Pulmotec (Technetium-99m Lung Ventilation Aerosol Kit)

What Is Pulmotec and What Is It Used For?

Pulmotec belongs to the class of medicines known as diagnostic radiopharmaceuticals. Unlike conventional drugs, a diagnostic radiopharmaceutical is not designed to treat disease; instead, it is administered in very small amounts so that clinicians can visualize how specific organs function. Pulmotec is specifically designed to produce a tiny radioactive aerosol that, when inhaled, is carried by the airstream into the lungs and deposits on the alveolar and bronchial surfaces in proportion to regional ventilation. A gamma camera then records the 140 keV photons emitted by technetium-99m during its decay, producing a detailed ventilation map of the lungs.

The kit is supplied as a sterile lyophilized (freeze-dried) formulation in a sealed vial. Radiolabelling takes place in the radiopharmacy by adding sodium pertechnetate (99mTc) freshly eluted from a 99Mo/99mTc generator. After a short incubation, the labelled solution is transferred to a disposable, shielded closed-circuit nebulizer designed specifically for radioactive aerosols. The nebulizer produces droplets in the sub-micron size range so that they bypass the upper airways, reach the alveoli and are not trapped in the nasopharynx. Only the inhaled portion reaches the patient; exhaled radioactivity is captured by charcoal filters inside the nebulizer housing to protect staff and the environment.

Within the Anatomical Therapeutic Chemical (ATC) classification, technetium-99m compounds used for lung imaging fall under V09EA — technetium (99mTc) compounds, pulmonary. Product licenses are held in multiple European countries and the preparation is also used in many nuclear medicine departments outside Europe under equivalent authorizations. Pulmotec is supplied exclusively to authorized nuclear medicine centers and is never dispensed to patients directly.

How Does Pulmotec Work?

The physics and pharmacology of Pulmotec are intimately linked. Technetium-99m is a metastable isotope that decays by isomeric transition, emitting a single gamma photon with an energy of 140 keV and a physical half-life of 6.02 hours. This photon energy is almost ideal for medical imaging: it is high enough to escape the lungs and thoracic cage and be detected externally, but low enough to be efficiently collimated and absorbed by the sodium iodide crystals used in single-photon emission computed tomography (SPECT) cameras. Because the imaging signal is produced by the radioactive nucleus itself, only a minute mass of active substance (usually in the nanogram to microgram range) needs to be administered — far below any threshold at which pharmacological effects would occur.

The radiolabelled aerosol droplets are carried from the nebulizer into the mouthpiece by a stream of room air during normal tidal breathing. Once inhaled, deposition of the particles within the respiratory tract is governed by three physical mechanisms: inertial impaction in the large airways (important only for larger droplets), sedimentation in the small airways, and diffusion in the alveoli. Because Pulmotec is designed to produce sub-micron droplets, most of the activity that reaches the alveoli is deposited by diffusion and sedimentation, closely following regional ventilation. Areas of the lung that are well ventilated show intense uptake; areas that are poorly ventilated because of airway obstruction, emphysema, or parenchymal disease show reduced uptake.

Once deposited on the alveolar epithelium, the labelled particles clear slowly by two routes. Smaller molecular components are absorbed across the alveolar-capillary membrane into the systemic circulation, where the radiolabel is predominantly excreted in the urine as free pertechnetate. Particulate components are cleared more slowly by mucociliary transport up the bronchial tree, followed by swallowing and excretion in the feces. Biological half-lives in the lung vary from 30 minutes to several hours depending on the aerosol formulation and the condition of the alveolar epithelium. The short physical half-life of 99mTc ensures that essentially all radioactivity has decayed within 24–48 hours.

Approved Diagnostic Indications

Pulmotec and equivalent 99mTc lung ventilation aerosols are approved by regulatory authorities for a range of diagnostic indications. The most frequent is the ventilation component of a V/Q study, but the tracer has several other important uses.

