identification and Verification

Proper patient identification is the foundation of safe CT imaging. The technologist verifies identity with at least two unique identifiers, typically the full name and date of birth or the medical record number, before any procedure. The patient is asked to state the name and date of birth (an open-ended question rather than "Are you John Smith?"), and the answers are compared with the wristband and the requisition. A room number is never an identifier. The requisition or electronic order is compared with the patient's information to ensure the correct examination is performed on the correct patient; any discrepancy must be resolved before scanning. Electronic systems improve accuracy but do not replace direct verification.

Medical History Evaluation

A thorough history supports both safety and diagnosis. The technologist reviews the clinical indication and gathers previous imaging, surgical history, current medications, and known medical conditions. Key elements are summarized below.

HistoryElement	WhyItMattersinCT
Allergyhistory	A prior allergic-like reaction to iodinated contrast is the strongest predictor of a future reaction .
	Document the agent the type and severity of the reaction and its treatment Shellfish or povidone- , , .
	iodineallergydoesnotpredictacontrastreactionandisnot"iodineallergy"
Renalfunction Diabetesandmetformin	Risk of contrast-induced acute kidney injury; guides whether IV contrast is given the volume a1nd , , metformininstructions MetforminmayneedtobewithheldaftercontrastinpatientswitheGFRbelow30oracutekidney injury

HistoryElement	WhyItMattersinCT
Thyroidconditions	Hyperthyroidism or Graves disease raises the risk of iodine-induced thyrotoxicosis; iodinated contrast
	interfereswithplannedradioactiveiodinetherapyorthyroiduptakescans
Pregnancystatus	Determinelastmenstrualperiodandpossibilityofpregnancyforallpatientsofchildbearingpotential;
	manyfacilitiesrequireanhCGtestwhenstatusisuncertainbeforeabdominalorpelvicimaging
Cardiacandrespiratory	Asthma and significant cardiac disease raise reaction risk and affect beta-blocker use for cardiac CT;
disease	heartrateandrhythmaffectcardiacCTquality
Implantedandexternal	Pacemakers neurostimulators insulinpumps andcontinuousglucosemonitorsmayneedtobe , , ,
devices	removedorkeptoutofthedirectbeamperthemanufacturer;metalcausesartifacts

Laboratory Values

The technologist must recognize the laboratory values that affect a CT examination and know when a value requires the radiologist's decision before proceeding.

Test	TypicalAdultReference	CTRelevance
Serumcreatinine	About 0 .6–1 .2 mg/dL	UsedtocalculateeGFR;arisingvaluesuggestsacutekidney
		injury
eGFR	90mL/min/173m²orhigheris .	Risk of contrast-induced AKI is mainly a concern below 30
	normal	mL/min/173m²orinacutekidneyinjury .
BUN	About7–20mg/dL	Elevatedinrenalimpairmentanddehydration
PT/INR PTT ,	INR about 0 .8–1 .1 (therapeutic	Bleedingriskbeforebiopsy drainage orotherinvasive , ,
	rangesarehigheronwarfarin)	procedures;manyprotocolsrequireINRofabout15orless .
Plateletcount	About 150 ,000–400 ,000/µL	Lowcountsraisebleedingriskforinterventionalprocedures;
		facilitythresholdscommonlyaround50000/µL ,
D -dimer	Negative(belowthelaboratory	A negative result helps exclude pulmonary embolism in low-risk
	cutoff)	patients;apositiveresultisnonspecificandoftenleadstoCT
		pulmonaryangiography
hCG	Negative	Confirmsorexcludespregnancy
WBC	About 4 ,500–11 ,000/µL	Elevatedininfectionandinflammation(appendicitis abscess) ,
Hemoglobin	About12–17g/dL	Afallingvaluemayindicateactivebleeding asintraumaorGI ,
		hemorrhage
Liverfunctiontests	ALT AST alkalinephosphatase , , ,	Abnormalinhepatobiliarydisease;supportliverprotocolselection
	bilirubinwithinreferenceranges

Communication and Patient Education

Effective communication establishes rapport and reduces anxiety. The technologist introduces themselves, explains the procedure in understandable terms, and sets realistic expectations about duration and sensations. Breath-hold instructions are explained and practiced before scanning; consistent commands prevent respiratory motion and misregistration between acquisitions. Patients receiving IV contrast are told to expect warmth, a metallic taste, and a sensation of needing to urinate, and to report itching, throat tightness, difficulty breathing, or pain at the injection site immediately. Post-procedure instructions cover hydration, diabetic medication guidance when applicable, and signs that require medical attention. Communication with the care team (nurses, the ordering provider, and the radiologist) follows the SBAR or a similar structured format when a problem arises.

Consent

ConsentType	DescriptionandCTExamples
Informed	Writtenconsentaftertheproviderexplainstheprocedure risks benefits andalternatives;thepatientmust , , ,
	be competent not sedated and able to ask questions Required for invasive procedures such as CT -guided , , .
	biopsy drainage arthrography andmyelography , , ,
Oral(verbal)	Thepatientstatesagreement;acceptableformanyroutineproceduresperfacilitypolicy
Implied	Agreementshownbyaction(extendinganarmforIVplacement)orpresumedinanemergencywhenthe
	patientcannotconsent

Minors require consent from a parent or legal guardian except where state law recognizes emancipated minors. A patient may withdraw consent at any time, and consent signed after sedation is given is not valid.

Time-Out Procedure

Before any invasive procedure, the team performs a time-out immediately before the procedure begins. All work stops while the team confirms the correct patient (two identifiers), the correct procedure, the correct site and side (marked when applicable), signed consent, relevant allergies and laboratory values, and the availability of needed equipment. Any team member may stop the procedure if a discrepancy is found.

Removal of Radiopaque Materials

Jewelry, hairpins, dentures, hearing aids, bras with underwire, clothing with snaps or zippers, ECG leads, and other metal within the scan range produce streak artifacts and are removed or moved out of the field when possible. Radiosensitive external devices such as insulin pumps and continuous glucose monitors are removed or kept out of the beam according to the manufacturer's instructions, and implanted devices such as pacemakers and neurostimulators are scanned quickly through the device when the device cannot be avoided.

Positioning and Immobilization

Proper positioning is essential for image quality and dose optimization. The anatomy of interest is centered at the gantry isocenter; miscentering causes inaccurate CT numbers, increased noise, and increased dose because the bowtie filter and tube current modulation assume a centered patient. Head-first or feet-first orientation depends on the region and protocol; most examinations are supine, with prone, decubitus, or oblique positions for specific indications (prone for CT colonography, prone for distinguishing a stone at the ureterovesical junction, prone for dependent lung changes). Arms are raised above the head for chest and abdominal imaging to reduce streak artifact and dose, and kept at the sides for head and neck imaging. Head holders, sponges, Velcro straps, and padding reduce motion; pediatric and uncooperative patients may need additional immobilization or sedation.

Questions on screening usually test the order of priorities: identify the patient, confirm the correct examination, then address contrast and renal risk. A shellfish allergy alone is not a reason to premedicate, and an eGFR of 30 or higher with no acute kidney injury does not require stopping metformin.