• Suspected acute pulmonary embolism: Paired ventilation and perfusion scanning identifies unmatched perfusion defects — segments of the lung that are ventilated but not perfused — the scintigraphic hallmark of pulmonary embolism. V/Q is often the test of choice in pregnancy, in young women to reduce breast radiation dose, in severe iodine allergy and in patients with reduced renal function or contrast-induced nephropathy risk.
• Chronic thromboembolic pulmonary hypertension (CTEPH): V/Q scanning has higher sensitivity than CT pulmonary angiography for chronic embolic disease of the small vessels and is explicitly recommended as the screening test in the European Society of Cardiology (ESC) pulmonary hypertension guidelines.
• Chronic obstructive pulmonary disease (COPD) assessment: Ventilation imaging visualizes the heterogeneity of emphysematous lung, identifies areas of air trapping, and helps quantify the functional contribution of each lung region. This is useful in planning lung volume reduction surgery or endobronchial valve placement.
• Pre-operative lung function mapping: Before lobectomy, pneumonectomy or lung transplantation, quantitative ventilation imaging predicts post-operative lung function by measuring the relative contribution of each lobe or segment to overall ventilation.
• Lung transplant follow-up: Ventilation scintigraphy helps detect bronchiolitis obliterans syndrome, airway anastomotic complications and single-lung graft dysfunction.
• Evaluation of suspected foreign body aspiration, bronchopleural fistula, and unilateral hyperlucent lung syndromes (Swyer-James).
• Research applications: Quantitative ventilation imaging is used in clinical trials of inhaled medicines, airway clearance devices and novel bronchodilators to measure regional deposition and response to therapy.

The versatility of the technique, combined with its very low radiation dose and excellent tolerability, explains why ventilation scintigraphy remains a core component of modern nuclear medicine practice despite the growing availability of CT pulmonary angiography and MRI-based pulmonary imaging.

What Should You Know Before Taking Pulmotec?

Every nuclear medicine examination must be preceded by a careful clinical justification that weighs the anticipated diagnostic benefit against the radiation dose and any procedural risks. The referring physician and the nuclear medicine specialist work together to confirm that Pulmotec ventilation imaging is the most appropriate investigation for the clinical question, that no recent examination already answers it, and that alternatives such as contrast-enhanced CT, MRI, or Doppler ultrasound have been considered where feasible. This stepwise approach, known as the ALARA principle (As Low As Reasonably Achievable), is codified in European and international radiation protection regulations.

Contraindications

Pulmotec and the resulting 99mTc-labelled aerosol must not be used in the following situations.

• Hypersensitivity: Known hypersensitivity to any component of the lyophilized kit, to sodium pertechnetate (99mTc), or to excipients disclosed in the Summary of Product Characteristics.
• Pregnancy (elective examinations): Elective diagnostic use of 99mTc-labelled aerosol is contraindicated. Where clinically urgent (for example, suspected life-threatening pulmonary embolism), the examination may still be performed because the fetal dose is small and the clinical benefit substantial.
• Severe uncontrolled bronchospastic disease: Active, severe, unstable asthma or acute severe bronchospasm is a relative contraindication because inhaled aerosols can theoretically precipitate bronchospasm in highly reactive airways. The test is usually deferred until the patient is clinically stable, or a perfusion-only scan is performed.
• Inability to cooperate with the breathing manoeuvre: Patients who cannot hold the mouthpiece, form a seal around it, or breathe regularly for 2–3 minutes may not achieve adequate aerosol deposition. Alternative ventilation tracers (such as 81mKr gas, where available) or perfusion-only imaging can be considered.

Warnings and Precautions

Although Pulmotec ventilation imaging has an excellent safety profile, several important precautions apply to every examination. Patients and caregivers should be informed about these in advance so that any questions can be resolved before the appointment.

Ionizing radiation: Every diagnostic dose of a technetium-99m-labelled aerosol exposes the patient to a small amount of ionizing radiation. The effective dose from a standard ventilation scan is approximately 0.3–1 mSv; a combined ventilation plus perfusion V/Q scan is approximately 1–2 mSv. This is substantially lower than the 3–10 mSv typical of CT pulmonary angiography and is comparable to a few weeks of natural background radiation. Over a lifetime, repeated radiological examinations contribute cumulatively to the stochastic risk of radiation-induced cancer, so each procedure must be individually justified.

Asthma and hyper-reactive airways: Any inhaled aerosol has the theoretical potential to trigger bronchospasm in patients with hyper-reactive airways. In practice, the use of pre-treatment with a short-acting beta-2 agonist (such as salbutamol) before the scan reduces this risk in known asthmatics, and the nuclear medicine department will keep emergency medication and oxygen available.

Pediatric patients: Children are more radiosensitive than adults because their cells divide faster and they have a longer life expectancy during which a radiation-induced cancer might develop. Pediatric activities are scaled down from adult activities according to the EANM Paediatric Dosage Card, using a body-mass-based multiplier. The minimum administrable activity recommended by the EANM must still be respected to ensure diagnostic image quality.

Infection control: The nebulizer system used for Pulmotec is a closed circuit with disposable patient-contact components. However, patients with active tuberculosis, multidrug-resistant organisms, or other transmissible respiratory infections must be disclosed in advance so that appropriate infection control precautions can be taken (negative-pressure room, HEPA filtration, staff PPE, single-patient disposable kit). Routine COVID-19 precautions apply where local guidelines require them.

Oxygen dependency: Patients on continuous oxygen therapy can usually undergo a Pulmotec scan, but their usual oxygen supplementation may need to be briefly interrupted or modified to allow the patient to breathe normally through the mouthpiece. The decision is individualized.

Radiation protection for staff and close contacts: After inhalation, patients emit small amounts of gamma radiation until the tracer has decayed and been excreted. Staff follow strict radiation protection procedures. Patients are generally advised to avoid close prolonged contact with pregnant women and infants for the first few hours after the examination, to drink plenty of fluids, and to follow any specific instructions given by the nuclear medicine department.

Pregnancy and Breastfeeding

Pregnancy status must be confirmed before any examination in women of childbearing potential. A urine or serum beta-hCG test is commonly performed. Detailed advice is provided below.

• Women of childbearing potential: The “10-day rule” or pregnancy test should be applied according to local protocol. If pregnancy cannot be excluded, the examination must be postponed unless clinically urgent.
• Pregnancy: Elective diagnostic use of Pulmotec is contraindicated. However, for suspected pulmonary embolism during pregnancy, a reduced-dose V/Q scan is often the preferred diagnostic test because the fetal dose is lower than from CT pulmonary angiography. In many centers a perfusion-only scan is performed first, and the ventilation scan is added only if the perfusion images are abnormal. The absorbed dose to the fetus from a combined V/Q scan with modern protocols is approximately 0.1–0.5 mGy, well below the threshold for deterministic effects.
• Breastfeeding: A small fraction of the administered radioactivity is systemically absorbed, excreted in urine, and a minor fraction passes into breast milk. The European Association of Nuclear Medicine (EANM) recommends interrupting breastfeeding for 12 hours after the examination, expressing and discarding milk during that period. Milk stored before the scan may still be used. Always follow the specific written guidance of the nuclear medicine department.
• Male fertility: Diagnostic doses have no clinically significant effects on male fertility. No specific contraceptive precautions are required.

Children and Adolescents

Ventilation scintigraphy with a 99mTc-labelled aerosol is used in children for the investigation of suspected pulmonary embolism (rare in children but important in specific populations such as those with antiphospholipid syndrome or nephrotic syndrome), congenital pulmonary malformations, foreign body aspiration, and follow-up of congenital diaphragmatic hernia. Pediatric administered activities must be scaled to body weight using the EANM Paediatric Dosage Card. A minimum administrable activity is defined so that image quality remains diagnostic. Cooperation with the mouthpiece is usually possible from school age; for younger children, a tight-fitting face mask may be used.

Driving and Operating Machinery

Pulmotec does not produce any known pharmacological effect on alertness, vision or psychomotor performance at the tracer doses used. Patients are usually fit to drive home after the examination, although underlying medical conditions (for example, severe dyspnea from acute pulmonary embolism) may independently affect driving safety. Follow the specific advice of the nuclear medicine department.

How Does Pulmotec Interact with Other Drugs?

Because the radioactive aerosol is delivered in nanogram quantities, it does not induce or inhibit cytochrome P450 enzymes and does not compete with other drugs for plasma protein binding in any clinically meaningful way. The concept of a “drug interaction” therefore differs from that for pharmacological medicines: rather than altering blood levels or toxicity, interacting medicines primarily affect how the aerosol is distributed within the lungs and how the free pertechnetate fraction is handled systemically, which can in turn influence how the scintigraphic images are interpreted.

For this reason it is essential to provide the nuclear medicine department with a complete and up-to-date list of all prescription drugs, over-the-counter products, inhalers, vitamins and herbal supplements taken in the preceding weeks. In many cases specific medicines must be paused for a defined interval before the examination, or their timing adjusted, and the referring clinician will usually give written instructions.

Major Interactions

The following categories of medicines have the most important effects on ventilation scintigraphy and frequently require dose timing adjustment, test postponement, or selection of a different tracer.

Minor Interactions

Several additional medicines and clinical factors can subtly affect ventilation scintigraphy. They rarely require discontinuation, but the interpreting physician should be aware of them.

What Is the Correct Dosage of Pulmotec?

Pulmotec is a radiopharmaceutical kit, not a patient-administered product in the conventional sense. What is administered to patients is the aerosolized, radiolabelled preparation produced from the kit. The prescribed quantity is expressed in becquerels (Bq), the SI unit of radioactivity, most commonly with the prefix mega (MBq, one million disintegrations per second). Activity is measured in a calibrated dose calibrator immediately before use because 99mTc decays by 50% every 6.02 hours. Administered activities must always be justified and optimized according to the ALARA principle and to international diagnostic reference levels (DRLs).

Because only a fraction of the activity loaded into the nebulizer actually reaches the lungs (the remainder is retained in the nebulizer, exhaled and captured by filters, or deposited in the oropharynx and swallowed), the concept of “administered activity” for a ventilation scan refers to the inhaled and deposited activity rather than the activity loaded into the nebulizer. Modern nebulizers and targeted aerosol formulations achieve a lung deposition efficiency of 10–20%, so approximately 25–40 MBq of a 150–400 MBq inhaled load is typically deposited on the alveolar surface. This is sufficient for high-quality planar or SPECT/CT ventilation imaging.

Adults — Typical Inhaled Activities

Children

Pediatric activities are scaled from the adult reference activity using the EANM Paediatric Dosage Card multiplier based on body weight. A minimum administrable activity is defined so that images remain diagnostic — below that minimum, the signal-to-noise ratio is too poor to answer the clinical question and the child is effectively exposed to radiation for no benefit. A suitable mouthpiece or face mask must be selected according to the child’s size.

Elderly

No specific dose reduction is required for elderly patients on the basis of age alone. However, elderly patients often have reduced tidal volume and vital capacity, which can increase central airway deposition and reduce alveolar penetration. Where possible, coaching on breathing technique before the inhalation improves image quality. Elderly patients with reduced renal function may clear free pertechnetate more slowly, slightly increasing the effective dose to the bladder wall; frequent voiding mitigates this.

Severe Respiratory Disease

Patients with severe airflow obstruction or ventilatory failure may have difficulty completing the 2–3 minute inhalation. In such patients, the deposition pattern may be predominantly central (large airways) rather than peripheral (alveolar), which must be taken into account when interpreting the scan. In extreme cases, an alternative technique such as 99mTc-Technegas (ultrafine carbon particles) may penetrate more peripheral airspaces more effectively. The choice of technique is made by the nuclear medicine specialist based on the clinical question and patient condition.

Missed Dose

Because Pulmotec is administered as a single inhalation on the day of examination in a hospital setting, the concept of a “missed dose” does not apply. If the appointment is missed, it should be rescheduled as soon as practical; the radiopharmacy can plan a new kit labelling around the new appointment.

Overdose

Because the administered activity is calibrated immediately before nebulization, accidental overdosing is extremely rare. In the unlikely event that a substantially greater activity is inhaled than intended, the patient’s radiation dose can be reduced by forced diuresis, frequent voiding of the bladder, and oral potassium perchlorate to block thyroid uptake of free pertechnetate. There is no specific pharmacological antidote, and symptomatic management is based on the radiation dose absorbed rather than on the trace chemical mass involved. Deliberate spill or accidental aerosolization outside of the closed nebulizer system is managed under the hospital’s radiation incident protocol.

What Are the Side Effects of Pulmotec?

Because only nanogram amounts of active substance are inhaled, Pulmotec does not produce classical pharmacological side effects. The side effects that have been reported are almost exclusively airway-irritation reactions, very rare hypersensitivity events, and anxiety-related symptoms. Large post-marketing surveillance databases and pediatric cohort studies consistently show adverse event rates well below 1 in 10,000 examinations for 99mTc-labelled ventilation aerosols.

Side Effect Frequency Overview

Radiation-Related Stochastic Effects

Even at the low activities used for diagnostic examinations, ionizing radiation carries a small theoretical long-term risk of stochastic effects — primarily a slightly increased probability of radiation-induced cancer over a lifetime. The risk from a single Pulmotec ventilation scan is estimated to be well below 1 in 100,000 per examination, depending on age and organ dose. This risk must always be compared with the benefit of obtaining a diagnosis that could materially change clinical management — for example, confirming or excluding pulmonary embolism, which is a leading cause of preventable death. Deterministic effects such as skin burns or hair loss do not occur at diagnostic doses; these are associated only with interventional fluoroscopy or therapeutic radionuclide administration, not with diagnostic scintigraphy.

Special Safety Considerations in Asthma

Patients with asthma are at slightly elevated risk of transient bronchospasm after any inhaled aerosol. Nuclear medicine departments routinely keep a short-acting beta-2 agonist, oxygen and resuscitation equipment immediately available for the duration of the scan. Patients with known asthma are usually asked to take their usual inhaled reliever on the morning of the appointment and to bring it with them. If significant wheeze develops during inhalation, the procedure can be paused, reliever medication administered and the remaining inhalation completed once symptoms have resolved.

Managing Side Effects

If a reaction occurs, it is treated symptomatically. Nuclear medicine departments are equipped with resuscitation equipment and are staffed by personnel trained to recognize and treat rare hypersensitivity reactions, following the same anaphylaxis algorithms used for iodinated contrast media and parenteral medications. Mild cough and throat irritation usually resolve spontaneously within minutes and do not require specific therapy. Anxiety-related symptoms respond to reassurance and a brief rest.

Any side effect, however mild, should be reported to the nuclear medicine staff and recorded in the patient’s medical notes. National pharmacovigilance reporting systems (Yellow Card in the UK, EudraVigilance in the EU, MedWatch in the U.S.) accept reports for radiopharmaceuticals as for any other medicine.

How Should You Store Pulmotec?

Pulmotec is a dual-regulated product: it is both a medicine (under pharmaceutical regulation) and a radioactive material (under radiation protection regulation). Storage conditions, handling and disposal are therefore defined jointly by the Summary of Product Characteristics and by national radioactive substances legislation (for example, the UK Environmental Permitting Regulations, the European Basic Safety Standards Directive, or equivalent national statutes).

Unlabelled Kit Storage

• Temperature: Store in a refrigerator at 2–8 °C. Do not freeze. The lyophilized formulation is stable within this range for the duration of its shelf life.
• Original packaging: Keep the vial in the original carton, protected from light.
• Access: Store in a dedicated, locked radiopharmacy area accessible only to authorized personnel.
• Shelf life: As printed on the kit label, typically 12 months from the date of manufacture. Do not use after the expiry date.
• Handling before use: Allow the vial to reach room temperature before radiolabelling. Inspect for intact closure and absence of any discoloration of the lyophilisate.

Labelled Preparation Storage

• Immediate use preferred: The radiolabelled preparation is best used as soon as possible after labelling to maximize activity and radiochemical purity.
• If retained: Store the labelled vial in its lead pot at room temperature (15–25 °C) and use within the period specified in the Summary of Product Characteristics, typically up to a few hours after labelling.
• Do not refrigerate or freeze the labelled preparation.
• Quality control: Radiochemical purity must be verified by thin-layer chromatography or a validated alternative before patient administration.

Nebulizer Handling and Infection Control

The shielded nebulizer used with Pulmotec is a single-patient disposable device. After use, it contains residual aerosol and 99mTc activity and must be handled as radioactive waste. The outer shielded housing is decontaminated between patients according to the department’s radiation protection procedures. Charcoal and HEPA filters capture exhaled radioactivity and are replaced on a scheduled basis.

Disposal of Expired or Residual Product

Expired kits and any residual labelled product are stored in a dedicated decay area until the 99mTc activity has fallen below national clearance limits (typically after 10 physical half-lives, or about 60 hours), after which they may be disposed of as conventional pharmaceutical waste if permitted by local regulations. Where this is not permitted, they are returned to the manufacturer or disposed of as radioactive waste through an authorized contractor. Patients and visitors should not be allowed unsupervised access to stored or used generators or nebulizers.

Keep all medicines and radioactive sources out of the sight and reach of children. Never dispose of radioactive materials via ordinary wastewater, household waste or landfill. These rules protect both public health and the environment.

What Does Pulmotec Contain?

Pulmotec is supplied as a sterile kit for radiopharmaceutical preparation. The technetium-99m radiolabel is not present at the time the kit is manufactured; instead, it is added in the radiopharmacy on the day of use. Understanding the system’s composition helps explain why the finished inhalation preparation is essentially a dilute aqueous solution containing only a nanomolar concentration of 99mTc species, together with inert excipients needed for particle formation and stability.

Active Substance and Excipients

• Pulmotec lyophilisate: Sterile lyophilized formulation designed to form a 99mTc-labelled aerosolizable solution upon reconstitution with eluate from a 99Mo/99mTc generator.
• Radionuclide (added in the radiopharmacy): Technetium-99m (99mTc), physical half-life 6.02 hours, obtained as sodium pertechnetate (99mTc) from a licensed 99Mo/99mTc generator (for example, Poltechnet).
• Reconstitution fluid: Sterile, pyrogen-free 0.9% sodium chloride (saline) for injection, supplied separately by the user.
• Final preparation: Clear, colorless aqueous solution, pH close to physiological, free of visible particulates, suitable for nebulization.
• Excipients: Inert carriers and pH adjusters as disclosed in the Summary of Product Characteristics. No preservatives are added.

Physical and Radiochemical Characteristics

Available Presentations

Pulmotec is supplied in multi-dose vials of sterile lyophilisate. Each kit is labelled on the day of use with a freshly eluted 99mTc activity in the range of 740–1,480 MBq, sufficient for multiple patient doses depending on the schedule. The nebulizer required to deliver the preparation is supplied separately as a dedicated, single-patient, shielded device with built-in exhalation filtration to capture residual radioactivity and protect staff.

Packaging: Each carton contains one sterile vial of lyophilisate, a package leaflet, and product documentation. Pulmotec is manufactured by the National Centre for Nuclear Research POLATOM (NCBJ POLATOM) in Otwock-Świerk, Poland, one of Europe’s largest radiopharmaceutical producers.